Gel permeation chromatography of polyoxymethylene

Gel permeation chromatography of polyoxymethylene has been studied using N,N-dimethylformamide as the solvent. Polyoxymethylene samples used here are a copolymer of tetraoxane with 1,3-dioxolane and a commercial polyoxymethylene whose molecular weight distributions are moderately broad. Their intrinsic viscosities [η] range from 1.4 to 2.8 dl/g. Factors affecting chromatograms are discussed, and the operating conditions were determined by using the analytical scale GPC. On the basis of these operating conditions, the molecular weight fractionation of polyoxymethylene was carried out by using the preparative scale GPC. It was found that polyoxymethylene can be effectively fractionated to give seven to ten fractions each of them containing the fractionated polymer ranging in weight from 0.2 to 8 mg when 40 mg polymer sample was used for a run of the measurement. The fractionated polymers were also found to have a narrow molecular weight distribution within a single peak, and their M_w/M_n values decrease with increasing molecular weight.     

Gel permeation chromatography: universal calibration for rigid rod and random coil polymers

The g.p.c. behaviour of poly (γ-benzyl-l-glutamate) (PBLG) samples, polystyrene standards and poly(2-vinyl pyridine) has been examined in N,N-dimethylacetamide (DMA) at 80°C. Solution viscosity measurements show that DMA is a good solvent for the flexible random coil polystyrene and that it promotes a helical rigid-rod shaped PBLG. Comparison of polystyrene and poly (2-vinyl pyridine) confirms that polystyrene separates strictly according to steric exclusion and that polymer/gel interactions are not involved. A PBLG calibration curve predicted from the polystyrene calibration by the [η] M universal calibration procedure was used to calculate average molecular weight and M_peak data from the PBLG chromatograms. The calculated $\text{M}\text{?}{}_{\mathrm{v}}$ values are in good agreement with experimental data. Plots of log [η] M_peak against retention volume for PBLG and polystyrene were coincident. These results suggest that the product [η] M is a valid universal calibration parameter for PBLG and polystyrene which have significantly different shapes. Comparison of theoretical equations relating the diameter of polystyrene hydrodynamic spheres to the half-length of PBLG helices suggests that the parallel-plane model may be a useful mathematical representation of pore geometry.     

Gel permeation chromatography: Differential operation

Operation of gel permeation chromatographs in the differential mode provides a sensitive method for detecting small differences in molecular weight distribution between similar samples. The solvent used in this case is a dilute solution of the reference polymer in an organic solvent. This solution is used in both the reference and the separation column. Samples of the material to be compared are injected in the normal manner. Only differences between the samples are reflected in the resulting chromatogram. For process control, this offers a simplified data presentation and should lead to easier detection of changes in operating conditions.     

Gel permeation chromatography of heated fats

The high and low molecular weight components of heated fats have been separated with gel permeation chromatography. With Sephadex LH-20, as well as with Biobeads SX-1, the high molecular weight components of heated fats may be directly separated when chloroform, acetone, chloroform-methanol or tetrahydrofuran are employed as swelling agents and eluting solvents. Presented at the AOCS Meeting, Ottawa, September 1972.     

Gel permeation chromatography calibration based on fractal geometry

The previously developed model [Polym Bull 2000, 44, 525] used to characterize the porous gel inside a gel permeation chromatography (GPC) column, has been extended to also include the interstitial space between the macroscopic gel particles. The hydrodynamic dimensions for 12 polystyrene (PS) standards, measured by GPC with differential refractive index (DRI), differential viscometry (VISCO), and multiangle laser light scattering (MALLS) detectors, have been used to determine the fractal parameters of the polystyrene–divinylbenzene gel corresponding to four commercial columns. The new developed model enables to predict the calibration curve for the sets of coupled columns based on the parameters of each column. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 771–777, 2004     

Gel permeation chromatography measurements on PVC resins and plasticisers

The value of gel permeation chromatography (g.p.c.) measurements of PVC resins is discussed in relation to quality control of commercial suspension types. Some examples of simple solvent fractionation and precipitation with methanol are given. In addition, chromatograms of selected plasticisers are shown for analytical identification together with an indication of an approximate determination of the mol. wt. of plasticisers ranging from 400–10,000. Finally a short discussion of the influence of the parameters of operation, i.e. flow rate, volume of injection and concentration of the solution in tetrahydrofuran, is given. It is concluded that g.p.c. determinations of weight-average mol. wt. are in fair agreement with light-scattering measurements.     

Gel permeation chromatography: Dispersion effects on molecular weight monitor-installed gel permeation chromatograph

Computer simulation was carried out to examine the performance of a molecular weight (MW) monitor-installed gel permeation chromatograph (GPC), by taking account of the effects of limited column resolution according to Tung's phenomenological scheme. Efficiency of GPC fractionation was discussed also in the same light. For simulated GPC fractionation results of model polymers having log-normal distribution, various average MW's and MWD functions were calculated from the data obtained by the MW monitor method as well as the conventional MW calibration methods, and compared with the given true values. The MW monitor method generally tends to predict narrower distributions than the true ones, as opposed to the conventional calibration methods which usually predict broader distributions. For certain simple cases, semiquantitative relation between the extent of column resolution and these deduced average MW's was derived. The efficiency of GPC fractionation (as judged, for example, by the polydispersity of recovered fractions) is limited by such factors as fraction size, column resolution, and polydispersity of the original sample itself.     

