自增强高性能聚合物的成型工艺同力学性能间相关性研究——1.超高分子量聚乙烯的应力诱导结晶理论和其自增强作用

本文发展了一种高分子量聚合物熔融体的应力诱导结晶结构形态模型,它是由微晶聚集体(以下简称微区)-高分子链组网和缠结网的网络结构组成。基于上述模型,把二种网中的单个链组作为独立的统计单元和形变单元,计算了二种网中单个链组的末端距分布函数,进一步计算了二种网和总网的形变自由能。在此基础上,讨论了诱导结晶结晶机理和自增强聚合物网络自由能的依赖性,并着重地研究了超拉伸高聚物的起始熔点拉伸比间的关系。用超高分子量聚乙烯膜和超取向高密度聚乙烯纤维的起始熔点和拉伸比的实验数据进行处理,得到理论予期的近似直线关系,初步验证了聚合物网应力诱导结晶理论。     

簇离子Mo_3S_4M~（n＋）中M与Mo成键作用及电子光谱（M＝Fe、Ni，n＝4；M＝Cu，n＝5）

应用ＩＮＤＯ／Ｓ半经验量子化学方法，对簇合物离子Ｍｏ３Ｓ和Ｍｏ３Ｓ４Ｍｎ＋（Ｍ＝Ｆｅ、Ｎｉ，ｎ＝４；Ｍ＝Ｃｕ，ｎ＝５）分别进行分子轨道计算。根据计算得到的簇离子中的原子表观电荷和成键指标，说明Ｆｅ、Ｎｉ、Ｃｕ＋与Ｍｏ３Ｓ成键作用的相对强度依次是Ｆｅ－Ｍｏ＞Ｎｉ－Ｍｏ＞Ｃｕ＋－Ｍｏ。比较了用含组态作用的ＩＮＤＯ／Ｓ方法计算得到的电子跃迁能与实验得到的电子吸收光谱值，并讨论了吸收峰归属情况。对于Ｍ为Ｆｅ、Ｎｉ的簇离子Ｍｏ３Ｓ４Ｍ４＋，最低能量的电子跃迁吸收峰起源于异金属间电荷转移跃迁（ＭＭ’ＣＴ）；而Ｍｏ３Ｓ４Ｃｕ（５＋）簇离子观察到的吸收峰主要是Ｍｏ３Ｓ芯的局域内电荷转移跃迁。根据理论计算结果，由Ｃｕ＋离子到Ｍｏ３Ｓ的电荷转移跃迁谱线，大约在４６０００ｃｍ－１以上才能观察到吸收峰。从Ｍｏ３Ｓ４Ｆｅ４＋次低能量吸收峰的实验值１６６００ｃｍ－１和理论值１６５００ｃｍ－１与Ｍｏ３Ｓ的最低能量吸收峰的实验值１６６００ｃｍ－１和理论值１６９００ｃｍ－１比较，表明无论从理论上或实验上都能证实簇离子Ｍｏ３Ｓ４Ｆｅ４＋在能量为１６６００ｃｍ－１处的吸收峰是起因于Ｍｏ３Ｓ芯的局域内电荷转移跃迁。     

Synthesis and formulation of vinyl-containing polyacids for improved light-cured glass-ionomer cements

Vinyl-containing poly(acrylic acid-co-itaconic acid) copolymers were synthesized and used to formulate light-curable cements containing reactive glass fillers (Fuji II LC). The conditions for light curing were studied and optimized. Effects of molecular weight (MW), grafting ratio, comonomer, liquid composition, powder/liquid (P/L) ratio, glass powder and aging were evaluated. The results show that the vinyl-containing glass-ionomer cements (GICs) prepared in this study exhibit higher compressive strength (CS, 225.6 MPa), diametral tensile strength (DTS, 28.4 MPa) and much higher flexural strength (FS, 116.4 MPa), as compared to commercial Fuji II LC GIC (186.6 in CS, 19.1 in DTS and 57.1 in FS). The optimal light-exposure time was found to be around 10 min, and concentrations of CQ and DC were 0.5% (by weight) and 1.0%, respectively. Effects of MW, grafting ratio, P/L ratio and content of polymer in the liquid formulation were significant. The highest strengths were found for the optimal formulations where the MW was 15,000 (weight average), grafting ratio 25 mol%, P/L ratio 2.7 and liquid composition 50:20:30. During aging, the cement showed an increase of strength over the first week and then no change for a month. SEM analysis suggests that more integrated microstructures and smaller glass particles can lead to higher FS and higher polymer content in GICs leads to tough fracture surface and plastic deformation.     

