Subject segmental size

Polymer theory of dilute solutions predicts universal behaviour for key static properties of the polymer chains in the limit of very high degree of polymerization. The main thing of interest here is that these properties depend only on the overall extension of the chain and not on its chemical character or individual segment size. Thus, it was felt imperative to analyze the molecular properties of HEC in this well established framework. Aqueous solutions of HEC, having molecular weights Ml = 9 X 10" Da, M2 = 7.2 x 10 Da and M3 = 1.3 x 10 Da, were subjected to viscosity studies and the intrinsic viscosity, (t/), of each sample was determined (Fig. 25). The calculated value of intrinsic viscosity were 1.16, 7.28, 9.77 dL g for samples with molecular weights Mi, M2 and M3 respectively. 

The portal segments and the hepatovenous segments are, however, subject to considerable individual variations with respect to their size and the position of their boundaries. This point must always be considered in cases of hepatectomy. For this reason there is, as yet, no general agreement about the designation of the segments. (16, 28, 70)... 

As has already been stated, the verified possibility of extending the reduced variables principles to ABS resins makes it possible to treat these typical heterophase systems as blends of amorphous homophase polymers and plasticizers. One possible explanation is that over the experimental y range it is not possible to separate the contributions of the two different phases, and the materials will behave as homophase polymer. In fact, long-time molten polymer rheology experiments measure viscoelastic processes over the entire molecule, and, as a consequence, molecular compatibility is evaluated (13). On the other hand, high frequency and/or low temperature tests involve the main chain as well as the side chains of the polymer system the segmental miscibility of the polymer-polymer system is then evaluated. It is important in experimental measurements of polymer compatibility to evaluate the actual size of the volume subject to the test. 

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