聚苯乙烯齐聚物的高效尺寸排除色谱的研究——Ⅱ.折光指数增量的分子量依赖性

对齐矣物中各单分散组分的折光指数增量、尺寸排除色谱响应面积与重量分数之间的相互关系作了数学分析。折光指数增量的分子量依赖性完全起源于端基效应，提出了一个对高分子的尺寸排除色谱谱图，作掀光指数增量改正的理论方程，其中包含端基与结构重复单元的分子量以及两者折光指数增量的比值，此比值可事先用Lorenz-Lorentz或Gladstone-Dale方程计算得到，理论的推断从苯乙烯齐聚物的HPSEC实验数据得到了证实。     

定量SEC法同时测定短链共聚物的组成和分子量

由于端基对整体高分子链光学性质的贡献，短链高分子的折光指数增量有明显的分子量依赖性．从整体高分子链折光指数增量依从各结构组成单元折光指数增量的重量分数加和律，指示同一高分子链改变端基后，如分别测定它们的折光指数增量。由其差值可以同时获得链干的分子量和折光指数增量，对共聚物言，从链干的折光指数增量又可进而估定共聚物的组成．这一原则特别适用于具有显著端基效应的短链高分子．本工作用定量尺寸排除色谱方法测量具有不同端基的环氧乙烷－环氧丙烷共聚物苯溶液的折光指数增量，以考验此原则，获得了满意结果．     

示差折光和光散射双检测体积排除色谱的绝对定量化

讨论了示差折光和光散射联用双检测体积排除色谱的绝对定量化的原理,强调指出了试样注入量在数据处理中的重要作用.测量注入试样的这两种检测器的检测常数,可以同时得到试样的折光指数增量和重均分子量的绝对值.这一方法除了适用于各种均聚物外,还可以应用于高分子混合物的分析.此时,如将混合物看作为单一溶质,从所得折光指数增量和重均分子量,可对它们的组成作出定量分析,还可以判断共混物两个组分之间有无分子缔合等现象的产生.这一方法应用于聚甲基丙烯酸甲酯/聚苯乙烯(PMMA/PS)混合物的溶液,指明在四氢呋喃中两者产生缔合而形成了复合物.     

聚苯乙烯齐聚物的高效尺寸排除色谱的研究——Ⅰ.链长分布

用高效尺寸排除色谱以紫外吸收光度计寿检测器,测定了一个以正丁基锂引发的聚苯乙烯齐聚物的链长分布。讨论了端基对实验的紫外吸收响应以及理论的链长分布函数中各个半分散组分重量分数的影响。引进了一个端基改正因子以获得真实的重量链长分布。实验数据可以用两个Poisson分布的叠和精确描述。与单一Poisson分布的偏离相信是由于聚合反应物混合方式的变化所致。     

端基对超支化高分子性质影响的研究

对端羟基脂肪族超支化高分子的端基进行了乙酰化和硅烷化改性，研究了不同端基对超支化高分子的玻璃化温度，折光指数增量以及特性粘度的影响。结果表明，端基的极性减小使超支化高分子的玻璃化温度降低，不同端基的超支化高分子的折光指数增量也有很大差异，而强极性的端基使超支化高分子在溶液中易产生团聚作用。由于端基在超支化高分子中所占比重较大，端基是影响超支化高分子性质的重要因素。     

聚苯乙烯齐聚物的高效尺寸排除色谱的研究——Ⅰ.链长分布

 用高效尺寸排除色谱以紫外吸收光度计寿检测器,测定了一个以正丁基锂引发的聚苯乙烯齐聚物的链长分布。讨论了端基对实验的紫外吸收响应以及理论的链长分布函数中各个半分散组分重量分数的影响。引进了一个端基改正因子以获得真实的重量链长分布。实验数据可以用两个Poisson分布的叠和精确描述。与单一Poisson分布的偏离相信是由于聚合反应物混合方式的变化所致。     

