Preparation and characterization of star ABC triblock copolymer of ethylene oxide,styrene and methyl methacrylate

A universally significant method,which combines the anionic polymerization with photoinduced charge transfer polymerization,for preparation of soluble star ABC triblock copolymer of ethylene oxide,styrene and methyl methacrylate,was described.The poly(ethylene oxide) (PEO) block was formed by initiation of phenoxy an-ions using p-aminophenol protected by Schiff's base as the parent compound Then the charge transfer system composed of PEO chains with deprotected-amino end groups and benzophenone initiated the polymerization of styrene and methyl metnacrylate sequentially under UV irradiation.The formed star triblock copolymer of styrene,ethylene oxide and methyl methacrylate could be purified by thin-layer chromatography (TLC) and characterized by IR,1H NMR,GPC (gel permeation chromatogrphy) and PGC (pyrolysis gas chromatography).     

一种两亲性嵌段共聚物胶束的制备及其对叶酸的负载和控制释放

采用可逆加成-断裂链转移(RAFT)聚合合成了以丙烯酸异丁酯(IBA)、甲基丙烯酸2-二甲氨乙酯(DMAEMA)无规共聚嵌段与聚丙烯酸-2-羟丙酯(PHPA)组成的两亲性两嵌段共聚物(P( IBA-co-DMAEMA)-b-PHPA),并用凝胶渗透色谱(GPC)、核磁共振波谱(1H-NMR)及红外光谱(FTIR)对其进...     

Separation of naphthoquinones and lipophilic vitamins by gel and thin-layer chromatography.

A separation of naphthoquinones on silica gel and on silica gel impregnated with polyethylene glycol 200 by thin-layer chromatography was compared with gel permeation chromatography (GPC) on styrene-divinylbenzene copolymer S-832-gel using tetrahydrofuran as mobile phase. Factors affecting the separations attainable are discussed, and it is concluded that GPC is a suitable method for the determination of K vitamins in natural materials.     

凝胶色谱法测定聚丙烯腈相对分子质量的验证

采用窄分布的聚苯乙烯和聚甲基丙烯酸甲酯分别对凝胶色谱柱进行标定,测定了聚丙烯腈的相对分子质量。聚苯乙烯、聚甲基丙烯酸甲酯标定法得到聚丙烯腈的重均相对分子质量分别为5.008×10^5,2.929×10^5,两种标定方法所得数据相差较大。采用光散射法验证窄分布标准样品标定测试数据的准确度,得到聚丙烯腈的重均相对分子质量为1.485×10^5,与窄分布聚合物标定凝胶色谱法得到的数据相差很大,表明凝胶色谱标定法测定聚丙烯腈的相对分子质量是一种相对方法,其量值无法实现准确溯源。     

Reactions of polystyryl anions with carbon dioxide and oxygen. Analysis of products by silica gel chromatography

Polystyryllithium was prepared by anionic polymerization. This “living polymer” and the polystyrylmagnesium bromide derived from it were treated with carbon dioxide (solid or gas). The highest yields of carboxylic acid were obtained when solid carbon dioxide was used with polystyryllithium or by treatment of polystyrylmagnesium bromide with gaseous carbon dioxide. The products from the reaction of polystyryllithium with oxygen were polymeric ketone X, the alcohols IXa and IXb, and coupling products (e. g., XI). The various functionalized and unfunctionalized polystyrene products were isolated by chromatography on silica gel and were characterized by gel permeation chromatography (GPC), thin layer chromatography (TLC), and high-performance liquid chromatography (HPLC) in combination with chemical transformations.     

STUDIES ON POLY(ETHYLENE TEREPHTHA LATE)-POLY(TETRAMETHYLENE ETHER) MULTIBLOCK COPOLYMER.Ⅰ.COMPOSITIONAL HOMOGENEITY

The compositional homogeneity of a poly (ethylene terephthalate)-poly (tetramethylene ether) multiblock copolymer sample with low content of hard segment was examined by GPC, TLC, and solubility method. The copolymer sample was found to have a uniform composition as a function of elution volume over the major portion of sample from GPC method. However within one elution fraction, the copolymer chains, although having the same hydrodynamic volume, may have some difference in composition. Two fractions with different composition were obtained by precipitation in ethanol. Some low molar mass copolymers were also separated by a TLC technique from the copolymer sample.     

