Liquid (melt) heat capacities and heats of vaporization of oligomers of poly(hexamethylene sebacate)

The liquid heat capacities and heats of vaporization of three linear esters of poly(hexamethylene sebacate) with hexylcapped end groups (M(mol. wt.) = 370, 655, and 939) have been determined. The heats of vaporization of the oligomers measured at a mean temperature were corrected to 323.15 to 523.15°K by use of the experimental liquid (melt) heat capacities and the calculated gas heat capacities. The corrected heats of vaporization were fitted to the equation ΔH_v = S(T)M^α + I(T), where the temperature dependence of the slope and intercept are represented, respectively, as S(T) = ClnT + K_o and I(T) = a T + b_o, and α is an exponent. The results indicate (at corresponding molecular weights and constant temperature) that the ratio of the liquid heat capacities of the oligomer ester and the n-alkane, and similarly the ratio of the heats of vaporization, depend on the number of carboxyl groups in the oligomer ester chain.     

Blends of polycarbonate and poly(hexamethylene sebacate): I. Physical properties

The compatibility of polymer blends of high-molecular-weight polycarbonate (PC) and high-molecular-weight poly(hexamethylene sebacate) (HMS) were characterized. Samples were prepared by solution blending them In methylene chloride followed by doctor blade casting. Optical spectroscopy, tensile stress-strain, differential scanning calorimetry, and dielectric relaxation spectroscopy were employed to determine the physical and mechanical properties of the blends. These high-molecular-weight blends exhibit a limited solubility of HMS In PC as evidenced by a decrease in the glass-transition temperature of PC. In fact, HMS solubility increases PC mobility sufficiently to allow partial crystallization of PC. Over most of the composition range, HMS phase separates and crystallizes.     

煤液化油馏分蒸发焓的测定方法

蒸发焓是液相物质重要的热力学性质,结合煤液化油窄馏分的特点进行了蒸发焓测定方法的选择,在对蒸发焓的各种测定方法分析总结的基础上,指出了各种方法的使用范围、优缺点及其研究现状,归纳和探索了适合于煤液化油馏分这类复杂混合物的蒸发焓测定方法。     

Blends of polycarbonate and poly(hexamethylene sebacate): II. Effect of molecular weight on compatibility

Blends of polycarbonate (PC) and poly(hexamethylene sebacate) (HMS) with two different molecular weights were prepared and their thermal properties were studied via differential scanning calorimetry. It was found that the high molecular weight PC (HPC) and high molecular weight HMS (HHMS) were partially miscible as evidenced by the decrease in glass transition temperature of HPC in the blends. This partial miscibility is attributed to the interaction of the carbonyl dipole of the ester group and the highly polarizable aromatic carbonate structure. When the low molecular weight PC or HMS was used, the compatibility was enhanced because of the increased entropic contribution to the Gibbs free energy of mixing. In all the blends prepared, the PC crystallized as a result of the plasticizing effect of HMS. Bisphenol-A diphenyl carbonate (dimer) was synthesized and used as the dimeric model of PC. This material was found to be an excellent diluent for HPC. A single glass transition was found in the HPC/dimer system and the temperature was dependent on the composition. The Couchman's equation was found to fit very well the glass transition temperature versus composition relationship for this system. A single glass transition was also found in the HHMS/dimer system. The melting point depression analysis was performed and resulted in a very low heat of fusion for the 100% crystalline HHMS. It may suggest that the dimer and HHMS are not completely miscible in the amorphous region.     

