Molecular Size and Morphology of Single Chains of Poly(sulfobetaine methacrylate)

The effects of the concentration of sodium chloride in an aqueous solution(c_NaCl) and the temperature on the molecular size of poly(sulfobetaine methacrylate)(PSBMA) were studied via viscometry and dynamic light scattering(DLS). The morphology of single-chain PSBMA was determined by atomic force microscopy(AFM). The results demonstrate that the hydrodynamic diameter of PSBMA can be expressed as a continuous function of c_NaCl, with the molecular size of PSBMA increasing and eventually approaching an asymptotic value with increasing c_NaCl. The molecular size of PSBMA at a lower c_NaCl(0.04 mol/L) increases with increasing temperature, which is the opposite of the temperature effect at a higher c_NaCl(2.0 mol/L). Therefore, the internal structure of PSBMA chains in solutions with a low salt concentration differs from that in solutions with a high salt concentration. In addition, the morphology of single chains of PSBMA appears to be spherical, containing 89% void space, and the apparent size of the dried chains is almost identical to that in solution.