Method development in interaction polymer chromatography

Determination of the chemical composition distribution of copolymers of styrene and butadiene by gradient polymer elution chromatography

Characterization of low-molar-mass polymers by gradient polymer elution chromatography I. Practical parameters and applications of the analysis of polyester resins under reversed phase conditions

Concurrent ring-opening and atom transfer radical polymerization for synthesis of block copolymers, and their comprehensive chromatographic characterization

Synthetic polymers typically show dispersity in molecular weight and potentially in chemical composition. For the analysis of the chemical-composition distribution (CCD) gradient liquid chromatography may be used. The CCD obtained using this method is often convoluted with an underlying molecular-weight distribution (MWD). In this paper we demonstrate that the influence of the MWD can be reduced using very steep gradients and that such gradients are best realized utilizing recycling gradient liquid chromatography (LC↻LC). This method allows for a more-accurate determination of the CCD and the assessment of (approximate) critical conditions (if these exist), even when high-molecular-weight standards of narrow dispersity are not readily available. The performance and usefulness of the approach is demonstrated for several polystyrene standards, and for the separation of statistical copolymers consisting of styrene/methyl methacrylate and methyl methacrylate/butyl methacrylate. For the latter case, approximate critical compositions of the copolymers were calculated from the critical compositions of two homopolymers and one copolymer of known chemical composition, allowing for a determination of the CCD of unknown samples. Using this approach it is shown that the copolymers elute significantly closer to the predicted critical compositions after recycling of the gradient. This is most clear for the lowest-molecular-weight copolymer (Mw = 4.2 kDa), for which the difference between measured and predicted elution composition decreases from 7.9% without recycling to 1.4% after recycling.

The complete characterization of polymers requires the evaluation of both the molecular weight and chemical composition distributions. Size exclusion chromatography and liquid chromatography at the critical condition (LCCC) are two methods often used to obtain these distributions. Recently, matrix-assisted laser desorption ionization (MALDI)–time of flight (TOF) mass spectrometry has been used for polymer characterization. The application of packed capillary SEC and LCCC is illustrated here for the characterization of poly(propylene glycol) based materials. Especially in the case of critical chromatography, packed capillary chromatography separations were achieved that were not possible using analytical-scale critical chromatography. In addition, the off-line combination of packed-capillary SEC and LCCC with MALDI-TOF is described. ©1999 John Wiley & Sons, Inc. J Micro Sep 11: 53–61, 1999

Chemical composition distribution of styrene-ethyl methacrylate copolymers studied by means of t.l.c./f.i.d.: effect of high conversion in various polymerization processes

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDetermination of chemical composition and molecular weight distributions of high-conversion styrene-methyl methacrylate copolymers by liquid adsorption and size exclusion chromatographySadao. MoriCite this: Anal. Chem. 1988, 60, 11, 1125–1128Publication Date (Print):June 1, 1988Publication History Published online1 May 2002Published inissue 1 June 1988https://doi.org/10.1021/ac00162a008RIGHTS & PERMISSIONSArticle Views197Altmetric-Citations65LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (445 KB) Get e-Alerts Get e-Alerts

Ethylene/1-olefin copolymers have held industrial significance for a considerable period. A series of copolymers with identical molar mass and varying 1-hexene levels were synthesized using supported metallocene catalyst. Various analytical techniques were used to characterize the copolymers, focusing on the effect of increasing 1-hexene content on their chemical properties, specifically chemical composition distribution (CCD). Initially, the investigations carried out by differential scanning calorimetry (DSC) revealed broad and asymmetric thermograms with the presence of a distinct shoulder in samples with higher 1-hexene content. Furthermore, HT-GPC with IR5 detector revealed uniform chemical composition (1-hexene concentration) along the molar mass axis. Examination of the chemical composition distribution (CCD) was conducted using two variants of high-temperature liquid adsorption chromatography (HT-LAC), namely solvent gradient interaction chromatography (SGIC) and thermal gradient interaction chromatography (TGIC). Initial testing by employing solvents common to HT-LAC showed that the elution behavior did not correspond with the distinct thermal properties DSC. In the next step, new desorption-promoting solvents were identified using a recent approach that integrates structure retention relationships (SRR), a measure of solvent–stationary phase interactions, with Hansen solubility parameters (HSP), assessing polymer–solvent interactions. The broad and asymmetric CCD in samples with higher SCB, characterized by a main peak and a shoulder, was confirmed by SGIC using newly identified desorption-promoting solvents identified via the SRR–HSP method. This CCD profile was also corroborated by TGIC using a binary solvent mixture as the mobile phase.

