Molecular mass, determination Gaussian

This method was widely used by Mangaray et al. The authors have presented [11] as the Gaussian function of (8j - 82). Therefore, dependence (1/ ()ln[Ti]j /= /(8,) can be expressed by a straight line intersecting the abscissa at a point for which 8 = 8j. For natural rubber and polyisobutylene, the paraffin solvents and ethers containing alkyl chains of a large molecular mass were studied. For polystyrene, aromatic hydrocarbons were used. For polyacrylates and polymethacrylates esters (acetates, propionates, butyrates) were used. The method was used for determination of 8j of many polymers. " In all cases, the authors observed extrema in the dependence of [tj] = f(8,), and the obtained values of 82 coincided well with the values determined by other methods. But for some polymers it was not possible to obtain extremum in dependence of [q] = f(8,). ... 

Neutron reflectometry has also been used to determine the structure of the surface excess layer in aqueous solutions of polyethylene oxide (Lu et al. 1996). Only two relative molecular masses were used ( 20000 and 90000) but no differences in the reflectivities and the volume flection profiles were observed for the 0.1 wt% solutions used. Volume fraction profiles that were either three layers or the sum of two half Gaussians were both found to represent the data well figure 5.22 shows both of these models of the surface excess for the poly(ethylene oxide) with a relative molecular mass of about 20000. 

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