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Questions related to Polymer Chemistry
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Dear researchers,
Selecting polymer is one of the most important factors affecting on the final properties and performance of the membranes as well as the method of membrane fabrication.
What is the most excellent polymer for membrane distillation process? Why?
Best regards
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Dear Foroogh Khodadadi, the essential key is the hydrophobicity of the polymer matrix. It seems that polysulfone copolymers and composites are the most favored. Please have a look at the following documents. My Regards
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I have immersed some composite material specimen in artificial seawater. I need to check if the material is leaching into the water. Basically to check if some hydrocarbon of epoxy is present in the artificial seawater. Which technique should I use ?
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Dear Muralishwara Kakunje, TOC (total organic carbon) in water is the classical way. Just use one of these techniques such as the spectroscopic ones. My Regards
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I have prepared quaternized PVA. I want to measure the degree of substitution of quaternized polymer by titration. In literature, potassium chromate is mentioned as an indicator but I have potassium dichromate in my lab. Can I use this salt instead potassium chromate? AgNO3 solution is used for the titration.
Thanks for your help.
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Yes but also FTIR (point 2.4), elemental analysis via chemical or spectroscopic techniques is another way. If you are close to a biology institute, you may find Kjeldahl analyzer. My Regards
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Hello,
I would like to synthesize about 10g powder per batch of low molecular weight PMMA.
I have tried a bulk polymerisation using AIBN initiator, equal parts MMA and toluene, and Benzyl Mercaptan as a chain transfer agent, polymerising at 80-90dC for 30mins and then drop wise add in methanol but the dried polymer is not a powder and remains a sticky glue.
I am currently trying to increase AIBN and decrease BM amounts but doesnt seem to reach my desired qualities.
Does anyone have any ideas on how to adapt this method or is there a different method that may give better results?
Sigma adrich has this product https://www.sigmaaldrich.com/AU/en/product/aldrich/200336 which is basically what I want to produce (I will be adding other polymers in once I have sorted out the base recipe which is why I cannot just purchase).
Thank you.
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No thanks, if you decided on precipitation polymerization, then the best will be if it is done via one of the living/controlled polymerization techniques. Best of Luck in your work.
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Dear Researchers :
I have this question and I have an hypothesis:
Why Natural HDPE, when extruded at temperatures about 100 °C (around) it has a white (but pale white), and then when the polymer cools down it color turns between white an yellow.
I understand that this phenomenon it is a general case of all LLDPE, LDPE and HDPE , and in all fabrication processes : Extrusion, injection, molding, pressing, etc.
So this is fundamentally, a chemical characteristic of the material ...
It has to do with a change in the Oxygen concentration in the material ?
Thank you all in advance,
Best Regards !
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Dear Franklin Uriel Parás Hernández, both degradation and crystallization are behind the change in color aspect. My Regards
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We are trying to determine the Mw of a polyphenylene oxide-based ionomer that is functionalized with quaternary amine groups. The polymer is dissolved in NMP. How Can this be done ?
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viscosity method
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Need a reference to understand what is lumped parameter in the case of polymerization and how we can calculate lumped parameters.
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In polymer chemistry, the concept of lumped parameters arises when you hypothesize to design such a set up of polymer studies where you wish to describe all the essential states of the as-developed system that affect the behavior and performance of the system. You can refer to the following article:
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I am studying the aging effects of the ink mixture containing particles and resin. Sometimes I can observe particle precipitation in the bottom of the vial. But sometimes I cannot observe, and the ink mixture looks more like gel. So what could happen chemically in the ink mixture?
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Dear Kaiyue Deng, most likely this is a dispersion which have strict stability conditions. Any thing that may causes breaking one or more of these conditions provoke destabilization of the dispersion, and consequently the system manifestes by precipitation or phase separation. Among these sources, ageing, evaporation of the dispersing medium, failure of the protecting colloid surfactant, and so on. My Regards
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I saw literature that frontal polymerization can be used in 3D printing of composites. The curing can be triggered briefly by external heat source, and the thermal front wave can travel from the external heat source side to convert monomer to polymer. How to control the heat rate in composites curing?
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You may be interested by this reference: Gold nanoparticles are used to generate heat locally by photothermal effect and cure PDMS:
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I want to synthesize PEG stabilized AgNPs and in literature different concentrations are reported. What is the scientific reason of adding PEG in AgNPs.
Suppose in one report researchers have added PEG 600 uL in 50 mL water and AgNO3 was 1 mM. In another study, 1 mM AgNO3 but the PEG 6000 48 mL of 1%.
How does the concentration of PEG and its molecular weight effect the AgNPs synthesis and stabilization?
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Based on the expected diameter of your nanoparticles and their content in the dispersion, you can calculate the concentration of PEG of a certain molar mass, which will cover the surface of your nanoparticles with a monomolecular scrap. From a given diameter and number of nanoparticles, you can calculate the amount of silver nitrate.
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I have seen in the papers that some additives added to polymers for producing foams?
Could you please explain what is the main function of these additives?
cross linker
surfactant
blowing agent
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Dear Helena Mirzabeigi, in brief
- crosslinker is a polyfunctional compound responsible for interconnecting chains during polymerization so that a 3D network is formed.
- surfactant is used to controle cell size and to protect against collision and collapse.
- blowing agent is the chemical that generates a gas responsible for cells formation (foaming) during the polymerization reaction progress. Please have a look at the following links. My Regards
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Hi people I am attaching a File Please help me how do I explain this rheology Trend? What does it say?
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In the observed frequency window your molecules do not interact much and the material behaves more viscous. If you go to higher frequencies, G' and G'' approach and if you go to even higher frequencies, they'll probabely cross (G'>G''). This is related to your molecules entangling. If they are entangled, they can't react to deformation at higher frequencies as a liquid any more. The entanglements are a kind of physical crosslink at high frequencies, while at low frequencies the molecules can slide past each other.
