Polymer Conformation under Confinement.

The conformation of polymer chains under confinement is investigated in intercalated polymer/layered silicate nanocomposites. Hydrophilic poly(ethylene oxide)/sodium montmorillonite, PEO/Na⁺-MMT, hybrids were prepared utilizing melt intercalation with compositions where the polymer chains are mostly within the ~1 nm galleries of the inorganic material. The polymer chains are completely amorphous in all compositions even at temperatures where the bulk polymer is highly crystalline. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) is utilized to investigate the conformation of the polymer chains over a broad range of temperatures from below to much higher than the bulk polymer melting temperature. A systematic increase of the gauche conformation relatively to the trans is found with decreasing polymer content both for the C⁻C and the C⁻O bonds that exist along the PEO backbone indicating that the severe confinement and the proximity to the inorganic surfaces results in a more disordered state of the polymer.

Angular dependence in infrared linear dichroism: a reevaluation of the theory.

Parameters such as the viewing angle and the extinction ratio (the ratio of the transmitted light over the total light intensity that reaches the sample) are very important in the design of novel optical devices such as new types of polarizers, liquid crystal displays, etc. The initial aim of this work was the comparison of experimentally obtained results to the currently accepted theoretical model that is based on Zbinden's theory of intensity ellipsoid. Due to observed discrepancies between the above theory and experimental data, a new mathematical model was generated in order to adequately explain the experimental results. This new theory allows the calculation of light absorbance at every combination of azimuthal and tilt angles in complete agreement with the experimentally determined values. In addition, in this paper we settle, once and for all, the confusion that exists in the spectroscopic literature with regard to the dependence of absorption and transmission values vis-à-vis the angle of incidence of the incoming light. We conclusively show that it is absorptance (alpha) and not absorption or absorbance (A) which shows a cos(2) dependence on the angle formed by the electric vector and the dipole.