Thermal Cycloimidization Study of Polyimides and Poly(amide imide)s Synthesized from Low-Temperature Solution Polymerization

Polyimides (PI)s and Poly(amide imide)s (PAI)s containing di/tri-structural arrangements of monomer constituents were synthesized from 1,2,4,5 benzenetetracarboxylic anhydride/3,3′,4,4′ benzophenonetetracarboxylic dianhydride, diamines and trimellitic dianhydride chloride, i.e., a mixture of dianhydrides and diamines, using low-temperature solution polymerization. The majority of the resulting polymers were readily soluble in polar aprotic solvents such as dimethylformamide, dimethylsulfoxide, dimethylacetamide, etc. Thermal cycloimidization studies by thermogravimetic analysis (TGA) and Fourier transform infrared spectroscopy (FT-IR) revealed that the rate of cycloimidization was much faster during the initial 15 min, and then occurred at much slower rates till the completion. The activation energies (Ea) for thermal cycloimidization of poly(amic acid)s was calculated from the rate of mass loss of the polymer heated at different temperatures according to the Coats and Redfern method. PI and PAIs derived from diamines containing single cyclic/benzene ring structures, such as m-phenylenediamine and 1,3-cyclohexanebis(methylamine), showed less amount of char yield than those having two benzene rings and separated by methylene, sulfone, or ether linkages. The structure of both diamine and trimellitic chloride had a profound effect on the polymer chain mobility, as indicated by the big variation in the glass transition temperatures. Thermally stable polymers were developed into membranes and tested for their mechanical strength by dynamic mechanical analysis(DMA).     

聚对苯二甲酸丁二醇酯/聚(对苯二甲酸丁二醇酯-e-己内酯)二元结晶共混体系的相容性和结晶行为

聚对苯二甲酸丁二醇酯(PBT)/聚(对苯二甲酸丁二醇酯-e-己内酯)(PBT-PCl)是一个新制备的具有分子间排斥相互作用的A/AxB1?x型两元结晶共混体系. 根据两元平均场模型,报道对苯二甲酸丁二醇酯(BT)与"-己内酯(CL)结构单元的相互作用参数为0.305. DSC研究发现,此共混物呈现了与典型的共聚物/均聚物共混物不同的结晶特征. PBT-PCL影响PBT链的活动力和晶片堆积;同时PBT-PCL的结晶受到先期结晶的PBT晶粒的阻滞. 尽管拥有相同的BT单元,共混的两组分在组成变化范围内仍没有形     

Crystallization of poly(phenylenesulfide)/amorphous polyamide blends: DSC and microscopic studies

Poly(phenylenesulfide) (PPS) is a high-performance engineering thermoplastic with exceptional thermal and chemical resistance. The results of crystallization behavior of blends of PPS with amorphous polyamide (PA) are presented. The melting and crystallization behavior was studied using differential scanning calorimetry (DSC), and the crystalline morphology was studied using optical microscopy. The results of thermal analysis indicate that the blends exhibit composition-dependent melting point depression. Optical microscopy studies showed the uniform distribution of amorphous nylon in PPS spherulites. The presence of amorphous nylon enhanced the growth rate compared to that for the neat polymer. The observed changes in the equilibrium melting point crystallization behavior, and spherulitic growth rate are explained.     

Miscibility, Crystallization, and Rheological Behavior of Solution Casting Poly(3-hydroxybutyrate)/poly(ethylene succinate) Blends Probed by Differential Scanning Calorimetry, Rheology, and Optical Microscope Techniques

应用差示扫描量热、流变及偏光显微镜等方法研究了聚3-羟基丁酸酯/聚丁二酸乙二醇酯(PHB/PES)共混体系的相容性、结晶和流变行为．相图显示该共混体系有两个玻璃化转变,但PHB的熔点随其含量的减少而降低,这个结果证明该共混体系是部分相容的,同时应用偏光显微镜观察体系结晶形态的发展证实了这个结论．依赖于结晶温度和组成,PHB和PES能同时结晶,也能分步结晶,且PHB的球晶生长速率随PES含量的增加而增大．对于部分相容的聚合物共混体系,共混组成对球晶生长速率的影响也做了详细地讨论．     

