Characterisation dilute solution methods

Characterisation of Gum Rubber Using Dilute Solution Methods... 

The dilute solution methods have been used for characterising polymers since day one of polymer science. Measurements of dilute solution viscosity, osmotic pressure and light scattering have been well-established in theory as well as in practice. They are described practically in every textbook and in many review articles. More than 30 years have passed since the introduction of size exclusion chromatography (or gel permeation chromatography CPC), which provides fractionation data very conveniently. This chapter is not intended to be a review of these methods. It is directed to examining how useful these methods are with respect to sensitivity, reproducibility, and reliability. Stated differently, the question is whether or not differences in processability can be explained on the basis of information available from the dilute solution methods. 

As described in Chapters 1, 2 and 4, gels are present in many gum rubbers, exerting a critical influence on their processability. For gel-containing rubbers, the dilute solution methods are not applicable, because gels are removed by filtration. Therefore, the determination of gel content is the first order of the business in the characterisation of gum rubbers. 

The long relaxation times introduced by the long branches of commercial gum rubbers have significant influence, even though the amount of the branched fraction may be very small. In the characterisation using dilute solution methods sometimes the branched fraction is filtered off. Then, the interpretation of the processability becomes very difficult. 

In this chapter a method is proposed for finding the fractal dimension (D) of a macromolecular coil in solution, which uses only the characteristic viscosity of the polymer in an arbitrary solvent and a 0 solvent. Several examples are given to illustrate the applicahility of the proposed method to biopolymers of different classes. From D, one can determine a number of other important parameters characterising the behaviour of polymers in dilute solutions. 

Electro-Optic Methods for Characterising Macromolecules in Dilute Solution... 

In this brief survey the author will outline a number of electrooptical methods in current use and give illustrative results wiiich demonstrate their practical utility. Theory for the various effects will be given predominantly for cylindrically symmetric molecules which are rigid, uncharged and non-interacting as this is the best developed to date and allows a useful comparison between the methods. Reference will be made to work done on flexible systems. The object of this survey is primarily to introduce those scientists who are on the look-out for novel methods to characterise macromolecules in dilute solution to electro-optic experiments and to demonstrate the potential and versatility of the methods. The selected illustrative data on various polymer solutions are not intended to be comprehensive. They have simply been drawn from studies conducted in the author s research group. 

Initially fermentation broth has to be characterised on the viscosity of the fluid. If the presence of the biomass or cells causes trouble, they have to be removed. Tire product is stored inside the cells, the cells must be ruptured and the product must be freed. Intracellular protein can easily be precipitated, settled or filtered. In fact the product in diluted broth may not be economical enough for efficient recovery. Enrichment of the product from the bioreactor effluents for increasing product concentration may reduce the cost of product recovery. There are several economical methods for pure product recovery, such as crystallisation of the product from the concentrated broth or liquid phase. Even small amounts of cellular proteins can be lyophilised or dried from crude solution of biological products such as hormone or enzymes.2,3... 

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