离子液体汽化焓的测量方法

离子液体具有蒸气压低、不易挥发、导电能力强、化学性质稳定、可循环利用等特点,具有以下作用：能够替代有机溶剂作为绿色环保的新型溶剂;可以作为催化剂催化化学反应;可以作为电解质溶液参与电化学反应,制作新型电池;可以作为吸附气体的吸附剂等。过去人们认为离子液体不挥发,也不能测量它们的汽化焓,回顾了近年来离子液体的相关研究成果,发现陆续有研究者提出测量离子液体汽化焓的方法,鉴于目前缺少相关总结工作,将系统性地介绍这些方法并阐述其原理,为今后的离子液体研究提供指导。     

Pervaporation separation of styrene–ethylbenzene mixture using poly(hexamethylene sebacate)‐based polyurethane membranes

A series of poly(hexamethylene sebacate) (PHS), with molecular weight in a range of 890–2200, based polyurethanes (PU), were synthesized by solution polymerization with different kinds of isocyanate and chain extender and two kinds of polymerization methods. All the PHS‐based PU membranes exhibited selectivity towards styrene during the pervaporation of styrene–ethylbenzene mixtures, and the properties of sorption and pervaporation were related to the composition of the PU membranes. Membranes with a low hard‐segment content and by two‐stage polymerization method exhibited high permselectivity. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 753–761, 1999     

UV curing behavior of methacrylated hyperbranched poly(amine‐ester)s

Methacrylated hyperbranched poly(amine ester)s as oligomers in radiation curing resins have a lower viscosity and a higher cure speed. Their viscosity was reduced sharply when an amount of a monomer was added or the temperature was increased. Their polymerization rate and final conversion of the double bond differ with the variation of the chemical structure of the end group, molar mass, and monomer content. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 51–57, 2001     

Morphology of poly(hexamethylene oxide) fractions

The supermolecular structure of crystallised molecular weight fractions of poly(hexa-methylene oxide), covering the molecular weight range (M) 4.5. × 10³ to 8. 5 × 10⁴, was studied by polarised light microscopy and small angle light scattering. Different forms were observed as a function of molecular weight and crystallisation temperatures. Perfect spherulites are formed after rapid crystallisation, and these forms deteriorate as both the molecular weight and crystallisation temperature increase. The morphology in the isothermal crystallisation region corresponds to an intermediate state which represents a transition from spherulites to hedrites.     

Crosslinking of poly(arylene disulfide)s and poly(arylene sulfane)s derived from cyclic(arylene disulfide) oligomers

Cyclic(arylene disulfide) and polycyclic(arylene sulfide) oligomers were synthesized by catalytic oxidation of arylenedithiols or arylenetrithiols with oxygen in the presence of a copper‐amine catalyst. These cyclic(arylene sulfide) oligomers can undergo free radical ring‐opening polymerization at an elevated temperature in the melt or solution. Polycyclic(arylene sulfide) oligomers can be used to crosslink poly(arylene disulfide)s and poly(arylene sulfane)s derived from cyclic(arylene disulfide) oligomers and elemental sulfur. The crosslinking reactions were investigated by differential scanning calorimetry and by solubility of the cured products. The minimum concentrations of polycyclic(arylene sulfide) oligomers for producing a well crosslinked poly(arylene disulfide) and poly(arylene sulfane) are 7 wt % and 10 wt %, respectively. The crosslinking reactions between poly(arylene disulfide)s, poly(arylene sulfane)s, and triallyl‐1,3,5‐triazine‐2,4,6(1H,3H,5H)‐trione (TTT) were also investigated. TTT is more efficient for crosslinking than the synthesized polycyclic(arylene disulfide) oligomers. The crosslinkable poly(arylene disulfide)s and poly(arylene sulfane)s could be potentially used as high temperature coatings, sealants, adhesives, and as matrices for high performance thermoset composites. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3069–3077, 1999     

Alkylation of poly(n-vinylpyrrolidone-co-vinylamine) with esters of phosphorous acids

Alkylation of amino groups bounded to a polymer chain with esters of phosphorous acids was studied in order to obtain physiologically active polymers. Poly(N-vinyl-pyrrolidone-co-vinylamine) was chosen as a polymer-carrier. The phosphorous acid esters used were dimethyl hydrogen phosphonate, dimethyl methanephosphonate, trimethyl phosphate and bis-(2-chloroethyl)-hydrogen phosphonate. The composition and structure of the isolated final products was proved by IR- and NMR-spectroscopy and elemental analysis. It is established that alkylation takes place to various extents. The obtained alkylated phosphorous-containing polymers exhibit herbicidal activity and could find application as plant growth retardants.     

