Saccharides-Based Polymers for Low Environmental Impact Adhesive Formulations

The growing demand for sustainable materials has driven the development of polymeric formulations containing biomonomers and/or bioadditives derived from renewable resources for high-performance applications. Among the various industrial sectors, the identification of more sustainable comonomers for classic adhesive formulations, such as vinyl and acrylic systems, is of particular relevance. In this context, the presence of hydroxyl functionalities is essential to promote post-cross-linking during joint formation, thereby ensuring suitable resistance to high thermohygrometric stresses. Saccharides are recognized as the most versatile building block to prepare biopolymers with different architectures; however, their industrial exploitation remains limited by the challenging preparation of polymerizable monomers, which could require complex multistep procedures. In this work, we describe the free radical copolymerization of allyl-functionalized saccharide monomers (allyl α,α'-trehalose, and allyl methyl glucopyranoside) with ethyl methacrylate and vinyl acetate to obtain copolymers suitable for nonstructural, post-cross-linkable adhesive applications. The selected saccharide monomers are characterized by a straightforward, protecting-group-free, one-step synthesis and have been previously employed for the preparation of low-molecular-weight polymers and oligomers, for example, in wood-protective applications. To extend their applicability to film-forming systems, such as adhesives, appropriate comonomers and molar ratios were chosen to achieve higher molecular weights, as required for effective adhesive performance. Indeed, the presence of a saccharide monomer allows the replacement of units with a high environmental impact, such as N-methylol acrylamide, commonly present in commercial adhesive formulations. Characterization by Nuclear Magnetic Resonance, Fourier transform infrared, differential scanning calorimetry, and size exclusion chromatography was performed to determine the composition, thermal properties, and molecular weight distribution. Adhesion tests on beech wood specimens have been performed both with and without an isocyanate cross-linker to demonstrate the potential of our saccharide-based copolymers as renewable components for adhesive systems with low environmental impact, providing an alternative to conventional formulations.