苯乙烯-异戊二烯星形嵌段共聚物的玻璃化转变温度及中间相松弛

用线膨胀仪和动态粘弹谱仪测定了具有不同分子量和不同支化度的规则星形苯乙烯-异戊二烯嵌段共聚物的玻璃化转变温度。T_g(s)和T_g(I)值均依赖于共聚物的形态结构、支化度和分子量。其中分散相的玻璃化转变温度T_g(s)所受影响更为显著。中间相松弛被确认。     

星形聚苯乙烯的链缠结和松弛过程

本工作用应力松弛仪测定了一组等支链长不同支化度星形聚苯乙烯的松弛谱,探讨了支化结构对松弛谱橡胶平台区粘弹行为的影响,用“管子”模型对松弛谱进行了计算机模拟,从分子运动观点上解释了星形聚合物的粘弹特性:     

星形聚苯乙烯本体粘弹性对结构的依赖性

用应力松弛法研完了一组4—12支链星形聚苯乙烯本体的粘弹性。从应力松弛主曲线测定了零切变粘度η_0、稳态柔量J_e~o和其它流变学参数。结果发现,零切变粘度和最大松弛时间τ_m强烈地依赖于聚合物的分子尺寸,并且可以用无扰特性粘度或折合分子量来描述。η_0和τ_m随支化度增大而增大。实验还直接证实了支链长度相同的星形聚合物的J_e~o与支链数目无关,但是星形聚合物的稳态柔量比具有和支链间分子量相同的线形聚合物的稳态柔量大。     

一组线型聚苯乙烯和星形支化聚苯乙烯的凝胶色谱与热场流分级方法的比较

本文应用热场流分级方法,在两种不同的场强下(△T=30℃、△T=50℃),测试了一系列窄分布聚苯乙烯标样和星形支化聚苯乙烯的淋出体积V_r和分子量M的依赖关系。星形支化物的臂数不同,但臂的分子量相同,上述样品进行了GPC测试,实验表明,由TFFF得到的支化的与线型聚苯乙烯在V_r～M关系上的差别大于GPC的结果,表明链结构对扩散系数的影响大于对分子体积的影响。     

星形SIS嵌段共聚物的动态力学性能

本文报导了用粘弹谱仪对组成相同、支链分子量相同而支化度不同的,以及支化度相同、支链分子量不同的系列星形SIS嵌段共聚物的测试结果,实验发现:支链分子量是影响各相玻璃化转变温度和动态杨氏模量E′的主要因素,支化度对各相玻璃化温度影响很小,但是对E′影响是明显的。     

用13CNMR研究星形聚苯乙烯溶液的分子运动(Ⅰ)

用VarianFT-80ANMR谱仪,对结构规则的星形聚苯乙烯在d₄-邻二氯苯和CDCl₃溶液中的¹³CNMR自旋-晶格弛豫时间、线宽和NOE进行了测定。研究了分子量、浓度、溶剂和分子结构对弛豫的影响,并用相关时间的log-X²分布函数模型解释了实验数据。     

铜铁矿CuCrO2空穴传输材料增强反式钙钛矿太阳能电池的光电压(英文)

聚3,4-亚乙基二氧噻吩/聚苯乙烯磺酸具有良好的透光性和柔韧性以及较好的热稳定性,是反式钙钛矿太阳能电池常用的空穴传输材料,但聚3,4-亚乙基二氧噻吩/聚苯乙烯磺酸的酸性和吸湿性不可避免地会影响钙钛矿太阳能电池的长期稳定性,其能级与钙钛矿材料能级的不完全匹配会造成钙钛矿太阳能电池的开路电压较低.本文应用水热法合成的p型铜铁矿CuCrO₂纳米颗粒作为反式结构[(FA PbI₃)_0.87(MAPbBr₃)_0.13]_0.92(CsPbI₃)_0.08基底钙钛矿太阳能电池的空穴传输材料.结果表明,反式结构钙钛矿太阳能电池的开路电压以聚3,4-亚乙基二氧噻吩/聚苯乙烯磺酸为空穴传输材料时的908 mV提升至以CuCrO₂为空穴传输材料时的1020 mV.紫外光电子能谱测试表明CuCrO₂与钙钛矿材料之间的能级匹配优于聚3,4-亚乙基二氧噻吩/聚苯乙烯磺酸与钙钛矿之间的能级匹配,电化...     