Blends of polycarbonate and poly(hexamethylene sebacate): IV. Polymer blend intrinsic viscosity behavior and its relationship to solid-state blend compatibility

The intrinsic viscosities of blends of bisphenol-A polycarbonate and poly(hexamethylene sebacate) have been measured in chloroform as a function of blend composition for a variety of molecular weight species. The compatibility of the polymer blend mixtures is characterized by the parameter δb, from the Krigbaum and Wall theory. Using T_g of the blend as a measure of bulk solid-state compatibility, a correlation is obtained with the Krigbaum and Wall parameter δb for each of the molecular weight pairs studied. Slopes of the correlation are invariant, as expected, as the chemical composition is the same for the different molecular weight pairs studied.     

聚癸二酸丙三醇酯的合成及电纺支架的制备

通过熔融共缩聚反应,将1∶1和1∶2两种摩尔比的丙三醇和癸二酸合成可生物降解的聚癸二酸丙三醇聚酯弹性体(PGS),并对其性能进行测定,1∶1组PGS与左旋聚乳酸(PLLA)共混,应用静电纺丝方法构建组织工程支架。结果表明,PGS弹性体具有优异的亲水性能和可生物降解性能,PLLA改性电纺的PGS支架符合组织工程支架材料的基本要求。     

Synthesis and characterisation of copolyesters from poly(ethylene terephthalate) and poly(hexamethylene terephthalate)

Copolyesters containing poly(ethylene terephthalate) and poly(hexamethylene terephthalate) (PHT) were prepared by a melt condensation reaction. The copolymers were characterised by infrared spectroscopy and intrinsic viscosity measurements. The density of the copolyesters decreased with increasing percentage of PHT segments in the backbone. Glass transition temperatures (T_g). melting points (T_m) and crystallisation temperatures (T_c) were determined by differential scanning calorimetry. An increase in the percentage of PHT resulted in decrease in T_g, T_m and T_c. The as-prepared copolyesters were crystalline in nature and no exotherm indicative of cold crystallisation was observed. The relative thermal stability of the polymers was evaluated by dynamic thermogravimetry in a nitrogen atmosphere. An increase in percentage of PHT resulted in a decrease in initial decomposition temperature. The rate of crystallisation of the copolymers was studied by small angle light scattering. An increase in percentage of PHT resulted in an increase in the rate of crystallisation.     

Synthesis and characterization of poly(hexamethylene terephthalate/hexamethylene oxamide) alternating copolyamide (alt-PA6T/62)

As a representative polyoxamide, poly(hexamethylene oxamide) (PA62) has good comprehensive performance. However, the high T_m (330°C) creates an obstacle for processing. To improve the processability of PA62, poly(hexamethylene terephthalate/hexamethylene oxamide) alternating copolyamide (alt-PA6T/62) was synthesized by hexamethylene diamine-terminated 6T6-diamine and dibutyl oxalate via solution/solid state polycondensation. Random copolyamide (ran-PA6T/62) was also synthesized for comparison. The structure and properties of the copolymer were analyzed by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Wide-angle X-ray diffraction (WAXD) and the saturated water absorption test. The NMR results confirm the alternating structure of alt-PA6T/62. The DSC and TGA results demonstrate that the novel alternating copolyamide alt-PA6T/62 (T_m = 321°C, T₅ = 420°C) exhibited better thermal properties than those of ran-PA6T/62 (T_m = 294°C, T₅ = 412°C). The saturated water absorption of alt-PA6T/62 was found to be 3.2 wt%. These results revealed that the novel alt-PA6T/62 had an alternating sequence distribution, showed a high melting point as well as good processability and thermal stability, and possessed low saturated water absorption and excellent dimensional stability.     

