Conformational Characteristics, Configurational Properties, and Thermodynamic Characteristics of Poly(ethylene terephthalate) and Poly(ethylene-2,6-naphthalate)

Abstract

Conformational analysis of poly(ethylene terephthalate) (PET) and poly(ethylene-2,6-naphthalate) (PEN) has been carried out by the refined rotational isomeric state (RIS) scheme coupled with ab initio molecular orbital (MO) calculations for a model compound, ethylene glycol dibenzoate (EGDB). 1H and 13C NMR experiments for unlabeled and 13C-labeled EGDBs yielded bond conformations of the central O−CH2−CH2−O bond sequence. The MO calculations satisfactorily reproduced not only the experimental bond conformations but also the dipole moment and molar Kerr constant observed from EGDB. The aromatic ring and ester group of EGDB render its intramolecular interactions more complicated than those of poly(ethylene oxide) with the same O−CH2−CH2−O bonds; CO···H−C and C−O···H−C close contacts and dipole−dipole interactions are simultaneously formed in EGDB. The characteristic ratio of PET, derived from the refined RIS calculations using the MO energies for EGDB, exactly agree with those determined from small angle neutron scattering experiments for the melt. Thermodynamic quantities on PET and PEN, evaluated from the RIS calculations, have well characterized melting and crystallization behaviors of these polyesters.

Elucidation of conformational characteristics and configurational properties of poly((R)-3-hydroxybutyrate) by ab initio statistical mechanics

“…Intramolecular attractive interactions of polyesters are so complicated that the sources of their conformational characteristics can not be simply assigned to well-defined close contacts between atoms (atomic groups). 7 As shown in Figure 4, however, the stable conformers of monomer seem to exhibit some close contacts between the methine proton and carbonyl oxygen ( $ 2.4 and 2.6-2.7 Å ) or ÀO À oxygen (2.56 Å ). The molecular geometry was optimized at the B3LYP/6-311 þ G(2d,p) level.…”

“…The U 2 -U 4 and U a -U c matrices are filled with unity and zero; only the existent conformations are expressed by unity. This formulation was employed for aromatic polyesters such as poly(ethylene terephthalate) (PET) 7 and poly(trimethylene terephthalate). 8 Conformations around four bonds 3-6, 4-7 or 5-8 of dimer were also subjected to the geometrical optimization at the B3LYP/6-311 þ G(2d,p) level, and a number of conformations were found to be absent and hence removed from the ensemble (see Supplementary Table S1, Supplementary Information).…”

“…By ab initio statistical mechanics calculations and nuclear magnetic resonance (NMR) experiments, we have attempted to reveal its intrinsic conformational characteristics. In recent years we have tacked conformational analyses of aromatic polyesters, 7,8 and the methodology there could be expected to be developed for PHB. Here, we have employed the refined RIS algorithm 9 that (1) adopts 27 Â 27 statistical weight matrices including up to four-bond correlations (between atomic groups separated by six bonds), (2) eliminates nonexistent conformations from the ensemble and (3) employs ab initio molecular orbital (MO) calculations to derive reliable conformational free energies and geometrical parameters.…”

Influence of the mixing time on the phase structure and glass‐transition behavior of poly(ethylene terephthalate)/poly(ethylene‐2,6‐naphthalate) blends

“…However, PEN is more expensive and, therefore, less attractive for industrial use. 1,2 A desirable combination of the economics of PET and the superior properties of PEN can be achieved through the blending of these two polymers. The phase structure, transesterification reactions, crystallization, and physical characteristics of PET/ PEN blends have been studied, and different miscibility levels have been reported.…”

Computational design of polymers: poly(ester amide) and polyurethane

“…It is well-known that the CH 2 -CH 2 bond adjacent to the O-C bond in O-(CH 2 ) z -O sequences of esters and ethers prefers the gauche form, 53 and that the gauche stability of the bond generally decreases with increasing number of methylene units between the two oxygen atoms. 13,14,33,34,[54][55][56] If the ester and amide groups of the poly(ester amide)s (…”