Additivity Factors in the Binding of the Diethyltin(IV) Cation by Ligands Containing Amino and Carboxylic Groups at Different Ionic Strengths

Complex formation constants were determined potentiometrically (by a ISE-H⁺, glass electrode) in the systems, M²⁺ – L^z – H⁺ [M²⁺ = (C₂H₅)₂Sn²⁺, L^z = malonate, glycinate and ethylenediamine] at t = 25 ^∘C and 0.1 mol-L⁻¹≤ I/ ≤ 1 mol-L⁻¹ in NaCl_aq (0.1 mol-L⁻¹ ≤ I ≤ 0.75 mol-L⁻¹ for the ethylenediamine system). Thermodynamic values of formation constants, at infinite dilution, are [± 95% confidence interval, ^Tβ_pqr refer to the equilibrium, pM²⁺ + qL^z + rH⁺ = M_pL_qH_r^(2+z+r)]: for malonate, log₁₀ ^Tβ₁₁₀ = (5.47 ± 0.10); for glycinate, log₁₀ ^Tβ₁₁₀ = (9.54 ± 0.08), log₁₀ ^Tβ₁₁₁ = (12.97 ± 0.10); and for ethylenediamine, log₁₀ ^Tβ₁₁₀ = (10.47 ± 0.10), log₁₀ ^Tβ₁₂₀ = (16.17 ± 0.12) and log₁₀ ^Tβ₁₁₁ = (15.46 ± 0.10). The dependence on ionic strength of the formation constants was modeled by a simple Debye–Hückel type equation and by the SIT approach. By analyzing the stability of the species in the three different systems we found a simple additivity rule that can be expressed by the relationship: log₁₀ K = 6.46 n_N + 3.96 n_O − 0.60 (n_N²+ n_O²), with a mean deviation, ε(log₁₀ K) = 0.15 (K = equilibrium constant for the interaction of the organometal cation with the unprotonated or protonated ligand, n_N = number of amino groups and n_O = number of carboxylic groups of the ligand(s) involved in the formation reaction of complex species).     

Investigation of solution and solid-state properties of poly(R,R,4,4-cyclohexylidene diphenylene diphenyl-4,4-disulfonate)

Solution and solid-state properties of poly(R,R^′,4,4^′-cyclohexylidene diphenylene diphenyl-4,4^′-disulfonate) (PS-6: R=R^′=H; PS-7: R=CH₃, R^′=H; PS-8: R=R^′=Cl; PS-9: R=CH₃, R^′=Cl and PS-10: R=R^′=Br) have been determined and discussed in terms of nature of the substituents. Ultrasonic velocity (2 MHz) and acoustical parameters of PS-7 and PS-9 solutions in chloroform, 1,2-dichloroethane and tetrahydrofuran (THF) at 30, 35 and 40 °C have been evaluated to understand the effect of methyl and chlorine groups, concentration, and temperature on molecular interactions. The data are interpreted in light of solvent-polymer and polymer-polymer interactions. Predominant solvation is observed in THF system and the least in chloroform system at all three temperatures. The structural change is observed above 2%. Both the polymers possess structure-forming tendency and it is supported by positive values of S_n.The densities of PS-7 and PS-9 determined by floatation method are in excellent agreement with calculated values but those determined by specific volume method differ remarkably from calculated values due to solvation effect. PS-7 and PS-9 possess respectively tensile strength of 38.4 and 1.1 N/mm²; electric strength of 16.2 and 25.0 kV/mm and volume resistivity of 5.7×10¹⁶ and 1.0×1017Ωcm. The low tensile strength of PS-9 is due to low molecular weight, rigid and brittle nature of the polymer chains. PS-6 to PS-9 are thermally stable up to about 349-379 °C while PS-10 up to about 279 °C and involved two-step degradation. DTA thermograms indicated T_g at about 204-226 °C. High activation energy indicated rigid nature of the polymer chains and the positive magnitudes of ΔS* indicated less ordered transition state. The nature of the substituents (CH₃, Cl and Br) affected thermal, mechanical and electrical properties.     

Oscillator Strength Calculations with the Compromised Orbitals

The oscillator strength has been calculated from a common set of compromised orbitals, instead of sets of the two separately optimized non-orthogonal orbitals for the two states involved in the transition. Inaccuracies of two types arose from the calculations were assessed by investigating simple atomic and molecular systems.     

