TGIC Separation of PS-b-P2VP Diblock and P2VP-b-PS-b-P2VP Triblock Copolymers According to Chemical Composition (original) (raw)
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Molecular characterization of block copolymers by means of liquid chromatography
European Polymer Journal, 2000
The full adsorption±desorption (FAD) procedure was applied to the selected model di-and tri-block copolymers. The dynamic integral desorption isotherms were measured for various homo-and block-copolymers of poly(methyl methacrylate) and poly(glycidyl methacrylate) in a system of non-porous silica±dichloroethane adsorli± tetrahydrofuran desorli. The aim was to evaluate separation selectivity of the FAD approach toward molar mass and chemical composition of macromolecules. It was demonstrated that under optimum conditions the FAD procedure can discriminate parent homopolymers from di-block copolymers, as well as di-block from tri-block copolymers when the adsorptivities of blocks dier suciently. The molar mass of both kinds of polymer chains aected the course of their desorption in present system of adsorbent±adsorli/desorli. Consequently the block copolymers studied could not be eectively fractionated according to their composition by a single FAD procedure. A combined method, full adsorption±desorption plus size exclusion chromatography was proposed for the species with selectively adsorbing blocks to provide a two dimensional fractionation of block copolymers. #
Macromolecules, 2000
Liquid adsorption chromatography at critical conditions (LACCC) in normal and in reversedphase modes provides independent information on the molar mass distributions of both blocks of poly-(methyl methacrylate)-block-poly(tert-butyl methacrylate), even if no information about the precursor is available. In addition, the amount of unreacted precursor can be determined, even if its molar mass is comparable to that of the total block copolymer. The reversal of elution order by changing of stationary and mobile phases makes it possible to independently characterize each block in the SEC mode of the LACCC system. Thus, complete structural information is obtained even without using two-dimensional chromatographic techniques.
Macromolecules, 2002
In this study we fractionated polystyrene-block-polyisoprene diblock copolymers (PS-b-PI) prepared by anionic polymerization into fractions which have a narrower distribution in molecular weight as well as in chemical composition. The strategy was to use two-dimensional HPLC: reversed phase HPLC to fractionate PI block and normal phase HPLC to fractionate PS block with a minimal effect of the other block. The working principle of the separation method was confirmed for a low molecular weight PS-b-PI (2.4 kg/mol). With the aid of matrix assisted laser desorption/ionization mass spectrometry, we found that the separation method could resolve each mer of the PS-b-PI. We extended the application to a high molecular weight diblock copolymer (24 kg/mol) and established the method as a promising tool to further fractionate block copolymers into molecular species better defined in molecular weight as well as in composition. We observed a significant variation in average molecular weight as well as in composition of the fractionated samples. These variations were large enough to show different morphologies for the fractions taken from the same mother block copolymer.
Journal of Chromatography A, 2014
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Journal of Separation Science, 2010
Liquid chromatography under limiting conditions of desorption (LC LCD) enables fast, base-line discrimination of both parent homopolymers from various diblock copolymers in one single step. The low molecular admixtures are fully separated, as well. General rules are discussed in detail for selection of mobile phases and temperature applied in LC LCD of block copolymers. Typical practical separation examples are presented. It is shown that both the composition of the well-selected LC LCD mobile phase and the temperature of experiment may vary in a broad range without affecting the basics of method. This implies that the method is robust and user friendly.
Polymer, 2010
The novel separation method, liquid chromatography under limiting conditions of desorption, LC LCD enables rapid one-step discrimination of both parent homopolymers from diblock copolymers. The lowmolecular admixtures/impurities can be base-line separated, as well. The general rules for selection of the LC LCD columns are reviewed. Bare silica gel column packings are discussed in detail. Selected examples of separation are presented. They demonstrate that the principle of LC LCD separation is not affected by the particle size and initial purity of bare silica gel column packing nor by its effective pore diameter and volume. However, appropriate choice of the packing pore size facilitates base-line separation of particular sample constituents. Important may be the column history; columns saturated with previously adsorbed polymers may lose their performance. Up to a certain limit, success of the LC LCD separation does not depend on the column efficiency and reasonable results can be obtained even with the columns packed with rather big particles. This indicates possibility of the large-scale preparative applications and feasibility of the high-speed LC LCD separations.