新型高活性催化剂乙烯气相聚合的研究(Ⅵ)——锌化合物对催化剂及产物性能的影响

研究了新型高活性乙烯气相聚合催化剂TiCl₄、Ti(OBu)₄/MgCl₂、SiO₂和ZnCl₂/醇/AlR₃体系中ZnCl₂-AlEt₃/SiO₂重量比和锌化合物含量对气相均聚合的影响,比较了2种不同催化剂Cat# A和Cat# B的聚合反应动力学及性能差异.催化剂中锌化合物作为复合载体的重要组分,可显著改善产物分子量调节效果.通过比表面积、SEM、DSC以及FTIR对催化剂和聚合物的形态、结构及性能进行了分析和表征.结果表明,均聚产物与采用MgCl₂作载体的催化剂制备的产物相比,支化度较高,结晶度较低,熔融峰较宽.发现Cat#B制得的均聚产物具有新颖的熔融双峰.     

GPC普适标定对星形支化聚苯乙烯适用性的实验验证

用GPC-连续型粘度计-小角激光光散射光度计三联用装置研究了GPC普适标定对星形支化聚苯乙烯试样的适用性问题.结果证实:支化度因子g'≥0.131时的所有星形聚苯乙烯级分,普适标定均适用;但对g'<0.131时的星形支化聚苯乙烯高支化级分,普适标定将不能适用.     

液相共存成分对氨法脱碳吸收液解吸CO2的影响研究

考察了烟气中SO₂、NO_x和CO₂与氨水的反应机理,研究了模拟解吸液解吸过程中主要液相共存成分,如(NH₄)₂SO₃、(NH₄)₂SO₄、NH₄NO₃、NaCl、NH₄Cl和(NH₄)₂CO₃对CO₂解吸的影响.研究表明,不同液相共存成分、质量分数、pH值、表面张力等对CO₂解吸产生一定影响,大部分液相共存成分的存在,会降低脱碳溶液CO₂的解吸量.质量分数低于10％的液相共存组分对脱碳吸收液CO₂解吸过程的制约作用依次为(NH₄)₂SO₃>NH₄NO₃>(NH₄)₂SO₄>NaCl>(NH₄)₂CO₃.因此,在碳捕集前应对烟气中的杂质成分进行脱除,减少其对解吸液理化特性的影响.     

The Glass Transition Temperature and Liquid1-Liquid2 Relaxation of Star-Shaped Polystyrene

The glass transition temperature T and relaxation temperature T11 of a series of regular star-shaped polystyrenes were measured by using torsional braid analyzer(TEA) and linear dilatometer.The results showed that Tg for star-shaped polymer increases with increas-ing branching degree whan the molecular weights of branch chains arethe same,but it is lower than that of linear polystyrene with the same molecular weight.The liquid 1iquid relaxation temperature T11 and the intensity of loss peak of star polystyrene also depend on branching degree.Two-Tg transitions in star polystyrenes with DVB microgel nodule were proved by comparing two types of star polystyrenes.     

Universality in eight-arm star polystyrene and methylcyclohexane mixtures near the critical point

Measurements of the coexistence curve and turbidity were made on different molecular mass samples of the branched polymer-solvent system eight-arm star polystyrene in methylcyclohexane near its critical point. We confirmed that these systems belong in the Ising universality class. The location of the critical temperature and composition as well as the correlation length, susceptibility, and coexistence curve amplitudes were found to depend on molecular mass and the degree of branching. The coexistence curve diameter had an asymmetry that followed a "complete scaling" approach. All the coexistence curve data could be scaled onto a common curve with one adjustable parameter. We found the coexistence curve amplitude to be about 12% larger for branched than linear polystyrenes of the same molecular mass in either solvent cyclohexane or methylcyclohexane. The two-scale-factor universality ratio R was found to be independent of molecular mass or degree of branching.     

Hydrodynamic and electrooptical properties of star-shaped heteroarm fullerene (C60)-containing polymers in solutions

Star-shaped heteroarm polymers with a C₆₀ branching center and polystyrene and poly(2-vinylpyridine) arms of equal molecular masses have been studied by the methods of molecular hydrodynamics (translational diffusion and viscometry) and electrooptics (the Kerr effect). The experimental hydrodynamic data are interpreted in terms of the regular star model. The molecular masses and hydrodynamic sizes of star-shaped heteroarm polymers in solutions are estimated. A comparison of these values with the corresponding parameters of linear polymer-analogs (polystyrene and poly(2-vinylpyridine)) makes it possible to characterize the branching degree of macromolecules. The study of the electrooptical properties of the heteroarm polymer in benzene demonstrates the tendency of macromolecules toward aggregation.     

