Control of molecular weight using RITP-soap free emulsion polymerization

Control of molecular weight using RITP-soap free emulsion polymerization
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The reversible iodine transfer polymerization (RITP) - soap free emulsion polymerization of styrene in the absence of light was carried out using potassium persulfate (KPS) under argon atmosphere at 80 °C for 7 hours and the polymer properties were compared to those obtained from the soap free emulsion polymerization. The variables were the KPS concentrations, molar ratios between KPS and iodine, polymerization temperatures and monomer contents. The characteristics were investigated in terms of the monomer conversion, weight- average molecular weight and number average particle size. In the RITP-soap free emulsion polymerization, the conversion retarded and reached to 67 ~ 92% with increased KPS contents from 1 to 4 wt% due to the presence of iodine, and the particle size dramatically increased with no particular change in the molecular weight, implying that the unstable PS particles were formed in the presence of iodine. As the solid content increased, the monomer conversion increased, molecular weight decreased and the particle size increased with the increased KPS content and [KPS]/[I2] ratio in addition to the particle stability dependency. The best solid content was 40 wt% and this was equally the same as that in the presence of sodium dodecyl sulfate (SDS) in the RITP-emulsion and in the absence of SDS in the soap free emulsion polymerization. Thus, the use or nonuse of stabilizer in the RITP-emulsion polymerization does not matter in obtaining stable spherical particles with controlled molecular weight for industrial application.
Chapter 1. INTRODUCTION 1 Chapter 2. THEORITICAL BACKGROUND 3 2.1 Control of Free-Radical Polymerization by Chain Transfer Methods 3 2.1.1 Traditional Methods of Chain Transfer 3 Thiols as chain transfer agents 4 Halomethanes as chain transfer agents 6 Disulfides as Chain Transfer Agents 7 Other reagents as Chain Transfer Agents 9 2.1.2 The catalytic Chain transfer Process 10 2.1.3 The Addition-Fragmentation Chain Transfer Process 11 2.1.4 The Reversible Addition-Fragmentation Chain Transfer Process 13 Thiocarbonylthio Compounds as RAFT Agent 15 Mechanism of RAFT Polymerization with Thiocarbonylthio Compounds 16 RAFT Polymerization 17 Chain transfer Constants 18 Degree of Livingness 22 2.2 Reverse Iodine Transfer Polymerization 23 2.2.1 Introduction on Reverse Iodine Transfer Polymerization (RITP) 23 2.2.2 Study of the RITP Mechanism 26 2.2.3 Study of the Inhibition
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College of Engineering(공과대학) > Chemical Engineering (화학공학) > Theses(화학공학 석박사 학위논문)
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