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Low-temperature-meltable elastomers based on linear polydimethylsiloxane chains alpha, omega-terminated with mesogenic groups as physical crosslinker: a passive smart material with potential as viscoelastic coupling. Part II-viscoelastic and rheological properties
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SYSNO ASEP 0535690 Document Type J - Journal Article R&D Document Type Journal Article Subsidiary J Článek ve WOS Title Low-temperature-meltable elastomers based on linear polydimethylsiloxane chains alpha, omega-terminated with mesogenic groups as physical crosslinker: a passive smart material with potential as viscoelastic coupling. Part II-viscoelastic and rheological properties Author(s) Horodecka, Sabina (UMCH-V) RID, ORCID
Strachota, Adam (UMCH-V) RID, ORCID
Mossety-Leszczak, B. (PL)
Kisiel, M. (PL)
Strachota, Beata (UMCH-V) RID
Šlouf, Miroslav (UMCH-V) RID, ORCIDArticle number 2840 Source Title Polymers. - : MDPI
Roč. 12, č. 12 (2020), s. 1-31Number of pages 31 s. Language eng - English Country CH - Switzerland Keywords reversible networks ; self-assembly ; self-healing Subject RIV CD - Macromolecular Chemistry OECD category Polymer science R&D Projects GA19-04925S GA ČR - Czech Science Foundation (CSF) Method of publishing Open access Institutional support UMCH-V - RVO:61389013 UT WOS 000602471700001 EID SCOPUS 85094108439 DOI 10.3390/polym12122840 Annotation Rheological and viscoelastic properties of physically crosslinked low-temperature elastomers were studied. The supramolecularly assembling copolymers consist of linear polydimethylsiloxane (PDMS) elastic chains terminated on both ends with mesogenic building blocks (LC) of azobenzene type. They are generally and also structurally highly different from the well-studied LC polymer networks or LC elastomers: The LC units make up only a small volume fraction in our materials and act as fairly efficient physical crosslinkers with thermotropic properties. The aggregation (nano-phase separation) of the relatively rare, small and spatially separated terminal LC units generates temperature-switched viscoelasticity in the molten copolymers. Their rheological behavior was found to be controlled by an interplay of nano-phase separation of the LC units (growth and splitting of their aggregates) and of the thermotropic transitions in these aggregates (which change their stiffness). As a consequence, multiple gel points (up to three) are observed in temperature scans of the copolymers. The physical crosslinks also can be reversibly disconnected by large mechanical strain in the ‘warm’ rubbery state, as well as in melt (thixotropy). The kinetics of crosslink formation was found to be fast if induced by temperature and extremely fast in case of internal self-healing after strain damage. Thixotropic loop tests hence display only very small hysteresis in the LC-melt-state, although the melts show very distinct shear thinning. Our study evaluates structure-property relationships in three homologous systems with elastic PDMS segments of different length (8.6, 16.3 and 64.4 repeat units). The studied copolymers might be of interest as passive smart materials, especially as temperature-controlled elastic/viscoelastic mechanical coupling. Workplace Institute of Macromolecular Chemistry Contact Eva Čechová, cechova@imc.cas.cz ; Tel.: 296 809 358 Year of Publishing 2021 Electronic address https://www.mdpi.com/2073-4360/12/12/2840
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