Study On The Polymerization And Kinetic Behavior Of Organosilicon-acrylate Latex With Core-shell Structure Using Fluorescence Probe Technique

The organosilicon-acrylate latex with a silicon core and an acrylic copolymer shell has been widely studied due to its excellent performance. However, because of its complex system, and most of the methods for analyzing the reaction mechanism of these polymerizations usually do not give molecular information and therefore the fluorescence probe technique is used for monitoring polymerization processes. The ratio I1/I3 can be correlated to the polarity of the environment surrounding the probe. The values of I1/I3 for probe pyrene changed when the morphology of latex particle changed during the emulsion polymerization process. Therefore, it can be used to study the emulsion polymerization process on the molecular level. In this paper, both the polymerization process and kinetic behavior of the organosilicon-acrylate latex with core-shell structure was studied by fluorescence probe technique. The results showed that fluorescence probe technique can be used to monitor the process and kinetic behavior of the organosilicon-acrylate latex effectively. The following aspects were discussed in this paper:①The micro-environment and polymerization process of organosilicon-acrylate latex with core-shell structure were studied by analyzing the intensity ratio of the first vibronic peak (λ=373nm) to the third vibronic peak (λ=384nm) of pyrene (I1/I3), the intensity of Raman scattering in the fluorescence spectrum and the pyrene excimer fluorescence. The experimental results revealed that: (1) the polymerization behavior and micro-environment of organosilicon-acrylate latex with core-shell structure were studied effectively by analyzing the variation of the ratio I1/I3 of pyrene during the polymerization process; (2) the variation of particle size was revealed qualitatively by the variation of the intensity of Raman scattering in the fluorescence spectrum during the polymerization process; (3) the existence of core-shell structure and interpenetrating polymer net work (IPN) structure in latex particles were demonstrated by the appearance of pyrene excimer fluorescence. Meanwhile, the characterization results of particle size analysis and TEM were in good agreement with that. Therefore, the pyrenyl probes can be effectively used to obtain the molecular information about the polymerization behavior, particle size, core-shell structure and interpenetrating polymer net work (IPN) structure of organosilicon-acrylate latex during the polymerization process. ②The kinetic behavior of the organosilicon-acrylate latex with core-shell structure was studied by fluorescence probe technique firstly and effectively. The results showed that during the shell stage, |K|∝R, which were the absolute value of the slope of I1/I3 and the average polymerization rate, respectively. Therefore, there was a positive correlation between the |K| and R, and we could characterize R by calculating the value of |K| semi-quantitatively. According to this, we found that: (1) the average rate of polymerization increased with the increase of the mass of the anionic emulsifiers in the composite emulsifier, and met the maximum when mAS:mOP=3:1; (2) the average rate of polymerization increased with the increase of the mass of the composite emulsifier, and met the maximum when the mass ratio of composite emulsifier to monomer was 7%; (3) the average rate of polymerization first increased with the increase of the mass of the initiator, and then reached its equilibrium value when the mass ratio of initiator to monomer was 0.9%; (4) the average rate of polymerization first increased and then decreased with the increase of the pH, and met the maximum when pH=1.③Because of the poor conversion and lack of enough sampling points, it was difficult to characterize R by calculating the value of |K| semi-quantitatively during the core stage. Therefore, the average polymerization rate only can be characterized qualitatively, and the results showed that the value of I1/I3 increased during core stage.④A good performance emulsion was obtained when mAS:mOP=2:1, the mass ratio of composite emulsifier to monomer was 5%, the mass ratio of initiator to monomer was 0.7%, pH=1 during the core stage, and pH=3 during the shell stage, respectively.