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Jan Lebduska - One of the best experts on this subject based on the ideXlab platform.

  • characterization of alkyd resins by size exclusion chromatography coupled with a multi angle light scattering photometer
    Analytica Chimica Acta, 2006
    Co-Authors: Daniela Vareckova, Stepan Podzimek, Jan Lebduska
    Abstract:

    An on-line multi-angle light scattering detector (MALS) coupled with size exclusion chromatography (SEC) has been used for the determination of Molar Mass and size Distribution of alkyd resins. Molar Mass Distribution of alkyd resins is usually determined by SEC using calibration by polystyrene standards (PS). Since the molecules of alkyd resins are significantly more compact than those of linear polystyrene the Molar Mass determined by conventional SEC is incorrect. The correct Molar Mass can be obtained using an on-line MALS detector that eliminates the column calibration. In addition, it allows sample differentiation in respect to their degree of branching. It was found that highly branched alkyd molecules have abnormal elution behavior.

  • characterization of alkyd resins by size exclusion chromatography coupled with a multi angle light scattering photometer
    Analytica Chimica Acta, 2006
    Co-Authors: Daniela Vareckova, Stepan Podzimek, Jan Lebduska
    Abstract:

    An on-line multi-angle light scattering detector (MALS) coupled with size exclusion chromatography (SEC) has been used for the determination of Molar Mass and size Distribution of alkyd resins. Molar Mass Distribution of alkyd resins is usually determined by SEC using calibration by polystyrene standards (PS). Since the molecules of alkyd resins are significantly more compact than those of linear polystyrene the Molar Mass determined by conventional SEC is incorrect. The correct Molar Mass can be obtained using an on-line MALS detector that eliminates the column calibration. In addition, it allows sample differentiation in respect to their degree of branching. It was found that highly branched alkyd molecules have abnormal elution behavior.

Anti Viikna - One of the best experts on this subject based on the ideXlab platform.

  • Crystallisation behaviour of high density polyethylene blends with bimodal Molar Mass Distribution: 2. Non-isothermal crystallisation
    European Polymer Journal, 2004
    Co-Authors: Andres Krumme, Arja Lehtinen, Anti Viikna
    Abstract:

    Abstract Crystallisation of high density polyethylene (HDPE) blends with broad bimodal Molar Mass Distribution was investigated by differential scanning calorimetry (DSC) under non-isothermal conditions. The blends were prepared by blending a high Molar Mass PE (Mw=330 kg/mol, Mw/Mn=4.8) and a low Molar Mass linear PE (Mw=34 kg/mol, Mw/Mn=10) in different ratios in xylene solution. The samples were analysed by the normal DSC at different crystallisation rates and by a thermal fractionation technique. The blends and their parent polymers behaved according to general expectations i.e., crystallinity and density decreased when the Molar Mass of the samples increased. Additionally, non-linear relationships between MM and different analysed parameters were found. Small addition of the high Molar Mass parent polymer to the low Molar Mass parent polymer increased crystallisation temperature, although the general trend was decreasing. Furthermore, a complicated relationship between the reciprocal of crystallisation half-time and sample composition was found. The value increased first with increasing Molar Mass, reached a maximum when the average Molar Mass of the blend was between 150 and 200 kg/mol and then decreased. The detected maximum correlated with the broadest Molar Mass Distribution of the blends. The crystallinities and densities of the blends with the broadest Molar Mass Distribution also deviated from the linear correlation between them and Molar Mass. The Avrami index under non-isothermal conditions was analysed with a method developed by Harnisch and Muschik. The results indicated that thermal nucleation and spherical growth regimes are present in all studied materials.

