Synthesis and characterization of waterborne bio-based hybrid isocyanate-free poly (hydroxy urethane)-poly(methacrylate) latexes with vitrimeric properties

Abstract

Non-isocyanate poly(urethane)s (NIPU)s have emerged as an environmentally friendly alternative for conventional polyurethanes, but several challenges remain towards their wide-scale adoption (e.g., attainment of high molecular weights for sufficiently effective mechanical properties and ease of application). Adopting NIPUs as hybrid polymer-polymer particles with methacrylic monomers is one route towards obtaining higher overall molecular weight, improving properties, and introducing advantages of methacrylate functionality. First, NIPU latex was synthesized using dicarbonate terminated poly (propylene glycol) and the commercial vegetable oil-based diamine Priamine 1075 via step miniemulsion polymerization yielding stable particles with sizes <220 nm. Then, the NIPU latex was used as the seed for the synthesis of hybrid NIPU-poly(methacrylate) particles via conventional radical emulsion statistical copolymerization of a long side chain (13 alkyl groups) alkyl methacrylate (C13MA) and isobornyl methacrylate (IBOMA). Two polymeric phases were observed in cryo-microtomed TEM of the dried latexes at ambient temperature, indicating core-shell phase-separated morphologies. Moreover, 2-acetoacetoxyethyl methacrylate (AAEMA) was introduced in the formulation containing the methacrylate phase to impart dynamic covalent crosslinking into the hybrid via ketone-amine vinylogous urethane formation, resulting in materials with stress relaxation up to 90% at 130 °C and one-time recycled films with similar stress-strain profiles as the original films.