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Refractometric investigations of thin organic films

Kr. PETROVA1, Kr. NIKOLOVA2, V. LEONKIEVA1, S. KITOVA3, S. SAINOV1,*

Affiliation

  1. Central Laboratory of Optical Storage and Processing of Information, Bulgarian Academy of Sciences, 1113 Sofia, Acad. G. Bonchev Str., bl. 101, Bulgaria
  2. Physics Department, University of Food Technologies, Plovdiv, Bulgaria
  3. Central Laboratory of Photoprocesses, Bulgarian Academy of Sciences, 1113 Sofia, Acad. G. Bonchev Str., bl. 101, Bulgaria

Abstract

We have investigated the refractive indices (RI) of different polymer and gelatine films using a specially constructed two-wavelength laser refractometer. The critical angle is determined by the disappearance of the diffraction orders, well separated by the metal grating at 532 and 632.8 nm. The following polymers have been investigated: “Styrenic-A”, “Polyacrylate”, “Paraloid B72” and “Cellulose” as well as normal and Cr3+-hardened gelatine. The data obtained from the two-wavelength RI measurements are used for the dispersiometric analysis following Wemple and DiDomenico’s one-oscillatory model. RI differences between the sample-air and the sample-substrate interfaces are identified. In the case of normal gelatine, this difference depends on the type of substrate. Based on the Lorentz- Lorenz relation, the RI change is attributed to the density increase, governed by the adhesion forces, as well as the free volume re-distribution near the sample surface. The polar and dispersion components of the free surface energy of the substrate and gelatine layer are determined. On the basis of the results, the reversible work of the adhesion between the gelatine layer and different substrates is estimated..

Keywords

Optical polymers, Refractive index, Dispersion coefficients.

Submitted at: Nov. 1, 2006
Accepted at: Feb. 15, 2007

Citation

Kr. PETROVA, Kr. NIKOLOVA, V. LEONKIEVA, S. KITOVA, S. SAINOV, Refractometric investigations of thin organic films, Journal of Optoelectronics and Advanced Materials Vol. 9, Iss. 2, pp. 464-467 (2007)