Block copolyetheresters

Summary Block copolyetheresters with hard segments of poly (pentamethylene p,p'-bibenzoate) and soft segments of poly (tetramethylene ether) have been prepared by melt polycondensation of dimethyl p,p'-bibenzoate, 1,5-pentanediol and poly(tetramethylene ether) glycol (PTMEG) with molecular weights of 650, 1000 and 2000. The polymer composition is governed by the charge molar ratio (x) of PTMEG to dimethyl p,p'-bibenzoate. The block copolyetheresters with x=0.05, 0.1 and 0.2 display a monotropic smectic phase due to the poly (pentamethylene p,p'-bibenzoate) segments. But the block copolyetheresters with x=0.3 exhibit no liquid crystalline behavior. The molecular weight of the PTMEG used has significant effect on the glass transition temperature and crystallizability of the polyether segments. It can be seen from the glass transition temperature results that the miscibility between amorphous parts of the polyether segments and those of the polyester segments is also dependent on the molecular weight of the PTMEG used.     

Block copolyetherester. Part 3: Preparation of block copolyetheresters by a terephthalic acid process in the presence of salts

The block copolyetheresters with hard segments of poly(butylene terephthalate) and soft segments of poly(tetramethylene ether) were prepared by a terephthalic acid (TPA) process in the presence of some salts. The preparations of a block copolyetherester under various conditions were first studied in a 1 L stainless steel reactor to find the best method. Then, the preparations of four block copolyetheresters were run in a pilot plant comprising a 200 L polyesterification reactor and a 200 L polymerization reactor under the suitable condition. The presence of some salts reduced the formation of tetrahydrofuran (THF), and also reduced the total reaction time in the pilot plant. The thermal properties and various mechanical properties of the block copolytheresters prepared by the pilot plant were investigated to evaluate the feasibility of this method.     

Preparation and properties of highly functional copolyetheresters

Block copolyetheresters with hard segments of poly(trimethylene 2,6‐naphthalene dicarboxylate) and soft segments of poly(tetramethylene ether)glycol 2,6‐naphthalene dicarboxylate were prepared by the melt polycondensation of dimethyl 2,6‐naphthalene dicarboxylate (NDC), 1,3‐propanediol (PD), and poly(tetramethylene ether)glycol (PTMEG) with molecular weights of 1000. The block copolyetheresters were characterized by ¹H‐NMR spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical analysis. The block copolyetheresters synthesized with NDC/PD/PTMEG were more heat resistant than those synthesized with dimethyl terephthalate/PD/PTMEG. The block copolyetheresters synthesized with NDC/PD/PTMEG showed stronger elastoplastic behavior than those synthesized with NDC/1,4‐butanediol/PTMEG. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 139–145, 2003     

Block copolyetheresters with poly(trimethylene 2,6-naphthalenedicarboxylate) segments: Effect of composition on thermal properties

Block copolyetheresters with hard segments of poly(trimethylene 2,6-naphthalenedicarboxylate) and soft segments of poly(tetramethylene oxide) were prepared by melt polycondensation of dimethyl 2,6-naphthalenedicarboxylate, 1,3-propanediol and poly(tetramethylene ether)glycol (PTMEG) of molecular weights of 650, 1000 and 2000. The block copolyetheresters were characterized by FTIR, ¹H NMR, DSC, X-ray diffraction, TSC (thermal stimulated current), DMA and TGA. It was found that the thermal transitions were dependent on the composition. As the charge molar ratio of PTMEG to dimethyl 2,6-naphthalenedicarboxylate, x, increased, the T_m and ΔH_m of the polyester segments decreased, which has been also confirmed by the X-ray diffraction data. The polyether segments of the block copolyetheresters derived from PTMEG2000 could crystallize after cooling, but those of the block copolyetheresters derived from PTMEG1000 and PTMEG650 could not crystallize. The DSC, TSC and DMA results show consistent T_g data of the polyether segments. Based on the shift in T_g of the polyether segments, the amorphous parts of the polyether segments and the amorphous parts of the polyester segments were immiscible for the block copolyetheresters derived from PTMEG2000, but became partially miscible for the block copolyetheresters derived from PTMEG1000 and PTMEG650. The TGA results indicated that composition had little effect on thermal degradation under nitrogen.     

