Structure-property relationships in functionalized PDMS elastomers for stretchable applications

Abstract

Polydimethylsiloxane (PDMS) elastomers are commonly used in flexible electronics, soft robotics, microfluidics, and biomedical devices due to their chemical stability, transparency, and biocompatibility; however, their inherent mechanical weakness and limited stretchability frequently limit advanced applications. This study conducted a thorough comparative analysis of vinyl-, hydroxyl-, and amino-terminated PDMS elastomers, concentrating on the impact of terminal functional groups and crosslinking chemistry on network structure, mechanical performance, and surface qualities. Elastomeric PDMS films are created utilizing high-temperature silicone vulcanization (HTSV), a hydrosilane-functionalized oligomer as a crosslinker, and peroxide-initiated radical hydrosilylation, with fumed silica added as a reinforcing filler. The degree of crosslinking was determined using gel fraction analysis, equilibrium swelling measurements, and Flory-Rehner crosslink density calculations. Mechanical parameters such as tensile strength, modulus, elongation at break, and toughness are investigated using uniaxial tensile testing. Fourier Transform Infrared Spectroscopy (FTIR) spectroscopy revealed structural evolution during crosslinking, while surface wettability, optical crack patterns, and fracture morphology were investigated by contact angle measurements, polarized optical microscopy, and scanning electron microscopy, respectively. Among the investigated systems, hydroxyl-terminated PDMS (H-PDMS) exhibited superior mechanical performance, achieving a tensile strength of ∼0.40 MPa, elongation of ∼255%, and toughness of ∼0.64 MJ·m −3 , demonstrating its potential for high-performance stretchable applications. In comparison, Sylgard 184 shows a higher modulus but much worse ductility and toughness due to its thick and inflexible crosslinked network. The findings reveal a clear structure-property relationship, revealing that controlled crosslinking via terminal functionality allows for the creation of soft, stretchable, and mechanically robust PDMS elastomers specially H-PDMS appropriate for next-generation flexible, photovoltaic PV module, biomedical and stretchable applications.