Sequence distribution and crystal structure of poly(ethylene/butylene terephthalate) copolyesters compared with poly(ethylene/trimethylene terephthalate) copolyesters

Abstract

Poly(ethylene/butylene terephthalate) (EB) copolyesters were synthesized from ethylene glycol (EG), 1,4‐butanediol (BDO), and dimethyl terephthalate with different molar volume ratios. The constitutional units, characterized by 13C NMR, revealed a random distribution in the molecular chain. Nevertheless, crystallites formed across the full range of EG/BDO composition can be observed with the use of a differential scanning calorimeter and a wide angle X‐ray diffraction method. The reflection profile of the EB copolyesters was deconvoluted. Also, in the poly(ethylene/trimethylene terephthalate) (ET) copolyesters previously studied, the crystal structure was dominated by the sequence distribution of the copolyesters. The crystal structures of EB and ET copolyesters, in comparison with the different constitutional repeating units in the molecular chain, are discussed in this study. The glass transition temperature of EB and ET copolyesters were analyzed, considering the copolymer composition and the sequencing of the monomers, and their values were compared to the Johnston's equation. In addition, the analysis of the melting temperatures of both the EB and the ET copolyesters was carried out. The equilibrium melting temperatures of both copolyesters were calculated according to the Hoffman‐Weeks extrapolative method. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 405–419, 2007

Chemical Structure and Microstructure of Poly(alkylene terephthalate)s, their Copolyesters, and their Blends as Studied by NMR

“…[ 195 ] One of the methods that has been proposed to overcome such drawbacks is copolymerization. [ 41,88,116,[195][196][197][198][199][200][201][202][203][204][205][206][207] In this kind of works, NMR has been invariably used in order to determine the comonomer composition and sequence distribution of the PTT copolyesters. One representative example is afforded by the study made on poly(ethylene-co -trimethylene terephthalate) (PE x T y T) copolyesters.…”

“…[ 93,229,[244][245][246][247][248][249][250][251][252][253][254][255][256][257][258][259][260][261][262] NMR has been again the technique of choice in all the above referenced works to characterize the PBT copolyesters including the precise determination of their compositions and microstructures. [ 87,88,116, One of these examples are the random copolyesters composed of 1,4-butanediol, adipic acid, and terephthalic acid, poly(butylene terephthalate-co -adipate)s (PBA x T y ). These copolyesters have turned out to be one of the most promising materials for technical applications, not only for their degradability and excellent physical properties but also for the availability of the monomers and moderate price level.…”

“…NMR is by far the technique of choice for the determination of the composition and chemical microstructure of PET copolyesters and terpolyesters . Regarding poly(ethylene terephthalate‐ co ‐isophthalate)s (PET x I y ), which are known to be the main PET modification used for plastic bottles, literature affords a good number of cases in which the copolyester is fully characterized .…”

“…However, PTT suffers certain drawbacks such as poor dyeability and too fast crystallization rate that cause difficulties in some manufacturing processes . One of the methods that has been proposed to overcome such drawbacks is copolymerization . In this kind of works, NMR has been invariably used in order to determine the comonomer composition and sequence distribution of the PTT copolyesters.…”

Syntheses of random PET‐co‐PTTs and some related copolyesters by entropically‐driven ring‐opening polymerizations and by melt blending: Thermal properties and crystallinity

“…The four signals of equal intensity, as expected for the different dyad sequences of random copolymers, are clearly visible 21, 24. The signal assignments in the figure are made on the basis of our data reported in the Supporting Information and by comparison with literature data 28–31…”