Copolyester studies. IV. Dyeing behavior of drawn and undrawn fibers derived from tetramethylene terephthalate–tetramethylene sebacate copolymers

Drawn and undrawn fibers of tetramethylene terephthalate–tetramethylene sebacate copolymers, containing up to 20 mol % of the latter, have been dyed in an infinite dyebath with a disperse dye. The dyeing process has been interpreted in terms of the equilibrium dye absorption, the half-time of dyeing, and the diffusion coefficient. Increasing sebacate content has been found to have a marked effect on the rate and level of dye uptake. Deviations from Fickian behavior have been observed for the drawn fiber and related to presence of voids.     

Copolyester studies. V. Preparation and characterization of tetramethylene terephthalate–poly(tetramethylene oxide) random block copolymers

Random block copolymers of tetramethylene terephthalate and polytetrahydrofuran (PTHF) were prepared by melt polycondensation. Five different molecular weights of PTHF were used in the polymerizations with up to 30% by weight incorporation. The copolymers so obtained were characterized in terms of their molecular weight by means of endgroup analysis and solution viscometry. Compositions were established by nuclear magnetic resonance spectroscopy. Thermal properties were studied by differential scanning calorimetry and dynamic mechanical methods. Melting and glass transition temperatures are discussed in terms of the structural differences, particularly the effect of polyether composition and block size on chain flexibility.     

Copolyester studies. VI. Melt spinning and mechanical properties of tetramethylene terephthalate–poly(tetramethylene oxide) random block copolymers

Fibers were prepared from tetramethylene terephthalate–polytetrahydrofuran (PTHF) random block copolymers, containing the latter in the range of molecular weights 1000–5000 with up to 30% by weight incorporation, using a conventional melt spinning technique. The spinnability of the copolymer and the mechanical properties of these undrawn fibers were evaluated. The changes in mechanical properties brought about by the incorporation of PTHF groups in 4GT units were related to the PTHF block size and content in the copolymer. X-ray diffraction data are also discussed briefly in terms of the structural differences.     

Copolyester studies. II. Melting and crystallization behavior of tetramethylene terephthalate–tetramethylene sebacate copolymers

The melting and crystallization behavior of poly(tetramethylene terephthalate) and its copolymers with tetramethylene sebacate (≯ 20 mol %) has been studied using differential scanning calorimetry (DSC). The effect of the sebacate concentration on equilibrium melting temperature and crystallization behavior is discussed in terms of the theory of equilibrium crystallization of random copolymers. The multiple-melting behavior of these systems is described and interpreted in terms of the theory of equilibrium melting of chain-folded crystals, together with molecular fractionation during crystallization and melting and recrystallization during the DSC scan.     

Crystallization behaviour of random block copolymers of poly(butylene terephthalate) and poly(tetramethylene ether glycol)

The morphology and crystallization behaviour of random block copolymers of poly(butylene terephthalate) and poly(tetramethylene ether glycol) have been investigated. Single crystals have been grown in thin films crystallized from the melt. Well defined lamellae, exhibiting (hkO) single crystal electron diffraction patterns have been observed in copolymers containing down to 49 wt% (0.83 mole fraction) poly(butylene terephthalate). WAXS and electron diffraction support a model of a relatively pure poly(butylene terephthalate) crystal core with the poly(tetramethylene ether glycol) (soft segment) sequences and short hard segments being rejected to the lamellar surface and the soft segment rich matrix. The lateral dimensions of the lamellae are determined by the number of hard segment sequences long enough to traverse the stable crystal size at the crystallization temperature. This leads to an initial population of crystals formed at T_c and a second set of smaller crystals that grow from the short hard segment sequences upon cooling to room temperature. The result is fractionation by sequence length due to a coupling of the sequence distribution with the stable crystal size at the crystallization temperature.     

