Jump to main content
Jump to site search

Issue 17, 2010
Previous Article Next Article

Soft shape memory in main-chain liquid crystalline elastomers

Author affiliations

Abstract

The field of shape memory polymers (SMPs) has been dominated by polymeric network systems whose fixing mechanism is based on crystallization or vitrification of the constituent chains, rendering such systems stiff in comparison to elastomers, gels, and living tissues. In this report, we describe the synthesis and characterization of liquid crystalline elastomers that exhibit both bulk and surface shape memory effects with compositionally dependent transition temperatures that determine the shape fixing and shape recovery critical temperatures. Main-chain, segmented liquid crystalline elastomers were synthesized using hydrosilylation linking of poly(dimethylsiloxane) oligomers with mesogenic dienes of two compositions and a tetrafunctional crosslinker. Calorimetric and dynamic mechanical analyses revealed two composition-determined thermal transitions for the LCEs, including a glass transition event at low temperatures (33 °C < Tg < 48 °C) and a first-order isotropization transition at higher temperatures (57 °C < Ti < 71 °C), each increasing with an increase in the concentration of the more slender, unsubstituted mesogenic diene, 5H. Despite the existence of a glass transition event, the materials remain soft at low temperature, a finding explained by vitrification of only the mesogen-rich layers within the smectic phase. Shape memory behavior was evaluated quantitatively and revealed excellent shape fixing and shape recovery values, generally in excess of 98%, with the recovery temperature depending on composition in a manner determined by the LCE phase behavior, particularly Tg. The temperature-dependent kinetics of shape memory were analyzed for a selected LCE composition, revealing exponential time dependence with rate constants that depended on temperature in an Arrhenius manner. Finally, the softness of the LCE SMPs was exploited to fix an embossed, micron-scale pattern on the surface and then recover the equilibrium flat state quite completely. We envision application of this surface shape memory phenomenon in the areas of soft lithography, especially microcontact printing and microfluidics.

Graphical abstract: Soft shape memory in main-chain liquid crystalline elastomers

Back to tab navigation

Supplementary files

Publication details

The article was received on 16 Nov 2009, accepted on 15 Jan 2010 and first published on 15 Feb 2010


Article type: Paper
DOI: 10.1039/B924050K
Citation: J. Mater. Chem., 2010,20, 3449-3457
  •   Request permissions

    Soft shape memory in main-chain liquid crystalline elastomers

    K. A. Burke and P. T. Mather, J. Mater. Chem., 2010, 20, 3449
    DOI: 10.1039/B924050K

Search articles by author

Spotlight

Advertisements