Sodium dodecyl sulfate binding to poly(N-isopropylacrylamide) microgel latex studied by isothermal titration calorimetry

Isothermal titration calorimetry was used to monitor the interaction of SDS with aqueous poly(N-isopropylacrylamide) (PolyNIPAM) microgel latex. The binding of SDS to polyNIPAM microgel is endothermic below the volume phase transition temperature and exothermic above it. Based on isothermal titration calorimetry, the CAC for SDS binding onto polyNIPAM microgel is below 0.17 mmolal, or does not exist, which is in contrast to the published CAC values for linear polyNIPAM which are between 0.4 and 0.8 mmolal.