Preparation and properties of MPEG-grafted EAA membranes via thermally induced phase separation

Graft reaction of poly(ethylene glycol monomethyl ether) (MPEG) onto poly(ethylene-co-acrylic acid) (EAA) through the esterification reaction of carboxyl groups on EAA chain with hydroxyl end groups in MPEG was performed. The results showed that the grafting degree increased with reaction time. Water contact angle measurements and protein adsorption experiments indicated that the hydrophilicity and antifouling properties of films were improved after EAA was grafted with MPEG. The microporous membranes of EAA grafted with MPEG (EAA-g-MPEG) and EAA were prepared via thermally induced phase separation (TIPS) process with di-n-octyl phthalate (DOP) as solvent. Phase diagrams for those systems were determined by time-resolved light scattering (TRLS) and differential scanning calorimetry (DSC). It was found that the binodal curve shifted to the lower temperature after EAA was grafted with MPEG, while changes of the dynamic crystallization temperatures were rather small. The membrane morphologies were investigated, which revealed that the pore sizes of EAA-g-MPEG membranes were smaller than those of EAA membranes.