Nonisothermal Crystallization Kinetics of Ethylene Vinyl Alcohol Copolymer with Poly(oxypropylene)diamine Intercalated Montmorrilonite

Films of ethylene vinyl alcohol copolymer (EVOH) and EVOH containing poly(oxypropylene)diamine intercalated montmorrilonite were prepared by solution casting. The nanostructures and viscosity were characterized by small angle x-ray scattering (SAXS), transmission electron microscopy (TEM) and rheological testing. The nonisothermal crystallization kinetics of the samples were investigated by the Ozawa's and Mo's methods and the crystallization activation energy by Kissinger's model. The SAXS and TEM analysis demonstrated that the nanoplatelets, with an intercalated structure, were dispersed in the EVOH matrix. The rheological tests showed that the incorporation of the modified clay could increase the viscosity of the composite system. The Mo's method more successfully described the nonisothermal ctystallization behavior of neat EVOH and its nanocomposites as compared with the Ozawa's method. Adding the nanoclays had a heterogeneous nucleation effect to accelerate the crystallization of EVOH despite hindering the macromolecular chains movement.     

锌离子对聚乳酸结晶和热性能的影响

本文发现了Zn(II)离子掺杂可以加快聚乳酸的结晶过程. 测试了三种Zn(II)盐(ZnCl₂、ZnSt和ZnOAc),并与其它离子Mg(II)和Ca(II)进行对照. FT-IR以及变温拉曼光谱分析发现,经Zn(II)离子掺杂后,聚乳酸的结晶度和结晶速率均增加,差示扫描量热技术以及X射线衍射分析也进一步证实. 差示扫描量热技术测定PLA/ZnSt-0.4 wt%材料的结晶率达到22.46%,PLA/ZnOAc-0.4 wt%材料的结晶率达到24.83%.     

The Surface Wettability and Adhesion of Poly(Ester Urethane)s and Poly(Ether Urethane)s

In this study the wetting characteristics of untreated and plasma-treated polyurethane thin films were investigated. The degree of wettability was investigated by measuring the contact angle formed between a liquid drop and the solid surface. The work of adhesion, interfacial free energy, spreading coefficient, and Girifalco–Good's interaction parameter changed significantly for plasma-treated polyurethane films. Both complete and partial wetting were analyzed from the spreading coefficient of liquid drops on the solid substrate.     

Nonisothermal Crystallization Kinetics of Poly(lactic acid) Nucleated with a Multiamide Nucleating Agent

Addition of a commercial available multiamide compound (N,N′,N′′-tricyclohexyl-1,3,5- benzenetricarboxylamide, defined here as TMC) into ecofriendly poly(lactic acid) (PLA) can accelerate the crystallization rate of the material remarkably and broaden its applications. In this paper, the nonisothermal crystallization behavior of biodegradable PLA nucleated by 0.3 wt.% of TMC was investigated by differential scanning calorimetry (DSC). The modified Avrami, Tobin, Ozawa, and Mo models were applied to describe the kinetics of the crystallization process. Various parameters of nonisothermal crystallization, such as the crystallization half-time and crystallization rate constant, reflected that TMC significantly accelerated the crystallization process. The activation energy values of the neat PLA and PLA/TMC blend, determined by the Kissinger method, increased with the addition of TMC. The study should be helpful for understanding the relationship between processing and properties of this material.     

