Thermosetting polymer networks exhibit stresses associated with polymerization-induced volumetric shrinkage that may result in deleterious effects, such as material optical anisotropy, warping, and even cracking.  Thiol-ene polymerizations have reduced polymerization shrinkage stress owing to their step-growth molecular weight evolution, delaying the gel-point and allowing for a greater amount of shrinkage to be dissipated by viscous flow.  In this work, we incorporate allyl sulfide reversible addition-fragmentation chain transfer (RAFT) functional groups into a thiol-ene network, which provides a bond rearrangement mechanism for post-gelation stress relaxation.  While we demonstrate a significant reduction of stress in comparison with a control thiol-ene system, these materials tend to have a sub-ambient glass transition temperature, making them unsuitable for many applications.  Thus, we also explore utilizing allyl sulfide RAFT functional groups in thiol-yne polymerizations as a low shrinkage stress glassy material.  Here we demonstrate a material possessing a super-ambient glass transition temperature as well as exhibiting an almost a factor of two less stress when compared with a negative control material.

Reversible addition—fragmentation chain transfer for low stress thiol-ene/-yne networks

240th National Meeting (2010)

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