ESR Study of Radicals in Conventional Radical Polymerizations Using Model Radicals Generated from Polymers Prepared by Atom Transfer Radical Polymerization

利用原子转移自由基聚合反应生成的模型自由基，用电子自旋共振（ESR）研究了常规自由基聚合反应中自由基的性质。我已经进行了ESR研究的自由基聚合中的自由基的直接检测的增长。在研究工作中，已观察到清晰和良好的分辨率的光谱。然而，在实验中没有得到关于所观察到的自由基的链长的信息。由于ESR谱已被用于估计自由基聚合的增长速率常数（kp），链长的信息是非常重要的。可控自由基聚合技术与ESR谱相结合，提供了甲基丙烯酸酯增长自由基链长的信息。原子转移自由基聚合（ATRP）可以制备具有给定链长和窄多分散性的聚合物。此外，通过ATRP制备的所得聚合物具有末端碳-卤素键。碳-卤素键可以通过与有机锡化合物反应而断裂以形成相应的自由基。我们可以观察到具有已知链长的自由基作为传播自由基的模型。在实验中，较短的（2 - 7单体单元的低聚物的混合物）和较长的（30 - 50，100-mer）模型自由基显示出不同的ESR谱。根据这些结果，我们可以通过ESR光谱区分所观察到的自由基的链长。通过原子转移自由基聚合制备了具有不同甲基丙烯酸酯/丙烯酸酯单体单元的模型二聚自由基前体，用于研究倒数第二单元效应。ESR也观察到了倒数第二个单元的空间和电子效应。

Electron Spin Resonance(ESR) study of radicals in conventional radical polymerizations using model radicals generated from polymers prepared by atom transfer radical polymerization was done. I have carried out ESR study of propagating radicals in radical polymerizations by direct detection of the radicals. In the research works, clear and well-resolved spectra have been observed. However, no information on chain length of the observed radicals had been obtained in the experiments. Since the ESR spectra have been used for estimation of propagation rate constant (kp) of the radical polymerizations, information of chain length is extremely important. Combination of controlled radical polymerization technique and ESR spectroscopy provided information of chain lengths of propagating radicals of methacrylates. Atom transfer radical polymerization(ATRP) can produce polymers with given chain lengths and narrow polydispersity. Moreover, the resulting polymers prepared by ATRP have terminal carbon-halogen bonds. The carbon-halogen bonds can be cleaved by reaction with organotin compounds to form corresponding radicals. We can observe the radicals with well-known chain lengths as model of propagating radicals. In the experiments, shorter (mixture of oligomers with 2-7 monomer units) and longer (30 50,100-mers) model radicals showed different ESR spectra. From these results, we can distinguish the chain lengths of observed radicals by ESR spectroscopy. Model dimeric radical precursors with different methacrylate/acrylate monomer units can be prepared by ATRP for investigation of penultimate unit effects. Steric and electronic effect from the penultimate units were also observed by ESR.