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Can anyone explain the relation between hydrodynamic size of a polymer with its adsorption capacity? Does a polymer with greater hydrodynamic size show better adsorption efficiency or vice versa?
Thanks in Advance
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For proteins, the hydrodynamic size refers to the diameter of a sphere with the same hydrodynamic properties as those possessed by the biomolecules
themselves. Thus the adsorption potential varies directly as the hydrodynamic size.
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I am relatively new to DSC. Recently, I ran DSC on starches but always got this broad endothermic peak which I could not explain. Please see the attached isotherm of a starch sample and my method is listed below.
1: Equilibrate at -50.00°C
2: Ramp 20.00°C/min to 220.00°C
3: Mark end of cycle 0
4: Isothermal for 5.00 min
5: Ramp 5.00°C/min to -80.00°C
6: Mark end of cycle 1
7: Ramp 15.00°C/min to 200.00°C
8: Mark end of cycle 2
9: End of method
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Thank you all for your answers. I am running an isothermal experiment to confirm if the peak is indeed coming due to the moisture loss.
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When i try to measure the viscosity of my sample via rotational Viscometer, the spindle continues to rotate without giving the readout. I have waited for as long as 30 minutes but to no avail. Can anyone please guide me what's the reason behind this? I would highly appreciate..
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If you have the manual, every thing is specified, if not, you can download it with the instrument specifications. Good Luck in your work
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I am interested in writing a book chapter on Vitrimer topic. But, I am not able to find any researcher doing book writing on this topic.
I would like to collobrate with researchers in wiritng a book chapter on Vitrimer Topic.
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Following the procedure below I obtain a solid polymer which after FTIR analyses I identified as a HDI trimer and not a polyurethane prepolymer formed by the union of PEG and HDI.
For the preparation of the pre-polymer, PEG400 diol, together with DBTDL (catalyst), were fed into a three-neck round-bottom flask reactor. Nitrogen flow was maintained for 20 min to provide an inert atmosphere. The mixture was stirred for 30 min at 60 °C. Then, HDI was added dropwise to the mixture and the reaction proceeded for another 1 h at 60 °C under N2 atmosphere, yielding an isocyanate-ended, viscous pre-polymer. The molar ratio of diol:HDI was kept constant at 2:3.
I tried drying the PEG under vaccum + molecular sieves, changing the NCO:OH proportion, the order of addition... How could I avoid this trimerization of the HDI and obtain the objective PEG-based polyurethane viscous prepolymer?.
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Dear Pedro Jesús Navarrete Segado, I think there is an important ecxess of NCO initial concentration, try reducing it or increase OH-PEG-OH initial concentration. Also make a re-check of the calculation step. My Regards
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Dear Researchers :
Can someone teach me how to go from a Concentration given in wt.% to a concentration given in phr ?
Or the two are numerically equivalent ?
I'll appreciate it !
Regards !:)
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Dear Franklin,
I have attached one file which I have made an example for transforming %w to phr. I hope it would be useful.
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I'm currently looking at the rheological properties of the polymer Xanthan Gum. focusing on its dynamic viscosity to be more specific. I'm assessing the effects of pH (ranging from 3.6 to 5.6, 0.4 increment, total of 6 pH's) on the dynamic viscosity of xanthan gum solution (dissolving xanthan gum powder into acetic buffer with equal ionic strength, concentration is kept at 0.04%).
Firstly, my viscosity data collected shows that, as pH increases from 3.6 to 4.0 then 4.4, the viscosity increases; but as I bring up the pH from 4.4 to 4.8, 4.8 to 5.2, then lastly 5.2 to 5.6, the increasing viscosity trend plateaus and the increase in viscosity is less significant compared to the 3.6-4.4 jump. At this range, does pH has an effect on the viscosity of xanthan gum based on its molecular configuration? Though some sources states that xanthan gum's viscosity remains stable and unchanged within the range of pH 3-12 at a high concentration like 1% not 0.04%, yet some suggest pH still plays an effect, though I'm not sure how on the chemical and molecular aspect.
A possible conjecture I can think of is the xanthan gum's order-disorder and helix-coil transition is affected by protonation. In figure 2, it demonstrates how electrolytes affect the structure of the polymer; in figure 3, it shows how at a state of a helical rod and no longer a random coil, it is capable to hydrogen bonds among each other. Hence, I'm wondering of pH plays an effect on it's structural transition, such that the increased intermolecular forces at the form of a helical rod would make it more viscous in solution.
Here are the resources I have used so far:
Brunchi, CE., Bercea, M., Morariu, S. et al. Some properties of xanthan gum in aqueous solutions: effect of temperature and pH. J Polym Res 23, 123 (2016). https://doi.org/10.1007/s10965-016-1015-4
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Dear Ryan Lo, you may find various stufies on this topic. Please have a look at the following free access RG fille. My Regards
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Generally observed at low strain rate for fine grained material.
For industrial scale
which are viable materials?
which parameters need to alter?
Kindly express your views.
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Agree with Mohammad Abboud sir
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cellulose
DNA
kindly extend the list.....................
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Natural polymers occur in nature and can be extracted. They are often water-based. Examples of naturally occurring polymers include silk, wool, DNA, cellulose, proteins, and the like.
Natural
Natural polymeric materials such as hemp, shellac, amber, wool, silk, and natural rubber have been used for centuries. A variety of other natural polymers exist, such as cellulose, which is the main constituent of wood and paper.
You can also check:
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Hello!
