Metal-Free Atom Transfer Radical Polymerization of PVDF-Based Block Copolymers Catalyzed by Organic Photoredox Catalysts

Abstract

Poly(vinylidene fluoride) (PVDF) and its copolymers represent a class of electroactive fluoropolymers with very attractive piezo/ferroelectric properties that can be chemically modified to achieve high-quality composites with improved properties. Here, the synthesis of poly(methyl methacrylate)-b-poly(vinylidene fluoride)-b-poly(methyl methacrylate) (PMMA-b-PVDF-b-PMMA) triblock copolymers via metal-free light-catalyzed atom transfer radical polymerization (ATRP) using organic photoredox catalysts (OPRC) and light of suitable wavelength is reported. Using benzoyl peroxide bearing an ATRP active group at both ends of the molecule, telechelic PVDF is synthesized, and is used as a macroinitiator in the metal-free, light-catalyzed ATRP in presence of methyl methacrylate (MMA), an OPRC, and light of suitable wavelength. Kinetic studies are performed by monitoring the monomer consumed in solution and by using 1H-NMR to calculate the formation of the new PMMA blocks. Three of the five tested OPRC, operating through an oxidative quenching pathway, guarantee a good control over the polymerization, confirmed by the constant concentration of radicals during the process and by the linear growth of the conversion versus the percentage of monomer consumed. Chain extension reactions are also performed to prove chain-end fidelity, as well as “light ON/light OFF” reactions to test the temporal control guaranteed by the external stimuli used to catalyze the polymerization.