Pakorn Opaprakasit

Sirindhorn International Institute of Technology (SIIT), · bio

Alcoholysis is a promising approach for upcycling postconsumer polylactide (PLA) products into valuable constituents. In addition, an alcohol-acidolysis of PLA by multifunctional 2,2-bis(hydroxymethyl)propionic acid (DMPA) produces lactate oligomers with hydroxyl and carboxylic acid terminals. In this work, a process for sizing down commercial PLA...

MXenes, a new family of two-dimensional transition metal carbides or nitrides, have attracted tremendous attention for various applications due to their unique properties such as good electrical conductivity, hydrophilicity, and ion intercalability. In this work, Ti3C2 MXene, or MX, is converted to MX-TiO2 composites using a simple and rapid microw...

A process for sizing down and functionalizing commercial polylactide (PLA) resin is developed by alcoholysis with 1,4-butanediol (BDO) and propylene glycol (PG) to medium-sized PLA-based diols, with lower cost than a bottom-up synthesis process. These are subsequently used as polyols in preparing polyurethanes (PU) by reacting with 1,6-diisocyanato...

Corrosion is a problematic and costly issue in various technological fields, especially in marine, automobile, rail, and building industries. To effectively cope with this issue, transition-metal carbides (Ti3C2Tx), a 2-dimensional conductive material, functionalized with polyaniline (PANI) have been developed and applied as anticorrosion additive...

Mn 3 O 4 nanograins incorporated into reduced graphene oxide as a nanocomposite electrocatalyst have been synthesized via one-step, facile, and single-pot microwave-assisted hydrothermal technique. The nanocomposites were employed as cathode material of fuel cells for oxygen reduction reaction (ORR). The synthesized product was thoroughly studied b...

A process for preparing emulsions of alkyl ketene dimer (AKD) nanoparticles via a nanoemulsion template (emulsion/evaporation) method has been developed. The effects of types and contents of stabilizing agents, i.e., anionic (sodium dodecyl sulfate, SDS), cationic (cetyltrimethylammonium bromide, CTAB), amphoteric (phosphatidylcholine, PC), and pol...

Biodegradable polylactide (PLA) is a promising alternative to conventional plastics. Although the material is degradable, a process for converting its post-consumer products to other value-added products is of interest. In this work, PLA-based nanofibers with a super-hydrophobic property are developed by using the chemical recycling products of PLA...

The utilization of ultrasonication in the preparation of polymeric nano/microparticles has attracted vast attention due to its simplicity with low cost and high energy efficiency. The occurrence of acoustic cavitation generated by the ultrasonication process can enhance droplet disintegration, allowing the improved stability of emulsions. In this s...

Stimuli-responsive controlled delivery systems are of interest for preventing premature leakages and ensuring precise releases of active compounds at target sites. In this study, porous biodegradable micro/nanoparticles embedded with thermoresponsive gatekeepers are designed and developed based on Eudragit RS100 (PNIPAM@RS100) and poly(N-isopropyla...

A process for surface modification of LDPE films has been developed by employing chitosan (CS), alkyl ketene dimer (AKD), and glutaraldehyde (GA). Surface roughness and polar reactive groups were generated on the film surfaces by etching with chromic acid at 30 min. The polar groups interact/react with CS/AKD/GA, forming a highly stable coating lay...

In this work, PLA/lignin composite films have been developed for packaging films. The composite films were prepared by a solution casting method. The lignin was prepared from black liquor from the paper industry, by extracting with acetic acids at 50°C. The lignin contents in PLA matrix were 0.5, 1, 3 and 5 phr. Fourier-transformed infrared spectro...

The effects of benzalkonium chloride (BKC) contents on the structure, properties, and ultrafiltration performance of chitosan-based nanocomposite membranes containing poly(ethylene glycol) and multi-walled carbon nanotube (chitosan/BKC/PEG/CNT) were examined. The membranes were prepared by a mixing solution method and phase inversion before being c...