Ive never made micelles before, but I gave it a go today and now I have some questions. I am generating thin films using my polymer solubilized in chloroform, evaporating in a rotovap, and then resolubilizing in water followed by 30 min of sonication. I currently (very sadly) do not have access to DLS, I am thinking about getting the Lens3 from Tosoh and analyzing my particles using MALS very soon, until then I dont have any physical characterization assays setup. As a very general description of my molecule, I have conjugated a hydrophobic molecule onto a cationic/hydrophilic polymer
1. What size flask is appropriate for 2mgs of polymer? I tried 100mL, 250mL, and 1L. the 1L sized flask was a bit cumbersome to do the hydration in and the thin films from the 100 or 250 mL flask dont look that thin
2. How quickly do I add water to the solution? Dropwise or all at once?
3. Should i start sonicating the micelles as they rehydrate? Should I rehydrate and then wait and then sonicate?
4. Does adding salt to micelles during hydration or after hydration change particle size?
5. How stable are cationic micelles in general in water or buffer? Hours? Days Weeks? The paper im referencing has no stability data
6. Are there any solvents that are not acceptable for forming thin films/micelles? Variants of my polymer are soluble in ethanol but not in chloroform so can I use ethanol instead?
Im still going through all the literature to find answers to some of my more basic questions, but any useful papers you can recommend would be very much appreciated and a big time saver for me!
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Micelle forming ability is dependent to your polymer physicochemical properties. Polymer charge and net charge in solution is important. Also HlB is a important parameter.
Furthermore you can use hhydrophobic fluorescence probes such as pyrene for study of micelles in your study. Block copolymers also without charge may generate micelle or reverse micelles in solution.
A book entitled as micelles , monolayers and biomembrane from M.N. jones is useful.
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After formation of PVA hydrogel through freeze thaw-method. It was dried in vacuum oven. To determine the porosity of the PVA film, ethanol displacement method is used. Does the PVA film dissolve in ethanol?
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Dear Noor Ul Ain, it is not specified whether it is a chemical or physical gel. PVA is slightly soluble in ethanol. Please have a look at the following attached files. My Regards
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PLA is an environmetal friendly polymers, however it could be more expensive than other conventional polymers like polyethylene and polyproplene. Is that true?? and what is expected for the trend of PLA trend in majet share of plastic industry?
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Dear all, most attractive applications of PLA are found in the biomedical field. The economic aspect may be just a matter of time, costless ressources and processes are being developped. Please check the following documents. My Regards
10.24966/FSN-1076/100048
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Is there a way to look at the properties of a base resin and the selected additives to be compounded into it to determin if there will be a blooming issue or what the correct loading level should be?
Polymers frequently used are Pebax (3533 -7233), PAs, and the various densities of PE.
Addatives would be Tinuvin 622SF, Irganox 1010, Colorants, and radiopacifiers.
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Yes, You can calculate solubility of the additives can be studied by migration (Overall migration limit) method by gravimetrically and also you can determine through UV-Vis spectrophotometer using some standard curves.
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Hello!
Ive been trying to use the ninhydrin assay to measure concentration of PEIMax accurately after dilution. PEIMax is deacetylated 22kDa linear PEI*HCl so it should only contain secondary amines and should supposedly only form yellow compounds that absorb at 440nm with ninhydrin reagent. When I run the ninhydrin assay with PEI however, i see an obvious purple color and i can make wonderfully reproducible and linear standard curves using either 440nm or 570nm absorbance. I am using the Sigma 2% ninhydrin + hydrindantin in pH5.2 LiAc, reacting at 80C for 10 min in a PCR plate sealed with nitrogen blanket (https://www.sigmaaldrich.com/US/en/product/sigma/n7285).
Anyone have any ideas as to why I might be seeing such strong absorbance at 570nm even though i dont have any primary amines in the sample to form Rheumann's purple?
Another point I suppose that might be worth mentioning is I reconstitute my PEImax in 0.1M HCl however Ive run HCl alone in the assay and not seen any color change.
Thanks in advance!
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I am producing polycaprolactone fibers by wet-spinning which is dissolved n DMF and using water as a coagulation bath. 
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The coagulation of polymers in a ternary system (polymer/solvent/non-solvent) occurs via a phase separation step. A polymer-rich phase will segregate form a polymer-lean phase, and this can occur via binodal or spinodal decomposition. In the first case, the separation will follow a nucleation-and-growth mechanism, which in the end will lead either to a globular microporous structure or to a cell-tunnel porous morphology (depending on what phase will nucleate, the polymer-rich or the polymer-lean one). In the latter case, simoultaneous and spontaneous separation of the two phases will occur, leading to a fibrillar microporous morphology.
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Hi,
The main point is that I would like to perform the molecular dyanamics of two organic small molecules, more specifically, two PEG-polymer with two molecules one on each that could potentially interact with each other. I would like to use MD to find out the interaction between two molecules when they installed on PEG polymer.
I summarized the question at the first:
1. What is the best way to perform the MD with two polymers or two small molecules (I tried with small size at first).
2. How could I analyze it (RMSD, RMSF with both molecules to its original state, paired RMSD, MMPBSA, contact surface and radius of gyration and etc.)?
3. Is there any references or tutorial that can guide me?
The following part is the methods that I tried:
First, I tried with Gromacs. But the parameterization of non-standard residues of small molecules is painful and not accurate with the server out there... The combination of two molecules into one topology file is also painful. So, I transfer to Desmond. Recently, I got my small molecules simulated with Desmond. I would like to analyze the trajectory file with RMSD, RMSF with both molecules to its original state, paired RMSD, MMPBSA, contact surface and radius of gyration. But, with the interaction diagram of Desmond, it cannot allow me to use two small molecules. It force me to use one protein and one ligand... I want to analyze the interaction of two small molecules instead. Or is there any some tricks to make it work?
Therefore, I tried with mdtraj, a python based MD analysis library.
The out.cms file (topology from desmond) cannot be recognized by the mdtraj...
So, I tried to convert the .cms to mol2 with VMD. But, it turned out the column of the atom coordinates is 9 instead of 7 that is recognizable by the mdtraj.
I created a script to remove the additional column. However, another error was raised
I got stuck here... How could I analyze the trajectory of two small molecules?
Should I re-run the MD with other program such as Amber or Gromacs?
