4—臂和7—臂星形支化聚苯乙烯的合成及其溶液性质

本文合成了不同分子量的5个4-臀星形聚苯乙烯和4个7-臂星形聚苯乙烯试样,用GPC粘度计联用装置对之进行了测定。提出了一种用良溶剂中的粘度数据,通过线性外推方法,得到θ条件下的g'_θ因子(=[η]_(b,θ)/[η]_(l,θ))的理论处理方法。对良溶剂中的g'因子(=[η]_b/[η]_l)和g'_θ因子之间的差异以及g'_θ因子与g_θ因子(=S_(b,θ)~z/S_(l,θ)~z)间关系式g'_θ=g'_θ~∈中的∈选值问题进行了详细的讨论,结果证实,∈不仅与支化类型有关,而且与支化程度有关,对4-臂星形聚苯乙烯,∈=1.487,而对7-臂星形聚苯乙烯,∈=1.14。4-臂星形聚苯乙烯的g'和g'_θ因子差别较小;对7-臂星形聚苯乙烯,两者间差别较大,不可忽视。     

星形支化聚苯乙烯模型化合物的合成及表征

本文用阴离子聚合方法,首先合成了线形‘活’的聚苯乙烯大分子阴离子,然后用二乙烯基苯为偶联成核剂,制备了十三个4-80臂较窄分子量分布的等臂长规则星形支化聚苯乙烯的模型化合物,并用GPC—粘度计联用装置对之进行了表征。     

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.     

13－臂星形文化聚苯乙烯的某些溶液性质

本文对合成的四个不同分子量的１３－臂星形聚苯乙烯试样，用ＧＰＣ－粘度计联用装置对之进行了测定．用良溶剂中的粘度数据，通过一定的线性外推，得到了它们在θ条件下的ｇθ’因子对良溶剂中的ｇ’因子和ｇθ’因子之间存在的差异以及ｇθ’因子与ｇθ因子间关系式中ε的选值问题进行了详细的实验验证和讨论，并与前文［７］所得４－臂和７－臂星形支化聚苯乙烯试样的结果进行了比较．     

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。     

用凝胶色谱与毛细管粘度计联用法研究顺丁胶的长链支化

本文讨论了用GPC与自动粘度计联用技术测定高聚物长链支化度的方法,将得到的实测关系[η](V)转化成校准关系[η](V_R)后,利用在同一淋出体积流出支化物和线型分子的([η]·M)乘积相等这一普遍原理,计算出各级分的支化因子g_i、总平均支化因子以及产生支化的临界分子量M~*,并讨论了检测器与粘度计连结管死体积△V及虹吸管残留液对支化参数计算值的影响。     

星形聚苯乙烯的玻璃化转变温度和液1-液2松弛

用扭辫仪(TBA)和线膨胀仪测定了一组规则的星形聚苯乙烯的玻璃化转变温度T_g和T_ll松弛。两种实验方法的结果表明:支链分子量相同的星形结构聚合物的T_g随着支化度增加而升高,但也发现星形聚苯乙烯的T_g却低于具有相同分子量的线形聚苯乙烯的T_g·液₁-液₂松弛温度T_ll和损耗峰的强度也依赖其支化度。与以二乙烯基苯为凝胶核的星形结构相比较,证实了后者的双T_g转变。     

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:     

聚乙酸乙烯酯的溶液性质及长链支化度

用粘度法,GPC和LALLS测定了线型及不同转化率的PVAc分级级份的粘度与分子量。提出了以线型和支化聚合物的K,α计算临界分子量的方法。讨论了表征PVAc长链支化的各种参数与分子量和转化率之间的关系以及不同条件下迭代法计算的支化频率λ的差异。实验结果表明,特性粘数和数均分子量乘积所表示的流体力学体积更适合GPC的普适标定概念。     

