Chemical and Enzymatic Modification of Chitosan to Produce New Functional Materials with Improved Properties

Chitin and chitosan are natural biopolymers with applications in different areas. However, to broaden its application area, research is needed to impart new functionality, develop new and better materials and to explore the whole potential of chitin/chitosan derivatives. These derivatives can be made by chemical and enzymatic synthesis. Here, the main classes of chitosan derivatives obtained by using green and sustainable conversion routes and as much as possible using green and/or bio‐based chemicals for modification and their potential areas for application are discussed

Tannic acid derived non-isocyanate polyurethane networks: Synthesis, curing kinetics, antioxidizing activity and cell viability

Bio-resourced non-isocyanate polyurethane (NIPU) network was synthesized to valorize a sustainable natural product (i.e., tannic acid, TA) toward biomaterials. Thus, a glycerol-based epichlorohydrin was glycidylated to form epoxidized TA (ETA). Facile chemical fixation of CO2 onto ETA was used to prepare carbonated TA (CTA) under normal conditions. Both aliphatic and aromatic amines were then used to convert CTA to NIPU networks. The networks were analyzed spectrally and thermally by FTIR, CP/MAS 13C NMR, and DSC, respectively. The amine-curing kinetics of CTA was evaluated based on Vyazovkin's advanced isoconversional method. The approach revealed different activation energies comparing to its epoxy counterpart, ETA. The TA-based NIPU possessed remarkable thermo-oxidation stability in comparison with its petroleum-based counterpart (OIT 2.38 vs. 0.12 min). The L929 fibroblast cells viability was used to evaluate the cytotoxicity and biocompatibility of the TA-based NIPU which proved its biocompatibility. Finally, the antioxidizing property of this polymer was ascertained by DPPH radical scavenging analysis. It was concluded that the value-added NIPU networks may be considered as good candidates for biomaterials

An Alcogel Based on Poly(2-acrylamido-2-methylpropane sulphonic acid) and the Effect of Neutralization Degree on its Swelling, Thermal and Mechanical Properties

Cross-linked polymeric organogels have attracted much attention in recent years. Most synthesized organogels are based on low molecular weight or denderitic materials. The study focuses on the preparation of an alcohol absorbent organogel based on 2-acrylamido-2-methylpropane sulphonic acid (AMPS) through cross-linking polymerization. Polyethylene glycol diacrylate-400 and ammonium persulphate were used as crosslinker and thermal initiator, respectively. Neutralization of acid groups increases swelling in superabsorbents. In this study, the effect of neutralization degree (N.D) on alcogel swelling was studied. The absorbency in alcohols and water are unexpectedly reduced with increased N.D. Also, the effect of N.D on thermal, mechanical and rheological properties was investigated, and found that increase in N.D leads to increased glass transition temperature, thermal stability and storage modulus

Crosslinkers of Different Types in Precipitation Polymerization of Acrylic Acid

Crosslinked poly(acrylic acid)s were prepared using two types of crosslinker by precipitation polymerization method in a binary organic solvent. N,N’-methylenebisacrylamide (MBA) and polyethylene glycol dimethacrylate (PEGDMA-330) were used as low-molecular weight and long-chain crosslinkers, respectively. The effect of various types of crosslinkers on polymer characteristics (i.e., gel content, equilibrium swelling, glass transition temperature, and rheological properties) was investigated. Maximum amount of viscosity was obtained by using long-chain crosslinker. The Flory-Rehner equation and rubber elasticity theory were used to discuss the network structure of polymer. It was observed that, the glass transition temperature (Tg) of the synthesized polymer containing PEGDMA-330 is higher than that of polymer containing MBA. Apparent and rotational viscosity were used to determine the optimal crosslinker type. In addition, the consistencycoefficient (m) and flow behavior index (n) parameter of Ostwald equation were investigated as well