The presence of microorganisms on filtration membranes can cause biofouling phenomena. In this study, poly(ether sulfone)- (PES)-based functional ultrafiltration membranes were developed by employing chitosan (CS) and ammonium chloride (NH4Cl) as antibacterial agents to enhance antibiofouling properties. A PES membrane was prepared using the phase...

A process for preparing polylactide-block-polyethylene glycol (PLA-b-PEG) copolymers has been developed and optimized by employing a transesterifi cation reaction in a melt-mixing process. The reaction was carried out in a counter-rotating mixer unit, using polyethylene glycol (PEG) and tetrabutyl titanate (TBT) catalyst. The effects of PEG weight...

The field of photonics and optoelectronics has opened up new avenues for the development of modern technologies with great impact. Research has progressed from a basic to an advanced level, starting from the atomic level through to the development of an optical system. The contribution to and the advancement in developing an optical system using me...

A detailed study on the synthesis of chitosan nanoparticles under ultrasonication is reported in this paper. By using this simple technique, chitosan particles in nanometer range can be easily prepared without using any harmful and expensive chemicals. The results show that increasing the ultrasonic irradiation time and ultrasonic wave amplitude ar...

Microneedle technology has received considerable attention in transdermal drug delivery system research owing to its minimally invasive and convenient self-administration with enhanced transdermal transport. The pre-drug loading microneedle method has been developed for several protein and chemical medicines. However, the protein activity and effic...

Oxoammonium cation (TEMPO⁺) is a powerful oxidant, generated from nitroxyl radicals (TEMPO). The compound has attracted vast attention as a promising selective oxidant in biology and materials fields. Although TEMPO is regarded as a “green” chemical, its use with halogenated co-oxidants has raised serious environmental concerns. In this study, a ha...

Poly(l-lactic acid) (PLLA) is a well-known biopolymer, usually synthesized via step-growth or ring-opening polymerization from lactic acid or a lactide monomer, respectively. PLLA microspherical particles are produced by dispersion polymerization with a ring-opening lactide monomer using a particular copolymer chain as a stabilizer. This is not eas...

Metal-organic framework (MOF), MIL-53(Al), coated magnetic nanoparticles (MNP) was developed in this work for highly efficient adsorption and removal of an antibiotic pollutant oxytetracycline (OTC) from water. The adsorbed OTC molecule, which is heat labile, can be degraded rapidly using inductive heating which also regenerates the nano-adsorbent....

Chitosan (CS) nanoparticles with antibacterial properties have been synthesized by the ionic gelation method using tripolyphosphate (TPP) as a crosslinking agent. Physicochemical properties of the resulting CS-TPP nanoparticles were examined by FTIR spectroscopy, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray, transmission...

The design of smart drug delivery carriers has recently attracted great attention in the biomedical field. Smart carriers can specifically respond to physical and chemical changes in their environment, such as temperature, photoirradiation, ultrasound, magnetic field, pH, redox species, and biomolecules. This review summarizes recent advances in th...

Biofouling due to biofilm formation is a major problem in ultrafiltration membrane applications. In this work, a potential approach to solve this issue has been developed by functionalization of chitosan-based membranes with benzalkonium chloride (BKC). The chitosan composite membranes consisting of poly(ethylene glycol) (PEG), multiwalled carbon n...

Chemical recycling is a promising approach for converting post-consumer bio-plastics, especially polyesters, into small-sized starting materials for other value-added products. In this work, a process for alcoholysis of polylactide (PLA) by various alcohols has been developed. The products are then employed as bio-based polyols in the production of...

The authors are grateful for support from the Center of Excellence in Materials and Plasma Technology (CoE M@P Tech), Thammasat University, and Prof. Bernadette Charleux for the supply of P(S27-b-AA120) samples.

Post treatments of polymeric products after fabrication, especially improvements of their crystallinity, are commonly applied to further enhance properties of the materials. In this study, a cold-drawing process in various environments is developed for poly(L-lactide) (PLLA) monofilaments, whose solvent-infusion mechanism is examined. Multiple neck...

