Investigating topological and group contribution predictive schemes for the heat capacity of polyzwitterions*

The specific heat capacity (c_p) for six zwitterionic polymers were measured using differential scanning calorimetry (DSC). Poly(sulfobetaine methacrylate) (PSBMA), poly(sulfobetaine acrylate) (PSBA), poly(ethyl sulfobetaine methacrylate) (PESBMA), poly(sulfobetaine methacrylamide) (PSBMAm), poly(sulfobetaine 2-vinylpyridine) (PSB2VP) and poly(sulfobetaine 4-vinylpyridine) (PSB4VP) were synthesized with changes of chemical structure in order to study effects of either the polymer backbone or the side group. Temperature modulated DSC (TMDSC) in scanning mode as well as quasi-isothermal (QI) TMDSC were used to determine c_p. The glass transition for PSBA and PESBMA was measured for the first time. PSBMA, PSBMAm, PSB2VP and PSB4VP thermally degrade prior to the glass transition allowing for measurement only of the solid-state c_p. Theoretical values of solid state c_p were calculated for the polyzwitterions using topological and group contribution methods and compared to the measured values. The modelled c_p accurately predicts only PSB2VP and PSB4VP. The discrepancy between the measured and predicted c_p values is likely due to the reduction of vibrational degrees of motion in the solid state for some of the polyzwitterions.