Remoldable Thiol–Ene Vitrimers for Photopatterning and Nanoimprint Lithography

• Published in: Macromolecules 2016-12, Vol.49 (23), p.8905-8913
• Main Authors: Lyon, Gayla Berg, Cox, Lewis M, Goodrich, J. Taylor, Baranek, Austin D, Ding, Yifu, Bowman, Christopher N
• Format: Article
• Language: English
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/acs.macromol.6b01281

Here, we introduce photocuring as a tool for the spatiotemporal control of vitrimer network synthesis via a photoinitiated thiol–ene polymerization. A difunctional norbornene monomer was synthesized containing ester linkages and pendant alcohol groups to participate in transesterification bond reshuffling reactions. The transesterification catalyst 1,5,7-triaza­bicyclo[4.4.0]­dec-5-ene (TBD) was shown to be highly effective in promoting transesterification in these networks at high temperatures, without interfering with external spatiotemporal, photoinitiated control over the thiol–ene polymerization and associated network formation. A strong Arrhenius dependence of the stress relaxation time with inverse temperature was observed from 145 to 175 °C, which suggests a relaxation controlled by the transesterification reaction rate, similar to previously studied thermally cured vitrimers. These thiol–ene vitrimers are implemented in nanoimprint lithography (NIL) for creating surface features, where imprinting may be performed repeatedly on the same sample due to the reversible nature of the bond exchange reactions. Because the networks are photocurable, hierarchical structures were generated by photopatterning and developing a microscale pattern and then performing NIL on the surface of this pattern.