Thermal properties of organo-montmorillonite-polysiloxane systems with varying degrees of exfoliation

Polymer-clay nanocomposites are widely investigated for improving thermal properties and controlling molecular transport; however, the relationship between clay exfoliation, diffusion-limiting effects, and degradation pathways remains insufficiently clarified, particularly in highly permeable polysiloxane systems. Despite extensive research on polymer-clay nanocomposites, the role of clay dispersion in controlling volatile-product evolution during thermal degradation has rarely been addressed systematically. The aim of this study was to elucidate how the degree of organo-montmorillonite (organo-Mt) exfoliation influences thermal degradation behavior and volatile-product release in polysiloxane networks. This work provides a systematic structure–property correlation linking clay exfoliation, volatile-product evolution, and degradation pathways. Montmorillonite was modified with alkyl (C 12 –C 16 ) and benzyl-substituted (BC 12 –BC 16 ) ammonium surfactants to obtain fillers with different dispersion states. Polysiloxane nanocomposites were prepared via Pt-catalyzed hydrosilylation and analyzed using thermogravimetric analysis coupled with FTIR and mass spectrometry (TG–FTIR–MS). The results show that thermal behavior is governed by a coupled effect of cross-linking efficiency and organo-Mt exfoliation. Poorly exfoliated systems exhibit reduced thermal stability and enhanced low-temperature volatilization, indicating facilitated redistribution reactions and rapid release of organosilicon species. In contrast, highly exfoliated benzyl-substituted organo-Mt suppresses low-temperature emission of volatile products and promotes higher ceramic yield. Spectroscopic analysis suggests a diffusion-limiting effect, inferred from suppressed volatile-product evolution during thermal degradation rather than from direct transport measurements. These findings highlight that tailoring the surfactant structure and resulting clay dispersion enables control over degradation pathways and thermal resistance of polysiloxane nanocomposites, which is relevant for applications requiring reduced volatile emissions and improved high-temperature performance.