Effect of ambient, excitation intensity and wavelength, and chemical structure on photodegradation in polysilanes
Effect of ambient, excitation intensity and wavelength, and chemical structure on photodegradation in polysilanes
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DOI：
10.1063/1.2809422
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发表时间：
2007-11-15
影响因子：
3.2
通讯作者：
Seki, Shu
中科院分区：
文献类型：
--
作者：
Sharma, Asha;Katiyar, Monica;Seki, Shu
通过测量溶液和薄膜中光致发光和吸收的变化，研究了二苯基和甲基苯基聚硅烷共聚物的光降解。在溶液中，降解机制是光断裂的硅-硅键，证实了凝胶渗透色谱。在薄膜中，也存在这种机制，但由于笼效应，速率降低。我们报告了在薄膜中观察到的额外降解机制，该机制对环境不敏感。这是由于在薄膜中聚硅烷链的变形段中形成了缺陷或陷阱。由于发生从较短片段到较长片段的能量转移，较短波长发射/吸收的光降解速率较慢。除了降解，共聚物膜表现出PL强度的初始增强，这是由于在照射过程中产生的热引起的链构象的变化。我们还研究了光降解行为的化学结构的影响，也评价聚（正丁基苯基硅烷），聚（正己基苯基硅烷），聚（正辛基苯基硅烷），和聚[双（对正丁基苯基）硅烷]聚硅烷。在两侧上添加庞大的烷基或芳基基团导致相对于光致断裂的改进的稳定性，但是由于缺陷或陷阱产生的降解甚至在溶液中也持续存在，这归因于这些聚硅烷的构象差异。基于实验证据，我们提出了一个物理模型的降解机制在聚硅烷。(C)2007年，美国物理学会。
The photodegradation of a copolymer based on diphenyl and methylphenyl polysilane has been investigated by measuring the changes occurring in photoluminescence (PL) and absorption in solution and film form. In the solution, the degradation mechanism is photoscission of the Si-Si bonds, confirmed by gel permeation chromatography. In the films also, this mechanism exists but with a reduced rate due to cage effect. We are reporting an additional degradation mechanism, observed in the films, which is not sensitive to the environment. It is attributed to formation of defects or traps in the deformed segments of polysilane chain in film. Photodegradation rate is slower for the shorter wavelength emission/absorption due to occurrence of energy transfer from shorter to longer segments. In addition to degradation, the copolymer films exhibit an initial enhancement in PL intensity, which is attributed to the changes in chain conformation caused by heat generation during irradiation. We have also investigated the effect of chemical structure on photodegradation behavior by also evaluating poly(n-butylphenylsilane), poly(n-hexylphenylsilane), poly(n-octylphenylsilane), and poly[bis(p-n-butylphenyl)silane] polysilanes. The addition of bulky alkyl or aryl groups on both sides leads to improved stability with respect to photoscission, but degradation due to defect or trap creation persists even in solution, which is attributed to the differences in conformation of these polysilanes. Based on the experimental evidence, we present a physical model for degradation mechanisms operating in polysilanes. (C) 2007 American Institute of Physics.