HBPS-PEO多臂星形聚合物电解质的合成及离子导电性的研究

通过叠氮化超支化聚苯乙烯(HBPS-N3)与端炔基聚乙二醇单甲醚(ay-PEO)的点击反应,合成了以超支化聚苯乙烯(HBPS)为核、不同分子量的聚氧化乙烯(PEO)为臂的多臂星形聚合物(HBPS-PEO),并利用ATR-FTIR,1H-NMR,GPC对合成的星形聚合物的结构进行了表征.将该种星形聚合物与双三氟甲基磺酰亚胺锂(LiTFSI)进行复合,制备了星形聚合物为基体的聚合物电解质,通过交流阻抗技术和DSC对该聚合物电解质的离子导电性能及热性能进行了研究.结果表明,星形结构可以在一定程度上抑制结晶的形成,这种新型的星形聚合物电解质的室温电导率明显高于相应的线形聚合物电解质,当n(EO)/n(Li)=40,PEO臂的分子量为1000时,该星形聚合物电解质的离子电导率最高,30℃时为6.7×10-5Scm-1,40℃时可以达到1.2×10-4Scm-1;TGA结果表明,制备的星形聚合物的初始分解温度(Tonset)都高于360℃,具有良好的热稳定性.     

COMPARISON OF GPC AND THERMAL FIELDFLOW FRACTIONATION METHODS FOR LINEAR AND STAR BRANCHED POLYSTYRENE SAMPLES

The Thermal Field-Flow Fractionation (TFFF) method was used to determine the elution volumeof a series of star branched polystyrene having different number of arms but the same arm molecularweigh and polystyrene standards with narrow distribution whose molecular weight ranged from5.0×10~4 to 8.6×10~5. Results were obtained by measuring at two temperature difference (△T=30℃and △T=50℃in THF. The same star branched samples were measured by means of GPC method.Comparison of Vr-Mrelationships obtained from TFFF and GPC showed that the displacement of V_r-M curves for star and linear polystyrene is larger than that in GPC. This difference is caused by theentirely different mechanism of separation for these two methods. As the controlling factor is hy-drodynamic volume of the polymer chain in solution for GPC, it is the diffusion coefficient of polymermolecules for TFFF. The experimental results indicate that the influence of variance of chain struc-ture on diffusion coefficient is stronger than that on the hydrodynamic volume and that TFFF tech-nique may be used as a method for characterizing branching of polymer molecules. For this pur-pose a proper theoretical model and more accurate experiments are needed.     

Gel permeation chromatography of polyethylene: Effect of long-chain branching

The effect of long-chain branching on the size of low-density polyethylene molecules in solution is demonstrated through solution viscosity and molecular weight measurements on fractionated samples. These well-characterized fractions are analyzed by gel permeation chromatography (GPC), and it is shown that the separation of the polymer molecules by this technique is sensitive to the presence of long-chain branching. By using fractions of branched polyethylene possessing differing degrees of branching, one observes that a single curve is adequate in relating elution volume to molecular weight. This calibration curve is applied in the GPC analysis of a variety of commercial low-density polyethylene resins and it is shown, by comparison with independent osmometric and gradient elution chromatographic data, that realistic values for molecular weight and molecular weight distribution are obtained. The replacement of molecular weight M by the parameter [η]M as a function of elution volume, leads to a single relationship for both linear and branched polyethylenes. This indicates that GPC separation takes place according to the hydrodynamic volumes of the polymer molecules. The comparison of data for polyethylene and polystyrene fractions suggests that this volume dependence of the separation will be observed for other polymer–solvent systems.     

Simulation of GPC‐Distribution Coefficients of Linear and Star‐Shaped Molecules in Spherical Pores

Simulations of the distribution coefficients of linear and star‐shaped polymers in spherical pores were performed in order to predict the GPC‐elution behavior of star‐shaped polymers relative to that of linear polymers. Self avoiding walks were generated on a tetrahedral lattice to simulate good solvent conditions. It was found that neither the molecular weight nor the mean squared radius of gyration of the polymer serves as a universal factor to determine the distribution coefficient. However, the calculated distribution coefficients correlate well with the calculated hydrodynamic radii even for different topologies. For molecules at same elution volume the ratios of molecular weights of star and linear polymer agree well with exact calculations for Gaussian chains. These ratios are nearly independent of pore geometry (spherical or cylindrical).     

