Graft-methoxy Poly Research Articles

Improving Hydrophilicity and Protein Resistance of Poly(vinylidene fluoride) Membranes by Blending with Amphiphilic Hyperbranched-Star Polymer

To endow hydrophobic poly(vinylidene fluoride) (PVDF) membranes with reliable hydrophilicity and protein resistance, an amphiphilic hyperbranched-star polymer (HPE-g-MPEG) with about 12 hydrophilic arms in each molecule was synthesized by grafting methoxy poly(ethylene glycol) (MPEG) to the hyperbranched polyester (HPE) molecule using terephthaloyl chloride (TPC) as the coupling agent and blended with PVDF to fabricate porous membranes via phase inversion process. The chemical composition changes of the membrane surface were confirmed by X-ray photoelectron spectroscopy (XPS), and the membrane morphologies were measured by scanning electron microscopy (SEM). Water contact angle, static protein adsorption, and filtration experiments were used to evaluate the hydrophilicity and anti-fouling properties of the membranes. It was found that MPEG segments of HPE-g-MPEG enriched at the membrane surface substantially, while the water contact angle decreased as low as 49 degrees for the membrane with a HPE-g-MPEG/PVDF ratio of 3/10. More importantly, the water contact angle of the blend membrane changed little after being leached continuously in water at 60 degrees C for 30 days, indicating a quite stable presence of HPE-g-MPEG in the blend membranes. Furthermore, the blend membranes showed lower static protein adsorption, higher water and protein solution fluxes, and better water flux recovery after cleaning than the pure PVDF membrane.

Thermosensitive and pH-Sensitive Polymers Based on Maleic Anhydride Copolymers

Amphiphilic copolymers with thermosensitive and pH-sensitive properties were prepared by grafting methoxy poly(ethylene glycol) (MPEG) of different molecular weights onto alternating copolymers of maleic anhydride with styrene and 4-tert-butylstyrene. Aqueous solutions of these graft copolymers exhibit lower critical solution temperatures (LCST). These LCST's are highly sensitive to changes in pH and salinity and to the presence of hydrophobic and hydrogen-bonding additives. The phase transitions are attributed to the cooperative effects of both hydrophobic interactions and intra/intermolecular hydrogen-bonding interactions.