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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 Druh ASEP J - Článek v odborném periodiku Zařazení RIV J - Článek v odborném periodiku Poddruh J Článek ve WOS Název 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 Tvůrce(i) 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, ORCIDČíslo článku 2840 Zdroj.dok. Polymers. - : MDPI
Roč. 12, č. 12 (2020), s. 1-31Poč.str. 31 s. Jazyk dok. eng - angličtina Země vyd. CH - Švýcarsko Klíč. slova reversible networks ; self-assembly ; self-healing Vědní obor RIV CD - Makromolekulární chemie Obor OECD Polymer science CEP GA19-04925S GA ČR - Grantová agentura ČR Způsob publikování Open access Institucionální podpora UMCH-V - RVO:61389013 UT WOS 000602471700001 EID SCOPUS 85094108439 DOI 10.3390/polym12122840 Anotace 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. Pracoviště Ústav makromolekulární chemie Kontakt Eva Čechová, cechova@imc.cas.cz ; Tel.: 296 809 358 Rok sběru 2021 Elektronická adresa https://www.mdpi.com/2073-4360/12/12/2840
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