Mechanical properties and molecular adhesion exhibited by inorganic–organic composite elastomers

Abstract

Polydimethylsiloxane (PDMS)-based organic–inorganic composites have attracted considerable attention due to PDMS's unique features, such as transparency, softness, biocompatibility, chemical stability, heat resistance, and insulation. To extend the lifetimes of organic–inorganic composites, high mixability and self-healing properties are needed. Herein, organic–inorganic composite elastomers with reversible cross-links featuring cyclodextrin (CD)-modified PDMS (PDMS-CD) and adamantane (Ad)-modified poly(alkyl acrylate) were prepared to achieve high mixability and molecular adhesion properties. PDMS-CD/P(EA-Ad) (x) was obtained by the solution polymerization of ethyl acrylate (EA) and an adamantane monomer (AdAAm) in the presence of PDMS-CD, where x is the molar ratio of Ad to βCD. The excess Ad units in PDMS-CD/P(EA-Ad) (5) result in high stretchability and effective self-healing properties based on molecular adhesion. Stress relaxation tests show that excess Ad units improve the reformation and exchange characteristics of reversible cross-links. A structural study using small-angle X-ray scattering (SAXS) reveals that many Ad units improve the mixability of PDMS and acrylate polymers, effectively reforming reversible cross-links and increasing the healing efficiency.