Tetraphenylthiophene-Functionalized Poly(N-isopropylacrylamide): Probing LCST with Aggregation-Induced Emission

A hydrophobic tetraphenylthiophene (TP) center with novel aggregation-induced emission (AIE) property was chemically linked to two poly(N-isoprppylacrylamide) (PNIPAM) chains to obtain thermoresponsive polymers to study the relationships between the lower critical solution transitions (LCSTs) and the AIE-operative fluorenscence (FL) emission. Three ethynyl-terminated PNIPAMs with different molecular weights were synthesized via controlled atom transfer radical polymerization (ATRP) using ethynyl-functionalized initiator. The PNIPAMs were then coupled with diazide-funtionalized TP (TPN3) via click reaction to obtain the desired TP-embedded polymers of Px (x = 1, 2, and 3). All three polymers show AIE-property from their solution fluorescence behavior in THF/hexane mixtures. In the aqueous solution, the TP-center served as a fluorogenic probe that reveals the LCSTs of polymers and its relation to the degree of TP labeling in terms of polymer concentration. The thermoresponsiveness of Px was demonstrated by ...