Reprocessable Biobased Statistical and Block Copolymer Methacrylic-Based Vitrimers with a Shape Memory Effect

Abstract

Transitioning to a circular bioeconomy requires shifting away from conventional petroleum-based thermosets to recyclable biobased materials. We developed reprocessable and shape-memory biobased vitrimers with controlled architecture and enhanced creep resistance. A series of prepolymers of lignin-based vanillin methacrylate (VMA), with a mixture of vegetable oil-derived methacrylic esters with an average alkyl side chain length of 13 units (C13MA), and glycidyl methacrylate (GMA) were synthesized: statistical copolymer poly-(C13MA-co-vMA), block copolymer poly(C13MA-block-VMA), and statistical terpolymer poly(C13MA-co-VMA-co-GMA). Reversible addition−fragmentation chain-transfer (RAFT) polymerization allowed control over the backbone structure of statistical and block copolymers with similar overall molecular weights and compositions. Vitrification via aldehyde-functional VMA units with isophorone diamine enabled dynamic imine crosslinking, while adding the epoxy-functional GMA into the statistical terpolymer precursor enabled hybrid static−dynamic crosslinking networks. Vitrimers showed excellent retention of thermomechanical properties after 4× reprocessing cycles. Microphase separation was confirmed in the "hard−soft" type of block vitrimers. While statistical vitrimers showed comparable tensile properties, self-assembled block vitrimers exhibited poor tensile strength. Additionally, we compared the creep control using microphase separation and a hybrid network. Both methods reduced creep (up to 84%), but hybrid crosslinking caused significantly slower stress relaxation. A temperature-triggered shape memory effect was incorporated into the statistical vitrimer with two shape-programming cycles. Combining C13MA and VMA presents a rich platform for greener vitrimers with highly tunable properties and functionalities.

Biobased and Biodegradable Shape Memory Polymers of Eucommia Ulmoides Gum and Polycaprolactone via Dynamic Vulcanization

“…Shape memory effects (SME) are commonly observed in various block copolymers, where the hard segments possess physical or chemical cross-linked points while the soft segments assume permanent and temporary shapes, respectively. However, block copolymers are usually formed by the introduction of various chemical bonds such as covalent bonds and dynamic bonds to form cross-linked network structures, which require complex chemical synthesis processes and high costs, making their application limited. , …”