用微量热法研究Zn（Val）Ac2在混合溶液中的稀释／结晶动力学

为了在量热实验中应用Burton Cabrera Frank(BCF)位错理论,设计了Zn(Val)Ac2在水 丙酮混合溶剂 中的稀释/结晶体系.为此,通过实验,首先确定了Zn(Val)Ac2在水 丙酮中稀释/结晶生长的最佳体积比为 1∶10.设计了测定该稀释/结晶生长过程的实验方法和框图,简要推导了该结晶生长过程的动力学方程,认为当 晶体生长过程中的BCF常数a和b远小于结晶生长速率常数k2和k1时,结晶过程即符合BCF理论.用微量热 法测定了反应体系分别在298.15、301.15、304.15和307.15K时的放热量及产热速率,计算得到了各温度下的 结晶生长速率常数k2×10-3和k1×10-3分别为3.60、3.92、4.22、4.47J/s和1.54、2.14、2.53、2.97L/s而相 应的BCF常数a×10-5和b×10-7的值分别为3.09、1.16、2.06、2.99J/s和1.10、0.53、1.03、1.66g/s,远比 k2和k1小,从而证明了该结晶过程符合BCF位错理论,说明在一定条件下,BCF位错理论可应用于微量热实 验中.     

Spectroscopic and ab initio characterization of the conformational states of the bis(perfluoro‐ ethanesulfonyl)imide anion (BETI−)

Ab initio calculations were combined with infrared and Raman studies to spectroscopically distinguish the two conformers of the BETI⁻ or bis(perfluoroethanesulfonyl)imide anion, [N(SO₂C₂F₅)₂]⁻, as was previously done for [N(SO₂CF₃)₂]⁻, the TFSI⁻ anion. BETI⁻ is predicted to exist, as does TFSI⁻, in two conformational states of C₂ and C₁ symmetries, the former being more stable by about 6 kJ mol⁻¹. This conformational isomerism produces weak Raman splittings that can be resolved only at low temperatures. Thus, solutions of LiBETI with glymes cooled down to 113 K exhibit a very intense Raman doublet at ∼745–740 cm⁻¹ characteristic of a quenched conformational equilibrium between the C₂ and C₁ conformers. Annealing of the (G3)₂:LiBETI solvate, where G3 is triglyme, leads to an ordered crystalline phase with all the anions in the C₂ conformation, as in the reference salt Me₄NBETI. This conclusion cannot be extended to all the systems in which the BETI⁻ anion interacts weakly with the cation, however, since the diglyme solvate, (G2)₂:LiBETI, contains both C₁ and C₂ anion conformers (in 2:1 ratio) at low temperatures independent of the sample's thermal history. The conformational splittings are larger in infrared, as illustrated by two absorption bands at 601 and 615 cm⁻¹ associated with the C₂ and C₁ anion conformers, respectively. It is possible to follow the relative intensities of these bands in a LiBETI solution with diglyme above room temperature up to 387 K. The C₂ conformer is found to be more stable than C₁ by 4.7 ± 0.7 kJ mol⁻¹. Copyright © 2006 John Wiley & Sons, Ltd.     

Crystallization of Lightly Sulfonated Poly(ethylene terephthalate) Ionomer. I. Isothermal Crystallization from the Melt

Thermal properties and overall rates of isothermal crystallization from the melt of a commercial ionic copolyester (K‐X/SPET) based on poly(ethylene terephthalate) (PET) were analyzed in detail over a composition range from pure PET to a copolymer containing 10.1 mol% of potassium‐neutralized sulfonated PET. For measurements, differential scanning calorimetry (DSC) was used. Copolyesters with the ionic group content of 4.4 mol% or more were unable to crystallize. The isothermal melt crystallization of the copolyesters was analyzed using both the Avrami and the modified Lauritzen‐Hoffman equations. It was found that both the overall rate constant, as well as the Avrami parameter for the primary crystallization stage, varied with the sulfonated unit percentage—but surface free energy and work of folding were practically independent of them. The observed changes in the thermal properties and the kinetic parameters of crystallization were attributed to the comonomer effects and the intermolecular aggregation of the ionic groups.     

Crystallization of Poly(Ethylene Oxide) in Thin Films

Crystallization of poly(ethylene oxide) (PEO) in thin films was studied using hot-stage polarized optical microscopy. Isothermal linear crystal growth rates were measured for various film thicknesses at various degrees of undercooling. At a given crystallization temperature, the linear crystal growth rate decreased exponentially with decreasing film thickness below a film thickness of 80 nm. Films showed similar spherulitic morphology down to a film thickness of 30 nm. Control experiments on hydrophilic and hydrophobic surfaces showed that surface chemistry affects stability of the polymer films and causes a competition between crystallization and dewetting.     

