Structure-Property Relationships of Polysiloxane Networks Containing Linear, Cyclic, and Tetrakis Units.

Polysiloxanes are a highly relevant family of polymers capable of producing glassy networks with excellent thermal stability; however, studies on the impact of backbone substitution are limited. Formulations comprising cyclic and linear polysiloxanes were prepared, and cross-linked polymer networks were subsequently formed via hydrosilylation. Optically transparent networks with varying degrees of rigidity were obtained, and the effects of the cyclic-to-linear ratio on the physical properties of the resulting networks were investigated. We demonstrate the preparation of cross-linked polysiloxanes and report thermal stability and transitions, thermal expansion behavior, and mechanical properties. Char yields ranged from 45.7 to 85.0% in nitrogen with no significant reductions under air, indicating the potential for high-temperature applications. Mechanical testing revealed that the incorporation of linear siloxane segments increased network flexibility, while cyclic siloxane structures resulted in rigid networks with lower thermal expansion. These results establish a direct relationship between siloxane precursor structure and the thermomechanical properties of cross-linked polysiloxane networks, providing insight into the design of polymer materials with tunable mechanical and thermal performance.