Dimethacrylate derivatives of dimer acid

Dimethacrylate monomers are used in a wide variety of crosslinked polymer applications, including adhesives, coatings, dental restoratives, and stereolithography. The advantages of rapid curing and good mechanical properties offered by these materials are countered by problems with dimensional changes during polymerization and long-term physical instability resulting from water sorption and loss of residual unreacted monomer. In this work, several examples of hydrophobic monomers based on a dimer acid structure were synthesized, and their monomeric and homopolymer properties were evaluated. The photopolymerization reactivity and conversion were investigated with near-infrared spectroscopy. Studies of the volumetric shrinkage, water sorption, and water contact angle and three-point-bend testing of the homopolymers were also carried out, with the results compared with those of commonly used dimethacrylate monomers. The new monomers produced higher degrees of conversion combined with lower polymerization shrinkage and water sorption values in comparison with conventional monomers. The relatively low crosslink density of dimethacrylates constructed from dimer acid produced polymers with high flexibility and low modulus, as expected; however, changes in the functionality of the group linking the dimer acid core with the methacrylate end groups induced significant property differences. On the basis of the properties demonstrated by the dimer acid monomers and their homopolymers, these new materials appear well suited for applications such as coatings and adhesives.