Tough photopolymers based on vinyl esters for biomedical applications

Abstract

Photocurable vinyl esters have recently been introduced as suitable alternatives to (meth)acrylates in biomedical applications. While (meth)acrylates exhibit good mechanical properties, their cytotoxicity and degradation products principally disqualify them from medical use. Vinyl esters exhibit much lower cytotoxicity and give biocompatible degradation products, but their disadvantage are relatively low mechanical properties, particularly brittleness. This study focuses on the identification of suitable functional groups that are capable of introducing enhanced impact strength into the vinyl ester network, for example, cyclic structures or urethane groups. A new pathway for the synthesis of vinyl esters carrying these groups was established and resulting monomers were tested regarding their photoreactivity and cytotoxicity. Mechanical properties and degradation behavior of the new materials were investigated as well. In addition, the thiol-ene reaction was utilized to enhance photoreactivity and tune hydrolytical degradation. The new vinyl esters exhibit excellent biocompatibility and good photoreactivity that can be significantly enhanced with thiols on to the level of highly photoreactive acrylates. Ultimately, the impact strength was improved by a factor of more than ten compared to commercial vinyl esters.

Toughness enhancers for bone scaffold materials based on biocompatible photopolymers

“…Especially, methacrylates can also be found as prominent examples for currently applied materials used in treatment of bone injuries (as bone cement) and in dental restoratives . Nevertheless, the applicability in this field is still limited due to the cytotoxicity of (meth)acrylates and their unfavorable degradation products (polyacids) …”

“…Vinyl esters (VEs) emerged as promising alternatives, showing favorable reactivity along with low cytotoxicity . However, homopolymers of, for example, divinyl adipate (DVA, the only multifunctional commercially available VE) are very brittle and frequently break during crosslinking owing the high shrinkage stress.…”

“…In addition to thiol–ene chemistry, there are several other methods known in literature to improve toughness in photopolymer networks, most of them derived from techniques used for epoxy resins . A very versatile approach is based on blending with high‐molecular‐weight substances.…”

Partially bio‐based tri‐ and hexaallyl monomers: Synthesis from naturally occurringmyo‐inositol and polyaddition with dithiols

“…Recently, various naturally occurring and thus renewable compounds have attracted much attention as the starting materials for developing multifunctional monomers. This is because the use of renewable compounds means a reduction in the consumption of fossil‐based resources, and provides more green and sustainable approaches to polymer materials . The focus of our research interest has been on the utilization of myo ‐inositol as a starting material for designing monomers to prepare linear and networked polymers .…”

Exploring Network Formation of Tough and Biocompatible Thiol‐yne Based Photopolymers

“…This suggests a higher biocompatibility of alkyne based building blocks. Moreover, it was shown that thiols based on mercapto propionic acid derivatives provide low monomer cytotoxicity …”