Preparation of Supramolecular Material from Amylosic Inclusion Complex with Thermoresponsive Guest Polymer Obtained by Vine-Twining Polymerization

Abstract

Amylose constructs supramolecular inclusion complexes with polymeric guests in phosphorylase-catalyzed enzymatic polymerization field, called ‘vine-twining polymerization’. However, such inclusion complexes have not exhibited specific property and processability as functional supramolecular materials. In a recent study, n amphiphilic triblock guest copolymer (poly(2-methyl-2-oxazoline-block-tetrahydrofuran-block-2-methyl-2-oxazoline, (P(MeOx-block-THF-block-MeOx)) was employed for the vine-twining polymerization to form soft materials from an amylosic inclusion complex. In this study, we investigated the vine-twining polymerization using a thermoresponsive triblock guest copolymer, that is, poly(2-isopropyl-2-oxazoline-block-tetrahydrofuran-block-2-isopropyl-2-oxazoline (P(iPrOx-block-THF-block-iPrOx)). The vine-twining polymerization at the temperature below the lower critical solution temperature (LCST) of PiPrOx gave the inclusion complex, while no inclusion by an enzymatically produced amylose took place at the temperature above the LCST of PiPrOx due to aggregation of P(iPrOx-block-THF-block-iPrOx) in aqueous buffer (polymerization solvent). The product's characterization results suggested that the cavity of the enzymatically elongated amylose chain included the PTHF block in the triblock copolymer by hydrophobic interaction. Accordingly, the outer PiPrOx blocks constructed spaces among the inclusion complex segments. Such higher-order structure formed supramolecular networks, leading to the formation of a hydrogel. The product showed thermoresponsive property depending upon the temperatures below and above the LCST of PiPrOx.