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Articulated Rigid-Rod Polymers Containing Benzobisoxazole and Benzobisthiazole Moieties

Published online by Cambridge University Press:  26 February 2011

Robert C. Evers  and
My Dotrong
Robert C. Evers
Affiliation:
Materials Laboratory, Air Force Wright Aeronautical Laboratories, Wright-Patterson Air Force Base, OH 45433-6533
My Dotrong
Affiliation:
University of DaytonResearch Institute 300 College Park Avenue, Dayton, OH 45469
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Abstract

Articulated rigid-rod polymers with 2,6-benzobisoxazole and 2,6-benzobisthiazole units in the backbone were synthesized by copolycondensation in polyphosphoric acid of 4,6-diamino-l,3-benzenediol dihydrochloride and 2,5-diamino-l,4-benzenedithiol dihydrochloride, respectively, with terephthalic acid and suitably-structured difunctional monomers. Early efforts centered on the incorporation of flexible diphenoxybenzene tructures into the polymer backbone while subsequent efforts involved the more thermooxidatively stable 3,3'-biphenyl- or 4,4'-(2,2'-bipyridyl)-structures. Under dilute reaction conditions, the copolycondensation reactions proceeded in the isotropic phase to yield polymers with inherent viscosities of less than 13dL/g (CH3 SO3 H, 25°C, 0.2g/dL). Later efforts carried out under higher concentration in the nematic state led to intrinsic viscosities as high as 20dL/g. Films which exhibited optical birefringence under crossed polars could be cast from methanesulfonic acid solutions of the polymers. Thermooxidative stability of the articulated polymers was evaluated by isothermal aging in air at 316°C and/or 371°C. Stability of the polymers was found to decrease with increased content of the flexible structures, with the loss of thermooxidative stability being more pronounced with the diphenoxybenzene structures.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 134: Symposium J – Materials Science and Engineering of Rigid-Rod Polymers , 1988 , 141
Copyright
Copyright © Materials Research Society 1989

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References

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