Gel permeation chromatography for characterization of graft copolymer

Summary The present paper describes the grafting of vinyl monomers onto cellulose nitrate in non-aqueous medium using benzoyl peroxide as a catalyst. The complete separation of the homopolymers and graft copolymer was carried out by selective solvent extraction. The graft copolymer was characterized by IR spectra. The GPC was used as a technique to differentiate between homopolymer, polymer mixture, polyblend, and graft copolymer.     

Gel permeation chromatography of vegetable-oil-based printing ink vehicles

The apparent weight-average molecular weights (M_w ) of ink vehicles made from soybean, safflower, sunflower, cottonseed, and canola oils were compared by gel permeation chromatography (GPC), and the correlation between viscosity and M_w of these vehicles was established. Apparent M_w of vegetable oil gels that were used in vehicle preparation were also obtained by GPC. © 1992 John Wiley & Sons, Inc.     

Infrared detection of polymers in gel permeation chromatography

A gel permeation chromatograph equipped with an on-line Grubb-Parsons infrared spectrometer is described. The versatility, specificity, sensitivity, and limitations of such an infrared detector are discussed with particular reference to spectrometer specification, eluent absorbance, and solute absorbance. A stable baseline is produced when this detector is operated at high temperatures, e.g., for the separation of polyethylene in o-dichlorobenzene at 135°C. Individual functional groups in a chemically inhomogeneous solute, such as a copolymer, may be monitored by repeated injections of the solute, changing the wavelength setting between separations. This procedure is illustrated with AB poly(styrene-b-t-butyl methacrylate) block copolymer in trichloroethylene at 35°C.     

Gel permeation chromatography of high molecular weight cellulose trinitrate

Gel permeation chromatography measurements have been made upon cellulose trinitrate in ethyl acetate using samples which have already been well characterized by light scattering and osmometry. Columns were calibrated using polystyrene standards and it has been shown that the hydrodynamic volume calibration applies to cellulose trinitrate provided that all the data are extrapolated to zero concentration. It has also been shown that the resolution of the columns (as measured by the rate of change with count of logarithm of intrinsic viscosity), and the deviation from the true value of the apparent hydrodynamic volume at any given concentration depends only upon the relative viscosity of the sample. The validity of the hydrodynamic volume calibration does not necessarily mean that both polymers are fractionated solely by an exclusion process. It is possible that both react reversibly with the gel, and that there are compensatory hydrodynamic effects.     

Gel permeation chromatography of starch and other uncharged polysaccharides

Summary The experimental results given in this paper concern the gel permeation chromatography of starch and other uncharged polysaccharides (dextrans, levan, scleroglucan,...) in organic solvent. The experimental conditions (solvent, columns) are proposed to get after direct solubilization the molecular weight distribution of the polymers using a refractometric and a light scattering detectors on line.Laboratoire Propre du CNRS associé à l'Université Scientifique et Medicale de Grenoble     

Gel permeation chromatography: A guide to data interpretation

The importance of data produced by gel permeation chromatography (GPC) in polymer engineering is emphasized. The steps involved in deriving a differential molecular weight distribution curve (dMWD) from the chromatogram obtained by GPC are outlined. Each step is described, indicating its importance. Several viscosity-molecular weight relationships, useful in the production of relevant calibration curves from the polystyrene calibration, are included. The presentation of results and experimental procedures are given.     

Salt effect on gel permeation chromatography of partially charged polymers

The effect of the addition of 0.1M LiBr to dimethylformamide (DMF) solutions of charged and uncharged polymers has been studied by GPC and [η] measurements. LiBr has a salting-out effect on polyacrylonitrile (with (PAN-S) and without (PAN) sulfonate sulfur), polystyrene (PS), and poly(vinyl acetate) (PVAc), which is seen by a decrease in [η] and an increase in the GPC retention time. The increase in retention time is, however, abnormally high for charged polymers. Association in PAN and PAN-S solutions in DMF can explain the experimental observations.     

Gel permeation chromatography of polyethylene. I. Calibration

An accurate GPC calibration is essential if computer techniques are to be utilized in obtaining the molecular weight distribution and degree of long-chain branching from an intrinsic viscosity and GPC trace of a polymer. The use of the National Bureau of Standards Linear Polyethylene Standard Reference Material, SRM 1475, to calibrate GPC is described. Employing this calibration, the Mark–Houwink relationship for linear polyethylene in 1,2,4-trichlorobenzene was established utilizing narrow molecular weight fractions derived through fractionation of SRM 1475 and other polymers. This Mark–Houwink equation was subsequently employed for the evaluation of high molecular weight fractions which were then used to extend the GPC calibration to the high molecular weight region not covered by SRM 1475. An iterative technique was used to obtain coincidence of the measured intrinsic viscosity and the viscosity calculated from the GPC data. The accuracy of the GPC calibration was demonstrated by obtaining coincidence of the measured and calculated viscosity of high and low molecular weight polymers of both narrow and broad polydispersity.