Macromolecules, 2001
In the chromatographic separation of macromolecules with a porous stationary phase, the retention is determined by both size exclusion and interaction mechanisms. At the chromatographic critical condition, the effects due to the two separation mechanisms compensate each other, and the retention of homopolymer molecules becomes independent of molecular weight. Liquid chromatography at the critical condition has attracted much interest for the characterization of block copolymers since it might permit the characterization of individual blocks of a block copolymer by making one block chromatographically "invisible". In this study, we critically examine this method using two sets of styrene-isoprene block copolymers designed to have one block length constant while varying the other block length. For these block copolymer systems we found that a block cannot be made completely "invisible" at the critical condition of its homopolymer, and the retention of block copolymers is affected to some extent by the length of the "invisible" block under its chromatographic critical condition.
Separation and Characterization of Block and Graft Copolymers by Thin-Layer Chromatography
Pure and Applied Chemistry, 1976
Feasibilities of thin-layer chromatography (TLC) and its combination with gel permeation chromatography in characterization of block and graft copolymers are discussed. The simplest application of TLC is to test the purity of block and graft samples having been subjected to purification treatment. TLC allows further to determine the compositional heterogeneity of block copolymers without interference of molecular weight, and to distinguish block samples by the difference in block sequence even on the same composition level. The latter applicability is illustrated for styrene-butadiene copolymers with different chain architecture. Finally two applications of TLC as a tool for characterization of graft systems are described: one is to isolate side-chain polymers truely grafted on mother polymer chains, and the other to isolate true graft copolymers from reaction products.
Macromolecules, 2019
Free solution capillary-electrophoresis (CE) is a powerful separation technique for the characterization of diblock copolymers. In this work, four series of double-hydrophilic anionic and cationic block copolymers, namely, poly(acrylamide)-block-poly(acrylic acid) (PAM-b-PAA), poly(acrylamide)-block-poly((3-acrylamidopropyl)trimethylammonium chloride) (PAM-b-PAPTAC), poly(ethylene oxide)-block-poly(acrylic acid) (PEO-b-PAA) and poly(poly(ethylene glycol) methyl ether acrylate)-block-poly(acrylic acid) (P(PEGA)-b-PAA), were synthesized by reversible additionfragmentation chain transfer (RAFT) polymerization and characterized by CE. The electrophoretic mobility distributions of the copolymers were transformed into distributions of composition ratio by introducing a retardation parameter, Xexp,, that represents the hydrodynamic drag retardation due to the neutral block of the copolymer. A linear correlation between Xexp and the ratio of the degrees of polymerization of each blocks was experimentally established and was consistent with the model of electrophoretic mobility of composite macromolecules with hydrodynamic coupling. Finally, the comparison of the distributions between the different copolymer families was significantly improved by considering the distributions in composition ratio compared to the electrophoretic mobility distributions, since it takes into account the differences in solvation, expansion and drag force according to the chemical nature of the blocks.
Effect of Block Copolymer Chain Architecture on Chromatographic Retention
Macromolecules, 2003
The chain architecture dependence of the retention behavior of block copolymers in the temperature gradient interaction chromatography (TGIC) and liquid chromatography at the critical condition (LCCC) was investigated. For the purpose, polystyrene (PS)/polybutadiene (PB) diblock (SB), SBS triblock, and BSB triblock copolymers were prepared by sequential anionic polymerization and further fractionated by reversed-phase TGIC to obtain a set of the block copolymers with high purity, narrow distribution, and matched block length. In the TGIC separation with C18 bonded silica stationary phase and a mixture of CH 2Cl2/CH3CN mobile phase, retention of the three block copolymers with matched molecular weight and composition shows a significant architecture effect: SBS elutes significantly earlier while BSB or SB elute later at similar retention volume. It indicates that the polymer-stationary phase interaction is less effective for the PB block located at the middle of the chain than the blocks located at the chain end. In LCCC separation at the critical condition for PB block, SBS is eluted early while SB and BSB were eluted later at the same retention time. Therefore, triblock copolymer with an invisible middle block behaves differently from those having invisible end block(s). This behavior is consistent with the theoretical prediction by Guttman et al.