Sensitive quantification of the surface Si–OH group in MQ silicone resins by benzoylation and GPC−UV analysis

Abstract

The content of the Si–OH group markedly affects the physical and chemical properties of MQ silicone resin (MQ) and its secondary processing products. However, current methods for the determination of the Si–OH group are still unsatisfactory due to their insensitivity and inaccuracy. Herein, an accurate analytical method has been developed for the determination of the active Si–OH group in MQ based on benzoylation and GPC–UV analysis. The UV-insensitive Si–OH group in MQ was converted to a UV-sensitive benzoyl group by the benzoylation with p-methoxy benzoyl chloride, which greatly improved its detection sensitivity. The interference of water was also excluded by the introduction of GPC separation. The effect of several derivatization parameters was investigated and optimized, and complete benzoylation of the Si–OH group in MQ was achieved under the optimized experimental parameters. Good linearity was obtained in a range of 0.425–42.5 μg/g for the content of the Si–OH group in MQ, with a correlation coefficient greater than 0.999. Reasonable reproducibility was also obtained, with the intraday RSD (N = 3) of 1.78 % and the interday RSD (3 days) of 3.98 %, respectively. This method has been successfully applied for the determination of the active Si–OH group in several commercial MQs.