Optical Properties In Solution Research Articles

Optical rotatory properties of synthetic polymers. I. Optical inversion of poly(propylene oxide)

Abstract(+)‐1,2‐Diethoxypropane, a model diether for the repeating unit of poly(propylene oxide), was prepared, and its behavior in solutions regarding optical rotatory dispersion and proton magnetic resonance was compared with those of the polymer. It was found that the model compound and the poly(propylene oxide) show essentially the same optical properties in solutions. By using the Brewster model of optical activity, it was concluded that the solvation of the polymer may well modify the polarizability of the optically active species to cause changes in the order of the polarizabilities of four atoms directly attached to the asymmetric carbon atom. The explanation is shown to be applicable also to some of related polymers.

An electronic simulator for transient processes

Molecular relaxation processes are often manifest through the transient changes in the optical properties of solutions of the molecules. Relaxation times are currently obtained by analysing the coordinates of photographic records of the transient behaviour and plotting suitable semi-logarithmic graphs. This procedure is laborious. A device is described herein which obviates this procedure. It enables experimental transient curves to be simulated almost immediately for the three important cases: (i) where a single exponential process is involved; (ii) where two such processes are summed together in the final response; (iii) where two such processes act in opposition in the final response. The last case is extremely difficult to analyse by the conventional geometric method mentioned above. Details are given of the design of the simulator and its mode of use. Typical results for each of the cases (i), (ii); (iii) are given with reference to measurements of the Kerr effect (electrically induced double refraction) of dilute macromolecular solutions.

Metal-ammonia solutions. V. Optical properties of solutions in the intermediate concentration region

Metal-ammonia solutions. V. Optical properties of solutions in the intermediate concentration region

Experimental theromodynamics of the helix-random coil transition. I. Influence of polymer concentration and solvent composition in the PBG-DCA-EDC system.

AbstractThe course of the reversible helix formation of poly(γ‐benzyl L‐glutamate) (PBG) dissolved in a mixture of dichloroacetic acid (DCA) and 1,2‐dichloroethane (EDC) was followed by measuring the heat capacity and the optical rotation of the system through the transition region. The results of these measurements indicate that the transition enthalpy ΔH the transition temperature Tc, and the Zimm‐Bragg parameter σ depend considerably on the PBG concentration as well as on the composition of the solvent. For the standard state of infinite dilution, however, a linear extrapolation of the measured ΔH if values results in a standard value ΔH° = 950 cal./mole, independent of the solvent composition. The results of the calorimetric measurements are discussed in relationship to changes in optical rotation. Some peculiarities in the measured thermodynamic and optical properties in solutions with relatively high content of dichloroacetic acid are reported.