Toward structural regulation and characterization of MQ silicone resins

MQ silicone resins, a class of highly branched hybrid macromolecules composed of one or more M (R3SiO1/2) and Q (SiO4/2) structural units, have garnered significant attention in recent years due to their distinctive structure and properties. However, on-demand control over their chemical structures remains a formidable challenge, particularly using sodium silicate as a precursor. In this study, we systematically manipulated various polymerization factors such as temperature, reaction time, molar ratio between M and Q precursors, ethanol quantity and stirring rate to exert on-demand control over the Q-to-Q condensation and M-to-Q end-capping co-condensation in the sodium silicate method. This approach enabled us to obtain a series of MQ silicone resins with controlled molecular weight (from 19400 to 3600 Da), silanol content (from 5.65% to 0.20%), and M/Q ratio (from 0.56 to 0.98). The resulting materials were characterized using combined techniques to elucidate the influence of polymerization conditions on the structure and properties of MQ silicone resins. Meanwhile, the formation mechanism of MQ silicone resins was discussed, offering a guideline for controllable synthesis of MQ silicone resins. Additionally, we have developed a facile method for determining the M/Q ratio using Fourier transform infrared spectroscopy. This work not only provides insights into engineering the chemical structures but also offers valuable characterization methods for MQ silicone resins.