Hepta(3,3,3-trifluoropropyl) Polyhedral Oligomeric Silsesquioxane-capped Poly(N-isopropylacrylamide) Telechelics: Synthesis and Behavior of Physical Hydrogels

摘要

Hepta(3,3,3-trifluoropropyl) polyhedral oligomeric silses-quioxane (POSS)-capped poly(N-isopropylacrylamide) (PNIPAAm) telechelics with variable lengths of PNIPAAm midblocks were synthesized by the combination of reversible addition-fragmentation chain transfer polymerization (RAFT) and the copper-catalyzed Huisgen 1,3-cycloaddition (i.e., click chemistry).The POSS-capped trithiocar-bonate was synthesized and used as the chain transfer agent for the RAFT polymerization of N-isopropylacrylamide.The organic-inorganic amphiphilic telechelics were characterized by means of nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC), Atomic force microscopy (AFM) shows that all the POSS-capped PNIPAAm telechelics exhibited microphase-separated morphologies, in which the POSS terminal groups were self-assembled into the microdomains and dispersed into the continuous PNIPAAm matrices.The POSS nanodomains could behave as the physical cross-linking sites and as a result the physical hydrogels were formed while these POSS-capped PNIPAAm telechelics were subjected to the solubility tests with water.These physical hydrogels possessed well-defined volume phase transition phenomena and displayed rapid reswelling and deswelling thermoresponsive behavior compared to control PNIPAAm hydrogel.