| Summary: | 碩士 === 國立臺灣科技大學 === 化學工程系 === 103 === The roles of dibenzyltrithiocarbonate (DBTTC) as both costabilizer and RAFT reagent in RAFT miniemulsion polymerizations of ST were investigated. The effectiveness of DBTTC costabilizer in retarding the Ostwald ripening process involved in the storage stability of miniemulsion is comparable to conventional low molecular weight costabilizers such as cetyl alcohol, but inferior to hexadecane. The major variables chosen for studying kinetics of miniemulsion polymerizations with DBTTC as RAFT reagent include the type of initiator (oil-soluble BPO versus water-soluble SPS) and levels of DBTTC and surfactant. At constant level of DBTTC, the rate of polymerization for the BPO-initiated polymerization is slower than that for the SPS-initiated polymerization. Furthermore, the polymerization rate decreases with increasing level of DBTTC for polymerizations initiated by BPO (or SPS). It is the monomer droplet nucleation that governs BPO-initiated polymerizations. In contrast, for SPS-initiated polymerizations, the probability for homogeneous nucleation to take place is greatly increased, especially for polymerizations with lower levels of DBTTC and higher levels of surfactant.
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