Copolyester studies. I. Preparation and characterization of tetramethylene terephthalate–tetramethylene sebacate copolymers

Tetramethylene terephthalate–tetramethylene sebacate copolymers containing up to 20 mol % sebacate have been prepared and characterized. Molecular weights and distributions have been evaluated using viscometry and gel-permeation chromatography. Compositions have been established by NMR spectroscopy. Thermal properties have been studied by differential scanning calorimetry and dynamic mechanical methods. Melting and glass-transition temperatures and moduli are discussed in terms of the structural differences, particularly the effect of composition on chain flexibility. Density and thermal methods of crystallinity determination are critically discussed for these systems.     

Dielectric properties of phase separated polymer solids: 2. Butanediol terephthalate-poly(tetramethylene oxide terephthalate) copolymers

The low frequency dielectric behaviour of copolymers of butanediol terephthalate with poly(tetramethylene oxide terephthalate) is reported. Comparison of the theories for interfacial polarization with experimental dielectric observations highlights the role of domain boundary conduction in such polar polymers.     

Copolyester studies. III. Melt-spinning,drawing, and mechanical properties of tetramethylene terephthalate–tetramethylene sebacate copolymer fibers

Fibers have been prepared from tetramethylene terephthalate–tetramethylene sebacate copolymers, containing up to 20 mol % of the latter, using a conventional melt-spinning technique. The mechanical properties of these undrawn fibers and of highly oriented fibers prepared from them have been evaluated. The changes in mechanical properties brought about by the introduction of sebacate groups in poly(tetramethylene terephthalate) have been related to the glass-transition temperatures of the copolymers and to the flexible nature of the sebacate unit. The formation of voids during a continuous drawing process and during mechanical testing is discussed.     

An NMR study on sequence distributions of block copolymers of poly(butylene terephthalate) and poly(tetramethylene glycol)

Summary The analytical methods to characterize the exact chemical composition and sequence distributions of block copolymers of poly(butylene terephthalate) and poly(tetramethylene glycol) (PBT/ PTMG) were reinvestigated by NMR spectroscopy. To obtain accurate information, the choice of the solvents, NMR experimental conditions, ¹H and ¹³C peak assignments and the methods of calculating various sequence parameters were closely examined. For phenol-d₆/tetrachloroethane(TCE) solutions of two copolymers having the hard segment (PBT) contents of 20 and 35wt.%, various sequence parameters were extracted from NMR spectra. In addition to that, we could accurately measure the actual number average molecular weight of PTMG segments within the copolymer by NMR. Measured average molecular weight of PTMG segments was used to calculate theoretical sequence distributions. The experimental and theoretical sequence parameters as well as chemical compositions were compared with each other. Received: 8 September 1998/Revised version: 31 March 1999/Accepted: 2 April 1999     

Synthesis and properties of poly(tetramethylene terephthalate-co-ethylene terephthalate)–poly(tetramethylene ether) segmented copolymers

A series of polyether–copolyester segmented copolymers ((PBT–PET)PTMG) based on hard segments of tetramethylene terephthalate–ethylene terephthalate copolyester (PBT–PET) and soft segments of poly(tetramethylene ether)(PTMG) was synthesized. The hard : soft segment weight ratio was 30 : 70 and the mole ratio of PBT : PET was 1 : 10; 1 : 6; 1 : 1; 3 : 1, respectively. Their mechanical properties, morphology, crystallization behavior and optical transparency were investigated and compared with poly(tetramethylene terephthalate)–poly(tetramethylene ether)(PBT–PTMG), as well as with poly(ethylene terephthalate)–poly(tetramethylene ether)(PET–PTMG), consisting of the equivalent composition ratio of hard and soft segments. It was found that the transparency could be improved by introducing a small amount of PBT into PET–PTMG through copolymerization. However, a decrease was observed in the transparency if more PBT was added. This is due to the fact that the copolymerization makes both crystallinity and crystallization rate decrease.     