The deposition of scale on membranes or container and pipe surfaces (clogging the system) is a costly issue in water treatment processes or water-cooling systems. To effectively cope with this issue, magnetic polymeric nanoparticles (MPNPs) have been developed and applied as promising scale inhibitors, due to their high surface-area-to-volume ratio...

Oxidation reactions of alcohols have been of interest due to their broad applications in different fields. Oxoammonium cation (TEMPO+) of 2, 2, 6, 6-tetramethyl piperidine-1-oxyl (TEMPO) is a high-potential oxidant for the selective oxidation of primary alcohols, with hydroxylamine (TEMPOH) as a side product. TEMPO or TEMPO+ has been widely applied...

A process for the chemical recycling of degradable polylactide (PLA) has been developed, to convert its disposable wastes into small-sized products for further use as value-added starting materials for specialty products. A microwave-assisted alcoholysis reaction, using diols and tetrabutyl orthotitanate (TBT) catalyst, was employed. The effects of...

Polymeric nanofibers with superhydrophobic property have attracted vast interest in various applications, especially oil/water separation. In this work, superhydrophobic PLA nanofibers have been fabricated by an electrospinning process and treatment with a hydrophobic agent, alkyl ketene dimer (AKD). AKD consists of a functional group that is speci...

Alteration of lipid raft organization manifesting as phase separation is important for cellular processes, such as signaling and trafficking. Such behaviors and dynamics of lipid membranes can be affected by external stimuli including both physical and chemical stimuli. In this study, we focused on osmotic-tension-induced phase separation. The effe...

Chemical recycling has attracted vast attention as one of effective solutions to deal with serious plastic waste problems. In this work, depolymerization of polylactide (PLA) by alcoholysis has been developed for converting PLA post-consumer products to value-added raw materials. Alcoholysis was conducted by using erythritol in a presence of tetrab...

A sonochemical approach is widely used as a routine protocol for graphene oxide (GO) preparation prior to adsorption applications, but there is a limited understanding of its effects on the GO sorption ability. Herein, using different types of sorbates, which are cation, cationic and anionic dye, the changes in sorption capacity along with the char...

The significant effects of annealing atmosphere on the thermal reduction of graphene oxide (GO) under different atmospheres, air and nitrogen, have been investigated and their distinct properties shown. Initially thermal annealing of both GO in air and nitrogen leads to elimination of unstable in-plane oxygen containing groups. For GO in air (A-RGO...

Biodegradable plastics have become interesting alternative materials in packaging applications, because of their lower environmental impacts. Among these, polylactide (PLA) has played a key role, pertaining to many of its excellent properties. However, its commercialization as packaging materials for products sensitive to light, gas, or temperature...

Biodegradable/biocompatible microspheres have been prepared from poly(lactic acid-co-glycidyl methacrylate), P(LA-co-GMA), copolymers by a phase inversion emulsification (PIE) process. As the copolymer contains unsaturated functional groups, this can be crosslinked by employing thermo-curing reaction. Effects of co-surfactant concentrations and the...

Effects of UV/photo-initiator treatments on crystal formation and properties of polylactide (PLLA) films are investigated. Camphorquinone and riboflavin photo-initiator solutions in methanol are employed in the treatment of amorphous quenched PLLA films. Results from FTIR, ATR-FTIR, DSC, XRD, and SEM show evidence of crystalline domain formation di...

Nanofibers of polylactide (PLA)/poly(vinylpyrrolidone) (PVP) blends, loaded with TiO2 nanoparticles, have been prepared by an electrospinning method. The electrospun fiber mats were characterized by ATR-FTIR, X-ray diffraction (XRD), SEM, EDX, and UV-visible spectroscopy to examine structures, functional groups, crystallinity, surface morphology, a...

