Rapid stress release through thiol–thioester exchange in phenylic crosslinked polymers

Abstract

The accumulation of stresses in thin films on substrates presents significant challenges in many materials science and technological applications. Excess residual stress can drastically impact material component and device performance, reliability and durability. This work demonstrates a strategy to control accumulated stress through a crosslinking and chain re-organization process, both in bulk films and on rigid substrates. An addition-type crosslinking reaction produced sufficient stress which could be released through a base-catalyzed thiol–thioester exchange reaction leading to chain-reorganization. A series of building block compounds with aliphatic and aromatic cores containing alkyne and thioester linkages were synthesized and tested for their stress formation and release capabilities. Compared to the aliphatic compounds, the aromatic building blocks produced higher stress upon crosslinking due to their rigid phenylic structure. Furthermore, the aromatic crosslinked films exhibited rapid stress release when exposed to a base produced by illumination of an incorporated photobase. The rapid stress release can be attributed to faster base diffusion resulting from the higher free volume in the phenylic crosslinked materials.