Control of Elongation Properties of Biocompatible Poly(2-Methoxyethyl Acrylate) Network Containing Silica Particles Similar to Biological Soft Tissue

In recent years, there have been active attempts to enhance resistance and provide new functions by incorporating nano-sized materials, known as fillers, into plastics and resins. In the medical field, biocompatible polymers are actively studied, with poly(2-methoxyethyl acrylate) (PMEA)gaining attention as an antithrombotic coating agent for medical devices. In our laboratory, we have succeeded in fabricating a soft yet tough PMEA-Silica composite elastomer by integrating silica nanoparticles into PMEA, a viscous liquid. Furthermore, this system can be 3D printed to create three-dimensional models. Given PMEA's inherent blood compatibility in composite materials, this composite is expected to be a promising candidate for new medical applications, such as small-diameter artificial blood vessels with inner diameters of 4 mm or less, whose development is currently lagging.<br/>The stress-strain relationship of this composite elastomer under uniaxial elongation exhibits non-linearity (J-type) with a significant increase in stress at high strain, similar to the characteristics of biological soft tissues. Focusing on the strain position at stress rise, the PMEA-Silica composite elastomer achieves about 350%, whereas biological soft tissues are on the lower strain side at about 100-200%. For biological soft tissues, this stress rise is crucial to prevent sudden failure during deformation.<br/>In this study, we aimed to establish a method to control the position of stress rise while maintaining J-shaped properties to develop materials more akin to biological soft tissues. Previous studies have shown that there is no chemical bonding at the PMEA-Silica interface in this composite elastomer. Therefore, we employed a silane coupling agent, 3(Acryloyloxy)propyltrimethoxysilane (APTMS), which has the same polymerization group as the monomer. APTMS was modified on the silica particle surface before compositing to form a bond point between the polymer chain and the silica nanoparticles.<br/>The results of uniaxial tensile tests of the elastomers with bonding points introduced at the polymer chain-silica interface revealed that this elastomer exhibits a new property of stress increase at lower strains than conventional materials, while maintaining flexibility at initial elongation. Furthermore, this property was successfully controlled by adjusting the coverage of APTMS, the amount of silica particles, and the amount of cross-linking agent.<br/>In the presentation, we will detail the mechanism behind the development of the new physical properties. The results of this research will ultimately lead to the provision of a material preparation method useful for practical artificial blood vessels.