In contrast to typical starch esterification in an aqueous solution, which are carried out at elevated to ambient reaction temperatures, a low reaction temperature was applied in this study to minimize the starch chain hydrolysis. The physical properties of the modified starch, obtained from an esterification of cassava starch with long-chain fatty...

Curable precursors for production of thermosetting (co)polyesters are developed based on poly(butylene adipate) (PBA), poly(ethylene terephthalate), and poly(lactic acid) (PLA). The precursors are prepared from methacrylation of their hydroxyl-terminated oligomers. These include commercial HO-capped PBA prepolymer (HO-PBA), and bis-2-hydroxyethyl t...

The work aims to develop a simple and low cost ammonia gas sensor based on reduced graphene oxide (rGO). Reduced graphene oxide doped with nickel sulfate (NiSO4/rGO) was used as a sensing material. The sensor was fabricated by a simple drop-cast and spin-coat technique. The performance of the nickel-doped reduce graphene oxide were studied in terms...

Surface grafting of biodegradable/biocompatible polylactide (PLA) films by a UV-assisted reaction has been developed by employing a hydrophilic acrylamide (Am) monomer, an N,N′-methylenebisacrylamide (MBAm) cross-linker, and a camphorquinone (CQ)/N,N′-dimethylaminoethylmethacrylate (DMAEMA) photoinitiator/coinitiator system. The accomplishment of t...

Standard techniques for quantitative measurement of polyacrylamide (PAm) contents grafted on polylactide (PLA) film substrates, P(LA-g-Am-co-MBAm), which are commonly used as cell culture substrates or scaffolds, and pH-sensitive absorbents have been developed with X-ray photoelectron (XPS), proton-nuclear magnetic resonance (¹H-NMR), and Fourier t...

Radioactive Cs is a major by-product of nuclear power plants, with high radioactivity and long half-life. It is highly soluble in water and is difficult to remove. In this study, pristine graphene oxide (GO) synthesized via a Hummer's method has been demonstrated as a very efficient Cs sorbent with the maximum adsorption capacity of GO found to be...

Menthol is a key ingredient in many of the traditional Thai aroma products such as potpourri and herbal air freshener. However, it suffers from the rapid evaporation and sublimation loss. In this work, microwave graphene oxide (mGO) has been prepared as sorbent and tested for the slow release of menthol. Menthol was loaded into microwave graphene o...

Stimuli-responsive controlled delivery systems are of interest for preventing premature leakages and ensuring precise releases of active compounds at target sites. In this study, porous biodegradable micro/nanoparticles embedded with thermoresponsive gatekeepers are designed and developed based on Eudragit RS100 (PNIPAM@RS100) and poly(N-isopropyla...

Amphiphilic surface-grafted poly(L-lactide-co-glycidyl methacrylate-graft-acrylamide-co-N,N’-methylenebisacrylamide) copolymer, P(LLA-co-GMA-g-AAm-co-MBAm) has been synthesized by a UV photopolymerization process. The grafted copolymer particles possess a combination of unique properties of biodegradable PLLA, PGMA, and PAAm polymers. The success o...

[6]-Gingerol (6 % w/v)-loaded cellulose acetate (12 % w/v CA; MW ~ 3 × 104 g/mol) fibers (375 ± 107 nm) were prepared by electrospinning at 7.5 kV. ATR-FTIR spectra indicated that the mixture was miscible at this composition. Differential scanning calorimetry revealed that [6]-gingerol was uniformly dispersed in the CA matrix and interrupted the hy...

Hydroxyl-capped polylactic acid (PLA) oligomers are prepared by glycolysis reaction of PLA with ethylene glycol (EG) and used as a macromolecular cross-linker for epoxidized natural rubber (ENR). The glycolyzed PLA (GPLA) with three different molecular weights (2000, 10,000, and 44,000 g mol−1) are prepared by varying the glycolysis conditions. Eff...