Nanostructured thermotropic PBLG-PDMS-PBLG block copolymers

We report on the nano-organization and the thermal behavior of a series of triblock copolymers composed of a central soft polydimethylsiloxane (PDMS) and two polypeptide (poly-γ-benzyl-l-glutamate) blocks. Peptide blocks with varied lengths and therefore different secondary structures (β-sheet or α-helical) were attached to the PDMS central block. These two blocks are incompatible and microphase separate into different morphologies elucidated by polarized optical microscopy (POM), small-angle light scattering (SALS), X-ray spectroscopy (SAXS, WAXS) and atomic force microscopy (AFM). We demonstrate that the relative ratio of PBLG to PDMS direct both the type of nanodomain morphologies formed and also modifies the transition temperature. Each of these block copolymers have shown a reversible transition associated to its thermotropic liquid crystal behavior. At temperatures above the transition, the self-assembled structures are disrupted and prevented the organization at larger scales.     

Synthesis and characterization of block copolyetheresters with poly(tetramethylene 2,6-naphthalenedicarboxylate) segments

The block copolyetheresters with hard segments of poly(tetramethylene 2,6-naphthalenedicarboxylate) and soft segments of poly(tetramethylene oxide) were prepared by melt polycondensation of dimethyl 2,6-naphthalenedicarboxylate, 1,4-butanediol, and poly(tetramethylene ether) glycol (PTMEG) with molecular weights of 650, 1000, and 2000. The block copolymers were characterized by Fourier transform infrared and ¹H-NMR spectroscopy, differential scanning calorimetry, thermogravimetric analysis (TGA), and X-ray diffraction. The block copolymer compositions were governed by the charge molar ratio (x) of PTMEG to dimethyl 2,6-naphthalenedicarboxylate. It was found that the thermal transitions were dependent on the compositions. As x increases, T_m and ΔH_m of the polyester segments decrease due to the decrease in the sequence length. The X-ray diffraction data also indicate that the crystallinity of the polyester segments decreased as x increased. The molecular weight of the PTMEG used has a significant influence on the glass transition temperature (T_g) and the crystallizability of the polyether segments. The polyether segments of block copolymers derived from PTMEG 2000 could crystallize after cooling and showed a T_g of about −67°C, independent of x. However, the polyether segments of copolymers derived from PTMEG 1000 and PTMEG 650 could not crystallize, and the T_g of the polyether segments decreased as x increased. This is described as the difference in the miscibility between amorphous parts of the polyether segments and those of the polyester segments. The TGA results indicate that the composition had little effect on the nonisothermal thermal degradation under nitrogen. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1411–1418, 1997     

Block polymers from isocyanate-terminated intermediates. III. Preparation and properties of cured diene–urea block polymers

Isoprene–urea and butadiene–urea block polymers have been prepared by reaction of isocyanate-terminated prepolymers with diamines and diisocyanates. It was found that the per cent of blocked urea in these copolymers is dependent on the isocyanate–diamine stoichiometry. Stress–strain data were obtained on sulfur-cured copolymers. Stress levels at any given extension were directly dependent on the urea content, however, ultimate strength was maximized at about 35 wt-% urea. Slight variations in urea structure produced rather dramatic changes in the modulus of these cured elastomers. Diamine–diisocyanate stoichiometry did not affect the physical properties of these cured copolymers at equal or excessive diamine concentrations. However, at excess diisocyanate levels, elastomeric properties deteriorated rapidly. Finally, stress–strain properties were affected by polymerization solvent. Copolymers prepared in hexane gave higher values of stress at low strains than corresponding elastomers prepared in toluene. These latter results are explained in terms of the nonaqueous emulsion in which the urea blocks form.     