Currently, I am setting up AmberTools21 and try to use Antechamber to parameterize the molecules and try to perform the MD and analysis with AmberTools. But, I don't know if it will work...
Please give me some advice, guide and suggestions. Thank you so much!
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I have never needed to do contact surface analysis so I will not be able to help you much with this. But if you check MDAnalysis documentation and examples, I believe you should find what you need (https://www.mdanalysis.org/). Try this for example: https://userguide.mdanalysis.org/stable/examples/analysis/distances_and_contacts/contacts_within_cutoff.html
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Im thinking about trying to synthesize some poly beta amino esters, however Im not sure if the chemistry is air sensitive or just water sensitive. The reaction is a polymerization reaction between amines and acrylates via Michael addition.
Also was wondering if you are supposed to remove the inhibitors from the monomers using inhibitor removal resin or keep them in, the materials and methods sections of these PBAE synthesis papers dont mention it, but it seems like something that would be necessary.
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Dear Nikhil Goel, it is not air sensitive. Inhibitors in C=C monomers are active against radical species, but their elimination prior to their use is necessary, at least they are considered as impurities. Please have a look at the attached file. My Regards
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Hi,
I'm studying a styrene acrylic polymer latex with Trilon C (chelating agent DTPA Diethylenetriaminepentaacetic acid) in the formula but I am observing unexpectd effects.
When I remove Trilon C from my formula with tap water, I get a viscosity below 3000 cP, which is logical given divalent cations lower the viscosity. When I use Trilon C I usually get a viscosity around 6000 cP.
I then thought of doing an experiment with ultrapure water :
- without Trilon C I get a viscosity around 6000, which is what I want
- with Trilon C (still with ultrapure water), I get unexpectedly high viscosities
My question is thus does anyone know what can happen in that last case ? Theoritically there is (almost) nothing to chelate.
Thanks in advance, I'll take any bit of thought you can have!
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Trilon C- The active ingredient contained in the Trilon® C types is diethylenetriaminepentaacetic acid (DTPA or DTPA-H )- (a aminocarboxylic acid with 5 functional groups) or its salts. Complex formation is the most important property of trilon C types. Their ability to form water-soluble complexes with polyvalent ions (i.e calcium, magnesium, lead, copper, cadmium, zinc mercury, manganese, iron aluminum) over a wide range of pH 1 to 13.5 may explain the variation in the viscosity. Depending on types of ions are present in your system, different complexes will be formed. I think these soluble complexes will have considerable effect on viscosity. Please look in to what type of complexes are formed and how they influence the rheology of solutions. Thanks,
Dr. B R Gupta, Retd, Prof., I I T Kharagpur, India
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Hi all,
I am planning to disperse metal nanoparticles in superglue (cyanoacrylates) and acrylic adhesives. What would be the methodology for that? I guess just sonicating won't be an option since cyanoacrylate will start polymerizing as soon as it comes in contact with any nucleophile in the surrounding environment or substrate. What could be a more feasible option? Thanks in advance.
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For adhesive formulation, cyanoacrylate & filler are not promising method. So, you will find out that traditional superglue is also clear, transparent, without any filler (even nano filler).
The filler always has some moisture, which can initiate the curing process of cyanoacrylate. So the mixture is always unstable.
Today, silver sintering (acrylate & peroxide & nano silver filler) is popular in semiconductor industry (high thermal, low VR, high reliability). You might search 'silver sintering' as key words in publications & patents. But those raw materials is very expensive.
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Hi there,
It is clear that we use many types of hydrophilic additives containing hydroxyl groups in the PES dope solutions to provide a less hydrophobic membrane.
Is there any physical interaction between the sulfone group of PES polymer chains and hydroxyl groups of hydrophilic additives in the membrane matrix?
Best regards
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Dear Foroogh Khodadadi, if you are suspecting Hydrogen bonding between SO2 and OH groups, sulfone group is a poor H-forming group due to the orientation of H-donor-acceptor counterparts. Please check the following documents. My Regards
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The manufacturers seem to recommend NMP but that only reaches around 25 wt% solid. The dispersion solution will be used for fiberglass coating applications, and requires a 40+% solid content. Wavertree seems to have created a solvent mix (WV900) that can achieve the required solid concentration, but they don't seem to disclose what the solvent mix actually contains.
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Dear Ryan Lampon, please check the following free access patent. My Regards
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A novel polymer designed by me in laboratory has water absorption capacity more than 100%. I was wondering if I am doing it right. Kindly enlighten me about this issue. Many Thanks
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Hello Noor,
100% Water absorption or sorption capacity of polymer signifies that it is so hydrophilic or porous material like sponge(depending upon the polymer) such that it is absorbing dry equivalent water of your polymer. Depending upon the application you will work on, such water sorption dynamics will decide it's failure or success. For example high water sorption in polymer electrolytes is considered good for physicochemical and electrochemical properties but it simultaneously affects the mechanical stability because of hydrophilic polymer electrolyte dilution. Even beyond some critical limits the electrochemical property compromises. If in case your application is different you can mention it in your comment and we can help you in a better way. I hope it helped. If in case you need any reference to support some proof of concept you can ask accordingly.
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I have seen lots of papers for LCST of PNIPAM in water (around 310K, dependent on tacticity), and I have seen plenty of papers regarding the cononsolvency of PNIPAM in water+methanol.
My question is, does PNIPAM also show a coil-to-globule transition in methanol? Is there any work investigating this?
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The following document gives the essential about the phenomenology of LCST of polymers. Good Luck in your work.
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Hello,
I did a opt-freq (1 dimension) PBC job with DFT 6-31g/d,p method to a polymer, job was successful but I don't know how to read values (like HOMO-LUMO energy gaps, bond lengths etc.) from the .out file. I need these values for each calculation for monomer, dimer, trimer... to make graphs. 
I am a beginner in PBC calculations, if anyone can help me, I'll be greatful.
Best regards.
