Intrinsic viscosity single point

The molecular weight of SAN can be easily determined by either intrinsic viscosity or size-exclusion chromatography (sec). Relationships for both multipoint and single point viscosity methods are available (18,19). Two intrinsic viscosity and molecular weight relationships for azeotropic copolymers have been given (20,21) ... 

Frequently occurs that extrapolations do not have a common value at their origin ordinates. These deviations may be caused by inadequate lineal extrapolations. The above mentioned is the routine method used for [q] determination. The procedure is laborious and consumes a considerable amount of time and reactive because of this, several equations were developed which estimate intrinsic viscosity at one single concentration and do not require a graphic. They are known as "single-point" methods. 

Chee K.K. A critical evaluation of the single-point determination of intrinsic viscosity. Journal of Applied Polymer Science 34, 3 (1987) 891-899. 

Curvale, R.A., Cesco, J.C. 2009. Intrinsic viscosity determination by "single-point" and "double-point" equations. Applied Rheology 19, 5, 53347. 

Due to the high sensitivity of the viscometer, accurate readings of viscosity responses can be made with sample h gi values much less than 1.1. Therefore, saitple solutions of very low concentration can be analyzed in the viscometer to produce a single point intrinsic viscosity determination without the need of concentration extrapolation. As shown in Figure 7 for a polystyrene saitple, any h- u determination at the value of... 

LALS) in THF and the intrinsic viscosity of five of the samples was measured by the single point method. Combining the LALS data with the intrinsic viscosity work allows one to obtain the Mark-Houwink constants, and a, by plotting log[77] vs logMw. For PIPTBK, and a in THF at 25° were found to be 5xlO-3 ml/g and 0.75 respectively. 

The opportunity to measure the dilute polymer solution viscosity in GPC came with the continuous capillary-type viscometers (single capillary or differential multicapillary detectors) coupled to the traditional chromatographic system before or after a concentration detector in series (see the entry Viscometric Detection in GPC-SEC). Because liquid continuously flows through the capillary tube, the detected pressure drop across the capillary provides the measure for the fluid viscosity according to the Poiseuille s equation for laminar flow of incompressible liquids [1], Most commercial on-line viscometers provide either relative or specific viscosities measured continuously across the entire polymer peak. These measurements produce a viscometry elution profile (chromatogram). Combined with a concentration-detector chromatogram (the concentration versus retention volume elution curve), this profile allows one to calculate the instantaneous intrinsic viscosity [17] of a polymer solution at each data point i (time slice) of a polymer distribution. Thus, if the differential refractometer is used as a concentration detector, then for each sample slice i. 

Molecular Weight. The viscosity average molecular wei t of the homopolymer and copolymers was determined from single point determinations of viscosity of a 0.25% solution in Fisher purified cyclohexane at 30.0 + 0.01° C. The molecular wei t is calculated from the intrinsic viscosity, [q], using the relationship ( ... 

Masuelli, M. A., Illanes C. I. 2014. Review of the characterization of sodium alginate by intrinsic viscosity measurements. Comparative analysis between conventional and single point methods. Int. J. 

Zhao, Z. H., Sun, H. Z., Sun, M. K. 2002. Single point method to determinate the intrinsic viscosity of carboxymethylated chitosan. Marine Fisheries Research Chinese) 23 41-43. 

The most commonly used type of viscosimeter for the determination of the intrinsic viscosity or for single point measurements is the capillary viscosimeter. As the reproducibility with this type of viscosimeter depends on the clean execution of the measurement, a detailed description of the proceedings for a viscosimetric measurement is given below. 

Single point measurements are commonly used to determine the intrinsic viscosity via the so-called Fikentscher K-value. This method is, as shown in Determination of the intrinsic viscosity by viscosimetric measurements in Chap. 4, only applicable under very special conditions and should not be used anymore. Generally, single point measurements only serve for the determination of a viscosity value. 

The measurement of intrinsic viscosity using capillary viscometers can be a labour intensive and time-consuming exercise. However, polymer chemists undertaking characterisation studies in this way have been spared a significant amount practical work as a result of the development of so-called single point equations . These provide a method by which intrinsic viscosity can be determined when the flow time for the polymer solution is determined at only one concentration and compared to the flow time for that of the solvent alone. Solomon and Ciuta [23] proposed the following equation for use ... 

Alternatively the intrinsic viscosity (rjiy) can be estimated from a single point measurement by using (6.8), which showed more than 99 % accuracy at relatively low concentrations [2]. 

A simple way to estimate the molecular weight of PBIs is the measurement of intrinsic viscosity (f/iv) of the polymer in solution at a fixed temperature (normally 25-30 °C). The intrinsic viscosity is obtained by plotting the specific viscosity (tj p) as a function of the polymer concentration and extrapolating to zero concentration. In order to simplify the measurement process, a single-point method was proposed to calculate the tjiy from using (7.1) [35,50-52], where C is the polymer concentration in a concentrated acid, e.g., 96 wt% sulfuric acid. 

Shroff RN (1965) Single-point determination of intrinsic viscosity. J Appl Polym Sci 9 1547-1551... 

The above method is very inconvenient for studying the kinetics of polymer photodegradation in solutions. Considerable time and effort would be saved if, instead of determining rj i for a series of solutions, a single determination at a known concentration might be used to give [f/] directly. Many one-point intrinsic viscosity methods have been developed. Numerous relationships have been proposed, and these have been thoroughly reviewed [624]. 

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