Property Modulation of Poly(vinyl alcohol)s via Controlled Incorporation of α-Methyl Groups Using Alkenylboron Monomers

Abstract

Radical copolymerization of vinyl- and isopropenyl-type boron monomers followed by side-chain oxidation enabled the synthesis of α-methylated poly(vinyl alcohol)s (PVAs), which are difficult to obtain by conventional methods. The composition ratio of the resulting vinyl alcohol (VA)–isopropenyl alcohol (IPA) copolymers was tunable in a wide range (VA/IPA = 84/16 – 7/93 mol%) by adjusting monomer feed ratios in the copolymerization step. All copolymers were amorphous in the bulk state regardless of their composition ratios, despite the semi-crystalline natures of both VA and IPA homopolymers. In solution, copolymers with specific compositions exhibited solvent-dependent thermal-responsive behavior: lower critical solution temperature (LCST)-type transitions in water and upper critical solution temperature (UCST)-type transitions in acetone.