Determination of molecular-weight distribution and average molecular weights of block copolymers by gel-permeation chromatography

The problem of preparation of a block copolymer of precise molecular-weight distribution (MWD) and with heterogeneous composition on the basis of gel-permeation chromatography (GPC) data has been investigated. It has been shown that in MWD calculations the distribution f(p) of the composition p in individual GPC fractions should be taken into account. The type of the f(p) functions can be simultaneously established by an independent method, such as use of adsorption-column or thin-layer chromatography sensitive to the composition of the copolymer. It has also been shown that the actual f(p) may be replaced by a corresponding piecewise distribution, of simple form, without decrease in the precision of calculation of the MWD and average molecular weights of most known block copolymers.     

Morphology and grafting reactions in core/shell latexes

The particle morphology and percent grafting were investigated as a function of the crosslink density of the seed latex in two systems of core/shell latexes of polybutadiene/polymethyl methacrylate (PB/PMMA) and styrene–butadiene rubber/polymethyl methacrylate (SBR/PMMA) prepared by seeded emulsion polymerization at 50°C. The thin layer chromatography/flame ionization detection (TLC/FID) technique was used to characterize the grafting efficiency of the core/shell latexes. The percent grafting of the shell polymer was found to decrease with increasing the crosslink density of the core material. The particle morphology and precent grafting were also investigated as a function of composition and structure of the core material in four core/shell latex systems: polybutadiene/styrene–acrylonitrile copolymer (PB/SAN), (styrene-butadiene) random copolymer/styrene acrylonitrile copolymer (S:B/SAN), polystyrene : polybutadiene/styrene-acrylonitrile copolymer (PS:PB/SAN) and Kraton/styrene-acrylonitrile copolymer (Kraton/SAN), which were prepared by direct emulsification for the seed followed by emulsion polymerization at 70°C for the shell polymer. Grafting and crosslinking of the core material were found to be competitive reactions depending on the microstructure of the seed latex.     

Simple solution for a complex problem: proanthocyanidins, galloyl glucoses and ellagitannins fit on a single calibration curve in high performance-gel permeation chromatography

This study was undertaken to explore gel permeation chromatography (GPC) for estimating molecular weights of proanthocyanidin fractions isolated from sainfoin (Onobrychis viciifolia). The results were compared with data obtained by thiolytic degradation of the same fractions. Polystyrene, polyethylene glycol and polymethyl methacrylate standards were not suitable for estimating the molecular weights of underivatized proanthocyanidins. Therefore, a novel HPLC-GPC method was developed based on two serially connected PolarGel-L columns using DMF that contained 5% water, 1% acetic acid and 0.15 M LiBr at 0.7 ml/min and 50 °C. This yielded a single calibration curve for galloyl glucoses (trigalloyl glucose, pentagalloyl glucose), ellagitannins (pedunculagin, vescalagin, punicalagin, oenothein B, gemin A), proanthocyanidins (procyanidin B2, cinnamtannin B1), and several other polyphenols (catechin, epicatechin gallate, epicallocatechin gallate, amentoflavone). These GPC predicted molecular weights represented a considerable advance over previously reported HPLC-GPC methods for underivatized proanthocyanidins.     

Two-dimensional liquid chromatography of PDMS-PS block copolymers

In this study, liquid chromatography at critical conditions of polystyrene (PS) and polydimethylsiloxane (PDMS) is used as the first dimension for the two-dimensional analysis of polydimethylsiloxane-block-polystyrene copolymers. Comprehensive two-dimensional liquid chromatography with size exclusion chromatography as the second dimension reveals information about the molar mass distributions of all separated fractions from the first dimension. Furthermore, fractions eluting at the critical conditions were collected and subjected to analysis in the second dimension at the critical adsorption point of the other block. These fractions were analyzed by Fourier transform infrared spectroscopy to determine their chemical compositions. The combination of the above approaches and the calibration of the evaporative light scattering detector for the first-dimension analysis yield deep insights into the molecular heterogeneity of the block copolymer samples. The composition of the samples and the chemical composition of the real block copolymer are also calculated by combining the results obtained at both critical conditions.     