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In general, there are two ways to get the values of HOMO and LUMO if you do not use an other supporting software: First, you get them from the population analysis of output file; Second, you get them from Edit --> MOs tab of Gaussview software. Furthermore, nice to share an outstanding chapter about Fukui functions and Local softness of Prof. Henry Chermette as attached file. Have a good day@@@
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Dear all
What are the best books in chemistry that can be used for curriculum design "i.e. for Materials Chemistry"?
Please write the name of the best books that you read/know in the field of "chemistry"? General Chemistry, Organic, Physical Chemistry, Inorganic, Biochemistry, Polymer synthesis, Polymer Chemistry, Computational Chemistry, Solvents and Solvation theories, Analytical Chemistry, Electrochemistry, etc [...] and Chemistry Laboratory Design.
Thank you very much
- - -
* Additional comment:
You can, also, send to me links (or the books' front page photo) or E books (PDF or any) here or in private message. Thank you!
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Top 3 Chemistry Books | Personal Statement Reading
  • 1) Periodic Tales: The curious lives of the elements - Hugh Aldersey-Williams.
  • 2) Obsessive Genius: The Inner World of Marie Curie - Barbara Goldsmith.
  • 3) H2O: A biography of water - Phillip Ball.
  • Bonus: Periodic Videos.
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hello! RP0! I working with materials of tire . now , I meet a question.HOW TO IMPROVE DRY GRIP OF TYRE , JUST CHANGE THE MATERIALS OF TREAD COMPOUND?
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Dear Chen,
in the past I worked a lot with amine modified SBR rubber (cheically modified) in a close cooperation with a german tyre maker. Taget was to reduce rolling resistance and wet grip. It worked pretty well. Maybe this concept also works to improve dry grip.
Regards,
Roman
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CRISPR-Cas9 is a powerful gene-editing tool. However, there are some problems in delivering it to some specific tissues. Viral vectors work well, but it presents issues with potential in carcinogenesis and immunogenicity. Polymers are used to deliver a great class of drugs, even when administered away from the target tissue. Can polymers be used to deliver CRISPR-Cas9 tools like is done with some drugs?
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Since polycarbonate is manufactured by condensation polymerization, the molecular weight distribution can be described by Flory-Schulz distribution.
The maximum value of polydispersity from Flory-Schulz distribution approaches 2.0.
However, the actual polydispersity of polycarbonate is around 2.4~2.7.
In this case, how could we describe the molecular weight distribution of a polycarbonate material.
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Dear Tatchaphon Leelaprachakul, the Flory and related theories are based some assumptions (which are far from real situations) to facilitate mathematical derivations. The values you obtained are may be due to the existance of branching, i.e., the chains are not perfectly linear. The following links discuss many of these cases. My Regards
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Dear all
My major is based on the experimental. I rare often go to get help from software.
I am looking for the software to simulate the possibility of chemical reaction between POLYMERS. The reaction was not reported yet in any paper. I tried to find somehow similar reaction between two polymers with similar functional groups. But, not successful. I tried to use MD simulation, but interaction parameters are completely unknown. Again, I tried to use the interaction parameters between two similar MOLECULES (and not polymers).
I am wondering if there any software to simulate the reaction properties including the possibility of the formation of the chemical bond, decomposition of the bond, equilibrium constant, the heat of reaction, is it equilibrium one or not, how the Temperature, pH, ionic strength, time …. Affect the reaction.
I don’t mind if the results come with some error since my synthesized polymer and my reaction not reported at all, although basically, it is very simple for the reaction between two functional groups. It is the reaction of –COOH with an amine (but both of them are a polymer).
It would be nice if I can design my polymers only with the 3-4 monomer (oligomer) and then try to see the results.
I don’t mind, I pay for software. The high cost is also OK. But, I am a Chemical Engineer, and my knowledge about chemistry is poor. I can get professional chemistry help.
Best regards
Rajabzadeh k. Saeid, Associate Professor
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Some software of quantum mechanics such as Gaussian, Hyperchem, Material Studio or Gamess could support you to solve well it.
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I've been trying to prepare polyimine based polymer in DCM/DMF/TOL solvent system.
First I let aromatic di-aldehyde reacted with di-amine with long carbon chains (4-6 carbons), as soft segments. After some time, I introduced aromatic di-amine, the hard segments, as chain extender, then the solvent became very turbid, showing that the solubility is not good.
Later I found the turbid solution can only be solubilized by AcOH.
The hard segment is very important to my project and I can't replace it, and the weight% is quite low already.
I was thinking if I could prepare the polymer all over but in pure HOAc, or high weight% of HOAc?
All my solvents are non-aqueous, or only trace of water coming from the formation of imine.
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Dear Bryan,
thank you for posting this interesting question on RG. As an inorganic chemist I'm not a specialist in polymer chemistry enough to give you a qualified answer. In this context I keep wondering about two things: Why are you expecting a soluble polymer when you use aromatic units as hard segments? And why do you want to work in nasty acetic acid when "normal" organic solvents will also work? To the best of my knowledge the formation of low-molecular weight Schiff bases from aldehydes and amines is often catalyzed by small amounts of acetic acid. Thus I assume that a few drops / ml of acetic acid will do in your case too. For some potentially useful information please have a look at the following relevant articles in which the formation of polyimines in various organic solvents has been studied:
Tuning the physical properties of malleable and recyclable polyimine thermosets: the effect of solvent and monomer concentration
and
Synthesis of imine bond containing insoluble polymeric ligand and its transition metal complexes, structural characterization and catalytic activity on esterification reaction
The first article is freely available as public full text on RG, while the second one is not. However, five of the authors have RG profiles, so that you can easily request the full text from one of them directly via RG (provided that it is of interest to you).
In any case I wish you good luck with your research work!
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Hello-I am currently writing a research proposal regarding degradation of certain polymers by bacteria but I am not sure what kinds of assays I should be running to identify particular secreted extracellular enzymes that are involved in breakdown of the polymer. Any suggestions would really be appreciated. 
