Optical absorption photoacoustic measurements for determination of molecular symmetries in a dichroic organic-film

Abstract

A novel approach to specify symmetries and main optical axes in anisotropic polymeric films is proposed. This method is based on the analysis of the optical absorption via the pulsed laser photoacoustic (PLPA)- technique in a common polarizer film, while rotating the polarizer axis at normal incidence. Since the PLPA-signals are directly proportional to the optical absorption, it is shown that a symmetric and complementary Malus's law can be obtained over full root mean square (RMS)- and correlation (CA)-analysis of the PLPA-signals. Such data processing reveals the main material directions of the constituting film molecules defining the symmetry structure of the sample. PLPA-results were compared to the pure optical transmission experiments and show unambiguous information, allowing this technique to be used in nonstandard and opaque polymeric films, where the analysis of the optical measurements represents a difficult task, and in general, in anisotropic media.

Anisotropic Photophysical Properties of Highly Aligned Crystalline Structures of a Bulky Substituted Poly(thiophene)

“…The variation of transmission exhibited a cos 2 Φ dependence, in accordance with Malus' law ( Figure 3c). 22 This result revealed that the spherulite of PDOPT exhibited an in-plane optical anisotropy with absorption polarization being perpendicular to the radial direction. These observations correspond to the change of color in the crystallized sample shown in Figure 1b.…”

Thermomechanical and Photophysical Properties of Crystal-Violet-Dye/H2O Based Dissolutions via the Pulsed Laser Photoacoustic Technique

“…In a typical PLPA experiment, the acousticwaves travel at the characteristic speed of sound of the excited material to reach a coupled piezoelectric detector; this allows the mechanical-electrical experimental interface to collect the PLPA-data from the sample on a digital oscilloscope for subsequent numerical analyses. The experimental simplicity to obtain photoacoustic signals has led to the development of several PLPA-based measurement devices which are commonly used for the accurate evaluation of thermal and optical properties of different materials such as organic and inorganic crystals, semiconductor, and polymer systems [2][3][4][5][6][7][8][9]. In summary, several physical and structural material characteristics can be efficiently studied by means of diverse PLPA-based techniques and the adequate data analysis thereof.…”

“…In fact, in recent works, we have successfully implemented the PLPA-technique to study structural anisotropies in different polymeric films (including commercially available organic polarizers and prepared spin-coated and coronapoled push-pull based molecular layers for nonlinear optical NLO-applications) and electrooptical dichroic organic-based dissolutions [2][3][4]. In this line of research, it is our aim to show in this contribution that the PLPA-technique can also be implemented to further study the material properties of these kinds of organic systems.…”

SpectroFlexia

“…We investigated the use of polarizing material to manipulate light. These polarizers are optical filters that can adjust the intensity of light by filtering out the mixed polarization into one single vector of polarization [7]. A method to manipulate sunlight is by directing a fixed polarizer towards the sunlight with a second rotatable polarizer in front of it, as illustrated in Figure 1.…”