Single-Capillary Viscometer Used for Accurate Determination of Molecular Weights and Mark—Houwink Constants

Lesec, James; Millequant, M.; Havard, Trevor

doi:10.1021/bk-1993-0521.ch014

Cited by 5 publications

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“…The glass capillary viscometer is widely used to measure the polymer molecular weight (M w ) and the activation energy of the viscous flow of polymer solutions [1,2], and thus is an experiment that almost all students who major in chemistry and polymer science learn. Its main principle is the Mark-Houwink equation [3]:…”

Section: Introductionmentioning

confidence: 99%

Accuracy improvement of the experiment determining macromolecular weight by capillary viscometer based on Monte Carlo simulation

Zhang¹

2020

Eur. J. Phys.

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In order to lower the experimental uncertainty when measuring the molecular weight of a polymer (Mw) with a glass capillary viscometer, error propagation from the measured flow times to the calculated Mw is analyzed by Monte Carlo simulation. New experimental designs are then proposed to achieve a lower experimental uncertainty for the same number of measurements in total. To simulate experiments, normally distributed relative flow time deviations are randomly generated and used to calculate Mw. It is found that the errors increase hugely from the flow times to the Mw. For example, a relative standard deviation (RSTD) of 0.5% of the flow times can lead to an RSTD of 15% to the Mw for the experiment design that measures the flow times of a pure solvent and four solutions of different concentrations in triplicate, and calculates the Mw based on them, as instructed in many laboratory manuals. Most importantly, the study reveals that the errors of the flow times corresponding to the pure solvent and solutions have a very different influence on the deviation of Mw. The flow times of the pure solvent and the solution with the lowest concentration have the most significant impact on the deviation of Mw. Finally, new experimental designs are explored and it is found that by only measuring the flow times of two solutions (the 10 g l−1 solution measured in triplicate and the 5 g l−1 solution measured nine times) and the pure solvent (measured in triplicate) the RSTD of Mw can be reduced by 33% compared with the case in which four solutions and the pure solvent are all measured in triplicate.

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Section: Introductionmentioning

confidence: 99%

Accuracy improvement of the experiment determining macromolecular weight by capillary viscometer based on Monte Carlo simulation

Zhang¹

2020

Eur. J. Phys.

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Size‐Exclusion Chromatography of Polymers

Trathnigg

2000

Encyclopedia of Analytical Chemistry

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Size‐exclusion chromatography (SEC) is a standard technique for determining molar mass averages and molar mass distributions (MMDs) of polymers. Sometimes the termsgel permeation chromatography (GPC) or gel filtration chromatography (GFC) are also used, but SEC should be preferred, because this term describes the mechanism much better: polymer molecules are separated according to their hydrodynamic volumes (which can be correlated with molar mass), with the larger size molecules exiting first followed by the smaller. Molar masses are determined either from a calibration or using molar mass sensitive detectors. In the case of copolymers, the knowledge of chemical composition along the MMD is required, which can be obtained from combinations of different concentration detectors. As the hydrodynamic volumes of different polymers are typically somewhat different, molecules with different chemical composition and different molar mass will be eluted in the same slice of the chromatogram. Obviously, a discrimination between such molecules requires a two‐dimensional separation, in which one dimension may be SEC, and the other one a chromatographic technique, which separates according to chemical composition rather than molar mass, such as liquid adsorption chromatography (LAC), liquid chromatography at the critical point of adsorption (often also called liquid chromatography under critical conditions, LCCC), supercritical fluid chromatography (SFC), temperature rising elution fractionation (TREF), etc. In the lower molar mass range, mass spectroscopy competes with SEC. The most frequently used technique is matrix‐assisted laser desorption/ionization time‐of‐flight mass spectroscopy (MALDI/TOF/MS), which cannot, however, provide quantitatively accurate MMDs. Due to its excellent resolution in molar mass, it can be combined with chromatographic techniques in order to increase the reliability of the analysis.

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Equipment and Materials

Pasch¹,

Trathnigg²

1999

HPLC of Polymers

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Single-Capillary Viscometer Used for Accurate Determination of Molecular Weights and Mark—Houwink Constants

Cited by 5 publications

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Accuracy improvement of the experiment determining macromolecular weight by capillary viscometer based on Monte Carlo simulation

Accuracy improvement of the experiment determining macromolecular weight by capillary viscometer based on Monte Carlo simulation

Size‐Exclusion Chromatography of Polymers

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