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Dear Tori,
I recommend you to check:
Handbook of detection of enzymes on electrophoretic gels.
Gennady P. Manchenko 2nd Ed.
CRC Press
ISBN 0-8493-1257-4
You can find a lot of protocols to detect enzymes by zymogram.
Best regards
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Dear Researchers :
Does anyone have experience or knows specific works about the study of Mechanical Properties (i.e. , tensile strength, yield stress, limit of elongation (%), elastic modulus, etc.) of Polymeric Matrices...
These could be:
- Polyethylene/Polypropelene (PP)
- another PP or PE co-polymer, ter-polymer, etc
- EPR
- EPDM
- HDPE, LDPE, LLDPE
or other plastics or elastometers blends
but when Al2O3 particles (or nps) are embedded in the matrix ??
I will appreciate any help, or any direction,
Best Regards !:)
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Dear Franklin Uriel Parás Hernández, literature is really rich with the subject you are studying. Please check the following documents. My Regards
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Hi!
It is known that amino-acid can be co-crosslinked with acrylamide by light. Yet can this reaction be motivated by heat instead of light?
Thanks!
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I just got α-Lactalbumin from sigma, but find it is quite hard to dissolve it. on its specification, it says 10 mg/ml solubility  in water for the protein and i tried to dissolve 1.5 mg/ml into deionized water by stirring more than one hour, and it failed to dissolve. then, ultrasonic treatment at 50 degree was also used but also failed. it is weird because α-Lactalbumin is widely known for use in food ingredient. how can it work with so bad solubility. looking forward to any suggestion from you, thanks!
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  1. Try dissolving in phosphate buffer (ph 7-8) containing NaCl.
  2. Can also increase the temperature of the buffer. Sometimes the proteins supplied by Sigma can have hard particles .
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Hi, could somebody enlighten me on the difference between the two diblock copolymers? For example, what happens if I had PMMA-b-PEO instead of PEO-b-PMMA? Or PMMA-b-PNIPAM instead of PNIPAM-b-PMMA?
Thank you so much!
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The A-B or B-A copolymer is regarding to the sequence of chemical bond to form between A monomer and B monomer. For example: ABS resin (Acrylonitrile - Butadiene - Styrene), it could not connect a other order. In the other hand, if A monomer and B monomer contain the same functional groups, A-B copolymer or B-A copolymer are the same structure. For example: Nylon 66 is synthesized by polycondensation of hexamethylenediamine and adipic acid.
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Hello, everyone!
I am using metal oxide/Graphene composite and electrospinning it using PVA/Water polymeric medium. When I deposit on the aluminum foil the surface is uniform with fewer flakes. I am speculating that this may be due to the polymer/solvent non-uniform evaporation from the surface due to annealing (450C for 2 hours). Can anyone suggest something from their experience about the annealing of metal oxide electrospun film for robust adhesion and uniform deposition? is these flakes normal? or do I need to change the polymer or solvent?
thanks in advance.
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This looks like it could come from the low wettability of the water on your substrate. You could measure the contact angle with your solution to make sure. In case this angle is effectively high you could try to do a plasma treatment of your substrate to increase wettability (if it can support it) but the best option would probably be to change the solvent.
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Dear all,
As many of the flexible microelectronics researchers, I work on developing devices which use one or multiple layers of thin-film polyimide as the substrate. Specifically, it's the spin-coating + curing type process to make a <10 um thick polyimide on a 4'' wafer. The polyimide I use is PI 2610 series from HD Microsystems.
However, I noticed that the recommended curing condition for the soft-bake step and the slow oven curing step is not really ideal. I almost constantly get a polyimide layer with non-uniformity or even defects notable by bare eyes. I tried a couple of different ovens together with several different vacuum settings. But got similar results. One experienced researcher explained that the temperature curve was likely the issue. And his group doesn't use the company recommended temperature curve.
So I'm hoping to ask whether anybody has similar experiences. Would you mind share some knowledge? This will be greatly helpful for me. Thanks so much in advance.
Thanks,
Dongxiao
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I've worked with PI-2600 quite a bit and have seen similar defects. I have found the surface clean to be crucial prior to deposition. I have adapted a 4:1 piranha clean for my substrates prior to spin coating. Also I've found it beneficial to allow the PI to spread prior to spinning and then spinning at a low speed for 10 sec to allow it to spread.
The baking step I developed is a 3 step process so minimize any gasification defects. It consist of 2 min at 120 ˚C, 2 min at 150 ˚C and 3 min at 180 ˚C. The sample is then cured in a furnace with 4 C/min ramp to 250 C where it's held for 50 min then 2 C/min ramp to 350 for an hour. I have achieved defect free PI with surface roughness of 0.5nm rms with this process.
Good Luck!
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Is it possible that the mechanism of stress corrosion cracking(SCC), in PLA is related to factors such as the crystallinity of the polymer, the pH of simulated body fluid, and the magnitude of the applied load?
Best regards.
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Dear Milad
The phenomenon of SCC normally occurrs in polycrystalline metallic alloys that are succeptible to a combined of corrosion,i.e.,chemical dissolution, and a tensile deformation. Therefore,the possibility of SCC of PLA is slim to impossible .
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Hi, I've encountered that PMMA-b-PEO exhibits LCST behavior, but in papers of Richardson, 1993; Cimmino et al., 1988; and Arai et al., 2012, the isotacticity of PMMA causes the block copolymer to adapt a UCST behavior instead. Why is that?
Thank you!
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Dear Max Tolentino, isotactic PMMA is crystalline (or crystallizable) polymer (or fragments). UCST in polymers (which in not common trend) is attributed mainly to crystallization and H-bonding. Please check the following documents. My Regards
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Hi!
I just got crazy with EDC and NHS this 2 reagents.