  • crystallisation behaviour of high density polyethylene blends with bimodal Molar Mass Distribution 1 basic characteristics and isothermal crystallisation
    European Polymer Journal, 2004
    Co-Authors: Andres Krumme, Arja Lehtinen, Anti Viikna
    Abstract:

    Isothermal crystallisation of high density polyethylene (HDPE) blends and their parent polymers was investigated. The blends having broad bimodal Molar Mass Distributions and various compositions were prepared by blending a high Molar Mass (Mw=330 kg/mol, Mw/Mn=4.8) and a low Molar Mass HDPE (Mw=34 kg/mol, Mw/Mn=10) in different ratios in xylene solution. The blends and their parent components were characterised by size-exclusion chromatography, dynamic rheological and density measurements. Crystallisation kinetics were studied using a polarised light microscope equipped with an in-house built hot stage and by differential scanning calorimetry. The Avrami theory was applied for crystallisation kinetics analysis. Such crystallisation kinetics parameters as nucleation rate, nucleation density, the Avrami index and cystallisation rate contant were determined for the blends and their parent polymers. According to the results obtained an increasing polydispersity of the sample had a slight increasing effect on the Avrami index, indicating gain in prevalence of the thermal nucleation over the athermal one. In all samples nucleation density increased continuously during crystallisation verifying that the presence of a certain thermal nucleation was typical for all the materials studied. Both the crystallisation rate constant and the nucleation rate decreased with increasing Molar Mass of the sample. The nucleation density increased proportionally to the increase in average Molar Mass and the values were larger at lower crystallisation temperatures. The formed supermolecular structure was found to be sensitive to the blend composition and crystallisation temperature. Irregular banded or non-banded spherulites were observed in the materials. Banding of spherulites was typical for the samples having higher average Molar Mass. The superstructures observed in this work were smaller and vaguer than the superstructures reported in the earlier studies of polyethylene materials having similar average Molar Mass but narrow Molar Mass Distribution.

Daniela Vareckova - One of the best experts on this subject based on the ideXlab platform.

  • characterization of alkyd resins by size exclusion chromatography coupled with a multi angle light scattering photometer
    Analytica Chimica Acta, 2006
    Co-Authors: Daniela Vareckova, Stepan Podzimek, Jan Lebduska
    Abstract:

    An on-line multi-angle light scattering detector (MALS) coupled with size exclusion chromatography (SEC) has been used for the determination of Molar Mass and size Distribution of alkyd resins. Molar Mass Distribution of alkyd resins is usually determined by SEC using calibration by polystyrene standards (PS). Since the molecules of alkyd resins are significantly more compact than those of linear polystyrene the Molar Mass determined by conventional SEC is incorrect. The correct Molar Mass can be obtained using an on-line MALS detector that eliminates the column calibration. In addition, it allows sample differentiation in respect to their degree of branching. It was found that highly branched alkyd molecules have abnormal elution behavior.

  • characterization of alkyd resins by size exclusion chromatography coupled with a multi angle light scattering photometer
    Analytica Chimica Acta, 2006
    Co-Authors: Daniela Vareckova, Stepan Podzimek, Jan Lebduska
    Abstract:

    An on-line multi-angle light scattering detector (MALS) coupled with size exclusion chromatography (SEC) has been used for the determination of Molar Mass and size Distribution of alkyd resins. Molar Mass Distribution of alkyd resins is usually determined by SEC using calibration by polystyrene standards (PS). Since the molecules of alkyd resins are significantly more compact than those of linear polystyrene the Molar Mass determined by conventional SEC is incorrect. The correct Molar Mass can be obtained using an on-line MALS detector that eliminates the column calibration. In addition, it allows sample differentiation in respect to their degree of branching. It was found that highly branched alkyd molecules have abnormal elution behavior.

Stepan Podzimek - One of the best experts on this subject based on the ideXlab platform.

