Effects of Ligand Binding on Relative Stability of Subchain Conformations of Weakly Charged N-Isopropylacrylamide Gels in Swollen and Shrunken States

摘要: The thermotropic collapse of the hydrogel copolymer N-isopropylacrylamide with acrylic acid (NIPA−AAc) upon heating has been studied by high-sensitivity differential scanning calorimetry. Curves polymer partial heat capacity have measured at different pH (from 2 to 11) and concentrations cationic ligands:  CaCl2, dodecyltrimethylammonium bromide (DTAB), cetyltrimethylammonium (CTAB). Dependencies main thermodynamic parameters gel collapsetemperature, enthalpy, width transition on ligand concentrationhave obtained. It found that is characterized a negative value increment Δtcp. Its average determined over all variables Δtcp = −0.62 ± 0.02 J/(g K). This result in accordance observed correlation between enthalpy temperature NIPA−AAc gel. free energy calculated as function concentration C...