Organosoluble and thermally stable modified poly(ether-imide-urethane)s bearing benzoxazole or benzothiazole pendent groups: synthesis and characterization

Preparation of new types of modified poly(ether-imide-urethane)s, P (O) a-c and P (S) a-c, with good thermal stability and improved solubility was investigated. Two new bis(ether-azide)s bearing benzoxazole or benzothiazole pendent groups were synthesized by treating 2-[3,5-bis(4-trimellitimido-phenoxy)-phenyl]benzoxazole (1 (O) ), or 2-[3,5-bis(4-trimellitimido-phenoxy)-phenyl]benzothiazole (1 (S) ) with ethyl chloroformate in the presence of triethylamine, and subsequent by a nucleophilic reaction with sodium azide, respectively. Two series of modified polymers with moderate inherent viscosities between 0.21 and 0.32 dL g(-1) were prepared from bis(ether-azide)s 2 (O) and 2 (S) with several aromatic diols in dry toluene under refluxing in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO, triethylenediamine) as a catalyst. The polycondensation reaction readily proceeded in desirable yields as one-pot reactions starting from 2 (O) to 2 (S) without the separate synthesis of the corresponding bis(ether-isocyanate)s. In addition, the corresponding unsubstituted poly(ether-imide-urethane)s, P (R) a-c, were prepared under identical experimental conditions for comparative purposes. All of the resulted polymers were thoroughly characterized by spectroscopic methods and thermogravimetry. The solubilities of modified polymer in common organic solvents as well as their thermal stability were enhanced compared to these of the corresponding unmodified polymers. The glass transition temperature, 10 % weight loss temperature and char yields at 800 A degrees C were, respectively, 13-28 A degrees C, 19-32 A degrees C and 3-7 % higher than those of the unmodified polymers.