Published online by Cambridge University Press: 26 February 2011
The preparation of small, representative research samples of polymers for evaluation in the form of a fiber has been a continuing problem because of the several complex and interrelated steps in going from the monomer to the polymer to the fiber. Such complexity can be magnified in the preparation of rigid rod polymers like cis-PBO, i.e., poly[benzo(1,2-d:5,4-d')-bisoxazole-2,6-diyl-1,4-phenylene]. PBO is a member of the group of high performance polymers generically labeled the PBZ family. With these polymers the additional factors of unreliable mixing, high viscosity, varying morphology, poor solubility, extended polymerization times, etc., present formidable experimental problems. especially when only small quantities of monomers are available.
A new laboratory process has been developed to overcome the difficulties enumerated above so that a dehydrohalogenated monomer mixture in an appropriate solvent can be polymerized rapidly with molecular weight control. The polymer is degassed and otherwise conditioned for spinning, transferred to the spin pump with controlled morphological change, and subjected to dry-jet wet spinning to prepare a fiber representative of the polymer. The spinning operation incorporates features characteristic of both solution processing and thermoplastic extrusion.
Typical fibers of cis-PBO prepared by the process are described.