Electrospinning zwitterion-containing nanoscale acrylic fibers

Free radical copolymerization of n-butyl acrylate and a sulfobetaine methacrylamide derivative provided high molecular weight zwitterionic copolymers containing 6-13 mol% betaine functionality, and the electrospinning of low Tg zwitterionomers was explored for the first time. Copolymerizations were performed in dimethylsulfoxide (DMSO) rather than fluorinated solvents previously reported in the literature. Dynamic mechanical analysis of zwitterionomer films revealed biphasic morphology and featured a rubbery plateau and two distinct thermal transitions. Electrospinning from chloroform/ethanol (80/20 v/v) solutions at low concentrations between 2 and 7 wt% afforded nanoscale polymeric fibers with diameters near 100 nm. The presence of only 6 mol% zwitterion allowed the formation of low Tg, free-standing, non-woven mats, and we hypothesize that zwitterionic aggregation rather than chain entanglements facilitated electrospinning at these relatively low solution concentrations. To our knowledge, this is the first report of electrospun zwitterionic polymers and these non-woven membranes are expected to lead to new applications for sulfobetaine copolymers.