聚芳醚酮分子结构、极化及分子量的谱学研究

聚芳醚酮在硫酸溶液中产生极化的主要因素包括质子化作用,硫酸的各种作用表明:聚合物分子结构中酮基含量或分子链刚性度增加时,硫酸的极化作用也增加,表现为UV谱红移,最大吸收峰显著增强及测得粘度与实际植偏差增大.由此,首次提出粘度法测定分子量时应考虑分子刚性等的影响.而用¹⁹F NMR法对合成的大量聚芳醚酮化合物分子量的定量研究表明,此法可由测得的端基氟含量,进而得到高聚物的数均分子量,无需校正.     

利用SU（2）_（q，s）量子代数的两参数变形振子实现讨论SU（2）_（q，s）相干态

利用ＳＵ（２）ｑ，ｓ量子代数的两参数变形振子实现构造出与Ｐｅｒｅｌｏｍｏｖ相干态形式不同的ＳＵ（２）ｑ，ｓ相干态．证明了ＳＵ（２）ｑ，ｓ，量子代数的表示基是正交的，并讨论了它的相干态的归一性和完备性．指出ＳＵ（２）ｑ，ｓ相干态的相干性受参数ｑ，ｓ的影响，它比单参数变形ＳＵ（２）ｑ相干态更具一般性．     

Melting and Crystallization Behaviors of Poly(Lactic Acid) Modified with Graphene Acting as a Nucleating Agent

Graphene (GN)-filled polylactic acid (PLA) nanocomposites were prepared through a solution blending method with GN weight percent ranging from 0.5 to 2?wt%. Rheological, melting and crystallization behaviors of the prepared PLA/GN nanocomposites were investigated by means of dynamic rheological measurements and differential scanning calorimetry (DSC). The shear viscosities of the PLA/GN nanocomposites decreased with increasing GN content, which was remarkably different from previous reports on the modifications using traditional nanofillers (e.g., clay, carbon nanotubes, etc.). The nonisothermal melt crystallization kinetic analysis suggested that GN served as a nucleating agent and could considerably promote the PLA’s crystallization through heterogeneous nucleation. Our findings suggested that at relatively low cooling rates (??≤?10?°C/min) even a small amount of GN promoted the nucleation and considerably increased the crystallization rate. However, the crystallinity began to decrease at higher cooling rates (e.g., ??≥?20?°C/min), especially when the GN content was high (e.g., 2?wt%), possibly owing to the GN aggregation effect considering PLA is a slowly crystallizing polymer.     

Crystallization kinetics, glass transition kinetics, and thermal stability of Se70−xGa30Inx (x=5, 10, 15, and 20) semiconducting glasses

Crystallization and glass transition kinetics of Se_70−xGa₃₀In_x (x=5, 10, 15, and 20) semiconducting chalcogenide glasses were studied under non-isothermal condition using a Differential Scanning Calorimeter (DSC). DSC thermograms of the samples were recorded at four different heating rates 5, 10, 15, and 20 K/min. The variation of the glass transition temperature (T_g) with the heating rate (β) was used to calculate the glass transition activation energy (E_t) using two different models. Meanwhile, the variation of the peak temperature of crystallization (T_p) with β was utilized to deduce the crystallization activation energy (E_c) using Kissinger, Augis-Bennet, and Takhor models. Results reveal that E_t decreases with increasing In content, while both T_g and E_c exhibit the opposite behavior, and the crystal growth occurs in one dimension. The variation of these thermal parameters with the average coordination number <Z> was also discussed, and the results were interpreted in terms of the type of bonding that In makes with Se. Assessment of thermal stability and glass forming ability (GFA) was carried out on the basis of some quantitative criteria and the results indicate that thermal stability is enhanced while the crystallization rate is reduced with the addition of In to Se-Ga glass.     