Star polystyrenes by anionic star–star coupling reactions with divinylbenzene

The incremental addition of divinylbenzene was used to generate star polystyrenes in a nearly full conversion of a living polystyrenyl anion. The dramatic increase in the molecular weight of the star polystyrenes with a limited supply of the living polystyrene supported the formation of gradient‐star polystyrenes through star–star coupling. The stoichiometric analysis of the star polymers revealed that their connection polymer had a shorter length than their branch polymer. The measured solution viscosity of the gradient‐star polymers greatly deviated from a linear correlation with the molecular weight and was in parallel to a theoretical simulation based on a highly branched structure of the gradient‐star polymer. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2579–2586, 2006     

Structural features of star-shaped fullerene (C60)-containing polystyrenes: Neutron scattering experiments

Structural features of star-shaped polyprotostyrene and polydeuterostyrene containing fullerene C₆₀ as a branching center have been studied by small-angle neutron scattering in benzene solutions. The results are compared with the corresponding characteristics of linear PSs, the molecular mass of which is equal to the molecular mass of one star arm in star-shaped macromolecules. The molecular masses of star-shaped polymers are estimated, and their branching center is shown to be hexafunctional. At relatively low concentrations of starshaped polymers in solutions, one can observe excluded volume effects, which are related by the presence of regions with higher densities at the center of a macromolecule. Using the Fourier transform of the scattering cross section, three-dimensional correlation functions are obtained, and the regular structure of stars is proved. Conclusions about the local correlations of units within one star arm and averaged correlations between units of neighboring arms within a given star are derived. An analysis of three-dimensional correlations shows that the centers of mass of all star arms are directed along orthogonal axes passing through the C₆₀ branching center of a star-shaped macromolecule.     

(Star PS)-block-(Linear PI)-block-(Star PS) Triblock Copolymers – Thermoplastic Elastomers with Complex Branched Architectures

Polystyrene-block-polyisoprene-block-polystyrene triblock copolymers were synthesized with star-shaped branching in the polystyrene phase. The block copolymers were formed through sequential anionic polymerization by first synthesizing linear polystyrene, followed by star coupling using 4-(chlorodimethylsilyl)styrene, then the polymerization of isoprene, followed by difunctional coupling with dichlorodimethylsilane. The polymerization was followed by gel permeation chromatography and the resulting copolymers were characterized by ¹H NMR spectroscopy to examine the polyisoprene microstructure.     

Separation of linear and star-shaped polystyrenes by phase distribution chromatography

The phase distribution chromatographic technique was optimized and applied for the separation of linear and star-shaped polystyrene (PS). For this purpose non-crosslinked, ultra high molecular weight PS coated on different supporting materials was used. The stability of the coating under chromatographic conditions was tested by thermo gravimetric analysis and microscopic techniques. The modification of different column packing materials was tested. Separation according to branching was indicated for different molecular weights of linear and star-shaped PS. The resolution of the separation was improved by changing the density of the stationary phase and the temperature. The separation results were supported by cloud point measurements and the determination of the critical conditions for linear and star-polymers at the same molecular weight.     

Molecular and hydrodynamic characteristics of star-shaped polystyrenes with one or two fullerene (C<Subscript>60</Subscript>) molecules as a branching center

The molecular properties of regular star-shaped polystyrenes with different numbers of arms (6, 12, and 22) and different structures of the branching center (one or two covalently bonded fullerene C60 molecules) are studied by static light scattering; translational diffusion; and viscometry in toluene, THF, and chloroform. The lengths of the arms for the studied polymer stars are found to be the same. (The molecular mass of the arm is 8.1 × 10³.) The molecular mass and hydrodynamic sizes of macromolecules are estimated. It is shown that the conformational and hydrodynamic characteristics of polymer stars remain practically unchanged on passage from THF to chloroform. Compared to the linear analog, star-shaped fullerene-containing PSs are characterized by a higher density of the molecular coil. The shape of their macromolecules differs insignificantly from spherical, in consistence with theoretical predictions for polymer stars with relatively short arms.     

具有相同臂长的系列星形聚苯乙烯的合成

星形聚合物可以作为研究高聚物支化效应的模型化合物。这方面工作已有报导。但是以多官能度的氯硅烷为偶联剂合成等臂长不同支化度的系列星形聚苯乙烯模型化合物的工作尚未见报导。本文报导了多官能度偶联剂和3、4、6、8、12臂的等臂长的系列星形聚苯乙烯样品的合成。