Effect Of Initiator And Emulsifier On Core-Shell Morphology In Poly (Butyl Acrylate)/Poly (Styrene) And Poly (Vinyl Acetate)/Poly (Styrene) Composite Latex Particles

The excellent of the performances of polymers formed by the core-shell emulsion strongly depended on the morphology of the latex particles. The prediction and control of composite latex particle morphology has been purchasing by researchers. Sundberg (1990's) proposed that the criterion of the ultimate particle morphology is the principle of minimum interface free energy change, and the theory was verified by Chen's fine experiment. This theory has been admitted widely in the past decades. But their procedure to get the basic thermodynamic data is too complex. A simplified estimate method must be proposed to get the basic thermodynamic data in order to apply the theory to morphology prediction of practical system. In recent years, a simplified estimate method to get the basic thermodynamic data was proposed by our laboratory, and it has been applied to practical system's morphology prediction. While the literatures are surveyed, the sensitivity analysis of the reliability of the simplified prediction method is given. We think that the system of core-shell can be classified into sensitive system and insensitive system. The different authors get the identical morphology results in the different experiment conditions in the insensitive system; the different authors get the different morphology results in the different experiment conditions in the sensitive system.In this paper, we use our simplified estimate method to distinguish the sensitive system and the insensitive system. A series of experiments was designed for a sensitive system and an insensitive system. Changing the types and the concentration of the initiator, changing the concentration of the emulsifier, we observed the change of the ultimately morphology of the latex particles, and validated the prediction results whether or not consistent with the experiment results.According to the literature data, the sensitivity of different system is calculated by the simplified estimate method. It is found that the system of PVAc/PSt is insensitive system and the system of PBA/PSt is sensitive system. The range of sensitivity of prediction for the systems are as follows: (-45%, 30%) for the system of PVAc/PSt, (-10%, 4%) for the system of PBA/PSt.There is little effect on system PVAc/PSt by changing types and concentration of initiator, changing the concentration of the emulsifier. The morphologies showed in TEM photos are all PSt as core and PVAc as shell. This proves that system PVAc/PSt is insensitive.There is great effect on system PBA/PSt by changing types and concentration of initiator, changing the concentration of the emulsifier. There are three kinds of morphologies such as core-shell, inverted core-shell, hemisphere showed in these TEM photos. It is hemisphere when using azobisobutyronitrile for both. It is PBA as core and PSt as shell when using 2% azobisobutyronitrile for BA and 2% potassium persulfate for St, irrespective of the monomer in first stage. It is PSt as core and PBA as shell when using 0.5% or 2% potassium persulfate for BA and 0.5% or 2% azobisobutyronitrile for St.Surface tension and polar of polymer in system PVAc/PSt were measured by method of suspension link and contact angle. There is difference between measured value and literature value. Morphology prediction by simplified method using measured value is consistent with TEM photos.We carried out supervising by a laser during determining experiment conditions. This method is immediate, visual, simple and convenient. We found that the difference of the polymerization methods and the solubility of monomer affect the polymerization kinetic seriously.Under the designed conditions, the uniqueness of morphology hi system PVAc/PSt, the variety of morphology in system PBA/PSt and uniformity of prediction by measured value and TEM photos provide forceful proof for simplified method and sensitivity analysis. It is proved that simplified method and sensitivity analysis can be popularized and bring convenience to morphology prediction.