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

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F61389013%3A_____%2F20%3A00535690" target="_blank" >RIV/61389013:_____/20:00535690 - isvavai.cz</a>

Nalezeny alternativní kódy

RIV/00216208:11310/20:10442367

Výsledek na webu

<a href="https://www.mdpi.com/2073-4360/12/12/2840" target="_blank" >https://www.mdpi.com/2073-4360/12/12/2840</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.3390/polym12122840" target="_blank" >10.3390/polym12122840</a>

Jazyk výsledku

angličtina

Název v původním jazyce

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

Popis výsledku v původním jazyce

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.

Název v anglickém jazyce

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

Popis výsledku anglicky

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.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10404 - Polymer science

Projekt

<a href="/cs/project/GA19-04925S" target="_blank" >GA19-04925S: Pokročilé inteligentní samoregenerující se nanokompozítní hydrogely citlivé na vnější podněty</a><br>

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2020

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Polymers

ISSN

2073-4360

e-ISSN

—

Svazek periodika

12

Číslo periodika v rámci svazku

12

Stát vydavatele periodika

CH - Švýcarská konfederace

Počet stran výsledku

31

Strana od-do

1-31

Kód UT WoS článku

000602471700001

EID výsledku v databázi Scopus

2-s2.0-85094108439