Polymer solution depolarized scattering

Photomultipliers are used to measure the intensity of the scattered light. The output is compared to that of a second photocell located in the light trap which measures the intensity of the incident beam. In this way the ratio [J q is measured directly with built-in compensation for any variations in the source. When filters are used for measuring depolarization, their effect on the sensitivity of the photomultiplier and its output must also be considered. Instrument calibration can be accomplished using well-characterized polymer solutions, dispersions of colloidal silica, or opalescent glass as standards. 

The addition of water causes the formation of a coagulated phase of PBT solutions in any of the solvents named above (of course, the amount of water tolerated varies with the solvent, with the PPA solvent being the most tolerant toward water) (4). In very dilute solutions, the water causes enhanced depolarized scattering, interpreted to be the result of the formation of aggregates in which the rodlike chains are in parallel arrays (10). In more concentrated solutions, a gel phase is created (11,12). In either case, the electronic absorption spectra is altered from that characteristic of the protonated chain to that characteristic of the deprotonated, dry polymer (10). In the following we will report observations on this phase transition. 

According to Flory and coworkers [58, 59], experimentally measured J hv contains a contribution i Hv(col) from transient, collision-induced depolarized scattering. At infinite dilution this contribution arises from the collision of individual polymer chains with solvent molecules. Hence it has nothing to do with the intrinsic optical anisotropy of the solute polymer. 

Viscosity measurements of solutions of low-molecular weight PBO in chlorosulfonic acid and other solvents yielded a Mark-Houwink exponent of 1.85, which is very close to the value expected for a rodlike polymer [45]. Depolarized dynamic light scattering of PBT solutions in chlorosulfonic acid resulted in a persistence length of 64 nm, which is one of the highest persistence lengths known when compared with those of other rigid-rod polymers [58]. 

Petekidis G, Vlassopoulos D, Galda P, Rehahn M, Ballauff M (1996) Determination of chain conformation of stiff polymers by depolarized Rayleigh scattering in solution. Macromolecules 29 8948... 

Certain general relations used with the polarized static scattering from isotropic solutions are gathered in this section. Relations for the depolarized scattering from isotropic solutions are given in the section on Isotropic Solutions of Semiflexible Chain Polymers, and the static scattering from ordered solutions is considered in the section on Nematic Solutions of Semiflexible Chain Polymers. 

Doty, P. Depolarization of Light Scattered from Dilute Macromolecular Solutions. I. Theoretical Discussion. J. Polymer Sci. 3, 750—762 (1948). 

Lin S, Lin J, Nose T, lyoda T. 2007. Micellar structures of block copol5mers with ordered cores in dilute solution as studied by polarized and depolarized light scattering. J Pol5un Sci Part B Polym Phys 45 1333 1343. 

The methods of the Kerr effect and the depolarization of scattered light have not so far been applied to the realm of high polymers, but it is conceivable that by their aid it will be possible to obtain data for relatively complex molecules on the symmetry and form of the particles and on the position of substituents. It should, of course, be emphasized that both methods are particularly sensitive to molecular interaction and they should therefore be applied as far as possible to the gaseous state or to that of dilute solution. 

Figure 9.1 Depolarized structure factor for Uthium molybdenum selenate in dilute propylene carbonate solution. The measured rod length is 2 (im. (From Patterson, G.D., Ramsay, D.J., and Carroll, RJ., Depolarized light scattering spectroscopy and polymer characterization, Analytica Chimica Acta, 189, 57,1986. With permission.)...

Depolarized light scattering spectroscopy was applied by Degiorgio, et al. to solutions of a fiuorinated latex polymer(10). The orientations of pairs of spheres are uncorrelated, so as discussed in Section 10.4 the VH spectrum is determined entirely by the self- part of the dynamic structure factor appropriate analysis of the VH spectrum determines both Ds and the rotational diffusion coefficient Dr. Degiorgio, et al. found that Ds(4>) and Dr(4>) are both accurately described, for... 

Semidilute solutions of rod-like polymers are also of basic interest in polymer science. In semidilute solutions, even at low concentrations, the rod molecules are overlapping and entangled but are still isotropic, having no liquid crystalline order. Combinations of static and dynamic, and polarized and depolarized light scattering could reveal characteristic features of the solution over the concentration range from the isotropic to lyotropic liquid crystalline regions. By DLS of depolarized components based on eqn [126], Zero and Pecora observed translational and rotational diffusion of polypeptides in semidilute solutions. 

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