Combining isosorbide and lignin-related benzoic acids for high-T_g polymethacrylates

The insertion of rigid aliphatic or aromatic building blocks in polymer structures is an efficient synthetic strategy towards high-T_g polymer materials. In the present work, we have functionalized isosorbide 5-methacrylate with various aromatic lignin-inspired esters to yield a series of isosorbide-2-aryl carboxylate-5-methacrylate monomers (ArIMAs) as single regioisomers. The selection of phenyl carboxylate side groups included benzoate, p-cyanobenzoate, meta/para-methoxybenzoates, and different vanillic acid esters. This afforded a range of seven bio-based monomers with different size, polarity, and substitutions. Polymerizations were carried out by conventional free radical initiation to obtain the corresponding high molecular-weight poly(aryl carboxylate isosorbide methacrylate)s (PArIMAs). The polymerizations were evaluated in different solvents, including toluene, EtOAc, γ-valerolactone, 2-MeTHF, and DMSO to identify the most suitable conditions. The polymers exhibited high glass transition temperatures (T_gs) in a broad range, from 80 to 168 °C, and were thermally stable up to 268 °C. Furthermore, dynamic rheology experiments indicated that the polymers were sufficiently stable for melt processing. The availability of the building blocks combined with the high stability of the polymers make these materials attractive for use as high-performance plastics and coatings.