Polyesters of 1,4‐cyclohexanedimethanol1

Abstract A series of polyesters of trans ‐1,4‐cyclohexanedimethanol was prepared and the melting points compared with those of the analogous series of polyesters prepared from p ‐xylylene glycol. Only slight differences in melting points were noted between the corresponding pairs of polyesters prepared from a single aliphatic dicarboxylic acid and from the two glycols. However, polyesters derived from aromatic dibasic acids and trans ‐1,4‐cyclohexanedimethanol melt at a higher temperature than the corresponding polymer from p ‐xylylene glycol. The probable molecular configuration of polyesters based on trans ‐1,4‐cyclohexanedimethanol is discussed. It is suggested that the diol moiety in the polyester can adopt a slightly contracted conformation so that the oxygen‐oxygen distance is less than in polyesters derived from p ‐xylylene glycol. This, together with the similar degree of rigidity and symmetry of the trans ‐1,4‐cyclohexylene and p ‐phenylene ring systems, is employed to explain the observed melting points. Polyesters prepared from cis ‐1,4‐cyclohexanedimethanol are also described. As expected from the lower degree of symmetry of the diol, these polyesters have lower melting points than the analogous compositions prepared from trans ‐1,4‐cyclohexanedimethanol. Polyesters of cis ‐1,4‐cyclohexanedimethanol and trimethylene glycol have similar melting points. It is suggested that a cis ‐1,4‐cyclohexylene ring and a methylene group have a similar effect on the melting point of a polyester. Copolyesters of cis ‐ and trans ‐1,4‐cyclohexanedimethanol with terephthalic acid do not form a minimum melting composition. Instead, they show a continuous change of melting point from that of the polyester prepared from one stereoisomer to that of the polymer prepared from the other isomer.