Xueqin Ren

Fabrication of dual-responsive cellulose-based membrane via simplified surface-initiated ATRP.

An independently temperature- and pH-responsive membrane was developed by simultaneously grafting poly(N-isopropylacryamide) (PNIPAAm) and poly[(2-(diethylamino)ethyl methacrylate] (PDEAEMA) from different sides of a crosslinked cellulose membrane. The synthesis was simplified by using surface-initiated activators regenerated by electron transfer for atom-transfer radical polymerization in a diffusion device. The grafted membrane was heterostructured. The grafted polymer layer thickness was linearly related to reaction time. The wettabilities of the double-membrane sides responded individually and reversibly to temperature and pH. The surface grafted with PNIPAAm shifted from hydrophilicity to hydrophobicity above the lower critical solution temperature. The PDEAEMA side was hydrophilic in acidic aqueous solution and hydrophobic under basic conditions. This dual-response cellulose membrane has potential applications in water treatment, separations, and other membrane applications.

Long-alkane-chain modified N-phthaloyl chitosan membranes with controlled permeability.

A series of N-phthaloyl acylated chitosan membranes with controlled permeability were synthesized by the regioselective protection of the chitosan amino groups as the corresponding phthalimides followed by reaction with the long-chain dodecanoyl chloride. Fourier transform infrared (FT-IR) and (1)H nuclear magnetic resonance ((1)H NMR) analysis suggested that the degree of substitution (DS) ranged from 2.8 to 3.6. Contact angles, water retention values and mechanical examinations demonstrated that the hydrophobicity and mechanical properties of the membranes were all improved significantly following the modifications, together with their solubility in many organic solvents. Thermal weight change analysis demonstrated that a higher DS provided enhanced thermal properties. The controlled permeability of the membranes was determined by measuring the diffusion of urea, and the amount of urea released decreased significantly with increasing DS. The comprehensive properties of the membranes could be tuned by regulating their DS values as required.