  • light scattering size exclusion chromatography and asymmetric flow field flow fractionation powerful tools for the characterization of polymers proteins and nanoparticles
    2015
    Co-Authors: Stepan Podzimek
    Abstract:

    Preface. 1 Polymers. 1.1 Introduction. 1.2 Molecular Structure of Polymers. 1.2.1 Macromolecules in Dilute Solution. 1.3 Molar Mass Distribution. 1.3.1 Description of Molar Mass Distribution. 1.3.1.1 Distribution Functions. 1.3.1.2 Molar Mass Averages. 1.4 Methods for the Determination of Molar Mass. 1.4.1 Method of End Groups. 1.4.2 Osmometry. 1.4.2.1 Vapor Pressure Osmometry. 1.4.2.2 Membrane osmometry. 1.4.3 Dilute Solution Viscometry. 1.4.3.1 Properties of Mark-Houwink Exponent. 1.4.3.2 Molecular Size from Intrinsic Viscosity. 1.4.3.3 Dependence of Intrinsic Viscosity on Polymer Structure, Temperature and Solvent. 1.4.4 Matrix Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry. 1.4.5 Analytical Ultracentrifugation. 1.5 Keynotes. 1.6 References. 2 Light Scattering. 2.1 Theory and Basic Principles. 2.2 Types of Light Scattering. 2.2.1 Static Light Scattering. 2.2.1.1 Particle Scattering Functions. 2.2.1.2 Light Scattering Formalisms. 2.2.1.3 Processing the Experimental Data. 2.2.2 Dynamic Light Scattering. 2.3 Light Scattering Instrumentation. 2.4 Specific Refractive Index Increment. 2.5 Light Scattering in Batch and Chromatography Mode. 2.6 Parameters Affecting Accuracy of Molar Mass Determined by Light Scattering. 2.7 Examples of Light Scattering Measurement in Batch Mode. 2.8 Keynotes. 2.9 References. 3 Size Exclusion Chromatography. 3.1 Introduction. 3.2 Separation Mechanisms. 3.2.1 Steric Exclusion. 3.2.2 Restricted Diffusion. 3.2.3 Separation by Flow. 3.2.4 Peak Broadening and Separation Efficiency. 3.2.5 Secondary Separation Mechanisms. 3.3 Instrumentation. 3.3.1 Solvents. 3.3.2 Columns and Column Packing. 3.3.3 Detectors. 3.3.3.1 UV Detector. 3.3.3.2 Refractive Index Detector. 3.3.3.3 Infrared Detector. 3.3.3.4 Evaporative Light Scattering Detector. 3.3.3.5 Viscosity Detector. 3.3.3.6 Light Scattering Detector. 3.3.3.7 Other Types of Detectors. 3.4 Column Calibration. 3.4.1 Universal Calibration. 3.4.2 Flow Marker. 3.5 SEC Measurements and Data Processing. 3.5.1 Sample Preparation. 3.5.1.1 Sample Derivatization. 3.5.2 Determination of Molar Mass and Molar Mass Distribution. 3.5.3 Reporting Results. 3.5.4 Characterization of Chemical Composition of Copolymers and Polymer Blends. 3.5.5 Characterization of Oligomers. 3.5.6 Influence of Separation Conditions. 3.5.7 Accuracy, Repeatability and Reproducibility of SEC Measurements. 3.6 Applications of SEC. 3.7 Keynotes. 3.8 References. 4 Combination of SEC and Light Scattering. 4.1 Introduction. 4.2 Data Collection and Processing. 4.2.1 Processing MALS Data. 4.2.1.1 Debye Fit Method. 4.2.1.2 Zimm Fit Method. 4.2.1.3 Berry fit Method. 4.2.1.4 Random Coil Fit Method. 4.2.1.5 Influence of Light Scattering Formalism on Molar Mass and RMS Radius. 4.2.2 Determination of Molar Mass and RMS Radius Averages and Distributions. 4.2.3 Chromatogram Processing. 4.2.4 Influence of Concentration and Second Virial Coefficient. 4.2.5 Repeatability and Reproducibility. 4.2.6 Accuracy of Results. 4.3 Applications of SEC-MALS. 4.3.1 Determination of Molar Mass Distribution. 4.3.2 Fast Determination of Molar Mass. 4.3.3 Characterization of Complex Polymers. 4.3.3.1 Branched Polymers. 4.3.3.2 Copolymers and Polymer Blends. 4.3.4 Conformation Plots. 4.3.5 Mark-Houwink Plots. 4.4 Keynotes. 4.5 References. 5 Asymmetric Flow Field Flow Fractionation. 5.1 Introduction. 5.2 Theory and Basic Principles. 5.2.1 Separation Mechanisms. 5.2.2 Resolution and Band Broadening. 5.3 Instrumentation. 5.4 Measurements and Data Processing. 5.4.1 Influence of Separation Conditions. 5.4.1.1 Isocratic and Gradient Experiments. 5.4.1.2 Overloading. 5.4.2 Practical Measurements. 5.5 A4F Applications. 5.6 Keynotes. 5.7 References. 6 Characterization of Branched Polymers. 6.1 Introduction. 6.2 Detection and Characterization of Branching. 6.2.1 SEC Elution Behavior of Branched Polymers. 6.2.2 Distribution of Branching. 6.2.3 Average Branching Ratios. 6.2.4 Other Methods for the Identification and Characterization of Branching. 6.3 Examples of Characterization of Branching. 6.4 Keynotes. 6.5 References. Symbols. Abbreviations. Index.

