ABSTRACT
The application of high temperature comprehensive two-dimensional (2D) liquid chromatography for quantitative characterization of chemical composition and molecular weight (MW) heterogeneities in polyolefins is demonstrated in this study by separating a physical blend of isotactic-polypropylene, ethylene-random-propylene copolymer, and high density polyethylene. The first dimension separation is based on adsorption liquid chromatography that fractionates the blend from low to high ethylene content. The second dimension is size-exclusion chromatography connected with light scattering (LS) and infrared (IR) detectors. The IR detector shows desired sensitivity and linearity for monitoring analyte concentrations in the eluent after 2D separations. In addition, the compositions of the analytes are also determined from the ratio of two IR absorbances at the specified wavelength regions, an absorbance for measuring the level of methyl groups in polyolefins and another absorbance for measuring concentration. The LS detector is used to determine absolute molecular weight of the analytes from the ratio of the light scattering signal to the IR concentration signal. The ability to obtain concentration, chemical composition, and MW of polyolefins after 2D separation provides new opportunities to discover structure-property relationships for polyolefins with complex structures/architectures.
Subject(s)
Chromatography, Affinity/methods , Chromatography, Gel/methods , Polyenes/chemistry , Hot Temperature , Linear Models , Molecular Weight , Polyenes/classification , Polyenes/isolation & purification , Polyethylenes/chemistry , Polypropylenes/chemistry , Reproducibility of ResultsABSTRACT
Infrared emission spectroscopy and multivariate calibration are used to provide a method for the quantitative analysis of liquid samples. Differing forms of the data including second derivative and interferogram representation are used for prediction of sample composition, thickness and temperature. Comparisons are made with transmission measurements of the same samples. In some situations emission measurements may be the preferred method of analysis.