离子液体凝胶聚合物电解质PP13TFSI-LiTFSI-P(VdF-HFP)的电化学性能 (cited: 1)

采用溶液浇铸法将N-甲基-N-丙基哌啶二(三氟甲基磺)亚胺(PP13TFSI)、二(三氟甲基磺)亚胺锂与偏氟乙烯-六氟丙烯共聚物(P(VdF-HFP))混合制备离子液体凝胶聚合物电解质(ILGPEs). 通过扫描电子显微镜观察发现,这种离子液体凝胶聚合物电解质由于液体相的均匀分布而具有疏松的结构. 采用电化学阻抗、计时电流法、线性扫描伏安法测试了电解质的离子电导率、锂离子迁移数和电化学窗口. 室温下离子液体凝胶聚合物电解质的离子电导率和锂离子迁移数分别是0.79 mS/cm和0.71,电化学窗口为0～5.1 Vvs. Li⁺/Li. 电池性能测试表明,这种离子液体凝胶聚合物电解质在Li/LiFePO₄电池中是稳定的,放电容量在30、75和150mA/g倍率下分别为135、117和100 mAh/g,电池经100个循环后容量保持在100%而几乎没有衰减.     

Synthesis and Kinetic Study of Thermal Cycloimidization of Novel Poly(Amide Amic Acid) to Poly(Amide Imide) by Thermogravimetric Analysis

A new series of fluorinated poly(amide imide)s (PAIs) were prepared by polycondensation of diamine amic acid (DAA) with isophthaloyl, terephthaloyl, or trimellitic anhydride chloride in dimethylformamide, and their subsequent thermal cycloimidization. DAAs were obtained by reacting 4, 4′ (hexafluoroisopropylidene) diphthalic anhydride (6FDA) with diamines in dimethylformamide at 0–5°C. The kinetics of thermal cycloimidization of poly(amide amic acid) (PAA) to PAIs was investigated by thermogravimetric analysis under isothermal conditions at four different temperatures, i.e. 175, 200, 225, and 260°C, for 75 min. A generalized equation to calculate the theoretical amount of weight loss upon complete imidization, i.e. T_w % = 18Nw/R _Mw, was developed. In the above equation numeral 18 corresponds to the molecular weight of water, N is the number of water molecules, which are eliminated per repeat unit of PAA upon cycloimidization, w is the weight of PAA taken for TGA, and R _Mw is the molecular weight of the repeat unit of PAA. The polymers were characterized by FT-IR spectra. Complete cycloimidization process is discussed in terms of monomer structure (diamines and acid chlorides), effect of imidization temperature and time, types of linkages (meta or para) present, and influence of electron withdrawing groups, such as sulfone, in the monomer structure. It was observed that cycloimidization occurred at a faster rate at the beginning, up to about 30 min, and then proceeded at a slower rate till the end of curing. The thermal and thermooxidative stabilities of PAIs were also investigated in nitrogen and oxygen atmosphere.     

用原子轨道强耦合方法研究H(1s) + H(2s)碰撞的反应截面

采用单电子的双中心原子轨道强耦合方法,研究了1-100 碰撞体系的激发、俘获和失去电子总截面,并分别与前人的理论结果和实验结果进行了比较。研究表明,采用双中心原子轨道强耦合方法得到的 体系激发到 过程和失去电子过程的截面与实验符合很好。     

用原子轨道强耦合方法研究H(1s)+H(2s)碰撞的反应截面

采用单电子的双中心原子轨道强耦合方法,计算了H(1s)+H(2s)碰撞体系H(2s)失去电子过程的总截面,并与前人的实验结果进行了比较.研究表明,采用双中心原子轨道强耦合方法得到的H(1s)+H(2s)体系H(2s)失去电子过程的截面与实验比较符合.同时,还给出了H(1s)+H(2s)碰撞体系H(2s)电离过程、H(1s)俘获电子过程和H(2s)退激发到H(1s)过程的理论截面.