Rheological properties of thermotropic liquid crystalline aromatic copolyesters

A series of thermotropic liquid crystalline polyesters based on p-acetoxybenzoic acid, naphthalene dicarboxylic acid, hydroquinone diacetate, and poly(ethylene terephthalate) were prepared via melt polycondensation. The anisotropic melts were studied by means of thermal optical testing, differential scanning calorimetry, scanning electron microscopy. X-ray diffraction, and rheological methods. It was found that the copolyesters in the mesomorphic state exhibit drastic shear-thinning and the experimental results indicate that the non-Newtonian Index n is in the range of 0.17 to 0.50, the flow-activation energies ΔE_η are 297.1 to 182.0 KJ/mol over the shear rate of 10 to 1000 S^?1 at temperature 225 to 270°C; and the mesomorphic copolymers are readily oriented during processing, resulting in highly oriented as-spun fibers.     

热致性液晶聚氨酯的合成及性能

以1,4-双（对羟基烷氧基苯甲酸）苯酯分别与2,4-甲苯二异氰乙酸酯（2,4-TDI）、二苯甲烷-4,4’-二异氰酸酯（MDI）反应制得聚氨酯。运用差热扫描量热分析仪（DSC）、偏光显微镜（POM）对其进行了表征。结果表明,合成的聚氨酯产物在一定温度范围内均为热致性向列型液晶体,其转变温度随着间隔基柔顺性的增加呈下降趋势。     

Dilute solution properties of thermotropic polymers: aromatic polyazomethines

The dilute solution properties of some polyazomethines have been investigated. Poly(nitrilo-2-methyl-1,4-phenylene nitrilomethylidine-1,4-phenylene methylidine) (MePNPM) was studied. The measurements of intrinsic viscosities, molecular weight and depolarization ratio were made in 96% sulphuric acid and in methane sulphonic acid for these polymers. A side by side aggregation is observed with time in the second solvent. In order to obtain a well defined law of viscosity, fractionation by gel permeation chromatography was made. A small amount of aggregated particles was observed for the samples which have been submitted to a thermal treatment. Nevertheless, a well defined law of viscosity has been obtained. From the viscosity law and the variation of the apparent molecular anisotropy, the rigidity of the molecule has been evaluated; the persistence length q which characterizes this rigidity has been found to equal $\text{150}\text{A}\text{?}\text{± 25}\text{A}\text{?}$.     

Structure and mechanical properties of blends of two thermotropic copolyesters

Blends of two thermotropic copolyesters, poly(ethylene terephthalate/p‐hydroxy benzoic acid) (20/80), EB, and poly(p‐hydroxy benzoic acid/2,6‐hydroxy naphthoic acid) (73/27), BN, were obtained in the melt state by direct mixing in an injection machine throughout the full composition range. They comprised an almost pure EB phase and a BN‐rich phase that contained some reacted EB. Important synergisms with most of the values above those of the two pure blend components were found at most compositions in the modulus of elasticity and the tensile strength. The synergisms appeared to be due to the concomitant effect mainly of an orientation of the components higher in the blends than in the pure components, and to a lesser extent, of a blending‐induced specific volume decrease.     

Effect of center block structure on the physical and rheological properties of ABA block copolymers. Part II. Rheological properties

The effect of the chemical structure of the center block on the rheological properties of ABA block copolymers with polystyrene end blocks has been investigated. The chemical structure of the center blocks investigated in the present paper are polybutadiene, polyisoprene, ethylene/butene copolymer, ethylene/propylene copolymer and polydimethyl-siloxane. The chemical structure of the center block was found to have a pronounced effect on the rheological properties of the ABA block copolymer melts. The long range relaxation times of these block copolymer melts increases with increasing incompatibility between the styrene block and the center block. However, the rheological properties of the block copolymers are not influenced significantly by the glass transition or the entanglement molecular weight of the center block.     

