Biomaterials based on low cytotoxic vinyl esters for bone replacement application

In recent days, additive manufacturing technologies (AMT) based on photopolymerization have also found application in tissue engineering. Although acrylates and methacrylates have excellent photoreactivity and afford photopolymers with good mechanical properties, their cytotoxicity and degradation products disqualify them from medical use. Within this work, (meth)acrylate‐based monomers were replaced by vinyl esters with exceptional low cytotoxicity. The main focus of this paper lies on the determination of the photoreactivity and investigations concerning mechanical properties and degradation behavior of the new materials. Tested monomers provide sufficient photoreactivity for processing by AMT. Mechanical properties similar to natural bone could be obtained by adding suitable fillers like hydroxylapatite (HA). The right ratio of hydrophobic and hydrophilic monomers allows the tuning of the degradation behavior. Finally, with the optimum formulation, cellular 3D structures were built using digital light processing. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

Vinyl Sulfonate Esters: Efficient Chain Transfer Agents for the 3D Printing of Tough Photopolymers without Retardation

The formation of networks through light‐initiated radical polymerization allows little freedom for tailored network design. The resulting inhomogeneous network architectures and brittle material behavior of such glassy‐type networks limit the commercial application of photopolymers in 3D printing, biomedicine, and microelectronics. An ester‐activated vinyl sulfonate ester (EVS) is presented for the rapid formation of tailored methacrylate‐based networks. The chain transfer step induced by EVS reduces the kinetic chain length of the photopolymer, thus shifting the gel point to higher conversion, which results in reduced shrinkage stress and higher overall conversion. The resulting, more homogeneous network is responsible for the high toughness of the material. The unique property of EVS to promote nearly retardation‐free polymerization can be attributed to the fact that after the transfer step no polymerizable double bond is formed, as is usually seen in classical chain transfer agents. Laser flash photolysis, theoretical calculations, and photoreactor studies were used to elucidate the fast chain transfer reaction and exceptional regulating ability of EVS. Final photopolymer networks exhibit improved mechanical performance making EVS an outstanding candidate for the 3D printing of tough photopolymers.