Separation and characterization of a viscosity index improver copolymer by high-performance liquid chromatography

Summary Characterization of a poly(styrene-alkyl methacrylate) viscosity index improver according to its chemical composition distribution and molecular weight distribution was carried out by liquid adsorption chromatography, size exclusion chromatography and infrared and ultraviolet spectrophotometry. The industrial polymer was fractionated by liquid chromatography using silica gel as adsorbent and a mixture of 1,2-dichloroethane and methanol as mobile phase. Each fraction was analyzed by size exclusion chromatography and infrared and ultraviolet spectroscopy. The number average molecular weight ranged from 10000 to 36000 and the weight average molecular weight from 19000 to 264000. The styrene content of the various fractions analysed was between 29.5% and 72.2%.     

酶促聚合和原子转移自由基聚合“一锅法”合成嵌段聚合物及其性能表征

用酶促聚合和原子转移自由基聚合相结合的"一锅法"合成了聚甲基丙烯酸正丁酯嵌段聚10-羟基癸酸[PBMA-b-P(10-HD)],通过核磁共振(1H NMR)、傅里叶红外光谱(FTIR)和凝胶渗透色谱(GPC)对其结构以及分子量与其分子量分布进行了表征,并通过动态光散射仪(DLS)和原子力显微镜(AFM)对聚合物在水溶液中的性质进行了研究.所得嵌段聚合物纳米粒子呈球形结构,平均直径为135 nm左右.     

Application of multifunctional initiation system in block copolymerization of ethylene oxide and methyl methacrylate

A block copolymer composed of hydrophilic and crystallinic polyethylene oxide and hydrophobic and non-crystallinic polymethyl methacrylate (PMMA) was prepared by sequential initiation of alkoxy-anion and charge transfer complex using p-aminophenol as parent compound. The structure of copolymer was characterized by GPC, IR, 1H NMR and DSC in detail. The propagation of PMMA chain is dependent on the molecular weight and concentration of the first block PEO and also the polarity of solvents. The reasons are discussed.     

Investigation of copolymers of styrene and ethyl methacrylate by size exclusion chromatography and gradient HPLC

Summary Copolymers of styrene and ethyl methacrylate have been separated according to composition by gradient HPLC on silica columns or CN bonded phase columns. This mode of separation according to composition was applied to fractions obtained by size exclusion chromatography (SEC). From viscosity and molecular mass data of copolymers with a styrene content ranging from 7.5 to 95.3 mass-% it can be concluded that SEC separates mainly by molecular mass even in this copolymer system. Thus, chromatographic cross-fractionation is possible by prefractionation by SEC and subsequent separation according to composition by gradient HPLC.

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Untersuchung von Copolymeren von Styrol und Ethylmethacrylat durch Ausschluß-Chromatographie und Gradienten-HPLC

     

Densimeter detector in gel permeation chromatography of copolymers

A commercially available densimeter with a vibrating stainless steel tube was used as a detector in the GPC analysis of styrene/methyl methacrylate copolymers under normal GPC operational conditions. The densimeter was thermostated to ±0.001°C and sample injection concentrations were 4.0 mg/mL. The copolymer samples were polydisperse in molecular weight but uniform in composition. A refractive index detector and the densimeter detector produced comparable estimates of the parameters of the molecular weight distributions. The densimeter is less sensitive to the effects of variations in copolymer composition than differential refractive index or ultraviolet detectors. The only serious drawback to the densimeter is a relative lack of sensitivity. Variations in composition of styrene/methyl methacrylate copolymers over a fairly wide range have no signficant effect on the relation between gel permeation chromatographic elution volume and copolymer molecular weight. In general, however, conventional means of summarizing these data are not applicable to compositionally heterogeneous mixtures. Instrumental and data-handling solutions to this problem are discussed.     

Composition analysis of poly(ethylene glycol)-poly(L-lactide) diblock copolymer studied by two-dimensional column chromatography

We used two-dimensional column chromatography to analyze the composition of a sample of presumably a diblock copolymer of poly(ethylene glycol) (PEG) and poly(L-lactide) synthesized from monomethoxy-terminated PEG. The first dimension of the separation is phase fluctuation chromatography to prepare fractions that contain various components of the copolymer in different ratios. The second dimension is size-exclusion chromatography, NMR, and HPLC at the critical condition of PEG. The PEG initiator has small amounts of diol-terminated dimeric components. We found that the copolymer sample contains a triblock copolymer and low-molecular-mass components in addition to the main part of the diblock copolymer. The SEC chromatograms show that the main part consists of two components with distinct peak lengths for the PLLA block. The low-molecular-mass components have a broad distribution in chemical composition. Phase fluctuation chromatography enriched the triblock copolymer and the diblock copolymer with the longer PLLA block in early fractions when the column was packed with carboxymethyl-modified porous silica. When the porous medium was PLLA-grafted silica, size exclusion dominated, but the low-molecular-mass components were separated according to their chemical composition.     