Thermal and crystallinity property studies of poly (L‐lactic acid) blended with oligomers of 3‐hydroxybutyrate or dendrimers of hydroxyalkanoic acids

Poly (L ‐lactic acid) (PLA) is a biodegradable polymer with slow crystallization rate. Oligomers of 3‐hydroxybutyrate (OHB) and dendrimers of hydroxyalkanoic acids with different molecular weights were blended with PLA in a hope to improve the crystallization ability and thermal stability of PLA, respectively. Four thermally‐degraded PHB products oligomers termed OHB‐1, OHB‐2, OHB‐3, and OHB‐4 with various number average molecular weights (M_n) of 4000, 7400, 14,000, and 83,000, respectively, were blended with PLA. The lower cold‐crystallization temperature (T_cc) and higher heat of cold crystallization (ΔH_cc) for blend of PLA/OHB‐1 suggested that thermally‐degraded OHB‐1 formed suitable crystal size during the cooling process and then acted as nucleation agents for PLA in the subsequent heating process. On the other hand, for the blending systems of PLA/dendrimers of hydroxyalkanoic acids, no obvious change on the thermal properties was observed compared with pure PLA except an improved PLA thermal stability possibly resulted from the crosslinking effects of the dendrimers © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Thermal and mechanical properties of block copolymers of poly(hexamethylene terephthalate) and poly(oxyethylene) units

Block copolyetheresters of poly(hexamethylene terephthalate) (6GT) with poly(oxyethylene) terephthalate (POET) units have been prepared by polycondensation and certain of their thermal, morphological and mechanical properties have been determined. The copolymers rich in 6GT or POET units show the crystalline characteristics of the single respective homopolymers, whereas in the middle of the composition range crystalline phases of both types coexist. Increase in the proportion of POET units causes a decrease in the melting and glass transition temperatures and in the crystallisation rates whilst concomitantly the mechanical properties change from fibrous to elastomer in type. The results are interpreted in terms of a polycrystallite model in which the compostion-dependent nature of the crystallites and tie bars determines the overall mechanical properties of the copolymers.     

蒸发焓及沸点估算的基团拓扑空间方法

基于传统基团划分方法提出了描述有机化合物分子拓扑结构的新方法,用基团模指数表征基团在分子中的位置,建立了有机化合物物性估算的基团拓扑空间方法.提出了估算正常沸点下蒸发焓ΔH_vb和沸点T_b的表达式,并分别用503种和669种有机化合物拟合出了相应的基团参数.蒸发焓ΔH_vb和沸点T_b估算的平均相对偏差分别为0.962%和1.40%.与广泛应用的其他方法进行比较,结果表明本方法具有更高的准确度和可靠性.     

Modification of poly(vinyl alcohol) fibers by hexamethylene diisocyanate

Poly(vinyl alcohol) multifilament yarn was modified by reaction with hexamethylene diisocyanate. The effects of reaction variables such as time, temperature, concentration of reagents, solvent, and atomosphere were studied. The role of solvent appears to be very important in the reaction. Dimethylformamide, on account of its swelling power, proved better than the solvents benzene, toluene, and dioxane. Physical properties of modified fibers were compared with those of the parent. Moisture regain of the modified samples decreased with increasing add-on percent. The elastic recovery was not improved, and there was little effect of the HMDI treatment on mechanical properties. The thermal stability of poly(vinyl alcohol) modified with diisocyanate with small add-on was slightly improved.     

Calorimetric,X-ray and infra-red investigations on poly(hexamethylene adipamide)

Summary In dependence on crystallization conditions three ranges with different crystal structure and heat of fusion were found by DSC,WAXS,and IR for unoriented PA 6.6 samples of densities between 1.10 and 1.17gcm^–3: Range I:_I triclinic, _c ^I =1.225 gcm^–3,H _M ^I = 235 Jg^–1. Range II:_II triclinic, _c ^II =1.165 gcm^–3, H _M ^II =185 Jg^–1. Range III:Continuous variation from _c ^I ,H _M ^I to _c ^II , H _M ^II . _a=1.095 gcm^–3 is independent of crystallization. conditions. The transition between _I and _II is probably due to changes of the chain conformation.