Biobased homopolymers and amphiphilic diblock copolymers containing guaiacyl (G) or hydroxyphenyl (H) lignin derivatives synthesized by RAFT (PISA)

Abstract

In this work, we exploited guaiacyl (G) and hydroxyphenyl (H) lignin derivatives, namely 4-vinylguaiacol (4-hydroxy-3-methoxystyrene) and p-hydroxystyrene, to engineer biobased homopolymers and amphiphilic diblock copolymers. Firstly, after adequate monomer protection, we obtained two homopolymers, poly(acetoxy-protected 4-vinyl guaiacol) (PAcVG) and poly(p-acetoxystyrene) (PAcST), by reversible addition–fragmentation chain transfer (RAFT) radical polymerization. We characterized their thermal properties and compared them with fossil-fuel-based polystyrene. Then, we used the RAFT-mediated aqueous emulsion polymerization induced self-assembly (PISA) technique to synthesize amphiphilic biobased diblock copolymers from potentially biobased hydrophilic macromolecular chain transfer agents (macroRAFTs) based on poly(acrylic acid). We extended macroRAFTs with each lignin derivative, targeting different degrees of polymerization for the hydrophobic block. The diblock copolymer formation was confirmed by size exclusion chromatography (SEC), while the physico-chemical properties of the in situ formed nanoparticles were determined by dynamic light scattering (DLS), (cryogenic) transmission electron microscopy ((cryo-)TEM) and small-angle X-ray scattering spectroscopy (SAXS). Colloidally stable, submicrometric spherical particles composed of the diblock copolymers are formed for all compositions with a tuneable diameter. These new biobased latexes, obtained by a RAFT-mediated aqueous emulsion PISA process, pave the way for the formation of a new class of biobased paints, coatings or adhesives.