Thermoresponsive poly (N-vinylcaprolactam)-g-galactosylated chitosan hydrogel: synthesis,characterization, and controlled release properties

Abstract

A dual (thermo- and pH-) responsive hybrid copolymer, poly(N-vinylcaprolactam) grafted galactosylated chitosan (PNVCL-g-GC) was synthesized by EDC/NHS crosslinking. PNVCL-g-GC exhibited a temperature-dependent phase change (LCST) at 32?°C in aqueous solutions. PNVCL-g-GC hydrogel scaffold was fabricated by freeze-drying, and evaluated as a delivery vehicle dependent on environmental pH and temperature. PNVCL-g-GC was characterized using ATR-FTIR, 1H-NMR, DSC, TGA, rheometry, and SEM. The swelling degree increased by the decrease both in temperature and pH. A faster BSA release was observed at 40?°C and at pH 7.2 from the cytocompatible and hemocompatible copolymer.     

Telechelic polymers by living and controlled/living polymerization methods

Telechelic polymers, defined as macromolecules that contain two reactive end groups, are used as cross-linkers, chain extenders, and important building blocks for various macromolecular structures, including block and graft copolymers, star, hyperbranched or dendritic polymers. This review article describes the general techniques for the preparation of telechelic polymers by living and controlled/living polymerization methods; namely atom transfer radical polymerization, nitroxide mediated radical polymerization, reversible addition-fragmentation chain transfer polymerization, iniferters, iodine transfer polymerization, cobalt mediated radical polymerization, organotellurium-, organostibine-, organobismuthine-mediated living radical polymerization, living anionic polymerization, living cationic polymerization, and ring opening metathesis polymerization. The efficient click reactions for the synthesis of telechelic polymers are also presented.     

Polymeric pH-sensitive membranes—A review

Significant progress has been achieved in recent years in the field of pH-sensitive membranes. In many cases, pH-sensitive membranes are systems for which the flux, membrane pore size, and solute rejection ratio may be manipulated by changing the pH. This review summarizes recent developments covering the preparation, pH-responsive properties, and applications in various disciplines. The pH-sensitive groups and the evaluation parameters for pH-sensitive membranes are reviewed and discussed. A variety of preparation methodologies, including blending, pore-filling, surface-grafting, and surface-coating techniques are described, and some of their salient features are highlighted. The flat-sheet form and hollow-fiber form pH-sensitive membranes are reviewed. Membrane pore size change and electroviscous effect are discussed. Furthermore, future perspectives of pH-sensitive membranes are discussed.