Rapid deswelling and reswelling response of poly(N-isopropylacrylamide) hydrogels via formation of interpenetrating polymer networks with polyhedral oligomeric silsesquioxane-capped poly(ethylene oxide) amphiphilic telechelics.

Hepta(3,3,3-trifluoropropyl) polyhedral oligomeric silsesquioxane-capped poly(ethylene oxide) telechelics (POSS-capped PEO) were synthesized via click chemistry. The POSS-capped PEO amphiphilic telechelics were incorporated into cross-linked poly(N-isopropylacrylamide) (PNIPAAm) to form the structure of physical interpenetrating polymer networks (IPNs). In the organic-inorganic networks, the POSS terminals of POSS-capped PEO telechelics were self-organized into microdomains to act as the physical cross-linking sites of PEO and the physically cross-linked PEO network was interlocked with the PNIPAAm network. It is identified that the organic-inorganic hydrogels resulting from the PNIPAAm network and the POSS-capped PEO telechelics displayed much faster response rates than the plain PNIPAAm hydrogels in terms of swelling, deswelling, and reswelling tests. The improved thermoresponse of hydrogels has been interpreted on the basis of the formation of the specific supramolecular structures in the hydrogels. The synergism from hydrophobic and hydrophilic components (i.e., POSS domains and PEO chains) is responsible for the improvement of hydrogel properties.