Barrier properties of a thermotropic liquid‐crystalline polymer

A developmental thermotropic liquid‐crystalline polymer (TLCP) made by Eastman (trade name LN001) was used for barrier property studies. This material is a highly aromatic TLCP with a T_m of 332°C. A permeability study was carried out to determine the chemical resistance of the TLCP. The permeability of methanol and toluene through a membrane of the TLCP was studied using a two‐part cell and a gas chromatograph to monitor the flux. The membranes of the TLCP and LDPE (as control) were made by compression molding. Both solvents had higher permeability through LDPE than TLCP and that of toluene was higher than that of methanol. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2457–2463, 2003     

氧化石墨烯改性热致液晶聚芳酯的结构性能研究

采用原位聚合法,通过熔融共聚制备了HBA/HNA-GO液晶聚酯复合材料。研究了不同添加量的氧化石墨烯对纳米复合材料形态、结构和性能的影响。通过对复合材料的研究发现,氧化石墨烯的添加不会破坏TLCP原有的微观结构,且能够提高HBA/HNA液晶聚酯的热稳定性,为进一步研制高性能热致液晶聚芳酯提供了一个很好的方向。     

Low-temperature air oxidation of caking coals. 2. Effect on swelling and softening properties

Three highly swelling bituminous coals (< 75 um > 63 um size) were pre-oxidized to various levels of weight gain and then their plastic properties monitored during carbonization. Additions of relatively small amounts of oxygen (<1–2% by wt) cause marked changes in swelling and softening properties. In general, oxidation causes: substantial reductions in volume changes, increases in softening and dilation temperatures, and a slight reduction in resolidification temperatures. For coals which exhibit high fluidities, slight oxidation results in an increase in expansion prior to destruction of swelling properties. For a given level of weight gain, reduction in plastic behaviour of a coal becomes more severe as the temperature of pre-oxidation is increased. Weathering studies indicate that exposure of an hvA bituminous coal to moist air at ambient temperature has more effect on subsequent swelling and softening properties than exposure to dry air. Fine coal particles stored for extended periods of time in atmospheres with even slight oxygen concentrations show definite signs of weathering. The plastic properties of an oxidized coal may be partially resotred by grinding to expose new surface.     

Novel block ionomers. III. Mechanical and rheological properties

Select rheological (dynamic viscoelastic) and mechanical properties of novel block cationomers and anionomers and their blends have been investigated. The block ionomers were linear di‐ and triblocks, and symmetric three‐arm stars comprising hydrophobic polyisobutylene (PIB) blocks attached to ionized poly(methacrylic acid) (PMAA^?X⁺, where X⁺ = Na⁺, Zn²⁺) and poly[2‐(dimethylamino)ethyl methacrylate] (PDMAEMA⁺I^?) blocks. The specific structures investigated were the well‐defined diblocks PIB‐b‐PMAA^? and PIB‐b‐PDMAEMA⁺ and their blends, the triblocks PMAA^?‐b‐PIB‐b‐PMAA^? and PDMAEMA⁺‐b‐PIB‐b‐PDMAEMA⁺ and their blends, and the three‐arm star anionomer Φ(PIB‐b‐PMAA^?)₃. For comparison, the properties of the precursor PIBs and unionized blocks have also been studied. Hydrogen bonding between the carboxyl groups of the PMAA blocks in PIB‐b‐PMAA diblocks leads to inverse micelles. Neutralization of the PMAA by Zn(AcO)₂ and quaternization of the PDMAEMA segments by CH₃I in the triblock copolymers and star copolymers yielded ionic domains, which self‐assemble and produce physical networks held together by coulumbic interaction. The physical/chemical characteristics of the domains control the viscoelastic behavior and mechanical properties of these block ionomers. The mechanical properties of the various block ionomers were significantly enhanced relative to the precursors, and they were thermally stable below the transition temperature. Further, the thermomechanical properties of these novel materials were satisfactory even above 200°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1516–1525, 2003     

Analysis of fat acid oxidation products by countercurrent distribution methods. V. Low-temperature decomposition of methyl linoleate hydroperoxide

