Polystyrenes intrinsic viscosity-molecular weight

Figure 2. Intrinsic viscosity-molecular weight data for polystyrene and polyvinyl chloride measured by osmometry and by SEC using broad MWD standard calibration (polystyrene (m) M = 7,06 X 10 in THF/1% PPG (O) [ ] =...

The first systematic evaluation of chain dimensions of stereoregular polymers in solution were reported by Danusso and Moraglio2). They studied both isotactic and atactic polystyrene by viscometry and osmometry, in benzene and in toluene, (both thermodynamically good solvents). They concluded that no difference could be observed in the intrinsic viscosity-molecular weight relationship, [tj] = k Ma, for the two stereoregular forms [see Fig. I]. However, they did find a noticeable difference between the second varial coefficients for the two stereoregular forms of equivalent molecular weight. These results were consistent with subsequent measurements on... 

Materials. Four samples of sodium poly(styrenesulfonate) (NaPSS) prepared by sulfonation of polystyrenes with narrow molecular weight distribution were purchased from Pressure Chemical Co. The characteristics of the samples, according to the manufacturer, are listed in Table I. The intrinsic viscosities of NaPSS in aqueous NaCl solution were measured using an Ubbelhode viscometer at 25 °C. 

SHEARING FLOW. Figure 3-14 shows the shear-rate-dependent viscosities of polystyrenes of various molecular weights in a couple of low-viscosity solvents, decalin and toluene (Noda et al. 1968 see also Kotaka et al. 1966). Plotted is the intrinsic relative viscosity, [r] l[r] o, against a dimensionless shear rate,... 

Polystyrene with a molecular weight of 1,000,000 in a theta solvent (ethylcyclo-hexane, 70°C) has an intrinsic viscosity of 0.75 dl/g. Calculate the steric factor. 

Fox and Floryf used experimental molecular weights, intrinsic viscosities, and rms end-to-end distances from light scattering to evaluate the constant in Eq. (9.55). For polystyrene in the solvents and at the temperatures noted, the following results were assembled ... 

The intrinsic viscosity of polystyrene in benzene at 25°C was measuredf for polymers with the following molecular weights ... 

The most widely used molecular weight characterization method has been GPC, which separates compounds based on hydrodynamic volume. State-of-the-art GPC instruments are equipped with a concentration detector (e.g., differential refractometer, UV, and/or IR) in combination with viscosity or light scattering. A viscosity detector provides in-line solution viscosity data at each elution volume, which in combination with a concentration measurement can be converted to specific viscosity. Since the polymer concentration at each elution volume is quite dilute, the specific viscosity is considered a reasonable approximation for the dilute solution s intrinsic viscosity. The plot of log[r]]M versus elution volume (where [) ] is the intrinsic viscosity) provides a universal calibration curve from which absolute molecular weights of a variety of polymers can be obtained. Unfortunately, many reported analyses for phenolic oligomers and resins are simply based on polystyrene standards and only provide relative molecular weights instead of absolute numbers. 

Figure 10 shows DRI and viscometer traces for the NBS 706 polystyrene standard. Based on the information from these two chromatograms in conjunction with the universal calibration curve, one can calculate the intrinsic viscosity EnJCv) and molecular weight M(v) at each retention volume as shown in... 

The use of a continuous GPC viscosity detector in conjunction with a DRI detector permits the quantitative determination of absolute molecular weight distribution in polymers. Furthermore, from this combination one can obtain Mark-Houwink parameters and the bulk intrinsic viscosity of a given polymer with a GPC calibration curve based only on polystyrene standards. Coupling these two detectors with ultraviolet and infrared detectors then will permit the concurrent determination of polymer composition as a function of molecular weight and... 

Studies of polystyrene standards in THF solvent are not uncommon. however, bothersome discrepancies still exist in the literature and in practice. For example, the published Mar 1<-Houw i nk parameters are in wide disagreement il. The purpose of this work is to examine a large number of PS standards from multiple suppliers, covering a wide range of molecular weights. T -,e intrinsic viscosities and GPC retention volumes have been measured and used independently to correlate and crosscheck the molecular weights provided by the suppliers. 

Dead Volume. The dead volume difference between the viscometer and DRI must be accounted for. Otherwise systematic errors in Mark-Houwink parameters K and u can occur. In the previous paper (16), a method developed by Lesec and co-workers (38) based on injecting a known amount of a very high molecular weight polystyrene standard onto low porosity columns was used. From the viscometer and DRI chromatograms, the apparent intrinsic viscosity [h] was plotted against retention volume V. A series of [n] vs. V plots are then constructed assuming a range of dead volume, AV. 

The following intrinsic viscosity values of some high molecular weight polystyrene fractions have been reportedf ... 

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