Photodegradation of polyimides. III. The effect of chemical composition, radiation source, atmosphere, and processing

Abstract

Polymide films made from diarylanhydrides with oxygen, carbonyl, and hexafluoroisopropylidene 6F bridging groups are photolabile when irradiated with unfiltered light from a medium‐pressure mercury lamp. The presence of oxygen is necessary to the photolytic degradation process, which results in the ultimate oxidative ablation of thin polyimide films. Films based on the 6F dianhydride containing a hexafluoroisopropylidene hinge group are the most unstable. However, photolysis of 6F dianhydride based polyimides in an inert atmosphere with either the unfiltered medium pressure mercury lamp or an electron beam results in no detectable changes even after long exposure times.

Alignment of a nematic liquid crystal induced by anisotropic photo-oxidation of photosensitive polyimide films

“…17 It was assumed that orientation and crystallization during processing may result in the enhanced stability of the PI film. 18,19 The results obtained by IR spectroscopy were further supported by UV-visible spectroscopy as seen in Fig. 6.…”

Data on Specific Polymers

“…Aromatic polyimides [567][568][569][570][571][572][573][574][575][576][577][578][579][580][581][582][583][584][585][586] have attracted considerable interest due to their excellent mechanical properties, thermal and oxidative stability, and chemical resistance. Several groups of materials are involved:…”

“…Products of photolysis include H 2 O, CO 2 , CO, and phthalic anhydride. 567,568 show that polyimides exposed to UV radiation (including unfiltered mercury lamp radiation) are stable in an inert atmosphere. When exposed in the presence of oxygen, anhydride is formed which suggests the following mechanisms: 569 It is estimated from -irradiation 569 studies that polyimides in satellites would receive over 30 years a radiation dose equivalent to 10 MGy or 50 MGy when used in a fusion reactor.…”

Orientational Transition of Liquid Crystal Molecules by a Photoinduced Transformation Process into a Recovery‐free Silicon Oxide Layer

“…[15,16] In general, the liquid-crystal (LC) alignment layer adopts various organic materials, such as polyimide and polyvinyl alcohol. [17,18] Currently, the light load and thermal budgets, which have been increasing in advanced LCDs, deteriorate organic materials, [19,20] thus decreasing the lifetime of the display. As a result, many people have begun intensive studies of inorganic alignment layers, [21][22][23][24] including diamond-like carbon and silicon oxide, with robust properties in search of an alternative alignment layer.…”