Heterogeneous Polymerization Of Styrene Or Chloroprene With Raft Agents

RAFT polymerization is one popular research direction in controlled radical polymerization. With respect to the homogeneous system, heterogeneous polymerization (bulk, solution) has more advantages (environmental protection, fast reaction rate, etc.). Therefore, the heterogeneous system becomes best practices of industrialized implementation for RAFT polymerization. Based on the mechanism of RAFT, the (mini)emulsion polymerization of styrene(St) and emulsion polymerization of chloroprene(CP) with different functional RAFT agents were investigated in this dissertation. The main contents are as follows:1. Four kinds of RAFT agents were synthesized: 2-(2-Carboxyethylsulfanylthiocarbonylsulfanyl) propionic acid (TTC), S-1-dodecyl-S'-(a,a'-dimethyl-a"-acetic acid)trithocarbonate(DDAT),dibenzyltrithiocarbonate(DBTTC) and S-Benzyl-S'-trimethoxysilylpropyltrithiocarbonate (BTPT). The effect of TTC, DDAT and BTPT on the styrene emulsion polymerization was investigated. As a result, inhibition in the system for using TTC and DDAT was found. Using BTPT, the molecular weight distribution could be controlled in 2 or less, the molecular weight increased linearly with conversion. However, bimodal distribution appeared at a high conversion and a large deviation between experimental molecular weight and theoretical molecular weight was found. Therefore, it did not achieve the desired effect.2. The effect of different RAFT agents on styrene miniemulsion polymerization was investigated. As a result, only with TTC, the molecular mass (Mn) of polystyrene (PSt) increased linearly with conversion and the polydispersity index (Mw/Mn) of the polymer was narrow, showing a significant characteristic of living polymerization. The effect of TTC concentration on St miniemulsion polymerization was investigated. The results showed that the molecular mass (Mn) of polystyrene increased linearly with conversion and the polydispersity index (Mw/Mn) of the polymer was narrow. An increase of TTC concentration led to a decrease of polymerization rate with a falling of Mn. Accordingly, the higher the concentration of TTC, the closer the Mn followed the line expected in an ideal living polymerization. The 1H NMR showed that the terminals of polystyrene chains is highly functionalized by TTC. In addition, the conductivity values were used to confirm the existence of carboxylic groups on the surface of the polystyrene nanospheres indirectly. Then, the effect of water-soluble initiators (KPS and V-50) and an oil-soluble initiator (AIBN) on minemulsion system showed that the mechanism of nucleation in different initiator systems was different-homogeneous nucleation played a predominant role on water-soluble initiator system and droplets nucleation was the main in oil-soluble initiator system. Using TTC, NPMI and St was copolymerized. The alternating copolymerization of NPMI and St not only improved the reaction rate but also the polystyrene homopolymer could be modified, which provided conditions for industrial production.3. The effect of DSCTSPA, DDAT and BTPT on CP emulsion polymerization was investigated. As a result, the controlling effect of DBTTC on CP emulsion was the most obvious(Mw/Mn?1.5). Then the effect of stirring speed, DBTTC concentration and initiator concentration on CP emulsion polymerization was investigated. The results showed that increasing speed, reducing the amount of DBTTC or increasing the amount of initiator could improve the stability of emulsion. The 1H NMR showed that the terminals of polychloroprene chains was highly functionalized by DBTTC. Through the pilot plant test, adhesive chloroprene rubber of CR-244 was prepared, which possessed excellent overall performance.