GPC/LALLS

Figure 3. Variation of the spreading factor with the elution volume. Key o> PS > PB> GPC-LALLS, PS.

Kolpak FJ, Cietek DJ, Fookes W, Cael JJ (1983) Analysis of lignins from spent alkaline pulping liquors by gel permeation chromatography/low angle laser light scattering (GPC/ LALLS) Appl Polym Symp 37 491-507... 

Table III contains the numerical results in Mn for the six different samples, for arms (lin) and stars (br). The values obtained by GPG-viscometry (V) and by GPC-LALLS (L) are in agreement. They ap-...

Table III. Number of Branches Per Star by GPC-Viscometry and GPC-LALLS...

Figure 11 represents the variations of < > as a function of the number of branches. The value strongly decreases when the number of branches in the stars increases. Again, a very good agreement is observed between GPC-viscometry and GPC-LALLS values. 

The characterization of star-branched polymers has been performed using triple detection because it was not obvious, in the beginning of this study, that universal calibration could be applied to star-branched polymers. In fact, the GPC software used handles experimental data as a double dual detection, GPC-viscometry and GPC-LALLS. Experimentally, it has been found that excellent agreement between results from these two sets of data can be obtained. GPC-viscometry uses a universal calibration curve and GPC-LALLS is free of any molecular weight calibration curve. Therefore, the universal calibration works well with very long chain branched polymers, even with a very particular... 

For both GPC/LALLS and intrinsic viscosity measurements, Burdick Jackson distilled-in-glass, UV grade tetrahydrofuran (THF) was used. GPC/LALLS e q>eriments were conducted at a constant, pulse-free solvent flow-rate of 1-0 ml/min. Solute concentrations were 0.1% (w/vol.) and the volume of injected solution ranged from 0.3 ml to 0.5 ml. Intrinsic viscosities for CTC in THF were measured at 25 C in a Cannon-Ubbelhode four-bulb shear dilution capillary viscometer (Size 50). Kinetic energy corrections were negligible eind the data were corrected for sheeu effects by extrapolation of n /c to zero shear rate (10). 

Accuracy and Reproducibility of GPC/LALLS. In Tcible I are shown molecular weight averages obtained from four successive analyses of the same CTC sample in order to assess the relative accuracy and consistency of the GPC/LALLS technique. As can be seen, the reproducibility of the technique is quite good with the average... 

Determination of K and from GPC/LALLS. The major assumption inherent in using GPC for the determination of polymer molecular weights and MWDs is that in solution the macromolecule is chroma-tographically fractionated according to its hydrodynamic volme. Unless monodisperse fractions of the polymer in question are availcdsle, one generally calibrates the GPC system by chromato-... 

M 70,000), for a given volume element, the GPC/LALLS technique predicts larger molecular weights than calculated from eq. tl3). The reversal of this trend at low molecular weights is probably due to imperfect column resolution at this extreme of the MWD and/or to expansion of the CTC coil at low molecular weights due to the bulkiness of the substituents and concomitant rigidity of the cellulose backbone (13). The former case will manifest itself in lower M values due to additional low molecular weight material while he latter would cause the solute to elute sooner than it would in an unexpanded state. 

We have repeated this procedure on a number of CTC prepeura-tions and have found invariably excellent superimposition of GPC/LALLS molecular weight data in the linear domain of the log CTC volume plot of Figure 6, which we view as indica-... 

Figure 6. Comparison of GPC calibration curves for CTC derived from intrinsic viscosity ond GPC/LALLS (9-0-) methods...

In the case of the nitrate, the data is taken from Sithola, et al. (17) while the CTC data is that determined by GPC/LALLS with CED intrinsic viscosities determined on the starting cellulose... 

Figure 7. Molecular weight—elution volume relationship determined by GPC/ LALLS for amylose tricarbanilate containing branched amylopectin tricarbanilate...

Malilii, F.B. Kuo, C.Y. Provder, T. Determination of the absolute molecular weight of a styrene-butyl acrylate emulsion copolymer by low-angle laser light scattering (LALLS) and GPC/LALLS. J. Appl. Polym. Sci. 1984,29, 925. 

ABSOLUTE MOLECULAR WEIGHT AND MOLECULAR WEIGHT DISTRIBUTIONS BY LALLS AND GPC/LALLS... 

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