DYNAMIC LIGHT SCATTERING STUDY ON TRANSLATION DIFFUSION OF 8-ARM STAR POLYSTYRENE IN GOOD AND THETA SOLVENTS

The technique of dynamic light scattering has been used to investigate the translation diffusion behavior of 8-arm star polystyrene (SPS)in a good solvent, tetrahydrofuran (THF) or benzene (BZ) and a theta solvent, cyclohexane (CH), by homodyne photon correlation spectroscopy .The intensityintensity autocorrelation function was analyzed by the method of cumulant. The translation diffusion coefficients have been obtained as a function of temperature and concentration. Under theta condition ,the non-concentration dependence of diffusion coefficient showed the unperturbed Gaussian state o the SPS molecular chain. The different hydrodynamic radii estimated from Stokes- Einstein equation reflected the stretch extent of the arm chain for regular star polymer. The data of diffusion activation energy of SPS in THF, BZ and CH were also obtained respectively.     

Universal calibration in GPC

The M[η]-elution volume calibration curve for gel-permeation chromatography (GPC) is based on the implicit assumption that the hydrodynamic volume of a solvated polymer species in the GPC columns is that which pertains at infinite dilution. This is not true of highly solvated high molecular weight fractions and results in apparent failure of this calibration in some instances. A model is presented to estimate hydrodynamic volumes of polymers at finite concentrations. The parameters required are polymer concentration, molecular weight, amorphous density, and the Mark-Houwink constants for the particular polymer–solvent combination. The calculated log (hydrodynamic volume)–elution volume relation provides a universal GPC calibration. The model accounts for the occasional shortcomings of the infinite dilution calibration and is essentially equivalent to it in noncritical cases. The use of the proposed calibration method is illustrated.     

Determination of polymer branching with gel-permeation chromatography. I. Theory

The effect of long-and short-chain branching in polymer molecules on gel-permeation chromatographic (GPC) separation is discussed. The calculation of calibration curves for branched polymers is developed from the universal calibration technique based on the hydrodynamic volume concept and previously established relationships for the effect of branching on molecular dimensions. Typical calibration curves are shown for different branching models and degrees of branching. As branching increases, the curves are shown to converge. Methods of characterizing branching and molecular weight distributions of franctions and whole polymers from GPC and intrinsic viscosity data are presented.     

四臂星形聚苯乙烯在良溶剂和0溶剂中分子扩散的光子相关光谱的研究

用光子相关光谱研究了四臂星形聚苯乙烯在良溶剂(四氢呋喃THF)和θ溶剂(环己烷CH)中扩散系数与溶剂的浓度和温度的依赖关系。用累积量方法分析光子相关数据给出了多分散样品的Z均扩散系数。在θ溶剂中,高于或低于θ温度时,聚合物在溶液中的分子扩散分别表现出具有在良溶剂与不良溶剂中的行为。外推浓度至零,得到无限稀时不同温度的分子扩散系数,借助Stokes-Einstein方程,给出了聚合物的流体力学半径。通过InD对I/T作图,得到了星形聚苯乙烯在THF与CH中的扩散活化能。     

凝胶色谱用微粒硅胶NWG

研制成功 NWG硅胶,粒度分别为 3—5μ和 5—10μ。经测试渗透极限为聚苯乙烯分子量4×10~4—7×10~6,分离容量V_i/V_0不低于0.6,柱效在 1×10~4塔板/米以上。可在10分钟内作分子量100—3×10~6样品的全分离。硅胶在不同流速下的行为符合物料平衡方程理论的预见。     

Polymer-Gel Interactions in GPC with Organic Eluents

Abstract

The displacement of hydrodynamic volume universal calibration curves to high retention volumes for some polymer-solvent systems is explained in terms of a network-limited separation consisting of a steric exclusion mechanism and a second mechanism resulting from polymer-gel interactions. This treatment is consistent with a thermodynamic interpretation of GPC separations in which the distribution coefficient (≥ 1.0) for polymer-gel interactions is determined by an enthalpy change for polymer partition or polymer adsorption in the porous packing. Examples of the application of the network-limited treatment to experimental data obtained with crosslinked polystyrene gels and inorganic packings are presented. Network-limited separations in which the distribution coefficient for polymergel interactions is less than unity correspond to partial exclusion by polymer incompatibility with the gel. Experimental data for the early elution of poly(vinyl acetate) are consistent with an incompatibility mechanism, giving a dependence of the distribution coefficient for polymer-gel interactions on the molecular weight of poly(vinyl acetate).