Synthesis, characterization, and electrospinning of zwitterionic poly(sulfobetaine methacrylate)

Poly(sulfobetaine methacrylate) (PSBMA) can be potentially utilized in filtration and wound dressing applications for which nanofibers structures are highly desirable. In this work, a series of PSBMAs with different molecular weights were synthesized, characterized, and electrospun into nanofibers. The polymer molecular weight was controlled by varying the amount of redox initiators in the free radical polymerization of SBMA, with the highest molecular weight achieved at an intermediate initiator concentration. From the intrinsic viscosity measurements, the Mark-Houwink parameters for PSBMA (at 21 °C in 0.2 M NaCl solution) was determined as a = 0.4071 and k = 2.06 × 10−3. Thermogravimetric (TGA) analysis shows that the PSBMAs were thermally stable up to at least 250 °C. Fourier transform infrared (FTIR) spectra indicate major structural changes of both polymer backbone and pendant groups by thermal degradation. Results from differential scanning calorimetry (DSC), TGA, and FTIR characterizations all demonstrate the existence of water strongly bound in PSBMA. DSC analysis also indicates different degrees of crystallinity for the PSBMAs of different sizes. Viscosity of the PSBMA solutions, a critical parameter for electrospinning, increased with the solution concentration and the polymer molecular weight. For the electrospinning of PSBMA, it was found that high solution concentration and high molecular weight favored the formation of smooth fibers while low solution concentration or low molecular weight led to the formation of beaded fibers or beads. Fiber diameters ranging from 200 to 570 nm were achieved by controlling solution concentration and polymer molecular weight. The characterization data and electrospinning results were finally correlated to explore the relationships between fiber formation, viscosity, molecular weight, and concentration.