Methylcis, trans diene conjugated linoleate hydroperoxide isolated by counterenrrent distritbution from 4°C, auatoxidation of methyl linoleate was stored in atmospheres of oxygen and of nitrogen at 4°C. in darkenss. Besides manometric changes, infrared and ultraviolet characteristics, peroxide value, diene conjugation, and molecular weights were followed on samples removed at various periods of storage up to 53 days. These same analyses were obtained on fractions obtained by counter-current distributions. Evidence for the reaction that occurs on storage in oxygen may be summarized thus: 1 mole oxygen absorbed by linoleate hydroperoxides destroys 1 molecis, trans diene conjugation, 1/2 mole peroxide group, and 1 mole linoleate hydroperoxide; dimers of varying polarities, scission acids, and isolatedrans bonds are formed. Since to volume changes were observed in the nitrogen storage of methyl linoleate hydroperoxide, changes in chemical and physical characteristics can only be related to time of storage. Storage in nitrogen at 4°C, destroys diene conjugation, peroxides, and linoleate hydroperoxide and produces dimers of varying polaritics, seission neids, and isolatedrans bonds. Destruction of diene conjugation was one-fourth as rapid in a nitrogen atmosphere as in oxygen. While differences in reactions and products were observed between oxygen and nitrogen storage, particularly in rates and in countereurrent distribution patterns, the similarity of products from oxygen and nitrogen storage is remarkable. One methyl linoleate hydroperoxide is formed regardless of storage atmosphere, dimirization and attendant destruction of double bonds and peroxides proceed. This is a laboratory of the Northern Utilization Research and Development Division, Agricultural Research Service, U.S. Department of Agriculture.     

Low-temperature properties of alkyl esters of tallow and grease

The low-temperature properties of mono-alkyl esters derived from tallow and recycled greases were determined for neat esters and 20% ester blends in No. 2 low-sulfur diesel fuel. Properties studied included cloud point, pour point, cold filter plugging point, low-temperature flow test, crystallization onset temperature, and kinematic viscosity. Compositional properties of the alkyl esters determined included water, residual free fatty acids, and free glycerol content. In general, the secondary alkyl esters of tallow showed significantly improved cold-temperature properties over the normal tallow alkyl ester derivatives. The low-temperature flow test did not show a 1:1 correlation with cloud point as previously observed with methyl soyate and methyl tallowate. For the homologous series methyl to n-butyl tallowate, ethyl tallowate had the best broad-spectrum low-temperature properties, both neat and when blended in diesel fuel. For the greases studied, both the normal and branched alkyl ester derivatives showed improved properties over corresponding tallow esters, especially with neat esters.     

Analysis and modeling of the mechanical properties of novel thermotropic polymer biomaterials

A series of random aromatic-aliphatic thermotropic copolyesters comprising p-hydroxybenzoic acid (HBA), vanillic acid (VA), 4,4′-sulfonyl bis(2-methylphenol) (dBPS) and three aliphatic diacids (Spacer), developed for potential applications in orthopaedic medicine, have been characterized in the context of their structure and mechanical properties. Each of the three polymers comprised the following molar percentages of monomer units 50/25/12.5/12.5 (HBA/VA/dBPS/Spacer). Oriented fibres prepared from the materials via melt-spinning have been analyzed using X-ray diffraction to evaluate order parameters describing the degree of molecular orientation and mechanical measurements to determine their tensile properties. In addition, measurements of the bulk isotropic and shear moduli of one polymer composition have also been performed. To obtain an understanding of the material properties the aggregate model due to Ward has been applied to the orientation dependence of the measured elastic moduli and the development of mechanical anisotropy.     

Thermal and rheological properties of blends of polystyrene and thermotropic liquid crystals

The rheological and thermal properties of composites of polystyrene (PS) and two liquid crystalline low-molecular-weight additives have been studied. Both additives act as plasticizers as evidenced by decreases in the glass transition and the melt viscosity. In addition both are miscible with PS over a broad range of concentrations. Partial phase diagrams of the two systems are presented and discussed.