尺寸排除色谱扩展因子的保留体积依赖性

尺寸排除色谱扩展函数的方差即尺寸排除色谱柱中单分散高分子峰的扩展因子,以窄分布聚苯乙烯标样用分子量分离和扩展效应同时标准的方法作了测量。简单的理论分析导出了一个方程以表示扩展因子的保留体积依赖性,其中包括四个具有明确物理意义并可实验测量的参数。该方程与实验数据符合得相当好,并解释了扩展因子极值出现的条件。     

定量体积排除色谱法不溶性高分子的折光指数增量

用定量体积排除色谱法，从示差折光检测器的响应测定了多种水溶性高子分子在纯水溶液中的折光指数增量，与常规静态方法所得结果相同。ＳＥＣ用盐水溶液作为淋洗液时，盐水溶液类同于混合溶剂，溶质与周围溶剂的色谱分离过程与透析过程等同。     

定量体积排除色谱法测定水溶性高分子的折光指数增量

用定量体积排除色谱（ＳＥＣ）法，从示差折光检测器的响应测定了多种水溶性高分子在纯水溶液中的折光指数增量，与常规静态方法所得结果相同，ＳＥＣ用盐水溶液作为淋洗液时，盐水溶液类同于混合溶剂，溶质与周围溶剂的色谱分离过程与透析过程等同。在有柱和无柱的色谱装置条件下，从示差折光的检测响应值可分别导得恒定化学位和恒定溶剂组成下的折光指数增量νμ和νｋ。中性的聚丙烯酰胺在ＮａＣｌ溶液中νμ＞νｋ，表明ＮａＣ１分子被高分子链优先吸附。聚电解质聚苯乙烯磺酸钠的νμ＜νｋ，表明水分子被优先吸附。     

混合溶剂作淋洗剂的体积排除色谱谱图中溶剂化高分子峰和溶剂峰之间内在关系的理论分析

根据体积排除色谱(SEC)研究高分子溶质优先溶剂化的基本原理,证明在SEC色谱图中被束缚溶剂产生的面积与自由溶剂产生的面积大小相等方向相反,在研究优先溶剂化时从高分子峰入手和从自由溶剂峰入手在理论上具有等价性.分析表明,通过对溶剂化高分子峰的研究,还可以得到另一个重要物理参数——恒化学位时高分子溶液的折光指数增量.     

Characterization of implant device materials using size-exclusion chromatography with mass spectrometry and with triple detection

A more complete understanding of the raw materials used for making implant device materials becomes increasingly important in the medical device industry. Often such detailed information requires utilization of a combination of analytical techniques. In this work, we characterize a poly(dimethyl siloxane) (PDMS) material using on-line size exclusion chromatography (SEC) with electrospray ionization (ESI) and matrix assisted laser desorption ionization (MALDI) mass spectrometry (MS) techniques. Here, we obtain detailed molecular compositional information such as repeat units, end group chemistry, and identification of impurities in both the high and low mass range. SEC with light scattering, viscosity, and refractive index detection (triple detection) is used to obtain information on a small quantity of high mass impurity that was undetected by both SEC-ESI and MALDI MS techniques. SEC with triple detection measures absolute molecular weights and molecular weight distributions. We compare average molecular weight values of the implantable device polymer obtained by SEC with triple detection, SEC-ESI, and SEC-MALDI MS techniques.     

Characterization of Xylansulfate by Size Exclusion Chromatography

Abstract

A sulfated, low molecular weight beech xylan was fractionated preparatively on Sephadex G-50 into ten fractions with molecular weights from 17 000 to 1 800. The degree of sulfation, refractive index increment, molecular weight, and specific optical rotation of each fraction was determined. The fractions were then used to calibrate a Sephacryl S–200 gel column for the molecular weight distribution analysis of xylansulfate.

The molecular weights, M _W, obtained by SEC for samples of xylansulfate were in good agreement (within 4 ± 1%) to the values derived by low angle light scattering.     

