Scaling parameters molecular weight dependence

To answer First, the concentration and molecular weight dependences of D, and Dp are considered. Second, having found that D, and Dp uniformly follow stretched exponentials in c, correlations of their scaling parameters and other polymer properties are examined. Third, for cases that examined a series of homologous polymers, a joint function of matrix... 

Recently, renormalization group calculations have been used to derive new scaling laws for the molecular weight dependence of the interaction parameter, Xab between unlike polymers (A and B) in a good solvent and the critical demixing concentration. The purpose of this paper is to present some experimental results which verify this theory for several mixtures of two polymers polystyrene (PS) - poly(dimethyl-siloxane) (PDMS), poly(methyl-methacrylate) (PMMA)-PDMS, PS-PMMA and PS-poly (vinylacetate) (PVAc). 

Here the scaling exponent v and scaling prefactor a are independent of polymer concentration, but may depend on polymer molecular weight. Phillies hydrodynamic scaling model predicts not only the molecular weight dependences of v and a but also approximate numerical values for both parameters(14). 

Now we compare the above osmotic pressure data with the scaled particle theory. The relevant equation is Eq. (27) for polydisperse polymers. In the isotropic state, it can be shown that Eq. (27) takes the same form as Eq. (20) for the monodisperse system though the parameters (B, C, v, and c ) have to be calculated from the number-average molecular weight M and the total polymer mass concentration c of a polydisperse system pSI in the parameters B and C is unity in the isotropic state. No information is needed for the molecular weight distribution of the sample. On the other hand, in the liquid crystal state2, Eq. (27) does not necessarily take the same form as Eq. (20), because p5I depends on the molecular weight distribution. 

Such approaches underpin the current popularity of RP-HPLC procedures for the purification of synthetic or recombinant polypeptides at the production scale, or analogous approaches employed in the HP-IEX of commercially valuable proteins. However, in some cases when linear scale-up methods are applied to higher molecular weight polypeptides or proteins, their biological activity may be lost due to unfavorable column residency effects and sorbent surface area dependencies. It is thus mandatory that the design and selection of preparative separation system specifically address the issues of recovery of bioactivity. Often some key parameters can be easily controlled, i.e., by operating the preparative separation at lower temperatures such a 4°C, or by minimizing column residency times. 

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