1. it only require 0.4/0.6mg every time, and it air-slake stick to the steel spoon every time, hard to exactly get the weight
2. it air slake, when I was busy weighing or in storage, and decompose
Thus is there any any smart way to fast and smartly weight it and store it longer?
Thanks!
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Dear Zonghan Gan, this RG thread and the other site give recommendations on their practical use. My Regards
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I have this basic question, since some Thermoplastic polymers such PE, or Polypropelene ..
PE via techniques of Cross-linking for example, can be turned to a Thermosetting polymer, ...
Any Thermoplastic, in theory, can be turned to a corresponding Thermoset polymer ?
Regards !
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Dear Franklin Uriel Parás Hernández, yes besicaly any thermoplastic polymer Can be crosslinked either by chemical, physical, or their combination processes. My Regards
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As you may know, the amino acid can be conjugated to the side chain of acrylamide, usually catalysed by TEMED and light (is it?). Is it a radical reaction?
We try to replicate this conjugation in micro gel bead in microfluidics. I did a preliminary experiment in a blank gel block, simply casting acrylamide-amino acid precursor into a well plate, then treating with TEMED and light. The conjugation get verified by further conjugating a GFP to the amino acid using EDC/NHS (not reacts with acrylamide)
However when I shape the precursor using microfluidics then treat with temed and light, the GFP cannot connect to the bead any more. I tryied different pH considering isoelectric point to induce extra affinity for conjugation, yet still not work. I also tried lengthen light treatment or increase TEMED, still not work. What is the problem and how should I fix it?
Thanks!
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Dear Zonghan, The concentration seems to be high, try diluting in few trial reactions to half, quarter and may be less, microfluidics parameters also need to be lowered.
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I am working on a protein drug delivery system mediated by hydrogel as a vehicle. Even though the formulated hydrogel exhibited more than 2000% swelling, it could not able to deliver the protein drug. Scanning Electron Micrograph shows the hydrogel has a non-uniform porous structure. However, the average pore size is larger than the size of the protein drug.
I suspect that, there could be some chemical bonds (e.g. hydrogen bond) formed between the hydrogel polymer groups and protein as there are hydroxyl groups present in the polymers. Is there any way to find out the possible interactions between the protein and hydrogel? If there are interaction, please suggest on how to prevent these interaction? I am avoiding the use of extreme pH in the process as it may degrade the protein which is stable at pH 6.5-7.5. Thank you very much.
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Dear Ruben Chandran, since the gel is not specified, and if it is a matter of strong secondary interactions, then you you have to disturb the structure (breaking) either by changing either the pH or playing on the ionic strength by addition of salt. This way, mainly H-bonds will vanish, and see if there is drug relase after. My Regards
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why number average molecular weight should be used to find degree of polymerization instead of weight average molecular weight?
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The degree of polymerization itself must be defined.
Are we talking about the degree of polymerization by weight or the degree of polymerization by number? Both exist and are expressed as follows:
Mn = M0*DPn
Mw = M0*DPw
where M0 is the molecular mass of the repeating unit.
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The simple polymer tests in that image incited these questions to me-
  • Why would red-hot copper wire burns with Green flame when polyvinyl chloride (PVC) is burnt on it but orange flame in case of polystyrene (PS) and polyethylene terephthalate (PET)? Is the HCl generated from burning PVC generates Cu(II) compounds upon reacting with copper in case of PVC, but not in case of PS or PET? But doesn't Hydrogen have higher reduction potential than Copper (EMF series), and copper may anyways oxidize in air at high temperature to provide a green-blue flame?
  • Why acetone reacts with PS but not PET? Acetone's (propanone) central C atom is not as much electropositive as methanal (formaldehyde), but still it can undergo nucleophilic addition. But while one alkyl group (ortho-para substituent) enhances electrophilic substitution reaction tendency in case of benzene ring of styrene in PS, two carboxylic groups in terephthalate causes benzene ring to be deactivated for electrophilic substitution in PET. Is this reasoning okay or is there anything wrong with it?
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One side is looking at density - whether it sinks or floats in liquids of different densities - water, alcohol, etc. Geologists do this with minerals - but they use bromoform (2.6 g/mL)!
the other side is using chemistry and solubility - flame tests to show presence of chlorine in PVC, what solvents different polymers dissolve in.
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I am currently running thermal polymerizations of compounds that form free radicals at elevated temperatures (T>120 degrees C).  I want to attempt to polymerize at discrete temperatures between 120 and 200 degrees C.  
Can I use AIBN radical initiator at these elevated temperatures without risk of explosion (in the literature it seems that AIBN is typically used at temps ranging from 60-80 degrees C)?  
If not, is there another radical initiator I can use at temperatures this high??
Thanks!
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Dear Mohamed Chaala, the best is the one that insures high solvation and low transfer reaction. The solvent is much more choosen with respect to the monomer first. My Regards
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I need to dissolve 6 and 9 g of PVC in 100 grams of MEK each. I've left the solutions to shake over night but the PVC did not dissolve. I increased the temperature to 50 Celcius to see if heat has an effect but it does not seem to work. What do I need to do to completely dissolve PVC in MEK?
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Dear all, you can enhance the solubility by using a MEK based mixture with any other solvent that accepted with regard to the biocompatibility ! Is MEK a biocompatible solvent ? I suggect using MEK-THF binary solution. My Regards
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Can the platinume powder or black platinume be choosed as a catalyst in the reaction between vinyl terminated PDMS and Hydrogen terminated PDMS(hydrosilation)?
We have done so but the silicone gel didnt cure at all even in elevated temperature and the platinume powder were remained unchanged;
So I want to know if the uncuring was the result of wrong catalyst choosing?
Or if it is possible to use platinume powder as a catalyst,what else should be done to solve the problem?
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Dear Atefeh Shiri "so is there any possible way to activate the isolated platinum black?" This is certainly an interesting question. I think that the answer is YES. You could dissolve your platinum black in aqua regia (HNO3 / HCl 3:1) and evaporate the resulting solution to give hexachloroplatinic acid:
This can then be used to prepare fresh platinum black. See e.g.
