Pressure-induced phase transition and solid-state polymerization of bis(trimethylsilyl)-substituted diacetylene (BTMSDA).

• Two phase transitions of BTMSDA are discovered at 1.2 GPa and 6.5 GPa. • Solid-state polymerization of BTMSDA is successfully induced at 6.5 GPa. • Phase transitions are reversible, whereas solid-state polymerization is irreversible. • First phase transition helps polymerization, while second phase transition competes with it. Solid-state topochemical polymerization (SSTP) reactions of diacetylenes (DAs) have garnered significant attention due to their crucial role in the synthesis and development of polydiacetylenes (PDAs). However, the SSTP reaction of bis(trimethylsilyl)-substituted diacetylene (BTMSDA) has not been reported until now due to its molecular stacking parameters seriously deviating from the conditions required for the SSTP reaction. To explore the possibility of the SSTP reaction of BTMSDA under high pressure, the structural evolution of BTMSDA in the range of 0∼12 GPa was investigated using diamond anvil cells combined with in situ Raman and infrared spectroscopy techniques. During compression, BTMSDA initially underwent a phase transition from DA-Ⅰ to DA-Ⅱ around 1.2 GPa. Subsequently, BTMSDA simultaneously experienced an SSTP reaction and another phase transition around 6.5 GPa, resulting in an uneven blue mixture consisting of the PDA-blue phase of Poly-BTMSDA and the DA-Ⅲ phase of BTMSDA. Upon decompression, the uneven blue mixture transformed into an uneven red mixture comprising the PDA-red phase of Poly-BTMSDA and the DA-Ⅰ phase of BTMSDA. Analysis reveals that the phase transitions were reversible, whereas the SSTP reaction was irreversible. Moreover, the first phase transition played a pivotal role in facilitating the SSTP reaction, while the second phase transition exhibited a competitive relationship with the SSTP reaction. This study not only deepens our understanding of the physicochemical properties of BTMSDA but also demonstrates the SSTP reaction of BTMSDA under high pressure. [Display omitted] [ABSTRACT FROM AUTHOR]