Crystallization, and morphology of poly(trimethylene terephthalate)/poly(ethylene oxide terephthalate) segmented block copolymers

A new type of poly(ether-ester) based on poly(trimethylene terephthalate) as rigid segments and poly(ethylene oxide terephthalate) as soft segments was synthesized and its crystallization behavior and morphology were investigated. Differential Scanning Calorimetry revealed that the copolymer containing 57 wt% soft segments presented a low glass transition temperature (−46.4 °C) and a high melting temperature (201.8 °C), suggesting that it had the typical characteristic of thermoplastic elastomer. With increasing soft segment content from 35 to 57 wt%, the crystallization morphology transformed from banded spherulites to compact seaweed morphology at a certain film thickness, which was due to the change of surface tension and diffusivity caused by increasing the soft segment content. Moreover, with the decrease of film thickness from 15 to 2 μm, the crystallization morphology of the copolymer (57 wt% soft segment) changed from wheatear-like, compact seaweed to dendritic. Scanning Electron Microscopy revealed that some flower-like crystals presenting in the bulk, which had been surprisingly found in the poly(ether-ester) segmented block copolymers for the first time. Possible mechanism was discussed in the text.     

Poly(sulfobetaine)s and corresponding cationic polymers. VII. Thermal degradation of copolymers derived from poly(acrylamide co-N,N-dimethylaminopropylmaleimide)

The copolymer prepared by copolymerizing acrylamide and maleic anhydride was imidized with N,N-dimethylaminopropylamine. The obtained acrylamide-N,N-dimethylaminopropylmaleimide (ADMAPM) copolymer was then reacted with propane sultone to yield an acrylamide-N,N-dimethylmaleimidopropyl ammoniopropane sulfonate (ADMMAPS) copolymer or then reacted with methyl iodide to yield a poly(methyl iodide quaternized acrylamide-N,N-dimethylaminopropyl maleimide) copolymer [poly(MIQADMAPM)]. The kinetic parameters, such as the reaction order, the activation energy, and the preexponential factor, of the thermal degradation were evaluated from thermal gravimetric curves for these two copolymers. The activation energy and preexponential factor of the poly(ADMMAPS) were higher than those of poly(MIQADMAPM) for Ozawa's method and van Krevelen's method. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 95–103, 1997     

SEM studies of cold-rolled spherulitic films of poly(tetramethylene terephthalate)

By using the method of scanning electron microscopy, a visual study was made of the macro-deformation of spherulitic deformation during the cold rolling of poly(ethylene terephthalate) (PET) and poly(tetramethylene terephthalate) (PTMT). By rolling solution cast films to different extension ratios, it was found that the surface material (nearest the rollers) appeared to deform first by the shearing action. With higher extension, the material toward the core of the film began to deform. In all cases, the deformation process tended to flatten the spherulites yet, in general, the spherulitic boundaries were maintained. It was noted that the same general behavior was observed for both PET and PTMT.     

Crystallization behavior and morphology of double crystalline poly(trimethylene terephthalate)/poly(ethylene oxide terephthalate) copolymers

Double crystalline poly(trimethylene terephthalate)/poly(ethylene oxide terephthalate) copolymers (PTT/PEOT), with PTT content ranging from 16.5 to 65.5 wt%, were synthesized by melt copolycondensation. The morphological transformation of samples from microphase separation to macrophase separation was investigated by gel permeation chromatography and transmission electron microscopy. Differential scanning calorimetry and in situ wide‐angle X‐ray diffraction suggested that all copolycondensation samples displayed double crystalline behavior. The melt‐crystallization peak temperatures (T_{m, c} values) of PTT chains monotonously increased with increasing PTT content and were higher than that of homo‐PTT when the content of PTT was above 30.6 wt%. Interestingly, T_{m, c} values of PEOT chains were also increased with increasing PTT content. Polarized optical microscopy revealed that all copolycondensation samples studied could form ring‐banded spherulites and band spacing increased with increasing T_c values. In addition, band spacing decreased with increasing PTT content at a given T_c. Strangely, although PEOT was the main component in all copolycondensation samples, spherulitic morphology formed by the advance crystallization of PTT did not change after PEOT crystallization. Only a subtle change of quadrant tones was detected. © 2012 Society of Chemical Industry     

