Green Synthesis of Soluble Polysilsesquioxane with Phthalimide Groups

Abstract

Soluble polysilsesquioxane containing side-chain phthalimide groups (PSQ-PhI) was synthesized via a solvent- and catalyst-free hydrolytic polycondensation reaction using 2-[3-(triethoxysilyl)propyl]-1H-isoindole-1,3(2H)-dione. The composition and structure of polysilsesquioxane was confirmed via 1H, 13C, and 29Si NMR spectroscopy, Fourier transform infrared spectroscopy, gel permeation chromatography, thermogravimetric analysis, dynamic light scattering, X-ray diffraction analysis, and elemental analysis. The synthesized silsesquioxane showed a monomodal molecular weight distribution. The average molecular weight of polysilsesquioxane is 11,200 Da, and the polydispersity index is 1.10. 29Si NMR analysis showed a half-peak width w1/2 3.1 ppm at δ −68.3, which corresponds to the PhI(CH2)3SiO3/2 unit and indicates an ordered structure in the polymer, with some defects caused by the presence of uncondensed silanol groups. PSQ-PhI showed good thermal stability (Td5% decomposition at 345 °C). The polysilsesquioxane-based coating was transparent in the visible region.

Recent progress in ladder-like polysilsesquioxane: synthesis and applications

“…In response to recent serious environmental concerns, there is a growing emphasis across various fields on adopting eco-friendly approaches, including efforts to shift the synthesis of silsesquioxanes towards greener methodologies. 159,160 Based on green chemistry principles, research aims to synthesize silsesquioxanes without using solvents or acid/base catalysts. Muzafarov's group synthesized LPSQ through the condensation of cis -tetraphenylcyclotetrasiloxanetetraol in a high-pressure steel reactor using an ammonia medium, 136,161,162 which eliminates the need for solvents and can enhance product solubility (Scheme 1e).…”

“…Research aims to synthesize silsesquioxanes under milder, catalyst-free conditions for green synthesis. Studies include using an isoindoledione-containing precursor at 70 °C for 8 h, 159 and employing microwaves at 20 W and room temperature for about an hour, 160 offering milder synthesis approaches compared to previous methods. Although these studies have yielded silsesquioxanes with undefined or random structures, further development of these research efforts is expected to achieve the environmentally friendly synthesis of well-defined LPSQs.…”