ratio the title polyester was prepared in the same manner as described in preparation 3 except that instead of the 20 3 g 0 10 mole of terephthaloyl chloride there were employed 15 225 g 0 075 mole of terephthaloyl chloride and 5 075 g 0 025 mole of isophthaloyl chloride the yield was 89 37 g of the title polyester preparation 6 poly tetramethylbisphenol a terephthalate co isophthalate structures i a and i b 50 50 molar ratio the title polyester was prepared in the same manner as described in preparation 3 except that instead of the 20 3 g 0 10 mole of terephthaloyl chloride there were employed 10 15 g 0 05 mole of terephthaloyl chloride and 10 15 g 0 05 mole of isophthaloyl chloride the yield was 94 39 g of the title polyester preparation 7 poly tetramethylbisphenol a terephthalate co isophthalate structures i a and i b 25 75 molar ratio the title polyester was prepared in the same manner as described in preparation 3 except that instead of the 20 3 g 0 10 mole of terephthaloyl chloride there were employed 5 075 g 0 025 mole of terephthaloyl chloride and 15 225 g 0 075 mole of isophthaloyl chloride the yield was 80 33 g of the title polyester.