Separation and enantioseparation of derivatized amino acids and biogenic amines by high-performance liquid chromatography with reversed and chiral stationary phases

A lignosulfonate sample was fractionated according to the solubility in ethanol-water. The fractions were analysed by aqueous size exclusion chromatography (SEC) combined with in-line multi-angle laser light scattering (MALLS), and by static MALLS. Satisfactory SEC results were obtained with aqueous phosphate buffer containing DMSO and SDS. The refractive index increment (dn/dc) varied from 0.186 to 0.205 ml/g, depending on Mw and the degree of sulfonation. The second viral coefficient (A2) was 7 x 10(-3) ml mol/g2. The weight-average molecular weight (Mw) of the fractions varied from 4600 up to 398 000 g/mol. and the polydispersity (Mw/Mn) varied between 1.3 and 3.5.     

Determination of pituitary and recombinant human growth hormone molecular weights by modern high-performance liquid chromatography with low angle laser light scattering detection

The determination of molecular weight for pituitary and recombinant human growth hormone (p-hGH/Crescormon and r-hGH/Protropin) has been performed. This has involved on-line coupling of size-exclusion chromatography (SEC) and gradient elution, reversed-phase high-performance liquid chromatography (RP-HPLC) with low-angle laser light scattering (LALLS) detection. A 5-microns, 300 A, Delta-bond octyl column was used. Traditional specific refractive index increment (dn/dc) and refractive index (n) measurements have been performed in order to derive absolute weight-average molecular weight (Mw) information for p-hGH and r-hGH. Known concentrations of each protein have been separated using reversed-phase gradients utilizing acetonitrile with on-line LALLS determination of excess Rayleigh scattering factors. Accurate Mw data has been obtained for both proteins under conventional RP-HPLC gradient elution conditions. SEC data of both hGHs were found to be concentration, mobile phase, and column dependent for the particular analyses. Both medium- and high-resolution SEC-LALLS studies were performed, and all of these determinations further confirmed our RP-HPLC results. On-line LALLs provides certain advantages in identifying aggregates that may be present, even in medium-resolution SEC, where incomplete resolution occurs. The on-line coupling of modern RP-HPLC for biopolymers with LALLS detection represents a major step forward in the ability of bioanalytical chemists to determine the nature (monomer versus higher-order aggregate) of such materials. Other classes of biopolymers should prove suitable for studies with the same RP-HPLC-LALLS-UV approaches.     

Solution properties of polymers of pyridinium and ammonium methacrylates

Solution properties of poly[1(2-hydroxyethyl)pyridiniumbenzene sulfonate methacrylate] and poly[1(2-hydroxyethyl)trimethylammoniumbenzene sulfonate methacrylate] were studied. Within a certain concentration range of some added low molecular weight electrolytes, phase separation occurs. The dependence of intrinsic viscosity on molecular weight was determined and the steric factor estimated for both polymers. For nonaqueous solvents, an extrapolation of the dependence of the refractive index increment of the polymer on the refractive index increment of the polymer on the refractive index of the solvent leads to an apparent refractive index of the polymer, different from the refractive index determined directly by the immersion method. Some peculiarities of light scattering in solutions with no electrolyte added are mentioned.     

Solution properties of polymers of pyridinium and ammonium methacrylates.

Solution properties of poly[1(2-hydroxyethyl)pyridiniumbenzene sulfonate methacrylate] and poly[1(2-hydroxyethyl)trimethylammoniumbenzene sulfonate methacrylate] were studied. Within a certain concentration range of some added low molecular weight electrolytes, phase separation occurs. The dependence of intrinsic viscosity on molecular weight was determined and the steric factor estimated for both polymers. For nonaqueous solvents, an extrapolation of the dependence of the refractive index increment of the polymer on the refractive index of the solvent leads to an apparent refractive index of the polymer, different from the refractive index determined directly by the immersion method. Some peculiarities of light scattering in solutions with no electrolyte added are mentioned.