Simultaneous determination of elastic and optical properties of polymers by high performance Brillouin spectroscopy using different scattering geometries

Abstract

General aspects of high performance Brillouin spectroscopy in polymers using special scattering geometries such as 90A-scattering geometry are discussed. Technical improvements are reported resulting in absolute accuracies up to 0.05 % for sound velocity determination. A method of data analysis is presented delivering simultaneously the complete set of elastic stiffness constants. The influence of birefringence on the Brillouin line shifts in anisotropic polymeric systems is estimated and techniques to reduce this influence are proposed. The determination of the principal refractive indices by Brillouin spectroscopy is discussed. Furthermore, a quantity D x, which is sensitive to hypersonic relaxation processes, is introduced.

Structure and anisotropy in polycarbonate III. Study of elastic and optical properties of oriented samples with the method of high resolution Brillouin spectroscopy

“…A convenient way to determine the complete elastic stiffness tensor and the main refractive indices of anisotropic materials with the method of high performance BS has been discussed extensively in a recent publication [7]. In the following, results from this work are used and only briefly reviewed here.…”

“…Using simultaneously all sound velocity data determined with the 90 A-and the 90 R-scattering geometries, all five independent elements of the elastic stiffness tensor can be determined by a least squares fit procedure [7].…”

“…Elastic and optical properties of the plate-like PC samples were determined using the 90A-and the 90R-scattering geometries [7,9].…”

“…A characterisation of the uniaxially oriented PC-samples1), is given in Table 1 in terms of stretching temperature Ts, birefringence An' (measured with a polarizing microscope at ~ = 545 nm but transformed to X = 514.5 nm), and stretch ratio ;ts (for samples [1][2][3][4][5][6][7]. ~s was determined from An' using an experimental curve of~s versus An' at a stretch temperature Ts = 160 ~ For more detailed information about the samples, the preceding publications [1,2] should be consulted.…”

Elastic and elasto‐optical properties of Rb1–x(NH4)xH2AsO4 mixed crystals studied by Brillouin spectroscopy

“…(2) The index of refraction of the crystals studied by comparison of the phonons frequency in the 90° and 180 o geometries [13,14]. For all crystals studied this method was applied and we determined values of the refraction indices.…”