Issue 19, 2012

Photoinitator surface segregation induced instabilities from polymerization of a liquid coating on a rigid substrate

Abstract

Periodic wrinkled surfaces have generated significant interest over the past decade as these structures can be easily fabricated over large areas with minimal fabrication cost, but these structures have generally been limited to thin films on soft elastomeric substrates, which limits their general applicability and utility. Here we present a simple methodology to generate wrinkled surfaces on rigid substrates by surface segregation of a photocatalyst. Upon ultraviolet light (UV) induced photopolymerization, increased catalyst concentration yields a cross-linked layer at the free surface that is supported on top of a more liquid-like bulk film due to differences in polymerization rate. Further polymerization of the underlayer provides the requisite mechanical stress (contraction due to polymerization) to create a wrinkled pattern. A system based upon the renewable monomer, furfuryl alcohol, that is cross-linked with a photoacid generator, triphenyl sulfonium triflate, is utilized to illustrate this concept. Moreover, the polymerized furfuryl alcohol can be transformed into amorphous carbon by heating at elevated temperatures in an inert environment. The role of photoacid generator concentration and substrate temperature on the wrinkle formation and morphology is presented. Finally, exposure through a simple mask can generate hierarchical structures with the wrinkled structure conforming to the geometric constraints of the photopatterned area, including curvilinear structures. This photocatalyzed surface segregation-based methodology provides a promising route to the facile fabrication of microstructured surfaces based upon the wrinkling instability.

Graphical abstract: Photoinitator surface segregation induced instabilities from polymerization of a liquid coating on a rigid substrate

Article information

Article type
Paper
Submitted
06 Jan 2012
Accepted
06 Mar 2012
First published
27 Mar 2012

Soft Matter, 2012,8, 5225-5232

Photoinitator surface segregation induced instabilities from polymerization of a liquid coating on a rigid substrate

J. M. Torres, C. M. Stafford and B. D. Vogt, Soft Matter, 2012, 8, 5225 DOI: 10.1039/C2SM00037G

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