Flourinated aromatic polyimide

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Patents

Oxygen- 18 isotopic enrichment of water

Fluorinated aromatic

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polyimide Pyromellitic acid dianhydride and 2,2'-bis(trlfluoromethyl)-4,4'diamin obiphenyl react in N , N - d i m e t h y l a c e t a m i d e to give a p o l y a m i c a c i d s o l u t i o n w h i c h is d r i e d , t h e n h e a t e d to form a p o l y i m l d e film. T h e r e p e a t i n g u n i t has the structure illustrated on t h e right. Its f l u o r i n a t i o n gives it increased gas solubility and p e r m e a t i o n coefficient, a n d t h e p a r t i c u l a r effect of i n t r o d u c i n g t r i f l u o r o m e t h y l g r o u p s i s to c a u s e s t e r l c h i n d r a n c e l e a d i n g to l e s s molecular Interaction and an

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W a t e r i n w h i c h t h e c o n t e n t of t h e o x y g e n - 18 I s o t o p e h a s b e e n i n c r e a s e d f r o m i t s v e r y low n a t u r a l v a l u e is u s e d in t r a c e r m e t h o d s in c h e m i s t r y a n d biology. Of t h e m e t h o d s for isotopic enrichment, neither electrolysis nor chemical isotope exchange reactions work s a t i s f a c t o r i l y for O - 1 8 . T h e r m o d f f f u s i o n is effective b u t slow. F r a c t l o n a t l o n d i s t i l l a t i o n Is well k n o w n , t h o u g h t h e f r a c t i o n a t i o n f a c t o r i s v e r y low ( 1 . 0 0 3 2 a t 100°C) b e c a u s e It is

'Fluorinated aromatic polylmtde'

i n c r e a s e d d i f f u s i o n c o n s t a n t over other polyimides.

Patent number: J P 3 2 1 7 2 2 0 Date: 25 S e p t e m b e r 1991 Inventor: S. Nishl Applicant: N i p p o n T e l e g r a p h & T e l e p h o n e Co.

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Oxygen Isotropic enrichment

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Membrane Technology