Styrene is polymerized in the presence of 4-methacryloyloxy-2,2,6,6-tetramethylpiperidine-1-oxy. The polymerization rate is higher than that using 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxy as counterradical. However, the molecular weight does not increase linearly with monomer conversion and the ultimate polydispersity is rather high. After posttreating with ascorbic acid, the molecular weight decreases and a narrow polydispersity is obtained. A branched or hyperbranched structure was thus suggested.

In this paper, the pan‐milling process and the pulverizing mechanism and efficiency of pan‐mill type equipment, which was designed and manufactured in our lab for pulverization, mixing, and stress reactions of polymers, have been studied. The effects of load and rotation speed of the equipment on the pulverizing of polystyrene was investigated by means of quantitative operation, particle size, and distribution measurement as well as theoretical analysis using the Rosin‐Rammler Function and the logarithmic normal distribution function. The results demonstrate that lower rotation and higher load are favorable to higher pulverizing efficiency and to the mode of surface pulverizing. As a result of the quite strong forces during pan‐milling, mechanochemical degradation takes place, which is a first‐order reaction.

The emulsion polymerizations of styrene in the presence ofa variety of TEMPO derivatives were investigated. Among the TEMPO derivatives we studied, 4-acetoxy-2,2,6,6-tetramethylpiperidine-1-oxy (ATEMPO) was a suitable candidate for a living radical polymerization in emulsion, because it provided an optimized balance between hydrophilic and hydrophobic character. For the emulsion polymerization of styrene in the presence of 4-hydroxy-2,2,6,6tetramethylpiperidine-1-oxy (HTEMPO), however, the slow initiation in aqueous phase due to the strong hydrophilic character of HTEMPO, hindered styrene polymerized in a living fashion. The emulsion polymerization of styrene in the presence of 4-benzoyloxy-2,2,6,6-tetramethyl-piperidine-1-oxy (BTEMPO) who was absolutely rich in organic phase, was uncontrolled and identical to conventional radical polymerization.

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The interactions between titanium oxide (TiO2) and polystyrene (PS) during the pan‐milling process were studied. The results show that TiO2 contributes to the crushing of PS when they are ground together. Compared with material prepared by the traditional method, the PS/TiO2 prepared by panmilling exhibits much better properties, such as impact strength, rheological behaviour and thermostability. It is a new method for preparing polymer material with high performance.

ABSTRACT:The kinetics, chain length and distribution of living free-radical polymerization with initiators of different homolytic rate constant, kd, were simulated by a Monte Carlo algorithm. The results show that, for the system with a lower kct (J0-5 -I0-4 s-1 ), the polymerization rate is much faster and chain length increases linearly with monomer conversion. However, for the system with higher kd, nonlinear increase in average chain length, and lower reaction rate are found in the simulation results. Low polydispersity indices were obtained for higher and lower kct.