Temperature-dependent dilute solution properties of polyacrylonitrile in N,N-dimethyl formamide and dimethyl sulfoxide

Effects of aging temperature and time on dilute solution properties of polyacrylonitrile (PAN) in N,N-dimethyl formamide (DMF) and dimethyl sulfoxide (DMSO) were characterized. In DMF, the intrinsic viscosity ([η]) showed little time-dependent change between 30 and 50 °C. Above 50 °C, however, the [η] was gradually decreased with aging time, suggesting the coil shrinkage. Such phenomenon indicated the deterioration of polymer solubility; i.e., lower critical solution temperature behavior. However, in DMSO which produced better solubility than DMF, the time-dependent decrease of the [η] and related LCST behavior was observed above 90 °C.