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Issue 22, 2010
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Solvent induced transition from wrinkles to creases in thin film gels with depth-wise crosslinking gradients

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Abstract

We investigated solvent induced transition of surface instability from wrinkles to creases in poly(2-hydroxyethyl methacrylate) (PHEMA) gels with depth-wise crosslinking gradients. The mode of surface instability and morphology of surface patterns was found to be dependent on the equilibrium linear expansion, which was a function of crosslinker concentration and the solventpolymer interaction. The maximum linear expansion was obtained when the PHEMA film was swollen in a good solvent, which had the Hildebrand solubility parameter (δs) close to that of PHEMA gels, 26.6 to 29.6 MPa1/2. In a relatively poor solvent (e.g. water), wrinkling patterns were obtained and the morphoplogy was determined by the concentration of the crosslinker, ethylene glycol dimethacrylate (EGDMA). In a good solvent, such as alcohol and alcohol/water mixture, the equilibrium linear expansion ratio increased significantly, leading to the transition from wrinkling to creasing instability. In an ethanol/water mixture, we systematically varied the ratio between ethanol and water and observed the transition from wrinkling to creasing when gradually adding ethanol to water, and the reverse transition when adding water in ethanol. The onset of the linear expansion ratio for creasing (αc,c) was again found dependent on EGDMA concentration: αc,c ≈ 2.00 and 1.3, respectively, for gels with 1 and 3 wt% EGDMA. Finally, we demonstrated confinement of the creases by combining swelling and photopatterning.

Graphical abstract: Solvent induced transition from wrinkles to creases in thin film gels with depth-wise crosslinking gradients

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Publication details

The article was received on 02 May 2010, accepted on 15 Jul 2010 and first published on 31 Aug 2010


Article type: Paper
DOI: 10.1039/C0SM00317D
Citation: Soft Matter, 2010,6, 5795-5801
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    Solvent induced transition from wrinkles to creases in thin film gels with depth-wise crosslinking gradients

    M. Guvendiren, J. A. Burdick and S. Yang, Soft Matter, 2010, 6, 5795
    DOI: 10.1039/C0SM00317D

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