Procuction of Polyacetylene from Polyethylene Induced by High Voltage Breakdown

聚乙烯(PE)高压击穿可生成一种新的聚乙炔，同时生成伯烷基团。迄今为止，还没有关于PE作为绝缘体击穿产生不稳定化学物种的详细报道，并用ESR方法对其进行了表征。因此，无论从基础科学的角度还是从工业应用的角度，都有必要了解PE粉末在击穿过程中产生的不稳定的化学物种，研究其击穿机理。本实验室设计了一种PE粉末击穿专用样管和电路。由此发现，在77K下，HVB生成伯烷基团(1)-CH_2CH_2-。通过对样品的热处理，发现该自由基转化为多烯基自由基(II)，-CH2-CH=CHn。观察到的自由基II的线宽表现出典型的运动变窄，类似于Zieglar型催化剂合成的聚乙炔的线宽。因此，表现为单重态ESR信号的多烯基自由基既可以称为孤子，也可以是稳定在普通聚乙炔主链上的-自由基。在室温下进行反应时，发现该反应产生的双键增加。同时还发现，以碘为电子受体的掺杂使PE中生成的聚乙炔的电导率提高了6-7个数量级。

It was demonstrated that a new polyacetylene can be produced by a high voltage breakdown (HVB) of polyethylene (PE)together with a formation of primary alkyl radical.No unstable chemical species created by the breakdown of PE as insulator are reported in detail and characterized by means of ESR method up to date as far as we know. Therefore it is necessary to know what kind of unstable chemical species are produced during the breakdown and to study the mechanism of breakdown of PE from view point of not only basic science but also industrial application as typical insulating materials.A special sample tube and electric circuit for the breakdown of PE powder were designed in our laboratory. Hence it was found that the primary alkyl radical (1),-CH_2CH CH_2-was produced by the HVB at 77K. And this radical was found to convert into a polyenyl radical(II),-CH_2-CH CH=CH_n by the heat treatment of the sample. The line width of the observed radical,II showed a typical motional narrowing, like that of polyacetylene synthesized by Zieglar catalyst. Therefore the polyenyl radical which showed a singlet ESR signal can be called soliton as well as -radical stabilized in the main-chain of the ordinary polyacetyleneThe double bond produced by the breakdown was found to increase when the reaction was carried out at room temperature. And also it was found that the conductivity of the polyacetylene created in the PE showed an increase of 6-7 magnitudes by doping with iodine as electron acceptor.