NMR study of phase separation in D_2O/ethanol solutionsof poly(N-isopropylmethacrylamide) induced by solventcomposition and temperature

摘要

1Hand ~(13)CNMR spectroscopies were applied to investigate phase separation in solutions ofpoly(N-isopropylmethacrylamide) (PIPMAm) in D_2O/ethanol (EtOH) mixtures induced bysolvent composition (cononsolvency) and temperature. Effects of EtOH content in D_2O/EtOH mixtures and temperature on the appearance and extent of the phase separationwere characterized. Differences in mesoglobules formed during the phase separationinduced by cononsolvency and temperature were found. For temperature-induced phaseseparation, ~(13)Cspin-spin relaxation times showed that besides the free EtOH expelled fromthe PIPMAm mesoglobules, there are also EtOH molecules bound in these mesoglobules.On the other hand, virtually no bound EtOH molecules were detected for mesoglobulesformed as a consequence of the cononsolvency. For PIPMAm random copolymerscontaining negatively charged methacrylate units the phase separation induced by solventcomposition was not observed.