Comparison of the photodegradation of parylene C and parylene N
Comparison of the photodegradation of parylene C and parylene N
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DOI：
10.1016/s0014-3057(99)00259-1
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发表时间：
2000-09-01
影响因子：
6
通讯作者：
Gardette, JL
中科院分区：
文献类型：
--
作者：
Bera, M;Rivaton, A;Gardette, JL
本文比较了聚对二甲苯（PPX-N 或聚对二甲苯 N）和聚（2-氯对二甲苯）（PPX-C 或聚对二甲苯 C）的光化学行为。通过 FTIR、紫外-可见光和发射分析、化学滴定和衍生反应、物理处理以及甲醇萃取后的 HPLC 鉴定，研究了在 lambda > 300 nm 照射下薄膜的光降解。实验结果表明PPX-C的光氧化涉及两个连续的步骤。 PPX-C 的光氧化最初暗示了直接光解过程，与 2-氯取代相关并引起特定的紫外线和红外线吸收结构的形成。然后，与之前报道的 PPX-N 相同的反应解释了 PPX-C 的光降解，涉及光诱导的亚甲基氧化以及芳环的氧化。由于大量断链，光产物主要是低分子量氧化物质。与光致变色速率相反，观察到PPX-C的光氧化速率低于PPX-N。这种效果归因于 PPX-C 薄膜的氧渗透性降低了五倍，再加上吸收紫外线的光解产物在氧化暴露的第一步中形成而导致的光衰减。 (C) 2000 Elsevier Science Ltd. 保留所有权利。
In the present paper the photochemical behaviours of poly(para-xylylene) (PPX-N or parylene N) and poly(2-chloro-para-xylylene) (PPX-C or parylene C) are compared. The photodegradation of films irradiated at lambda > 300 nm was studied by FTIR, UV-visible and emission analysis, chemical titration and derivatisation reactions, physical treatments and HPLC identification after methanolic extraction. The experimental results show that two successive steps are involved in the photooxidation of PPX-C. Direct photolytical processes, related to the 2-chloro-substitution and invoking the formation of specific UV and IR absorbing structures, are initially implied in the photooxidation of PPX-C. Then the same reactions as those previously reported for PPX-N account for the photodegradation of PPX-C, involving a photo-induced oxidation of the methylene groups as well as the oxidation of the aromatic rings. As a consequence of the numerous chain scissions, the photoproducts are predominantly low molecular weight oxidation species. Contrary to the rate of photodiscoloration, the rate of photooxidation of PPX-C was observed to be lower than that of PPX-N. Such an effect was attributed to a five time lower permeability to oxygen of PPX-C film combined with the light attenuation resulting from the formation in the first steps of oxygenated exposure of UV-absorbing photolysis products. (C) 2000 Elsevier Science Ltd. All rights reserved.