Properties of polyurethane–polystyrene graft copolymer membranes used for separating water–ethanol mixtures

Polyurethane prepolymers (PU) based on hydrophilic poly(ethylene glycol) (PEG), hydroxypropyl acrylic acid (HPA), 2,4-toluene diisocyanate (TDI), and butanediol (BDO) were prepared by one-step polymerization with butanediol as the chain extender. Polyurethane–polystyrene graft copolymers (PU-g-PS) were synthesized by free radical copolymerization of PU with styrene (ST), 2,2′-azobisisobutyronitrile (AIBN) was used as initiator and toluene as solvent. Experimental results showed that the crosslinked membranes of PU–PS graft copolymers could be used for separating ethanol–water mixtures. The highest value of the separation factor (α) of the crosslinked separation membranes can reach 17.3. Scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) were used to characterize the properties of PU–PS crosslinked membranes.