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Synthesis and application of oligo(vinylamine)
Abstract
Oligo(vinylamine) (OVAm) can be synthesized from oligo(N-vinylformamide) (OVFA) by hydrolysis of the formamide groups. The cationic polymerization of VFA is initiated with iodine, bromine, trifluoromethanesulfonic acid, or trimethylsilyl triflate in toluene at various temperatures. Chain structures, head group functionality, and MWD of the OVFA are investigated by 1H NMR spectroscopy, MALDI-TOF-MS, and GPC. OVFAs with narrow MWD are obtained in moderate yields (5–50%) at 253–313 K. The yields, average molecular weights, and chemical constitution of the OVFAs are strongly determined by the reaction temperature used. The acid or alkaline hydrolysis of the OVFAs leads to OVAm. The structure of the OVAms, based on different precursor OVFAs, is investigated by NMR spectroscopy and GPC. An application of the OVAm as a suitable polyelectrolyte component for organic/inorganic hybrid materials is described.
Vinylformamide (VFA) is cationically polymerized in various solvents at 273 K and reaction temperature by the following initiators: iodine, bis(4-methoxyphenyl)-methyl chloride/silica, triphenylmethyl chloride/silica, and trimethylsilyl triflate. In every case defined oligomers with narrow molecular weight distribution are obtained in moderate yield (20–50%). Acid hydrolysis of the obtained oligomers yields well defined oligovinylamine products. The cationic initiation mechanism of VFA is discussed in terms of the HSAB-concept†
Gegenstand der vorliegenden Arbeit ist die Untersuchung der kationisch initiierten Oligomerisation von N-Vinylformamid mit Iod, Brom, Trifluormethansulfonsäure und Trifluormethansulfonsäure-trimethylsilylester.
Quantenchemische Berechnungen zur Konformation und zur Elektronendichteverteilung von N-Vinylformamid, sowie zu seiner Reaktion mit Elektrophilen werden vorgestellt. Die Struktur der erhaltenen Oligomere wird mittels 1H- und 13C-NMR-Spektroskopie, MALDI-TOF-MS, GPC, IR-Spektroskopie, Thermogravimetrie und quantitativer Elementaranalyse untersucht. Die Abhängigkeit von Ausbeute, mittleren Polymerisationsgrad und Kopfgruppenfunktionalität der erhaltenen Oligo(N-vinylformamide) vom Initiator, sowie von der Polarität des Lösemittels, dem eingesetzten Monomer/Initiator-Verhältnis und der Reaktionstemperatur wird vorgestellt. Im Vergleich zum N-Vinylformamid werden N-Vinylacetamid, N-Methyl-N-vinylformamid, N-Methyl-N-vinylacetamid und N-Vinylpyrrolidon auf ihre Fähigkeit untersucht, mit Initiatoren der kationischen Polymerisation Oligomere zu bilden. Mit N-Deutero-N-vinylformamid als Monomer und der 2H-NMR-Analyse der erhaltenen Oligomere wird der Einfluß der NH-Eliminierung während der Oligomerisation von N-Vinylformamid untersucht.
Ausgehend von den experimentellen Ergebnissen wird ein für die Vinylpolymerisation neuer Mechanismus für die Oligomerisation von N-Vinylformamid vorgeschlagen und diskutiert.
N-Vinylformamide (NVF, N-ethenylformamide) is a precursor to amide and amine functional polymers and to other monomers, oligomers, and functional polymers. NVF shows attractive physical and toxicological properties and high reactivity, both in polymerization and in subsequent hydrolysis to cationic and reactive amine functional polymers or oligomers. NVF radical polymerization readily yields water soluble homopolymers with molecular weights from 10 to >10. Copolymerizability is similar to other vinyl amides. Unexpectedly, NVF will also undergo cationic oligomerization. Hydrolysis of polymers and copolymers with base or acid is facile, although reactions with neighboring groups (e.g., with coacrylate ester groups to give lactams) complicate copolymer hydrolysis.Reaction of NVF at the unusually acidic NH group allows reaction with isocyanates to give vinylacylureas or Michael addition to acrylates to give a family of new N-vinylformamidopropionate esters. These esters in turn react with functional amines to generate new families of divinyl, vinyl/alcohol functional, or vinyl/amino functional comonomers. Applications for NVF and its derived monomers and polymers appear numerous, in particular in radiation cure coatings, based on their good physical and toxicological properties.
Monolithic silica aerogels modified by amino-substituted organic groups with bulk densities between 0.07 and 0.16 g cm-3 were prepared by sol−gel processing of Si(OEt)4/(MeO)3Si(CH2)3NR‘2 mixtures (NR‘2 = NH2 or NHCH2CH2NH2), followed by drying of the wet gels with supercritical CO2. The Si(OEt)4/(MeO)3Si(CH2)3NR‘2 ratio was varied between 9:1 and 6:4. The ≡Si(CH2)3NR‘2 groups were completely incorporated in the aerogels in each case. Raman spectroscopic investigations showed that the precursors were rapidly consumed upon addition of water to the alkoxysilane mixtures. Gelling was slowed with an increasing portion of (MeO)3Si(CH2)3NR‘2. The structure of the aerogels was investigated by nitrogen sorption, small-angle X-ray scattering, and transmission electron microscopy. The polarity of the inner surface of the aerogels was rather low. The particle radii were in the range of 6.0−6.3 nm, the fractal dimension in the range of 1.3−1.6, and the BET surface area in the range of 300−430 m2 g-1, rather independent of the Si(OEt)4/(MeO)3Si(CH2)3NR‘2 ratio. The only exception was an aerogel prepared from 90% Si(OEt)4 and 10% (MeO)3Si(CH2)3NH2, which contains significantly larger primary particles and a smaller specific surface area. The results were interpreted that both precursor silanes are involved in the build-up of the aerogel network, contrary to results with organically substituted alkoxysilanes R‘Si(OR)3 without basic properties.
