Reaction Kinetics and Reduced Shrinkage Stress of Thiol鈥揧ne鈥揗ethacrylate and Thiol鈥揧ne鈥揂crylate Ternary Systems

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• 作者：Sheng Ye ; Neil B. Cramer ; Ian R. Smith ; Katerina R. Voigt ; Christopher N. Bowman
• 刊名：Macromolecules
• 出版年：2011
• 出版时间：December 13, 2011
• 年：2011
• 卷：44
• 期：23
• 页码：9084-9090
• 全文大小：856K
• 年卷期：v.44,no.23(December 13, 2011)
• ISSN：1520-5835

文摘

Thiol鈥搚ne鈥搈ethacrylate and thiol鈥搚ne鈥揳crylate ternary systems were investigated for polymerization kinetics and material properties and compared to the analogous pure thiol鈥搚ne and (meth)acrylate systems. Both thiol鈥搚ne鈥搈ethacrylate and thiol鈥搚ne鈥揳crylate systems were demonstrated to reduce polymerization-induced shrinkage stress while simultaneously achieving high glass transition temperatures (T_g) and moduli. Formulations with 70 wt % methacrylate increased the T_g from 51 卤 2 to 75 卤 1 掳C and the modulus from 1800 卤 100 to 3200 卤 400 MPa (44% increase) over the pure thiol鈥搚ne system. Additionally, the shrinkage stress was 1.2 卤 0.2 MPa, which is lower than that of the pure methacrylate, binary thiol鈥搚ne, and thiol鈥揺ne鈥搈ethacrylate control systems which are all >2 MPa. Interestingly, with increasing methacrylate or acrylate concentration, a decrease and subsequent increase in the shrinkage stress values were observed. A minimum shrinkage stress value (1.0 卤 0.2 MPa) was observed in the 50 wt % methacrylate and 70 wt % acrylate systems. This tunable behavior results from the competitive reaction kinetics of the methacrylate or acrylate homopolymerization versus chain transfer to thiol and the accompanying thiol鈥搚ne step-growth polymerization. The cross-linking density of the networks and the amount of volumetric shrinkage that occurs prior to gelation relative to the total volumetric shrinkage were determined as two key factors that control the final shrinkage stress of the ternary systems.