For getting information about the distribution of chemical composition, several model polymers were prepared under different polymerization conditions and were measured by critical adsorption point-liquid chromatography (CAP-LC). In the copolymer system of 8- and 9- (4-oxatricyclo[5.2.1.0 2,6 ]decane-3-one) acrylate (OTDA) and 2-ethyl-2-adamantyl methacrylate (EAdMA), the peak shapes of the CAP-LC chromatogram varied according to the polymerization condition although they indicated same molecular weight and averaged chemical composition. The difference of the CAP-LC elution curves was related to the chemical composition di stribution of copolymers for CA P-LC measurement combined with proton nuclear magnetic resonance ( 1 H-NMR). The terpolymers consisted of D -hydroxy- J-butyrolactone methacrylate (GBLMA), 2-methyl-2-adamantyl methacrylate (MAdMA) and 1-hydroxy-3-adaman tyl methacrylate (HAdMA) were prepared under various polymerization conditions . In the terpolymer system that had same molecular weight and average chemical composition, the solubility parameter (G) and the dissolution rate were measured. The G value and the dissolution rate curve were different among these terpolymers. It was suggested that the G value and the chemical composition distribution of these terpolymers have a significant influence on the lithographic performance. Keywords: ArF photoresist copolymer, chemical composition distribution, solubility parameter, critical adsorption point-liquid chromatography, CAP-LC

Chemical composition distribution of bacterial copolyesters

Environmental contextExtracellular polymeric substances (EPS) released by microorganisms are an important component of organic matter in the environment. EPS play an essential role in cell adhesion to surfaces, biofilm and floc formation, soil aggregation and stability and in the activated sludge of waste water treatment plants. EPS are complex mixtures containing components of different chemical nature and molecular size, which make their characterisation difficult. The present work explores the link between chemical composition and molar-mass distribution of the EPS released by the bacterium Sinorhizobium meliloti by using a combination of chemical, spectroscopic and fractionation techniques. AbstractThe chemical composition and molar-mass distribution of extracellular polymeric substances (EPS) produced by the bacterium Sinorhizobium meliloti have been characterised by combining asymmetrical flow field-flow fractionation (AFlFFF), chemical and spectroscopic techniques. The relationship between the EPS composition and molar-mass distribution has been studied by comparing the characteristics of EPS excreted by the wild type S. meliloti and by a mutant deficient in the production of high-molar-mass EPS, as well as by the analysis of total protein content in the collected AFlFFF fractions. Total organic carbon, protein and polysaccharide contents of the EPS were also determined. Obtained results demonstrate the existence of two major populations with weight-average molar masses of 1.40 × 105 and 4.57 × 105 g mol–1 respectively. The lower molar-mass population contained predominantly protein-like substances, detectable by UV-VIS spectroscopy, whereas the higher molar-mass population was rich in exopolysaccharides and exoproteins. These findings are in general agreement with the size distributions and chemical heterogeneity observed by nanoparticle tracking analysis, and the characterisation of the composition of all the EPS by different analytical techniques.

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.