Modification of the resistance of two epoxy resins to accelerated weathering using calcium sulfate as a photostabilizer

Epoxy-timber composites have received increasing attention during the last decades because there are many advantages related to their uses as construction materials in applications such as timber bridges. However, the durability of epoxy-timber composites under outdoor conditions has become a concern for many epoxy resins. This study evaluated the chemical, thermal, and mechanical properties of two cured epoxies, the product of the diglycidyl ether of bisphenol A with 2,4-trimethyl-1,6-hexanediamine (DGEBA-TMDA) and the analogous resin prepared with the hydrogenated diglycidyl ether of bisphenol A (HDGEBA-TMDA), each mixed with 2?wt. % calcium sulfate (CS). We hypothesized that the use of CS, as an inorganic UV absorber, could decrease undesirable effects arising from exposure to UV light, moisture, and extreme temperatures.

An accelerated aging chamber simulated natural weathering for 1, 2, 3, 4, and 6?months. Chemical changes in cured epoxy systems over time in the presence and absence of CS fillers were determined using Fourier transform infrared spectroscopy (FT-IR). Thermal degradation profiles before and after exposure to accelerated weathering were followed by thermogravimetric analysis (TGA). The glass transition temperatures (T_g) before and after accelerated weathering were measured, and the effect of accelerated weathering on the surface morphology of the epoxy systems was investigated by scanning electron microscopy (SEM). In the presence of CS, after 6?months accelerated weathering the tensile strength of DGEBA-TMDA reduced by 23.8?±?2.4%, compared to 46.5?±?5.5% in its absence, while the corresponding values for HDGEBA-TMDA were 21.4?±?2.1% and 28.7?±?1.8%.     

Separation of polar and non-polar analytes using dimethyl sulfoxide-modified subcritical water

Separations using methanol–water or acetonitrile–water mixtures at different temperatures have been well investigated in reversed-phase liquid chromatography. However, reversed-phase separation with dimethyl sulfoxide (DMSO)–water mixtures is much less studied. In this work, separations of polyhydroxybenzenes, phenol derivatives, benzene, toluene, ethylbenzene, and xylenes (BTEX), and polycyclic aromatic hydrocarbons (PAHs) with DMSO-modified subcritical water were performed at several temperatures to evaluate the effect of temperature on the elution strength of DMSO–water mixtures. The column efficiency obtained by using DMSO-modified subcritical water was also studied. Finally, the resolution of ethylbenzene and p-xylene was investigated.     

Dissociation quotients of succinic acid in aqueous sodium chloride media to 225°C

The first and second molal dissociation quotients of succinic acid were measured potentiometrically with a hydrogen-electrode, concentration cell. These measurements were carried out from 0 to 225°C over 25° intervals at five ionic strengths ranging from 0.1 to 5.0 molal (NaCl). The dissociation quotients from this and two other studies were combined and treated with empirical equations to yield the following thermodynamic quantities for the first acid dissociation equilibrium at 25°C: log K_1a=–4.210±0.003; H _1a ⁰ =2.9±0.2 kJ-mol^–1; S _1a ⁰ =–71±1 J-mol^–1-K^–1; and C _p1a ⁰ =–98±3 J-mol^–1-K^–1; and for the second acid dissociation equilibrium at 25°C: log K_2a=–5.638±0.001; H _2a ⁰ = –0.5±0.1 kJ-mol^–1; S _2a ⁰ =–109.7±0.4 J-mol^–1-K^–1; and C _p2a ⁰ = –215±8 J-mol^–1-K^–1.     

甲基丙烯酸N,N-二甲氨基乙酯与丙烯酰β-环糊精共聚水凝胶的合成及其性能研究

用不同的方法合成了两种结构不同的丙烯酰 β 环糊精酯 (β CD 3 A和 β CD 6 A) ,以此为单体与甲基丙烯酸N ,N 二甲氨基乙酯 (DMAEMA)通过氧化还原自由基引发聚合 ,合成出两类含 β 环糊精结构单元的新型水凝胶 .用核磁共振 ,红外光谱及元素分析对两种单体及共聚物的结构和组成进行了表征 .溶胀实验结果表明 ,两类水凝胶均具有较好的pH、温度及离子强度敏感性 ,且因其交联网络结构不同 ,其溶胀性能有所差异