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.     

Synthesis of pH-responsive amphiphilic diblock copolymers containing polyisobutylene via oxyanion-initiated polymerization and their multiple self-assembly morphologies

 Two pH-responsive amphiphilic diblock copolymers, namely polyisobutylene-block-poly[2-(N,N-dimethylamino)ethyl methacrylate] (PIB-b-PDMAEMA) and polyisobutylene-block-poly(metharylic acid) (PIB-b-PMAA), were synthesized via oxyanion-initiated polymerization, and their multiple self-assembly behaviors have been studied. An exo-olefin-terminated highly reactive polyisobutylene (HRPIB) was first changed to hydroxyl-terminated PIB (PIB-OH) via hydroboration-oxidation of C＝C double bond in the chain end, and then reacted with KH to yield a potassium alcoholate of PIB (PIB-O^-K⁺). PIB-O^-K⁺ was immediately used as a macroinitiator to polymerize DMAEMA monomer, resulting in a cationic diblock copolymer PIB-b-PDMAEMA. With the similar synthesis procedure, the anionic diblock copolymer PIB-b-PMAA could be prepared via a combination of oxyanion-initiated polymerization of tert-butyl methacrylate (tBMA) and subsequent hydrolysis of tert-butyl ester groups in PtBMA block. The functional PIB and block copolymers have been fully characterized by ¹H-NMR, FT-IR spectroscopy, and gel permeation chromatography (GPC). These samples allowed us to systematically investigate the effects of block composition on the pH responsivity and various self-assembled morphologies of the copolymers in THF/water mixed solvent. Transmission electron microscopy (TEM) images revealed that these diblock copolymers containing small amount of original PIB without exo-olefin-terminated group are able to self-assemble into micelles, vesicles with different particle sizes and cylindrical aggregates, depending on various factors including block copolymer composition, solvent polarity and pH value.     

Separation of styrene-methacrylate copolymers by composition using normal and reversed-phase high-performance liquid chromatography

The separation of styrene-methacrylate copolymers by chemical composition was studied using high-performance liquid chromatography (HPLC). With the combination of acrylonitrile (polar) gel and nonpolar eluent or of styrene (nonpolar) gel and polar eluent, poly(styrene-co-methylmethacrylate) was separated by the adsorption mechanism. The former is designated as normal and the latter as reversed phase. With other combinations, the copolymer was separated mainly by fractional dissolution mechanism. The sample eluted slightly earlier as molecular weight decreased. The molecular weight effect on the reversed-phase HPLC was smaller than that on the normal phase. A gel with an exclusion limit of 3 × 10³ exhibited greater molecular weight dependence and worse resolution than a gel with an exclusion limit of 50 × 10⁴. Poly(styrene-co-n-butyl methacrylate) also was separated on the basis of chemical composition by normal and reverse-phase HPLC. However, poly(styrene-co-t-butyl methacrylate) was separated only by reverse-phase HPLC. When octadecyl methacrylate gel was used instead of styrene gel in reverse-phase HPLC, a good separation was not obtained. This indicates a specific interaction between the phenyl group of the styrene gel and the sample.     

Separation of drugs by high-performance liquid chromatography with porous polymer resins.

The separation of cold drugs and neuroleptics by high-performance liquid chromatogarphy with the porous polymer resin DVB-MCL-O (or 11-30-0), which is a styrene-divinylbenzene-methyl methacrylate copolymer substituted with hydroxymethyl groups, was studied. This copolymer was compared with the commercial porous polymers Hitachi gel 3011, 3011-0 and 3030. A very small theoretical plate height was obtained by using DVB-MCL-O and methanol-ammonia solution (99:1) as the stationary and mobile phases, respectively. This combination was found to be the most suitable for the rapid separation of condensed aromatic ring compounds.