Birefringence adsorption

The electric light scattering effect of /3-FeOOH suspension, stabilized by NaCMC adsorption [12], resembles the electric birefringence effect of aqueous NaCMC with close charge density of the macromolecules (Figure 6). Since the NaCMC solution with concentration 2 X 10 2 g dm-3 gives a very weak scattered intensity, the electric birefringence data of Ookubo et... 

The phase shows poor birefringence beyond a narrow wavelength range close to the adsorption edge. 

Bian S, He J A, Li L, Kumar J, Tripathy SK. 2000. Large photoinduced birefringence in Azo dye/polyion films assembled by electrostatic sequential adsorption. Adv Mater 12(16) 1202 1205. 

However, when applying results of the type (57), it must be borne in mind that such equations apply to the amorphous constituent only, and must fail at advanced degrees of stretch where crystalliisation sets in since the influence of crystallisation on the double refraction of rubber-like polymers is considerable In addition to the intrinsic double refraction of the gel frame, the swollen gel may show structural double refraction and adsorption double refraction. The structural, or textural , birefringence is caused by the difference between the refractive indices of polymer substance and solvent. It was estimated by Wiener for rod-shaped particles and for platelets. Wiener s theory is not applicable to rods of molecular thickness, and the structual double refraction caused by oriented long-chain molecules has not yet been accessible to a reliable theoretical treatment. 

The adsorption double refraction results from orientated adsorption of solvent molecules on the polymer frame. There are indications that this effect plays a part in the double refraction of certain systems However, a theoretical approach to this type of birefringence does not exist. Notwithstanding these difficulties, Treloar ... 

ADSORPTION BIREFRINGENCE IN CELLULOSE NITRATE FILAMENTS ACCORDING TO VeRMAAS A X 10 ). 

These experiments show that one will always have to bear in mind the possibility of a component of birefringence due to adsorption, when dealing with swollen gels, a fact which sofar has been frequently overlooked. Particularly if this component is small, it will, however, not always be easily detectable. It may then be confounded with other effects and lead to erroneous conclusions. 

It should be remarked that the liquids concerned only show zntermicellar swelling and no trace of intramiceWzv swelling. Hence, the term adsorption birefringence seems to be justified. 

Many simulations of dynamic phenomena such as adsorption, electrophoretic motion, complexation, dilute solution viscosity, and electric birefringence have also been reported for polyelectrol5des, often for the purpose of gaining insight into experimental situations too complex for analytical theory. These... 

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