Chemical and Electrochemical Synthesis of Platinum Black
or the attached article.
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Which field is better for master's program?
1) Interfacial and surface chemistry: biosensing, electrochemistry, electronics
2) Materials and polymer chemistry: clean energy
3) Physical chemistry: superresolution microscopy, laser spectroscopy, biophysics
4) Catalytic processes: green chemistry
Actually I am keen on all 4 options and do not know which one to choose.( I have to choose one of them.)
Please share with me if you have information about these fields. I will be happy to know your point of view.
Comparison in terms of: the demand and needs of the community, the application, the novelty of the field and other factors that you think are important to consider.
Thanks.
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I would choose materials with unique properties.
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Hello we all know the electronegativity scale and concept of elements in the periodic table
However when it comes to whole materials such as polymers, nanomaterials and etc
How can we understand theoretically if the synthesized material is highly or poorly electronegative ??
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Dear Gabris Mahamid, the following documents are extremely important in case you want to go deeper in this subject. Also it is nice if you take a look at 'Israelchevilli's book' on intermolecular forces. My Regards
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Can some share synthesis procedure for dithiol PEG?
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The simplest method is to convert PEG into di-tosylate and after it to substitute tosylate with thiourea. It is well described in this article
10.1002/chin.200330066
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Basic dendrite formation of metallic alloys are explained by thermal and constitutional degree of supercooling and most-supercooled band of liquid somewhat ahead of solidification front that causes lateral growth for locally fast-grown structure. For ceramics, how would the crystallography and charge balance as well as defect structure would play role here? and what would be affect of long branch/aromatic group etc molecular effects for polymers? How much correct would be to draw conclusion about dendrite formation on metals/ceramics by studying similar effects during polymer solidification? What would be suitable polymer to study particular metals/ceramics, and from which theoretical basis?
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Ceramic solidification crystallography is highly depends on melt cooling rate and the densification degree during melt rapid solidification process. The cooling rate values of the ceramics melt and subsequent rapid solidification are thermodynamically produce different structure: amorphous, nano-crystalline, cellular and dendrite crystal. The higher the cooling rate produce amorphous structure and the very low cooling rate produce dendrite crystals structure.
Now, in term of ceramic structure defect, the bulk integrity is related to the type of applied technique for melting and cooling. For instance, pores can readily form and deteriorated the properties of the bulk structure deposited by thermal spraying technique, while by thermal explosion spraying showed a high relative density and no pores. This integrity play role in the thermokinetic part of the phase growth. In this respect, the work by the Zhonghai Xu et.al, [1] titled " Microstructure Evolution and Model Analysis of Al2O3/ZrO2 Hypoeutectic Ceramic During Rapid Solidification" and later the work by the Jiayu Pan et.al,[ 2] titled" Solidification mechanism and microstructure evolution of Al2O3-ZrO2 ceramic coating prepared by combustion synthesis and thermal explosion spraying" are very interesting to look at.
Best regards
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Is it possible to estimate the polar and dispersive surface energy components from MD simulation?
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It could be. General force field equations have several terms which may be explained as certain type of interaction. If you are calculating vdw, using the vdw term. For polar interaction, it might be chsllenging since it contains electrostatic force and hydogen bonding interaction.
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I am looking some resist strippers which can easily remove metal based polymer residue after post dry etch process.
I have some candidates below but not sure if they are compatible with doped silicon or not !!!
1. EKC265
2.ALEG 368
3.ACT AS-65
4.Techni strip Ni555
Is anyone can help me to find a stripper which is as effective as above and compatible with doped silicon too ?
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Hi i was trying to deposit the polystyrene nano fibers on aluminum substrate... Can anyone help me how to enhance the nano fiber's adhesion to the substrate? Like annealing pr vacuum drying ? Any related papers will help. Thanks
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There is a dopant for the vhb 4910 actuator tapes that have acetylene black or carbon black which is carbon grease (carbon black + pdms) commercially, I am making a robotic actuator but I don't know what is the difference at a chemical level between carbon black and carbon and why In some papers there is talk of a negative intrusive charge which, when placed as electrodes, having a thin layer of vhb 4910 in the middle, these electrodes are attracted by the high voltage that is applied, causing the vhb to be crushed, stretching or changing shape by attraction but I don't know why that dopant is the only one that works for the vhb 4910 and because it has that intrinsic charge or what is that intrinsic charge
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hello
  My thesis is defined base on acrylated Polyurethan. I used HEMA (hydroxy ethylmethacrylate) as a reactive diluent and benzophenone (BP) as a UV initiator with methyl diethanolamine as an accelator. But my system is so viscous and needs heating for adding photo initiator and proper mixing. I use 45º c for adding photo initiator and mixing. but most of the time it stat to crosslinking from the bottom of the sample container. I mean before curing with UV lamp it start crosslinking.
I thought that its because of BP . Its a thermal initiator too. so I need a UV initiator can be used in higher temperature. Could you please introduce appropriate one?
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Irgacure-2959
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Hi!
We are aiming to bind streptavidin to polyacrylamide surface. The EDC/NHS method bounced on me as a common method, utilizing the -NH2 of polyacrylamide and -COOH of streptavidin. Is there any unconsidered factors that may block this route? If EDC/NHS is viable to immoblise streptavidin to acrylamide, how should the reaction condition be set? Consider the static charge of polyacrylamide and streptavidin ( isoelectric point = 6), which pH is optimistic? Should we use a 2 step EDC/NHS xlk or 1 step?
Thanks!
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You may add 5 % of acrylic acid to your acrylamide. Subsequently, the polymer can be activated by a carbodiimide/NHS mixture.
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I have 2 excercise about determining composition of monomers (%) in the copolymer by H NMR. There are images of excercise. Can anyone help me solve it? Thank you!