Phase change behavior during the heating process of long-chain alkyl group-functionalized corner-opened POSS compounds

Abstract

In this study, we report the synthesis and characterization of trifunctional long alkyl chain-functionalized corner-opened polyhedral oligomeric silsesquioxane (CO-POSS) with various apex organic groups: isobutyl, phenyl, and 3,3,3-trifluoropropyl. These long alkyl chain-functionalized CO-POSS compounds were synthesized via hydrosilylation reactions between dimethylsilyl-functionalized CO-POSS and an alkene. The phase transition behavior and thermal stability of the long alkyl chain-functionalized CO-POSSs were investigated via differential scanning calorimetry (DSC), variable temperature X-ray diffractometry (VT-XRD), and thermogravimetric analysis (TGA). The melting points of the CO-POSS compounds decreased with the introduction of C12 alkyl chains, whereas the phase transition temperatures generally increased with chain length. Notably, several of the long alkyl chain-functionalized CO-POSS compounds exhibited an exothermic peak during the DSC heating process. Among them, the C12-alkyl-functionalized CO-POSS derivative with phenyl substitution showed a cold crystallization behavior. The thermal decomposition temperature of the compounds also increased with the addition of long alkyl chains, despite the higher content of flexible organic components. Long-chain alkyl group functionalized corner-opened POSS (CO-POSS) derivatives exhibited exothermic peaks during the heating process at temperature range from 5 °C to 35 °C. Among them, C12-alkyl functionalized CO-POSS derivative with phenyl-substitution showed a cold crystallization behavior. The thermal decomposition temperature of the compounds increased with the addition of long alkyl chains, despite the higher content of flexible organic components.