Polyterephthalates of 2,3‐disubstituted butanediols‐1,4: Effect of aliphatic substituents on Tg and Tm of the polyesters

Poly(2,3‐dialkylbutanediol‐1,4 terephthalates) with the alkyl substituents CH 3 , C 2 H 5 , n ‐C 3 H 7 , iso‐C 3 H 7 , n ‐C 4 H 9 , and n ‐C 10 H 21 , and n ‐C 16 H 33 were synthesized from the corresponding 2,3‐dialkylbutanediols‐1,4 and dimethyl terephthalate or terephthaloyl chloride. The substituents of the butanediol‐1,4 portion of the polyterephthalates influence the 13 C NMR chemical shifts of the carbon atoms near the branching site, the glass transition ( T g ), and the crystallizability. Small alkyl substituents do not change the T g of the polymers, whereas bulky substituents such as the isopropyl group increase the T g and long normal alkyl groups as substituents decrease the T g of the polymers. Crystallinity in these polyterephthalates was found only with CH 3 and C 16 H 33 as the 2,3‐dialkyl substituents in the butanediol‐1,4 portion of the polyester. This crystallinity of polyterephthalate of 2,3‐di‐C 16 H 33 substituted butanediol‐1,4 could be assigned to side‐chain crystallization of the paraffinic groups.