Academic literature on the topic 'Terpolymer hydrogels'

In this work, a series of thermally responsive terpolymers of N-isopropylacrylamide (NIPA) with three different comonomer contents was synthesized, and their swelling behaviour was studied as a function of composition and temperature. Temperature-sensitive, random cross-linked terpolymers of NIPA were prepared from methyl methacrylate (MMA), N-tert-butylacrylamide (NTBA), and acrylic acid (AA) using a free radical polymerization method. In the synthesis of terpolymer hydrogels, N,N-methylene bisacrylamide (BIS) was used as cross-linkers and ammonium persulfate (APS) as initiator. The NIPA content of the monomer feed varied from 80 to 50 mol %, and other comonomer feed varied from 40 to 5 mol %. The swelling equilibrium of these hydrogels was studied as a function of temperature and hydrophobic and hydrophilic comonomer contents. The swelling properties of the polymers were investigated in pure water at temperatures from 10 to 80°C. All of the synthesized gels were found to be sensitive to temperature. Glass transition temperature analyses and thermal analyses of the synthesized hydrogels were studied. The volume phase transition temperature and the swelling equilibrium (r) values of NIPA-based hydrogels synthesized in different feed ratios and in varying monomer contents were found in the range of 17–52°C and 14–51 g H2O/g polymer, respectively. The glass temperature (Tg) of the NIPA/AA/(MMA or NTBA) hydrogels synthesized with feed ratios of 50/40/10 was found to be 133 or 142°C, respectively. The initial and the end degradation that were determined for hydrogels at high temperatures indicated the quite good thermal stability of hydrogels. When the mass loss of the synthesized hydrogels was 50%, the temperatures were measured between 247 and 258°C.

In the past few years, the development of hydrogel properties has led to the emergence of nanocomposite hydrogels that have unique properties that allow them to be used in various different fields and applications such as drug delivery, adsorption soil containing, tissue engineering, wound dressing, and especially antimicrobial applications. Thus, this study was conducted in order to fabricate a novel crosslinked terpolymer nanocomposite hydrogel using the free radical copolymerization method based on the usage of 2-acrylamido-2-methylpropane sulfonic acid (AMPS), acrylamide (AAm), acrylonitrile (AN), and acrylic acid (AA) monomers and iron oxide (Fe3O4) magnetic nanoparticles and using benzoyl peroxide as an initiator and ethylene glycol dimethacrylate (EGDMA) as a crosslinker. The structure of the synthesized composite was confirmed using Fourier transform infrared (FTIR) spectroscopy and x-ray powder diffraction (XRD) measurements. Furthermore, the surface morphology and the magnetic nanoparticle distributions were determined by scanning electron microscopy (SEM) measurement. In addition, the swelling capacity of the hydrogel nanocomposite was measured using the swelling test. Lastly, the efficiency of the produced composite was evaluated as an antimicrobial agent for Gram-positive and Gram-negative bacterial strains and a fungal strain.

博士
國立交通大學
應用化學研究所
98
The main purpose of this study is to explore the steric bulky substituent effects on hydrogen-bond behaviors in poly(methyl methacrylate) terpolymers and poly(methacrylamides) derivatives. In poly(methyl methacrylate) terpolymers, small content of the bulky steric group into the PMMA-co-PMAA main chain does not sacrifice the fraction of hydrogen-bonded association in and does not cause Tg decrease. In addition, the steric bulky group plays the role of inert diluent to convert portion of the strong self-associated hydrogen bonded amide groups into inter-associated hydrogen bonding between carbonyl groups of ester units and amide unites. Excess amount of the bulky steric group can obstruct hydrogen-bond interaction, not only the inter-association between esters and amides but also the self-association of amides, and thus reduce Tg. In poly(methacrylamide)s, if the N-substitution possess resonance characteristic, i.e., aromatic group, the lone-paired electrons on nitrogen can delocalize over the π system of aromatic ring and carbonyl group simultaneously, and further, affect the hydrogen-bond-acceptor ability of C=O and hydrogen-bond-donor ability of N-H. Compared with cyclohexyl group, aromatic group as N-substitution can enhance the hydrogen-bond-donor ability of N-H and reduce the hydrogen-bond-acceptor ability of C=O through electron delocalization. Moreover, a planar delocalization, constructed by the aromatic-? system of pyridine in P4VP, the aromatic-? system and the carbonyl-? system of amide group in poly(N-phenyl methacrylamide)s via the lone-paired electrons on nitrogen atom of PNPAA, is formed to be a driving force to replace the self-association of amide units with inter-association to pyridine units, and thus better miscibility with P4VP is obtained. The inductive substitution at para position of aromatic ring in poly(N-phenyl methacrylamide), regardless of electron-donating or electron-withdrawing group, can further affect the electron delocalization over the benzene ring and the carbonyl π system via the lone-paired electrons on nitrogen atom, changing the electron-cloud density of N－H or C＝O groups and the strength of self-association and inter-association with P4VP. Moreover, comparing to electron-donating group (-OCH3), electron-withdrawing group (-Br) can strengthening inter-associative hydrogen-bonding interaction with pyridine units of P4VP. If the N-substitution is butyl group, the constitution of butyl group can not affect the hydrogen-bond-acceptor ability of C=O and hydrogen-bond-donor ability of N-H in poly(methacrylamide). However, compared with n-butyl group，t-butyl group is more steric bulky, and the steric strain in poly(methacrylamide)s cannot be reduced no matter how the steric bulky t-butyl group rotates around the C-N bond in amide units when the N-substitution is t-butyl group. In that case, there is few the constitutional isomeric effects on the hydrogen-bond-acceptor of the carbonyl group and the hydrogen-bond-donor ability of N-H group in poly(methacrylamide)s. The screening effect of the bulky steric t-butyl group reduces the KB in poly(t-butyl methacrylamide) and enhance the ratio KA/KB, and thus slightly enhance the miscibility between poly(methacrylamide) and P4VP. Finally, to assess possible solvent effects on the heterogeneity of the blends, TCE, a polar solvent that may be capable of forming relatively weak hydrogen bonds with the amide, and DMF, which can form strong hydrogen bonds with the amide, are chosen as alternative casting solvents. The blends cast from TCE display homogeneous single-glass-transition behavior but two clear Tg in the blends cast from DMF, to speak nothing of significant dynamic heterogeneity in the blends cast from DMF when examined by solid-state NMR. When DMF is used as the casting solvent, the total amount of hydrogen-bonding interaction, not only self-association but also inter-association, is reduced.