The research described in this thesis concerns the design, biotechnological production, and physiochemical study of large water-soluble (monodisperse) protein triblock-copolymers with sequential blocks, some of which are positively or negatively charged and self-assemble in response to a change in pH or co-assemble in response to oppositely charged polyelectrolytes (including each other). Such molecules displaying controlled self-assembly may lead to new biocompatible nano-structured materials like nano-wires, gels and fibers, with unusual material properties and potential technical and biomedical applications. First, the production and purification as enabling technology is described but the focus of this thesis is on the physiochemical behavior of the produced molecules, including the nano-structures formed, the kinetics of the structure formation and the material properties of the macroscopic gels resulting from the nano-structures. For producing monodisperse block copolymers with sequential blocks, we chose the natural protein production machinery of living cells, because monodispersity and sequentiality are hallmarks of proteins. First, DNA encoding various polypeptide blocks of the block copolymers was designed. Then, using a modular cloning approach, DNA blocks were built, enlarged to desired block size and connected to form whole genes that encode polypeptide block copolymers. The genes were transferred to the production host, the yeast Pichia pastoris, which when induced, secreted the various protein block copolymers production yields in the gram per liter range, such that various applications of these promising biomaterials become possible. However, choosing this biotechnological approach limited the polymer design to the 20 natural amino acids, but seen the large variation in structure and function of natural proteins, this, in practice, forms hardly any limitation. Three different nature-inspired poly-peptide blocks were used in the block copolymer designs: two very similar, but oppositely charged silk-like blocks, and one largely uncharged collagen like block. The silk-like blocks ("S") consist of an octapeptide glycine (G) alanine(A) repeat (GAGAGAGX)24, in which the X position is occupied either by a positively charged histidine residue (H) or a negatively charged glutamic acid residue (E), resulting in an either positively or negatively charged silk-like block: "SH" or "SE" respectively, the theoretical pKa being 7 and 4.3 respectively. These blocks are supposed to self- or co-assemble upon charge neutralization or compensation. The collagen-like blocks ("C") contains mainly glycine, proline, polar amino acids and a small number of charged residues. It is supposed to form a hydrophilic random coil in most aqueous environments. The four final products, all 802 amino acids long, were either positively charged, 66.1 kDa molecules denoted as SHCCSH and CSHSHC or negatively charged 65.7 kDa molecules denoted as SECCSE and CSESEC. The four different molecules showed different behavior depending on charge and block order. Three aspects of these molecules were studied: nano-structures, kinetics of structure formation, and material properties of pH change induced gels. Nano-structures, were investigated with a broad range of techniques including: transmission electron microscopy (TEM) cryogenic (cryo-)TEM, atomic force microscopy (AFM), CD spectrometry, small angle X-ray scattering (SAXS) and molecular dynamics modeling (MD). The four different polymers were triggered to form structures and 12 of these self- or co-assembled nano-structures were examined: 1-4) the four pH- induced self-assemblies, 5-7) CSHSHC with poly acrylic acid (PAA), or with a metal bis-ligand supramolecular polymer denoted as Zn-L2(EO)4, or with the (conducting) polythiophene (POWT) that was chemically modified to be zwitterionic, 8) CSESEC with POWT, 9-12) the four possible mixtures of the four different protein block copolymers. Except for the mixtures of protein polymers, which seemed to form kinetically trapped molecular networks, the self- and co-assemblies formed well defined μm long nanoribbons with a hydrophilic C block corona. The core structure, depended on the protein block copolymer used, and on the mode of charge compensation like pH and/or the type of polyelectrolyte used. Interesting features are: the unusual -roll, predicted with MD modeling for the SE block in the self-assembled ribbon core at low pH, the CC middle blocks of SECCSE and SHCCSH forming loops, analogous to flower-like micelles, and the templating of the conductive polymer POWT onto nanoribbons, that might have applications as nanowires. Kinetics of structure formation was only followed for CSESEC at low pH. CD spectroscopy at 200 nm was used to follow the conformational change associated with ribbon formation of CSESEC in time, in dilute, acidified solutions, revealing a nucleation and growth mechanism for CSESEC ribbons under a critical pH of approximately 4.5. Dynamic light scattering (DLS) measurements revealed that when the pH was increased, the ribbons dissolved and the formed gels melted, but they only did so above pH 5.4 which is much higher than the critical pH of ribbon formation. This pH region in which ribbons do not form, nor dissolve suggests a kinetic barrier to ribbon formation. The purified and freeze-dried CSESEC appeared to contain nuclei from which ribbon growth could start. To study the effect of block charge and block order, on the mechanical properties of self-assembling block copolymer hydrogels, we tested the physical behavior of CSESEC, SECCSE, and CSHSHC. Dynamic mechanical spectroscopy revealed differences in gelling kinetics and mechanical properties of the three different polymers. Remarkably, the SE containing polymer gels displayed non linear elasticity comparable to that of the actin gels and other biological gels. Consequently we see that like actin gels our gels consist of semi-flexible fibrils (nano-tapes). Moreover, exceptionally high dynamic elasticity moduli, exceeding 40 kPa, were reached already at concentrations as low as 1.5 wt%, without any additional crosslinking agent. Such highly rigid yet dilute gels are rare and sought after. CSHSHC gels were relatively week and formed slowly. Additionally we studied the effect of temperature on the mechanical properties of a CSESEC gel. The molecules self- and co-assembled into various nano-structures constituting various transparent gels, some of which extremely rigid. These structures and gels have potential biomedical and technological applications. The biotechnological approach for producing these four different monodisperse, sequential block copolymers, yielded amounts that make applications possible and presents an opportunity for the design and production of many more monodisperse and sequential (protein) block copolymers for building other nano-structures.

Conjugated rod-coil diblock copolymers self-assemble due to a balance of liquid crystalline (rod-rod) and enthalpic (rod-coil) interactions. Previous work has shown that while classical block copolymers self-assemble into a wide variety of nanostructures, when rod-rod interactions dominate self-assembly in rod-coil block copolymers, lamellar structures are preferred. Here, it is demonstrated that other, potentially more useful, nanostructures can be formed when these two interactions are more closely balanced. In particular, hexagonally packed polylactide (PLA) cylinders embedded in a semiconducting poly(3-alkylthiophene) (P3AT) matrix can be formed. This microstructure has been long-sought as it provides an opportunity to incorporate additional functionalities into a majority phase nanostructured conjugated polymer, for example in organic photovoltaic applications. Previous efforts to generate this phase in polythiophene-based block copolymers have failed due to the high driving force for P3AT crystallization. Here, we demonstrate that careful design of the P3AT moiety allows for a balance between crystallization and microphase separation due to chemical dissimilarity between copolymer blocks. In addition to hexagonally packed cylinders, P3AT-PLA block copolymers form nanostructures with long-range order at all block copolymer compositions. Importantly, the conjugated moiety of the P3AT-PLA block copolymers retains the crystalline packing structure and characteristic high time-of-flight charge transport of the homopolymer polythiophene (μ(h) ~10(-4) cm(2) V(-1) s(-1)) in the confined geometry of the block copolymer domains.

Characterization of chemical composition and particle size distribution of aerosols released during laser cutting of fuel debris simulants