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Competing Effects of Network Architecture and Composition on Polydomain Liquid Crystal Elastomers

Journal Article · · Macromolecules
Main-chain liquid crystal elastomers (LCEs) are synthesized to investigate the interplay of the composition and network structure on LCE nematic-to-isotropic (N–I) transitions. We focus on networks synthesized from liquid crystalline oligomers reacted with tri- or tetrafunctional nonmesogenic cross-linker molecules. We find that coupling between mesogens and the polymer backbone increases with the degree of cross-linking. However, this enhanced coupling competes with mesogenic dilution arising from the cross-linker molecules to determine the N–I transition temperature (TNI). When cross-linker molecules are dilute, the degree of cross-linking directly correlates to the change in TNI from the oligomer to LCE (ΔTNI) through mesogen–backbone coupling. In this regime, ΔTNI ranges from 2.9 to 12.2 °C and 2.9–13.9 °C for tri- and tetrafunctional cross-linkers, respectively. At high cross-linker concentrations, deviations from this linear relationship appear. Further, the fractional mesogen content within an oligomer chain induces molecular weight-dependent mesogenic dilution effects arising from the flexible spacer molecules. Analysis of the N–I transition peak reveals a maximum latent heat per gram of mesogen (ΔHNI,mes) for this system.
Research Organization:
Princeton University, NJ (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
Grant/Contract Number:
SC0023021
OSTI ID:
3014301
Journal Information:
Macromolecules, Journal Name: Macromolecules; ISSN 1520-5835; ISSN 0024-9297
Publisher:
American Chemical Society (ACS)Copyright Statement
Country of Publication:
United States
Language:
English

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