Viscometry specific viscosity

Viscometry has been used extensively to provide information on the hydrodynamic properties of solutions of block copolymer micelles. The specific viscosity, J7sP, divided by the concentration, can be used to determine the intrinsic viscosity, [r/], by extrapolation via... 

Viscometry The specific viscosity of each polymer from the bulk polymerization was measured in acetone at 30°C using an Ubbelohde dilution viscometer. Five concentrations in the range of 1.120 to 0.242 g/d poly(vinyl acetate) and polyvinyl trideuteroacetate) and 0.385 to 0.084 g/dl (poly(trideu-terovinyl acetate)) were run. Intrinsic viscosity was calculated by extrapolation of the Tlsp/c versus c plot to zero concentration. Number average molecular weights were calculated using the equation(20) [q] =1,0 x 10 1 [Mn] 0 72 which is in the mid range of the equations listed. 

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. 

These authors determined crystallinity (and thus S ) from x-ray diffraction data molecular accessibility and surface area of variously milled samples were obtained from iodine adsorption and BET measurements. Degree of cellulose polymerization was determined from viscometry of cadoxen-dlssolved solutions, with the specific viscosity extrapolated to zero concentration to obtained the intrinsic viscosity, [ri], from which in turn the viscosity average molecular weight M was estimated from the Mark-Houwlnk equation ... 

The former is a calibration-dependent procedure, and Mark-Houwink constants for the standards are readily obtained from calibration-viscometry measurements. These have been reported for PEG and PEO (29). For the latter method, however, a simple ratio of the concentration signal to the specific viscosity signal in a viscometry analysis yields the IVD (peak parameters, mass injected, and viscometer inlet pressure must be known). The IVD method is a calibration-indepetident procedure. By inputting the Mark-Houwink values, molecular weights can be calculated using the Mark-Houwink relationship. Because this procedure is calibration independent, it may hold significant value for quality or process control applications (28). 

Polymers 5 and 7 were furthermore studied by viscometry in ultrapure water, in the absence of salt. As an example, values of the reduced viscosity, T[sp/C of 7 are plotted against polymer concentration C. For both polymers, the reduced viscosity increased strongly with decreasing polymer concentrations, exhibiting a pronounced concave-upward relationship (Psp is the specific viscosity) (see Fig. 2). This behavior is typical of polyelectrolytes. ... 

One of the easiest means of determining the molar mass of a polymer is via viscometry. This yields the viscosity average molar mass, Mt . The viscosity of a polymer solution can be measured using capillary viscometers. The time for flow of the polymer solution through a given distance is measured and this is proportional to viscosity. The viscosity obtained by this method is expressed relative to that of the pure solvent. To determine molar mass, the intrinsic viscosity is required. It has this name because it relates to the intrinsic ability of a polymer to increase the viscosity of a solvent. The intrinsic viscosity [ j] is related to the specific viscosity jsp = 1 — rj/rjo, where rj is the viscosity of the polymer solution and rjo is that of the solvent via a virial equation in concentration resembling Eq. (2.9). It has been found empirically that for many polymer solutions the Mark-Houwink equation for intrinsic viscosity is obeyed ... 

Capillary flow viscometry has been extensively used to investigate micellar solutions of block copolymers. Values of sp/c, where is the specific viscosity, have been reported for dilute micellar solutions of various block and graft copolymers. The effects of temperature and... 

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