Characterization of non‐homogeneous polymers with size‐exclusion chromatography by implementing an on‐line viscometer

Abstract

The viscosity distribution of a polymer sample can be obtained by using an on-line viscometer as a detector in size-exclusion chromatography. This newly defined viscosity distribution is closely related to the molecular weight distribution and expresses weight fraction times intrinsic viscosity of species i as a function of the corresponding molecular weight times intrinsic viscosity (w, [q,] vs. MI [ql I). The intrinsic viscosity ([q]) and number-average molecular weight (M,) can be obtained directly from a viscosity distribution. If the Mark-Houwink exponent a is known (or approximately known) for non-homogeneous polymer the Mw/M, can be estimated from the viscosity distribution when the molecular weight distribution is approximated with a known distribution function. These estimates are independent of any other detector and are valid even for nonhomogeneous polymer samples. The relation between the moments of the viscosity distribution and the &?,/an is presented for two widely used distribution functions, the Log-Normal and the Generalized Exponential Distributions. Polymer characterization based on the viscosity distribution is shown to be a robust technique. It is particularly attractive in characterizing non-homogeneous polymers since it is solely obtained from on-line viscometer.

Arborescent Graft Copolymers: Highly Branched Macromolecules with a Core-Shell Morphology

“…The number-average molecular weights, M h n (ov), determined from the on-line viscometer data, are also reported in Table 2. The data analysis algorithm used 15 should allow calculation of an absolute number-average molecular weight based uniquely on the viscometer data. The method uses the so-called viscosity distribution, consisting of w i [η i ] as a function of M i [η i ], where w i , [η i ], and M i represent the weight fraction, intrinsic viscosity, and molecular weight, respectively, of the polymer in each slice analyzed.…”

“…standards. The number-average molecular weight of the sample is then calculated as the reciprocal of the -1 moment of the viscosity distribution:15 Comparison of M h n (ov) values in Table2and M h w (ls) values determined from static light scattering (Table…”

Estimation of Number-Average Molecular Weights of Copolymers by Gel Permeation Chromatography−Light Scattering

“…As shown by Goldwasser 15 and Rudin, GPC−viscometry yields true M n values for copolymers, even if the slices are heterogeneous. Their method relies on the validity of universal calibration for the copolymer under investigation whereas this requirement is not necessary for GPC−LS, i.e.…”

“…Goldwasser 15 and Rudin 16 proposed a method for the determination of M n of copolymers using exclusively an on-line viscosity detector together with a universal calibration curve, which overcomes the problem of compositional drift. The application of GPC-light scattering (GPC-LS) to copolymers has not yet reached much attention.…”

Hyphenated Techniques in Liquid Chromatography of Polymers

“…The application of refractive index and differential viscometer detection in SEC has been discussed by a number of authors [66][67][68]. Lew et al presented the quantitative analysis of polyolefins by high-temperature SEC and dual refractive index-viscosity detection [69].…”