DEVELOPMENT OF HIGH RESOLUTION ESR SPECTROSCOPY FOR DETAILED ANALYSIS OF RADICAL POLYMERIZATION

为了提高ESR谱的分辨率和灵敏度，人们在改进辐照透镜或腔体的基础上进行了几种试验，其中提高ESR谱分辨率和灵敏度的最有效的尝试是样品制备和测量技术的优化。温度、单体浓度、引发剂浓度、辐照时间、波长、强度、样品管形状等条件都会对分辨率和灵敏度产生影响。这些条件的精心优化对于高分辨率和高灵敏度是非常重要的。通过对改进后的光谱仪的测量条件的仔细优化，获得了新的结果。对甲基丙烯酸酯的ESR谱进行了详细的分析，显示出明显的链长依赖性。这是检测聚合物传播自由基的第一个明确的实验证据。对可逆加成断裂链转移(RAFT)体系中间基的检测也进行了尝试。观察到了分辨良好的中间自由基的ESR谱。从这些光谱中可以清楚地区分出苯丙基末端自由基和顺丁烯二酸酐的末端自由基。

In order to increase the resolution and sensitivity of ESR spectroscopy, several kinds of trials were made based on improvements of an irradiation lens or a cavity.The most effective trial to increase the resolution and sensitivity of ESR spectroscopy was optimizations of preparation of samples and technique of measurements. Many kinds of conditions, for example, temperature, concentrations of monomers and initiators, irradiation time, wavelength, intensity, shape of sample tube, etc, will influence the resolution and sensitivity. Careful optimizations of these conditions were very important for the high resolution and sensitivity.New results were obtained by careful optimization of the measurement conditions in the improved spectrometer. Detailed analysis of ESR spectra of methacrylates showed clear chain length dependence. It was a first clear experimental evidence for detection of polymeric propagating radicals. Detection of intermediate radicals of reversible addition fragmentation chain transfer (RAFT) systems was also tried. Well-resolved ESR spectra of intermediate radicals were clearly observed. From these spectra, styryl end radical was clearly distinguished from end radical of maleic anhydride.