The electron density distributions of the four possible configurational isomers of the monomer vinylformamide (VFA) and of the cationically propagating species were examined by means of quantum chemical calculations. They show that the electrophilic attack of the propagating chain at the carbonyl oxygen of the VFA monomer is kinetically controlled whereas the attack at the C=C bond of the VFA is thermodynamically controlled. For experimental proving of this theoretical argument, VFA is cationically polymerized in toluene at different reaction temperatures by means of iodine, trifluoromethanesulfonic acid (HOTf), and trimethylsiliyl triflate (TMST) as initiators. Head group functionality and molecular weight distribution (MWD) of the oligo(vinylformamide) (OVFA) were investigated by means of 1H NMR spectroscopy, matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS), gel permeation chromatography (GPC), and combustion analysis. In all cases, OVFAs with narrow MWD were obtained in moderate yield (5–50%) in the temperature range from 253 to 313 K. A reaction temperature below 253 K is not suitable for the cationic polymerization of VFA because no oligomeric products are obtained. The properties and chemical constitution of the OVFAs, such as the average molecular weight, yield, and the chain structure are strongly determined by the reaction temperature used. With increasing reaction temperature the head group functionality decreases and the yield of OVFA increases. The correspondence between the results of quantum chemical calculations with those of the experiments is discussed.
The chemistry and kinetics of various elementary reactions in the cationic polymerization of styrene, including propagation, depropagation, transfer, termination, and initiation, are discussed. The limiting conditions for living systems are then estimated from a master Arrhenius plot of the rate constants of these reactions as a function of temperature. This master plot demonstrates that although polymers with DP [approximately] 7 might be prepared at 50 C, polymers with DP [approximately] 1,500 could be prepared by decreasing the temperature to [minus]70 C. The effect of solvent on the relative contribution of the different reactions is also demonstrated. New living systems are similar to classic cationic systems but with better control due to fast initiation and slower polymerization rates as a result of reversible formation of dormant species.
A series of polyelectrolyte-containing silica composite materials have been prepared by sol−gel processing. These optically transparent composites have been characterized by scanning electron microscopy and UV−visible spectrophotometry. These materials can be processed into monolithic disks and thin films. The thicknesses of spin-coated films of these materials on glass can be varied from 0.13 to 3.5 μm as determined by an optical interference method. These materials are ion exchangeable and less brittle than the parent silica glass due to the incorporation of the organic polyelectrolyte. These new composites retain the nanoscale porosity and optical transparency into the ultraviolet of the parent silica sol−gel glasses, making them attractive host matrixes for the immobilization of ionizable dye molecules and chemical reagents. An optical pH sensing platform (0.9 × 2.5 cm) based on the electrostatic immobilization of HPTS (8-hydroxy-1,3,6-pyrenetrisulfonic acid trisodium salt) in a PDMDAAC (poly(diallyldimethylammonium chloride))−silica composite film was fabricated and evaluated. The results clearly demonstrate that this platform is easy to construct with high batch reproducibility and can be regenerated by simple solution ion exchange. The platform is usable in both the modes of absorption and fluorescence, making it versatile. Having a fast response time (ca. 2 s to more than 2 units of pH change), the platform is also highly resistant to dye leaching and storage degradation over a period of months.
Vinylformamide (VFA) is cationically polymerized in various solvents at 273 K and reaction temperature by the following initiators: iodine, bis(4-methoxyphenyl)-methyl chloride/silica, triphenylmethyl chloride/silica, and trimethylsilyl triflate. In every case defined oligomers with narrow molecular weight distribution are obtained in moderate yield (20–50%). Acid hydrolysis of the obtained oligomers yields well defined oligovinylamine products. The cationic initiation mechanism of VFA is discussed in terms of the HSAB-concept†
Sol-gel silicas were synthesized from the hydrolysis of tetraethoxysilane and N-beta-aminoethyl-gamma-aminopropyltrimethoxysilane in the presence of water and ethanol by using ammonium hydroxide or hydrochloric acid as base or acid catalysts, respectively. The influence of the type of the catalyst employed was studied by comparing the surface areas and pore sizes and volumes for both sol-gel silicas. Nitrogen elemental analysis and 13C and 29Si NMR spectra showed that both silicas present similar chemical compositions and structures. The electron-microscope results demonstrated that the particles are uniformly spherical and well shaped in both cases. The sol-gel silica obtained via basic catalysis presented relatively small spherical particles in comparison to those synthesized by acidic catalysis. The results obtained suggest that acidic catalysis is a better procedure for the synthesis of these organofunctionalized hybrid sol-gel silicas. Copyright 1997 Academic Press. Copyright 1997Academic Press