The thermal and mechanical behavior of poly(ethylene terephthalate) fibers incorporating novel thermotropic liquid crystalline copolymers

This investigation explores the potential of improving the performance of poly(ethylene terephthalate) fibers by incorporating novel thermotropic liquid crystalline copolymers. Fibers were obtained by melt extrusion and the effect of processing conditions, i.e., spinning temperature, stretch ratio, and post treatment evaluated. The fibers were tested for mechanical performance, dimensional instability (shrinkage), and the development of shrinkage stresses. A segmented block copolymer consisting of rigid-rod, diad, and flexible coil segments was found to improve the performance of poly(ethylene terephthalate) (PET) fibers. At a concentration of 20 wt %, the alternating block copolymer increased the tensile modulus of the fibers by 40% and decreased free shrinkage by 20% compared to neat PET. © 1994 John Wiley & Sons, Inc.     

Effects of catalyst on sequence distribution and transparency of poly(tetramethylene terephthalate)–poly(tetramethylene ether) segmented copolymers

Polyether-polyester segmented copolymer based on hard segments of tetramethylene terephthalate (PBT) and soft segments of poly(tetramethylene ether glycol) (PTMG) was synthesized by four kinds of catalyst: tetrabutyl titanate and magnesium acetate (Ti-Mg); tetrabutyl titanate and triethanolamine; tetra(isopropyl) titanate; and isopropoxy(triethanolaminato) titanate, respectively. Their segment sequence distributions were analyzed by ¹³C-NMR, based on different chemical shifts of aromatic quaternary carbons in the three different triad sequences. The effects of catalyst on sequence distribution and transparency were investigated. It was found that the copolymer has lower probability of B-T-B when Ti-Mg was used as catalysts, and results in higher transparency. © 1995 John Wiley & Sons, Inc.     

Polyester-polyether block copolymers. I. Wide-angle X-ray diffraction studies of poly(hexamethylene terephthalate)/poly(oxytetramethylene) and related block polymers

The crystallisation and orientation of the individual structural components of poly(hexamethylene terephthalate)/poly(oxytetramethylene) block copolymers have been studied by wide-angle X-ray diffraction. The crystallisation behaviour in the unstretched state is determined by the proportions and molecular weights of the polyether blocks. For copolymers containing less than 60 wt% of polyether of m. w. ≯ 2000, only the polyester segments crystallise spontaneously, but with polyether m. w > 2000 two crystalline phases are formed. Similar behaviour was found in block polymers from other readily crystallising polyesters, but with non-crystallising polyesters the polyether segments crystallised spontaneously. Moderate tensile deformation of the block copolymers from polyether of m. w. 2000 leads to the stress-reversible highly oriented crystallisation of the polyether whilst the polyester remains undeformed. At higher extensions, irreversible orientation of the polyester segments occurs. The observations suggest that the polyester and polyether segments form discrete regions since otherwise homogeneous crystallisation should occur.     

Synthesis and characterization of block copolymers from D,L-lactide and poly(tetramethylene ether glycol)

The copolymer from D ,L -lactide and poly(tetramethyene ether glycol) (PTMG) was prepared in bulk with an isotributyl aluminum–water–phosphoric acid complex catalyst as the initiator and characterized by H-NMR, GPC, and DSC. The effects of the temperature and the amount of PTMG on the polymerization rate and the molecular weight of copolymers were studied. The behavior of the degradation and delivery rate of Levonorgestrel microspheres in vitro was observed. The results show that the degradation and the delivery rate can be controlled by adjusting the molar rate of hydrophilic and hydrophobic segments of the copolymer © 1995 John Wiley & Sons, Inc.