A New Thermo-Sensitive Hydrogel: Poly(ethylene oxide-dimethyl siloxane-ethylene oxide)/Poly(N-isopropyl acrylamide) Interpenetrating Polymer Networks I. Synthesis and Characterization

Interpenetrating polymer networks (IPNs) composed of poly(ethylene oxide-dimethyl siloxane-ethylene oxide) (PEO-PDMS-PEO) ABA triblock copolymer and poly(N-isopropyl acrylamide) (PIPAAm) were synthesized. Transmission electron microscopy (TEM) and differential scanning calorimetry (DSC) studies of bulk IPNS revealed micro phase separation with partial phase mixing between two chemically independent networks. Aqueous equilibrium swelling curves were examined as a function of temperature. DSC thermograms of the swollen IPNS exhibited the same swelling transition temperature as that of PIPAAm, although the degree of swelling of IPNS was affected by polymer composition. These observations indicate that each network in the swollen IPNs exists independently and many have different morphology than the dried bulk state. The aqueous swelling-deswelling kinetics by temperature modulation of IPNs could be controlled by gel composition nd temperatures applied.

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