tailieunhanh - Polymer Thin Films Part 7

Tham khảo tài liệu 'polymer thin films part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Tridimensional surface relief modulation of polymeric films 139 temperatures of the material. The relaxation time reported is generally of the same order of magnitude with the isomerisation time. But in case of surface structuring under the action of laser radiation we have obtained for some of the studied materials very good time stability. In case of the photoresist irradiation we have obtained gratings lasting in good conditions as modulation depth and pitch for more than two years. Only if mechanically damages like scratches are produced the grating is damaged. Fig. 12. Surface relief grating relaxation after 24 h from the irradiation of the film of azopolysiloxane modified with azophenol 95-98 Irradiation conditions Fluence 17 mJ cm2 Intensity x 107 W cm2 Also in case of an azopolymer film surface structuration it is possible to observe the surface modulation evolution from disorder Fig. 10 left to order Fig. 10 right . In case of surface relief structuration of azopolymer films the stability of the induced SRG depends on the type of polymer. To analyze the time stability of the induced structures on the surface of azo-polysiloxane modified with thymine units films the samples were analyzed also after a month taking into account that the cist-trans relaxation curves under the visible light and in dark indicate relaxation times from 500 s to hours. The samples were kept at the normal ambient summer temperature. The microscope analyses evidenced the same structure without damage so their time stability can be reported Enea et al. 2008 . In case of a sample of polysiloxane modified with cu azophenol substitution degree 95-98 the time evolution of the structured surface was monitored up to 30 hours from the irradiation time. In Fig. 12 can be seen the microscope images of the grating induced under the action of laser radiation at 355 nm at 15 min. after irradiation moment and after 24h Apostol et al. 2009 . A sequence of microscope images is presenting the .