研究目的
Investigating the propagation kinetics of isoprene radical polymerizations in bulk and in solution to determine the activation parameters of kp over a wide temperature and pressure range.
研究成果
The study successfully determines the Arrhenius parameters and activation volume for isoprene kp, providing a relation for kp determination as a function of temperature and pressure. The findings indicate that non-activated olefinic hydrocarbon monomers like isoprene have high activation energies and low propagation rate coefficients compared to other monomers. The presence of a polar solvent slightly increases kp, but the effect is modest.
研究不足
The study is limited by the low polymerization rate and high volatility of isoprene, necessitating elevated pressures and temperatures for successful polymerization. The solvent influence on kp is modest and not extensively investigated.
1：Experimental Design and Method Selection:
The study employs pulsed laser initiated polymerization (PLP) combined with size-exclusion chromatography (SEC) to investigate the propagation kinetics of isoprene radical polymerizations. The PLP-SEC method is chosen for its reliability in determining propagation rate coefficients.
2：Sample Selection and Data Sources:
Isoprene is used as the monomer, with polymerizations carried out at elevated pressures (134 to 1320 bar) and temperatures (55 to 105 °C) to overcome low polymerization rates and high volatility.
3：List of Experimental Equipment and Materials:
A pulsed Coherent Xantos XS-500 excimer laser operated at 351 nm is used for PLP. The polymerization mixture includes isoprene and the photoinitiator DMPA. Polymer characterization is performed using size-exclusion chromatography with a Waters 515 HPLC pump and Knauer Smartline RI detector.
4：Experimental Procedures and Operational Workflow:
Polymerizations are performed in an optical high-pressure cell, with the reaction mixture expanded into methanol post-pulsing. The polymer is then dissolved in THF for SEC analysis.
5：Data Analysis Methods:
Molar mass distributions are analyzed to determine the propagation rate coefficients, with absolute polymer molar masses calculated based on universal calibration concepts.
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