  • truths and myths about the determination of Molar Mass Distribution of synthetic and natural polymers by size exclusion chromatography
    Journal of Applied Polymer Science, 2014
    Co-Authors: Stepan Podzimek
    Abstract:

    This article discusses various aspects of the determination of Molar Mass Distribution by means of size exclusion chroma- tography (SEC) in various application modes. The effects of erroneous specific refractive index increment ( dn /dc ), branching, column performance, and enthalpic interactions on the results obtained by different SEC techniques are discussed. Combination of SEC and a light scattering detector represents the most direct way to the Molar Mass Distribution of all natural and synthetic polymers as it completely eliminates the need for column calibration and to a certain extent eliminates the dependence of the obtained results on some operational variables such as flow rate, temperature, or injected Mass. A multiangle light scattering (MALS) photometer has become the most frequently used light scattering detector capable of determination of molecular size as another important polymer characteristic. This article contrasts SEC-MALS method with other application modes of SEC from the viewpoint of some frequent confusions and misunderstandings. V C 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40111.

  • characterization of alkyd resins by size exclusion chromatography coupled with a multi angle light scattering photometer
    Analytica Chimica Acta, 2006
    Co-Authors: Daniela Vareckova, Stepan Podzimek, Jan Lebduska
    Abstract:

    An on-line multi-angle light scattering detector (MALS) coupled with size exclusion chromatography (SEC) has been used for the determination of Molar Mass and size Distribution of alkyd resins. Molar Mass Distribution of alkyd resins is usually determined by SEC using calibration by polystyrene standards (PS). Since the molecules of alkyd resins are significantly more compact than those of linear polystyrene the Molar Mass determined by conventional SEC is incorrect. The correct Molar Mass can be obtained using an on-line MALS detector that eliminates the column calibration. In addition, it allows sample differentiation in respect to their degree of branching. It was found that highly branched alkyd molecules have abnormal elution behavior.

  • characterization of alkyd resins by size exclusion chromatography coupled with a multi angle light scattering photometer
    Analytica Chimica Acta, 2006
    Co-Authors: Daniela Vareckova, Stepan Podzimek, Jan Lebduska
    Abstract:

    An on-line multi-angle light scattering detector (MALS) coupled with size exclusion chromatography (SEC) has been used for the determination of Molar Mass and size Distribution of alkyd resins. Molar Mass Distribution of alkyd resins is usually determined by SEC using calibration by polystyrene standards (PS). Since the molecules of alkyd resins are significantly more compact than those of linear polystyrene the Molar Mass determined by conventional SEC is incorrect. The correct Molar Mass can be obtained using an on-line MALS detector that eliminates the column calibration. In addition, it allows sample differentiation in respect to their degree of branching. It was found that highly branched alkyd molecules have abnormal elution behavior.

