Liquid-crystallization induced reactions. Microstructure and morphology of copolyesters synthesized by transesterification of PET with some LCP monomers

• Published in: Polymer engineering and science Vol. 38; no. 9; pp. 1491 - 1505
• Main Authors: Tonti, Maria Silvia, Masseti, Marco, Poli, Giovanna, Paci, Massimo, Magagnini, Pierluigi, Forte, Claudia, Veracini, Carlo Alberto
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.09.1998; Wiley Subscription Services; Society of Plastics Engineers, Inc; Blackwell Publishing Ltd
• Subjects: Applied sciences; Chemical modifications; Chemical reactions and properties; Crystallization; Exact sciences and technology; Liquid crystals; Monomers; Organic polymers; Physicochemistry of polymers; Polyesters; Polyethylene terephthalate; Ethylene terephthalate polymer; Molecular structure; Sebacate copolymer; Temperature effect; Transesterification; Experimental study; Structure processing relationship; Random copolymer; Ester copolymer; Chemical modification; Morphology; Preparation; Crystal morphology; Ethylene terephthalate copolymer
• ISSN: 0032-3888; 1548-2634
• DOI: 10.1002/pen.10320

The transesterification of poly(ethylene terephthalate) (PET) with a mixture of sebacic acid (S), 4,4′‐diacetoxybiphenyl (B) and 4‐acetoxybenzoic acid (H), carried out under conditions expectedly favoring the formation of a p(ET‐SBH) random copolyester, produces biphasic materials with an isotropic matrix and a highly fibrous, liquid‐crystalline dispersed phase. Spectroscopic, calorimetric, microscopic and diffractometric characterization of the fractions separated by solvent extraction has shown that the two phases consist of practically random copolyesters having different average composition. Interestingly, the degree of aromaticity of the matrix is even lower than that of PET, whereas that of the minor phase is appreciably higher than that calculated for the SBH copolyester that would be produced from the monomer mixture in the absence of PET. This unexpected result is interpreted on the basis of an enthalpy‐driven progressive diffusion of aromatic‐rich material toward the mesophase which segregates at an early stage of the polycondensation within the isotropic mixture of low molar mass oligomers initially produced by the PET acidolysis. Thus, an increasing differentiation, rather than an equilibration, of the composition of the two phases takes place. It is noteworthy that, despite the strong compositional difference, the two phases of these products show fairly good compatibility and interfacial adhesion.