ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 40, Number 1
JKCSEZ 40(1)
February 20, 1996 

The binary random copolyesters of poly(butylene succinate-co-butylene terephthalate) (PBS/PBT) were synthesized and their sequence distributions were investigated over the entire range for PBS/PBT copolyester compositions by 1H NMR spectroscopy. The melting point (Tm) of these copolyesters were depressed gradually with the increase of dimethyl terephthalate (DMT) mol% in composition and appeared an eutetic behaviour which appears a minimum at ST3 (DMT 65.8 mol%). The melting behaviour of PBS/PBT copolyester was not directly depended on molar fraction (Xa) but on only the sequence propagation probability (P) which occurs in triad fraction. It also can be seen that when the succinate units (or terephthalate units) were abundant enough, PBS/PBT Copolymers formed only PBS (or PBT) crystal with complete rejection of the terephthalate units (or succinate units).