Number of the records: 1

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

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, ORCID}
Article number	2840
Source Title	Polymers. - : MDPI Roč. 12, č. 12 (2020), s. 1-31
Number 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

Number of the records: 1