Viscosity of high molecular weight polymers

Cowan, M.E., Garner, C., Hester R.D. and McCormick, C.L. (2001) Experimentally determined drag reduction efficiency and extensional viscosity of high molecular weight polymers in dilute aqueous solution. J. App. Poly. Sei., 82, 1222-1231. 

Most ophthalmic products, however, cannot be heat sterilized. In general, the active principle is not particularly stable to heat, either physically or chemically. Moreover, to impart viscosity, aqueous products are generally formulated with the inclusion of high molecular weight polymers, which may, similarly, be affected adversely by heat. 

A laminar-flow reactor (LFR) is rarely used for kinetic studies, since it involves a flow pattern that is relatively difficult to attain experimentally. However, the model based on laminar flow, a type of tubular flow, may be useful in certain situations, both in the laboratory and on a large scale, in which flow approaches this extreme (at low Re). Such a situation would involve low fluid flow rate, small tube size, and high fluid viscosity, either separately or in combination, as, for example, in the extrusion of high-molecular-weight polymers. Nevertheless, we consider the general features of an LFR at this stage for comparison with features of the other models introduced above. We defer more detailed discussion, including applications of the material balance, to Chapter 16. 

A useful quasi-quantitative technique allowing determination of the degree of association of such polymers was reported by Professor Morton(15). The viscosity of concentrated solutions of high molecular weight polymers is proportional to a power of their weight average molecular weight, M, viz.,... 

Hence, the viscosity of the solution of high-molecular weight polymers substantially decreases on addition of the oligomer salt and the viscometrically determined average degree of association, N, should allow a reliable determination of the equilibrium constant, K, of the athermal mixing process. 

Poly(arylenethioether phenylquinoxaline)s have been prepared from the reaction of a bis(chloroquinoxaline) compound with 4,4 -dimercaptodiphenyl ether [19]. The polymer of structure 4 had an unusually high intrinsic viscosity of 4.0 dL/g, a Tg of 243 °C and good solubility in NMP and chloroform. The greater nucleophilicity of the thiophenolate anion versus the phenolate anion allowed the formation of high molecular weight polymer from the... 

Advantages of emulsion polymerization are rapidity and production of high-molecular-weight polymers in a system of relatively low viscosity. Difficulties in agitation, heat transfer, and transfer of materials are minimized. The handling of hazardous solvents is eliminated. The two principal variations in technique used for emulsion polymerization are the redox and the reflux methods. 

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