Light scattering by polystyrene films containing carbon nanoparticles

UDC 535.361 Laser (λ = 0.63 μm) Mueller polarimetry at different angles of incidence and detection is used to measure the elements of the Mueller matrices of polystyrene films, as well as of polystyrene films modified by adding carbon nanoparticles (fullerenes or nanotubes). The complex index of refraction, depolarization index, and po- larizance (degree of polarization) of the test samples are determined. It is shown that adding even a small amount (1.0-3.5 mass %) of fullerenes or carbon nanotubes changes the depolarization properties of the modified polystyrene films. Depending on the illumination and observational geometry, these films are found to have different depolarization properties. Introduction. Adding fullerenes and carbon nanotubes to polymers extends the ways in which their properties can be modified (1). Polymer carbon nanocomposites can be used in the aerospace, electronics, and optoelectronics in- dustries as electrically conducting dyes, coatings, sealants, bonding materials, fibers, films, plates, and structural compo- nents (2). Thus, a comprehensive study by means of laser Stokes and Mueller polarimetry of the optical properties of polymers modified with carbon nanoparticles is of interest for basic research and as an applied problem in modern ma- terials science. Solving this problem will aid in formulating the physical foundations of new methods for remotely moni- toring the optical characteristics of scattering materials with inhomogeneous structures and will also reveal the most informative and reliable polarization diagnostic techniques for new polymer materials based on carbon nanoparticles. In this paper the optical properties of polystyrene (PS) films modified with carbon nanoparticles are deter- mined by laser goniophotometric (directional) Mueller polarimetry. Experimental Technique. The reflected (scattered) and transmitted (through the material) light can be repre- sented as a combined incoherent beam described by four parameters that form the four dimensional Stokes vector pa- rameter S (3-8), which is written as a column {I, P1, P2, P3}. The Stokes parameters I, P1, P2, P3 all have the dimensions of intensity and they fully characterize the polarization state of the light: I is the intensity of the light and P1, P2, and P3 are parameters that characterize primarily the horizontal polarization, polarization at an angle of 45 o , and right circular polarization. It is convenient to write the Stokes vector in the normalized form (3-8)