Glycolyzed polylactic acid (GPLA)-cured epoxidized natural rubber (ENR) is developed for use as a toughening agent for PLA resin. GPLA is obtained from chemical recycling of PLA resin by a glycolysis reaction. GPLA-cured ENR is then prepared by the crosslinking reaction of ENR with GPLA in an internal mixer. Chemical structures of the cured product...

Poly(ethylene terephthalate-co-lactic acid) (PET-co-PLA) copolymer with medium molecular weight was synthesized and blended with commercial polylactic acid (PLLA) by solution and mechanical blending methods to optimize its mechanical properties. Miscibility and properties of the blends were characterized. Miscible blends are achieved at all composi...

Nanofibers of poly(L-lactide-co-DL-Lactide) (PDLLAx) copolymers with DL-lactate (DLLA) contents of 0, 2.5, 7.5, and 50%, which exhibit strong structure/properties correlation, were fabricated by electrospinning. Effect of the copolymer structure and electrospinning conditions on morphology and properties of the fibers were examined by SEM, DSC, XRD...

Chitosan and polyethyleneimine (PEI) functionalized hollow latex (HL) particles were conveniently fabricated by coating poly(methyl methacrylate-co-divinyl benzene-co-acrylic acid) (P(MMA/DVB/AA)) HL particles with 5wt% chitosan or 14wt% PEI. The materials were used as formaldehyde adsorbent, where their adsorbent activity was examined by Fourier T...

Chitosan and polyethyleneimine (PEI) functionalized hollow latex (HL) particles were conveniently fabricated by coating poly(methyl methacrylate-co-divinyl benzene-co-acrylic acid) (P(MMA/DVB/AA)) HL particles with 5 wt% chitosan or 14 wt% PEI. The materials were used as formaldehyde adsorbent, where their adsorbent activity was examined by Fourier...

This research investigates the potential for grafting skim natural rubber with maleic anhydride to produce maleated rubber with the aim to increase value of skim natural rubber. In this study, grafting of skim natural rubber was compared to those of natural rubber block. Moreover, the effect of protein in skim rubber was also investigated by compar...

Curable precursors are prepared from chemical recycling of degradable polylactic acid (PLA) for development of aliphatic polyester thermoset materials. PLA resin (NatureWork 4042D) was de-polymerized via glycolysis under various conditions to produce PLA glycolysates (GlyPLAs), whose chain-ends mainly consist of hydroxyl groups with $\bar{M}_{n}$...

A large amount of radioactive cesium (Cs) has been released into natural environment following the nuclear accident in Fukushima, Japan in 2011. Much effort has been directed at capturing Cs and remediation of the contaminated environment. However, conventional sorbents, such as Prussian blue and zeolites cannot be easily recovered once spread into...

Aliphatic/aromatic copolyesters, which possess good mechanical property and degradability, are of immense interest. Standard characterization techniques for the copolymer structure and degradation behaviors have been developed. The techniques are applied to examine hydrolytic degradation of poly(ethylene terephthalate-co-lactic acid) in a phosphate...

Crosslinkable poly(lactic acid-co-glycidyl methacrylate), P(LLA-co-GMA), copolymer was systematically synthesized by ring-opening polymerization. Synthesis parameters, i.e., catalyst type, comonomer ratio and polymerization time and temperature were studied. The incorporated GMA content strongly affected the physical and thermal properties of the o...

Naproxen (NPX) drug-loaded magnetic nanoparticles (MNPs) have been prepared in a one-step process utilizing a biocompatible polylactide-grafted-chitosan copolymer. The copolymer serves both as a NPX drug carrier as well as a polymeric surfactant for the synthesis of MNPs without the use of any additional surfactant. Highly stable MNPs with high mag...

Polylactic acid/ethylene glycol triblock copolymer (LLA46EG46LLA46) was prepared and used in a crosslink process of epoxidized natural rubber (ENR) by employing a ring-opening reaction using Sn(Oct)2 as a catalyst. The OH-capped copolymer acts as a macromolecular crosslinking agent in the formation of ENR networks, leading to drastic enhancement in...