**1. Introduction**

Photoconducting agents and other photoelectronic compounds embedded in polymer films as nanocomposite films have attracted considerable attention, as they exhibit many useful

© 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

optical and electrical properties. Because of their large chemical and structural stability, as well as their optical and electrical properties, metallic phthalocyanines (MPcs) have been introduced into polymeric matrices as nanoparticles. A polymeric matrix composite (PMC) is a compound material consisting of a polymeric primary phase, or matrix, which is embedded in a secondary phase based mainly on matrix-reinforcing fibres and particles. The polymeric matrix enhances material stability, as it limits the introduction of environmental oxygen or water, which could reduce the potential usefulness of the MPcs. Nanostructuring also permits two other goals: to achieve optical homogeneity of the polymeric composite medium and to take advantage of specific properties of MPcs in their crystalline form. MPcs are usually ordered in crystalline arrangements, as their aromatic rings stack neatly. Due to the strength of π bonds, MPcs can be accommodated in a large number of different structures, which depend on the substituents they have. The type of structure determines the physical properties of a specific MPc, as well as its applications. The main modes of MPc molecular organization that may be observed are: (i) crystals, which can be in the alpha or beta allotropic forms (the beta polymorph being thermodynamically more stable). The two types are distinguished by the angle formed between the symmetry axis and the stacking direction. Alpha and beta crystals form angles of 26.5 and 45.8°, respectively. (ii) Liquid crystals, where Pcs are substituted by flexible lipophilic chains, which allow the formation by substituents of a quasi-liquid medium surrounding the in-plane aromatic nuclei, which overlap in columns distributed over two-dimensional positions with hexagonal or tetragonal symmetries. (iii) Thin films are solid structures whose thicknesses can be neglected for many physical purposes. In applications involving interaction with electromagnetic waves, thin-film thickness must be of the same order as the wavelength of the interacting disturbance. Thin films represent the Pcs arrangement most commonly considered for electronic applications. (iv) Skewer-structured polymers are obtained by polymerizing MPcs through bridge ligands; due to the variety of ligands that may be used and their properties, the distance between molecules can be controlled rather well and, thanks to the rigidity of the unidirectional connection in this type of structures, very good electronic and optical properties can be obtained from the material.

The purpose of this work is to report the generation of MPc crystals, their dispersion into a polymeric matrix and the evaluation of their optical and electrical properties in thin-film form. In this study, a polystyrene polymeric matrix was used. The materials thus obtained were characterized by different methods, including infrared (IR) and ultraviolet-visible (UV-Vis) spectroscopy, as well as scanning electron microscopy (SEM). First nanoparticles were synthesized in a molecular solution obtained from a supersaturated MPc solution. Second a solid composite was prepared by introducing pre-grown colloidal MPc particles into a polymeric matrix in a spin coating process. Spin coating leads to the production of uniform, flat, high-quality films or coatings. This process involves the application of a certain amount of nanoparticles suspended in a polymer and previously solved in an organic solvent. A small amount of the fluid is put on a substrate attached to a plate that is made to rotate at high speed, so that the resulting centripetal force spreads the suspension until the desired film thickness is achieved for the composite material. This process has four stages: deposition, centrifugation, de-centrifugation and evaporation. The evaporation of the fourth stage represents the main thinning mechanism for the film. After the film is deposited, it is annealed for 10 min at 90°C to accelerate matrix polymerization.

As some polymeric materials have conductivities similar to those of metals, they represent an important research area for the next generation of organic electronic devices. Conductivities in some polymers, such as poly(3,4-ethylenedioxythiophene) (PEDOT), are comparable to those of indium oxide or tin, while showing significant optical transmission. In this work, the electrical conductivity of the thin films was evaluated by means of a four-point technique. The films' electric properties and their dependence in the presence of radiation of several wavelengths were evaluated in order to determine whether this type of PMC films may have applications in the construction of electronic and optoelectronic flexible devices, such as OLEDs, photovoltaic devices and visual information devices. Additionally, the optical activation energies were evaluated by the Cody and Tauc methods from the transmittance values of the films at different thicknesses [1, 2].
