Poly(ethylene terephthalate) copolymers containing 5-nitroisophthalic units. I. Synthesis and characterization

Abstract

Poly(ethylene terephthalate‐co‐5‐nitroisophthalate) copolymers, abbreviated as PETNI, were synthesized via a two‐step melt copolycondensation of bis(2‐hydroxyethyl) terephthalate and bis(2‐hydroxyethyl) 5‐nitroisophthalate mixtures with molar ratios of these two comonomers varying from 95/5 to 50/50. Polymerization reactions were carried out at temperatures between 200 and 270 °C in the presence of tetrabutyl titanate as a catalyst. The copolyesters were characterized by solution viscosity, GPC, FTIR, and NMR spectroscopy. They were found to be random copolymers and to have a comonomer composition in accordance with that used in the corresponding feed. The copolyesters became less crystalline and showed a steady decay in the melting temperature as the content in 5‐nitroisophthalic units increased. They all showed glass‐transition temperatures superior to that of PET with the maximum value at 85 °C being observed for the 50/50 composition. PETNI copolyesters appeared stable up to 300 °C and thermal degradation was found to occur in two well‐differentiated steps. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1934–1942, 2000

Structures and properties of easily dyeable copolyesters and their fibers respectively modified by three kinds of diols

“…Although the agreement found between copolyester composition and feed might be, overall, acceptable, the SIP unit content was slightly less than the feed molar ratio, whereas the fourth unit content was slightly more than the feed molar ratio. Similar to the other researches on the polycondensation of copolyesters containing isophthalate unit,23–25 the slightly low SIP unit content in the prepared copolyester might be explained by the occurrence of side reaction cyclic dimerization of SIP during polycondensation. The fourth monomer possessed higher boiling point and lower volatility than EG, as mentioned earlier, thereby it was more difficult to extract during polycondensation, resulting in the slight richness of the fourth unit content in the prepared copolyester.…”

Poly(ethylene terephthalate) copolyesters derived from (2S,3S)‐2,3‐dimethoxy‐1,4‐butanediol

“…The whole pattern is similar in both spacings and intensities to the fiber pattern of PET and susceptible to be indexed, therefore, on the basis of the triclinic crystal lattice of PET with a 0 = 4.56 Å, b 0 = 5.94 Å, c 0 = 10.75 Å, α = 98.5°, β = 118°, and γ = 112° 17. This behavior is similar to that displayed by other PET copolymers whose crystal structures have been examined 11, 18. In PET copolymers composed of comonomeric units with markedly different geometry or size, like poly(ethylene terephthalate‐ co ‐5‐nitroisophthalate) or poly(ethylene terephthalate‐ co ‐5‐ tert ‐butyl isophthalate) copolymers, selective rejection of the minor component from the crystalline phase is reasonably assumed.…”

“…DMT and mixtures of EG and DMBD in the chosen proportions were subjected to melt polycondensation in two steps. This methodology has been previously used by us11 in the preparation of different PET copolymers. In the first step, transesterification of DMT with the mixture of the two diols was accomplished at 180–220 °C with the formation of methanol.…”

Poly(ethylene terephthalate) copolymers containing 5‐nitroisophthalic units. II. Crystallization studies

“…In the first stage, the microstructure of PETNI copolyesters in terms of comonomer distribution and sequence lengths was determined by NMR in solution. As previously reported,4 the copolymer composition could be readily determined from the aromatic proton resonances appearing in the 1 H NMR spectra. Furthermore, splitting of the methylene protons into three peaks corresponding to NI E NI, T E NI, and T E T dyads was observed between 5.02 and 4.95 ppm in the 1 H NMR spectra of PET 50 NI 50 , PET 70 NI 30 , and PET 80 NI 20 .…”

“…Apparently, it is the influence of the nitro group on the molecular mobility in the noncrystallized phase that determines the anomalous crystallization behavior displayed by PETNI. In this article, which complements the investigation on these copolyesters initiated in the previous article,4 we report the crystallization and crystal structure of these copolyesters. First, the copolymer chain microstructure is characterized by 13 C NMR in solution for the implications that it has on crystallite building.…”