BIOCOMPATIBLE POLYMER EMBEDDED IN LIGHT SENSITIVE MATERIALS: A STRUCTURE PROPERTY INVESTIGATIONS Yuvaraj A.R a , Gurumurthy Hegde a* , V. G. Chigrinov b , M.M.Yusoff a a Faculty of Industrial Sciences and Technology, Universiti Malaysia Pahang, 26300, Kuantan, Pahang, Malaysia. b Department of Electronic and Computer Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong *E-mail: hegde@ump.edu.my Keywords: HEC; photoalignment;Order parameter; Dichroic ratio;AFM; ABSRTACT Photoalignment properties on some of light-sensitive compounds exhibits photo and thermal stability. The distinguished alignment properties of this azo-dyes are more effective for photoalignment. An attractive feature of these dyes is its low curing temperature which is essential for plastic substrates to use it as flexible devices. The HEC is used with some light sensitive compounds to increase the adhesion on flexible (plastic) substrates. Photoalignment has been proposed and studied for a long time. Over the past twenty years, a lot of improvements and variations have been made for photoalignment [1,2]. A lot of work has been devoted to light sensitive aligning materials (especially photo alignment) [3]. The alignment of liquid crystal (LC) molecules is an important research/development subject, because it is a key process in the fabrication of LC displays and devices [1]. Right from the beginning, polyimide (PI) rubbing technique has been routinely used to align liquid crystals. However, it cannot satisfy strong demands of advanced technology. The preparation process of alignment layers made from such materials, however, requires high curing temperatures (190-220ºC) and a long time (about 30 min) for completing the imidization (curing) process and therefore they are not appropriate for use in LCDs with flexible substrates. HEC is the well known biocompactable polymer. HEC is a highly viscocus substance . Hence the mixture of SD-1 and HEC is used to increase the adhesion on the plastic substrates. N N N N O H OH O O H O OH NaO 3 S SO 3 Na (a) (b) Fig 1: Chemical structure of SD1(a) and HEC (b). The evolution of the polarized absorption spectra after UV illumination does not reveal any noticeable contribution of photochemical reactions [13], as the average absorption D ave = (D || + 2D⊥) / 3 remains the same for any fixe value of the exposure time. The order parameter S of CBY is equal to-0.13 at λ max = 372 nm. The dichroic Ratio (DR) and order parameter (S) of the azo dye chromophores were calculated using eqn (i) and (ii), where D || and D⊥ are the absorption of parallel and orthogonal polarized light with respect to the polarization of the actinic UV light, respectively. DR = D⊥ / D || --------- (i) S = (D || - D⊥) / (D || + 2 D⊥) ----- (ii) The UV/Vis absorption spectrum of SD-1and HEC is presented in Fig. 2.The absorption spectra which reveals UV irradiation time and also thermal back relaxation as shown in Fig. 3. Absorption wavelength of this material is about ~372 nm. UV/vis absorption spectrum was recorded using ocean optics HR2000 high resolution spectrophotometer. The order parameter and the dichroic ratio of the cell made by mixture of SD-1 and HEC materials shows a subsequent plateau with UV intensity due to an increase of the anisotropy of the surface physical properties of the alignment layer. As intensity increses, a decrease of the order parameter was abserved as shown in the figure 4. Where as dichroic ratio values increases with increase of intensity. It is probably due to nature of alignment layer or partial fragmentation of the azo dye molecules different modes of liquid crystals used especially in the liquid crystal display industry. Fig. 5. Is the photographic image of the flexible disply, then cell is made by using appropriate (calculated) quantities of SD-1 and HEC mixtures. In that picture, the bright portion is arised because of UV irradiation and the dark portion is masked area.