Characteristic ratio from intrinsic viscosity

For another synthetic ( conventional") vinyl polyelectrolyte, sodium polyacrylate, Takahashi and Nagasawa (42) have measured the intrinsic viscosity of a number of fractions under G conditions (1.056 N NaBr at 15° C) and report 11.0 as the characteristic ratio value of that polymer [using the value 0 — 2.87 10 for the universal parameter in equation (1)]. Both the polyvinylsulfonate and polyacrylate samples used by Eisenberg and Woodside and by Takahashi and Nagasawa were however of the conventional type, and thus composed of chains of unknown tacticity. This fact makes it more difficult to compare the experimental values with those dedudble from theories based on... 

CV. The intrinsic viscosity [ri] and can be obtained directly from the viscosity distribution, outlined earlier, in connection witli Equation (3). Now, a Mark-Houwink exponent [Equation (6)] can be approximated. The ratio n can then be estimated from the viscosity distribution when the molecular weight distribution is set equal to either a log normal or the even more widely applicable generalized exponential distribution. The parameters characteristic of either assumed molecular weight distribution are easily fit from the moments of viscosity distribution. Once this is done, all average molecular weights can be estimated in principle. Because of analytical uncertainties in the high-molecular-weight tails of the distributions of most synthetic polymers, however, it is wise to confine these estimates to... 

Table 16.1 Poly(acrylic acid) molecular weight (MW) characteristics. Included are the manufacturer s catalog values, reported polydispersity (ratio of weight to number-averaged MW) and those determined from the measured intrinsic viscosities...

A recent (smaller) list (496) of Theta Temperatures is mainly concerned with unperturbed dimensions. Since these dimensions are often evaluated from measurements at nontheta temperatures using various theories of intrinsic viscosity/molar mass, or (far less frequent) radius of gyration/molar mass relationships, reported theta temperatures are often not theta temperatures per se but the temperatures at which measurements in thermodynamically good solvents have been performed. A comprehensive list of imperturbed dimensions of various polymers can be foimd in Section VIl/1 of this Handbook and a list of characteristic ratios of polymethacrylates in (497). 

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