Viscometry data analysis

Absolute MWD can be measured using light scattering or viscometry combined with universal calibration. Compositional drift over the MWD of a polymer can be measured using a UV spectrophotometer and a differential refractive index detector. The increase in the available information also expands the complexity of data analysis. We discuss some of the concerns regarding data analysis that arise in multidetector SEC. 

J. W. Mays and N. Hadjichristidis, Polymer characterization nsrng dilnte solntion viscometry, in Modern Methods of Polymer Characterization (H. G. Barth and J. W. Mays, eds.), John Wiley Sons, New York, 1991, pp. 227-269. C.-Y. Kno, T. Provder, M. E. Koehler, and A. F. Kah, Use of a viscometric detector for size exclnsion chromatography, in Detection and Data Analysis in Size Exclusion Chromatography (T. Provder, ed.), American Chemical Society, Washington, DC, 1987, pp. 130-154. 

A complementary use of polymer viscometry is the indirect evaluation of the MWD of a polymer from dynamic viscosity measurements [28-30]. The methods used to correlate the MWD of polymers to rheological data are based on the previous determination of the polymer relaxation spectrum from linear oscillatory shear experiments [31, 32]. MWDs obtained from viscometric data analysis can help in the determination of the MWD curve from online measurements, or in cases where this curve cannot be easily determined from size exclusion chromatography (SEC) [30, 31]. 

Viscometry measurements were made in benzene at 30 °C and in TFE at 50 °C with uncalibrated Cannon-Ubbelohde dilution viscometers which gave solvent times greater than 100 seconds. The viscometers used had centistoke ranges denoted by viscometer sizes of 50 and 75 for benzene and TFE, respectively. Stock solutions were made up on gram solute/100 gram solution basis and converted to gram/deciliter via the solvent density at the temperature of measurement. The solvent densities used were d ene = 0.8686 (11a) and dlra = 1.3429 obtained from pycno-metric measurements (12). The density—temperature relationship for TFE obtained from regression analysis of the experimental pycnometric data is... 

A detailed structure characterization of isobutylene and 0-pinene copolymers has been carried out including homogeneity studies (by GPC), quantitative composition and sequence analysis (by PMR and reactivity ratios) and molecular weight determinations (by osmometry and viscometry). Analysis of our data leads us to conclude that isobutylene and 0-pinene can be readily copolymerized to reasonably high molecular weight materials and that the products are perfectly random, statistical copolymers showing no detectable tendency for blockiness . 

The historical emphasis on the trinitrate ester as the derivative of choice for early experimental work on the SEC analysis of cellulose and cellulosics and the continued use of the trinitrate in this capacity are readily understandable. Cellulose nitrate was known to be soluble in organic solvents, and a mild method for its preparation with a high nitrogen content (approximately 13.4% N compared to 14.1% N theoretically) was reported (130). In addition, cellulose trinitrate was extensively used in previous studies of cellulose by viscometry, osmometry, ultracentrifugation, and fractional precipitation. Thus, SEC data could be readily compared with existing data for the trinitrate derivative. 

Figure 10.17 The viscosity-temperature data set measured using thermomechanical analysis (TMA) indentation viscometry of the National Bureau of Standards (NBS), USA, 711 glass is compared to that obtained using the Vogei-Fuicher-Tammann [9] model issued by the NBS [32].

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