Polybenzobisthiazoles – Critical issues in their performance and properties - Polyimides and Other High Temperature Polymers - page 225

2. SYNTHESIS OF PBZTs FROM DIFFERENT ACIDS

A number of polymers having different modifications in the structures have been
synthesized or are currently being synthesized to obtain better properties. Two
fluorine containing aromatic polybenzobisthiazoles ( I , II ) [9] were synthesized by

the direct polycondensation of 4,4 -(hexafluoroisopropylidene) dibenzoic acid and

tetrafluoroterephthalic acid with 2, 5-diamino-l, 4-benzenedithiol dihydrochloride.
These PBZTs were amorphous and showed good resistance to organic solvents,
excellent mechanical properties, and high thermal stability. PBZTs and copoly-
mers having 2,5-dihydroxy bicyclo [2.2.2] octane (

′

[10] and triarylamino [11]
moieties have also been synthesised via diacid monomers.

III)

(I) PBZT with hexafluoroisopropylidene unit

(II) PBZT with bicyclo [2.2.2] octane moiety

(III) PBZT with tetrafluoroterephthalic acid

A PBZT was also synthesized using 1,4-bis (trichloromethyl) benzene [12]. A
PBZT with tetramethylbiphenyl was synthesized and was found to be more stable

at elevated temperatures than the parent PBZT. Although the weight loss starts at
505°C, i.e., 135°C less than the parent PBZT, but 80% weight is retained up to
900°C. All these efforts on the rigid-rod polybenzobisthiazole polymers have been
devoted to structural modifications of the rod-like polymers in order to get better