Well-defined patterns of surface functional groups have been achieved using, for example, self-assembled monolayers (SAMs), polymer grafting, and micro-contact printing. These methods enable control over the surface chemistry and surface energy of a material, and thus surface properties (e.g. wettability or reactivity); however, because these methods use (or require) hard materials, additional processing is necessary to modify the surface chemistry. We demonstrate systems that use soft, elastomeric polymers as supports for surface-chemical patterns. Specifically, we have covalently modified elastomeric polymers (e.g., polydimethylsiloxane) to fabricate homogeneous or heterogeneous patterns of chemical functionality. We show that by mechanically straining these functionalized polymer films, we are able to reversibly control the density of surface-bound moieties and thus the surface energy and surface chemical properties of the material. These systems operate by coupling surface chemistry with the mechanical properties of the elastomer. We have initially focused on the attachment of small molecules and fluorescent molecules, which enable convenient quantification of the strain induced changes to the surface (e.g., molecular density and pattern), and are now exploring chiral and/or self-ordering molecules (e.g., liquid crystal mesogens). We illustrate the applicability of these materials in the control of surface-energy-dependent processes such as nucleation and wettability. Unlike surface-chemical patterns based on hard materials, the systems we describe can be reversibly modified using strain, and could potentially be used in applications where surface properties need to quickly adapt to the environment.

Stretchable surface-chemical patterns

249th National Meeting (2015)

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