Size exclusion chromatography-viscometer

Haney, M. A., The differential viscometer. II. On-line viscosity detector for size-exclusion chromatography, /. Appl. Polym. Sci., 30, 3037, 1985. 

Novolac molecular weights were measured in THF at 35°C by high pressure size exclusion chromatography using a Waters Model 510 pump (flow rate=1.0 ml/min), 401 differential viscometer detector and a set of Dupont PSM 60 silanized columns. A universal calibration curve was obtained with a kit of 10 narrow molecular weight distribution, linear polystyrene standards from Toya Soda Company. Data acquisition and analysis were performed on an AT T 6312 computer using ASYST Unical 3.02 software supplied with the Viscotek instrument. 

A more sensitive viscometer than the drop-time glass capillary method is also needed in size exclusion chromatography (SEC) such as the gel permeation chromatographic (GPC) analysis of polymer molecular weight distribution (MWD). In an SEC system, a concentration detector is commonly used for providing the weight concentration profile of the polymer elution curve. 

The size exclusion chromatography for this study was done in the routine manner execept for the inclusion of an online viscosity detector called a Differential Viscometer <3> (Viscotek Corp., Porter, Texas, USAl. This instrument together with an RI concentration detector permits the calculation of intrinsic viscosities across the chromatogram. An IBM PC data system with software is also provided (5). The software acquires data from both detectors, and performs calculations of intrinsic viscosity and molecular weight distributions using the Universal Calibration Method. 

Size exclusion chromatography has been greatly enriched recently by the advent of two commercial detectors, the real-time differential viscometer (DV) and the low angle laser light scattering (LALLS) photometer. The only DV detector currently available is offered by Viscotek in Porter, TX, as the model 100. 

Molecular characterization of the polymers consisted of intrinsic viscosity measurements and size exclusion chromatography. The intrinsic viscosities were measured in a solvent mixture of phenol and o-dichlorobenzene using Cannon-Ubbelhode viscometers. Polyethylene terephthalate equivalent molecular weights were determined using a Waters 244 GPC in a solvent mixture of methylene chloride and hexafluoroisopropanol. The results from NMR, DSC, and molecular characterization are summarized in Table I. Techniques for the dynamic x-ray diffraction studies are described elsewhere (2). 

Size Exclusion Chromatography (SEC) is widely used technique polymer characterization. The standard configuration of a SEC apparatus consists of three parts (/-5), viz., a solvent-delivery system (equipped widi an injection port), the columns, and a differential refractive index (RI) detector. This basic configuration can be modified by adding an additional detector, either in series or in parallel to the RI detector (J-5). The second detector can be a viscometer (2), a concentration detector (3), an UV detector (4) or a Light Scattering (LS) device (5),... 

Figure 2.2 Typical setup of size-exclusion chromatography equipped with triple detection for determination of the moiecuiar weight of polymers without the need for prerequisite calibration. DRi, differential refractive index detector DV, differentiai viscometer I, injector MALS, multi-angle light-scattering detector (depending on the model, the scattered light is measured at 3 or 18 different angles) P, pump. The central unit includes a computer and software.

Figure 3.36. Size exclusion chromatography system with an on-line viscometer and a lightscattering detector allows to create the Mark-Houwink-Sakurada plot without fractionating the polymer somewhere else. The concentration is detected by a refractive index detector or an ultraviolet absorption detector.

Zhang ZR, Saetre R. Characterization of styrene copolymers using size-exclusion chromatography with on-line FT-IR and viscometer detectors. Int J Poly Anal Char 2007 12 185-201. 

Norwood DP, Reed WF. Comparison of single capillary and bridge viscometers as size exclusion chromatography detectors. Int J Polym Anal Char 1997 4 99-132. 

The measurement of the effects of mastication on the molecular weight of the rubber can be time-consuming even with sophisticated techniques such as size exclusion chromatography. The viscosity of natural rubber is usually measured by means of a Mooney rotating disk viscometer, an established method for following the effect of mill time and conditions. Adhesive formulators have successfully used this instrument to correlate Mooney viscosity to rubber end-use properties. 

---