Spectroscopic ellipsometry investigation of the swelling of poly(dimethylsiloxane) thin films with high pressure carbon dioxide
Spectroscopic ellipsometry investigation of the swelling of poly(dimethylsiloxane) thin films with high pressure carbon dioxide
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DOI：
10.1021/jp002592d
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发表时间：
2001-02-01
影响因子：
3.3
通讯作者：
Johnston, KP
中科院分区：
文献类型：
--
作者：
Sirard, SM;Green, PF;Johnston, KP
用椭圆偏振光谱原位测量了高压二氧化碳对聚二甲基硅氧烷(PDMS)薄膜的厚度和折射率的影响。薄膜的膨胀取决于薄膜的厚度和从折射率计算出的对二氧化碳的吸附。薄膜的吸附和溶胀值超过了块体薄膜。这些增加可能归因于聚合物薄膜-CO2和聚合物-二氧化硅界面上的过量二氧化碳，以及二氧化硅表面和二氧化碳对聚合物取向的影响。模型计算中讨论了熔融二氧化硅窗口的压力诱导双折射，并发现对热氧化物参考晶片和PDMS薄膜的修正是成功的。在二氧化碳由于临界吸附而高度可压缩的区域，观察到参考晶片上大量的二氧化碳表面过剩。
The thickness and refractive index of poly(dimethylsiloxane) (PDMS) thin films an silicon, exposed to high-pressure carbon dioxide, have been measured in-situ by spectroscopic ellipsometry. The swelling of the film is determined from the thickness and the sorption of CO2 from the refractive index. The sorption and swelling Values for the thin films exceed those of the bulk films. These increases may be attributed to excess CO2 at the polymer thin film-CO2 and polymer-silica interfaces and the influence of the silica surface and CO2 on the orientation of the polymer. Pressure-induced birefringence of the fused-silica windows was addressed in the model calculations and corrections were found to be successful for a thermal oxide reference wafer and the PDMS films. Large surface excesses of CO2 on the reference wafer were observed in regions where CO2 is highly compressible due to critical adsorption.