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Y. Mete, D. Grunenberg, B. Steyrer, J. Stampfl, C. Gorsche, R. Liska:
"A Heterotelechelic Oligomer for Tough Photopolymersvia Hot Lithography";
Poster: 5th European Symposium of Photopolymer Science, Mulhouse, France; 09-03-2018 - 09-06-2018; in: "5th European Symposium of Photopolymer Science", 5th European Symposium of Photopolymer Science, (2018), P26.

Methacrylate networks exhibit high mechanical strength and are deployed in various applications, e.g. decorative coatings, dental medicine and 3D-printing1. However, they exhibit high shrinkage stress and show brittle behavior due to their high crosslink density. One option to overcome these drawbacks, is the employment of higher molecular weight resins. Due to the higher viscosity of such resins, 3D-printing at elevated temperatures becomes inevitable. The recently introduced Hot Lithography2 technique is able to serve these requirements and allows to print resins with viscosities of up to 20 Pa s at elevated temperature.
As a second option, addition-fragmentation chain transfer (AFCT) agents3 can be utilized. By regulating the free radical chain growth the gel point is shifted to higher conversions, thus reducing polymerization-induced shrinkage stress. Consequently, tailored network architectures are obtained resulting in tougher materials.4
We hereby present a combination of both approaches, designing a heterotelechelic hybrid oligomer. The higher molecular weight oligomer is based on poly(propylene oxide) and combines a regulating AFCT group5 and a methacrylate group within the same molecule (Figure 1). This allows to avoid migration issues and results in low volatility, which is essential for processing at elevated temperatures.
We mixed the hybrid oligomer into a commercially available urethane dimethacrylate matrix using different ratios. Photopolymerization of these formulations led to higher conversions and reduced shrinkage stress. 3D-printed parts with improved toughness could be obtained via Hot Lithography. During the printing process the oligomer also acts as a reactive diluent without showing the volatility of conventional low molecular weight reactive diluents.

Heterotelechelic Oligomer, Tough Photopolymersvia Hot Lithography, decorative coatings, dental medicine and 3D-printing