Andres Krumme - One of the best experts on this subject based on the ideXlab platform.

  • Crystallisation behaviour of high density polyethylene blends with bimodal Molar Mass Distribution: 2. Non-isothermal crystallisation
    European Polymer Journal, 2004
    Co-Authors: Andres Krumme, Arja Lehtinen, Anti Viikna
    Abstract:

    Abstract Crystallisation of high density polyethylene (HDPE) blends with broad bimodal Molar Mass Distribution was investigated by differential scanning calorimetry (DSC) under non-isothermal conditions. The blends were prepared by blending a high Molar Mass PE (Mw=330 kg/mol, Mw/Mn=4.8) and a low Molar Mass linear PE (Mw=34 kg/mol, Mw/Mn=10) in different ratios in xylene solution. The samples were analysed by the normal DSC at different crystallisation rates and by a thermal fractionation technique. The blends and their parent polymers behaved according to general expectations i.e., crystallinity and density decreased when the Molar Mass of the samples increased. Additionally, non-linear relationships between MM and different analysed parameters were found. Small addition of the high Molar Mass parent polymer to the low Molar Mass parent polymer increased crystallisation temperature, although the general trend was decreasing. Furthermore, a complicated relationship between the reciprocal of crystallisation half-time and sample composition was found. The value increased first with increasing Molar Mass, reached a maximum when the average Molar Mass of the blend was between 150 and 200 kg/mol and then decreased. The detected maximum correlated with the broadest Molar Mass Distribution of the blends. The crystallinities and densities of the blends with the broadest Molar Mass Distribution also deviated from the linear correlation between them and Molar Mass. The Avrami index under non-isothermal conditions was analysed with a method developed by Harnisch and Muschik. The results indicated that thermal nucleation and spherical growth regimes are present in all studied materials.

  • crystallisation behaviour of high density polyethylene blends with bimodal Molar Mass Distribution 1 basic characteristics and isothermal crystallisation
    European Polymer Journal, 2004
    Co-Authors: Andres Krumme, Arja Lehtinen, Anti Viikna
    Abstract:

    Isothermal crystallisation of high density polyethylene (HDPE) blends and their parent polymers was investigated. The blends having broad bimodal Molar Mass Distributions and various compositions were prepared by blending a high Molar Mass (Mw=330 kg/mol, Mw/Mn=4.8) and a low Molar Mass HDPE (Mw=34 kg/mol, Mw/Mn=10) in different ratios in xylene solution. The blends and their parent components were characterised by size-exclusion chromatography, dynamic rheological and density measurements. Crystallisation kinetics were studied using a polarised light microscope equipped with an in-house built hot stage and by differential scanning calorimetry. The Avrami theory was applied for crystallisation kinetics analysis. Such crystallisation kinetics parameters as nucleation rate, nucleation density, the Avrami index and cystallisation rate contant were determined for the blends and their parent polymers. According to the results obtained an increasing polydispersity of the sample had a slight increasing effect on the Avrami index, indicating gain in prevalence of the thermal nucleation over the athermal one. In all samples nucleation density increased continuously during crystallisation verifying that the presence of a certain thermal nucleation was typical for all the materials studied. Both the crystallisation rate constant and the nucleation rate decreased with increasing Molar Mass of the sample. The nucleation density increased proportionally to the increase in average Molar Mass and the values were larger at lower crystallisation temperatures. The formed supermolecular structure was found to be sensitive to the blend composition and crystallisation temperature. Irregular banded or non-banded spherulites were observed in the materials. Banding of spherulites was typical for the samples having higher average Molar Mass. The superstructures observed in this work were smaller and vaguer than the superstructures reported in the earlier studies of polyethylene materials having similar average Molar Mass but narrow Molar Mass Distribution.