Phenomenological analysis of the light intensity dependence of the photoalignment process in azo-containing polymeric films

A phenomenological model is proposed to analyze the influence of the incident light intensity on the photoinduced anisotropy of an azobenzene-containing polymer film. The optical anisotropy was generated in the films by the incidence of linearly polarized light and monitored by transmittance measurements.

Figure 1

(a) Absorption spectrum of the polymeric film and (b) schematic representation of the polymeric structure.

Figure 2

(Color online) Experimental setup used for the transmittance measurements.

Figure 3

Typical curve of the normalized transmittance $T_N$ as a function of time $t$ for a film irradiated with $166.2\mathrm{mW}∕{\mathrm{cm}}^2$. The solid line is a fit made with expression (14).

Figure 4

Maximum normalized transmittance $T_{N\max }$ as a function of light intensity $I$. The solid line is the fit made with Eq. (15).