Facile synthesis of functionalized polysiloxanes with nonconventional fluorescence by oxa-Michael addition reaction

Abstract

Developing a novel methodology for the synthesis of functionalized polysiloxanes is highly desirable because of their extensive applications in engineering, textile, construction, electronics, and medical systems. Herein we introduce the oxa-Michael addition reaction as an efficient methodology to prepare a series of functionalized polysiloxanes from hydroxyalkyl-containing polysiloxanes and vinyl monomers using phosphazene base as the catalyst. The effects of various factors, including reaction time, feed ratio and solvent, were explored in this reaction. It was found that the reaction can be carried out under mild reaction (room temperature in 6 h to 24 h) with moderate to high conversion yields (60% to 99%). In particular, vinyl monomers with strong electron-withdrawing groups (e.g., cyano and sulfone groups) have higher reactivity, and the functionalized polysiloxanes can be obtained quantitatively or near-quantitatively. Interestingly, their molecular weights determined by gel permeation chromatography (GPC) reveal that the Si-O-Si skeletons were attacked by phosphazene base and re-arranged during the reaction, thus leading to improved molecular weights and more uniform molecular weight distributions in the final products than the original polysiloxanes. Moreover, these polysiloxanes exhibited intriguing nonconventional fluorescence due to the presence of unique chromophores, and those containing cyano and sulfone groups particularly exhibit the best fluorescence performance. More organosilicon materials could be developed under this simple strategy.