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A theoretical framework is presented to describe the optical properties of polarizers produced by tensile deformation of semicrystalline polymers containing dichroic dyes. In the model it is assumed that orientation of both the host polymer and guest molecule occurs in the f f i e mode. The development of optical anisotropy with Orientation is described using an aggregate model. The theory is employed to evaluate the optical Characteristics of the polarizers, i.e., dichroic ratio, order parameter, polarizing efficiency, and single-piece transmittance. Good agreement is observed between theoretical predictions and experimental data produced in this work on oriented linear polyethylendSudan Red polarizing films. It is shown that the model is useful to estimate the limiting polarizing efficiency and single-piece transmittance of the polarizing films at hand. IntroductionSeveral processes exist for the production of polymeric sheet polarizers, chiefly for use in the visible wavelength range.i-9 These polarizers are widely employed in, for instance, liquid-crystalline display applications. In most of the aforementioned processes, semicrystalline polymers, such as poly(viny1 alcohol) and polyolefins, are oriented by tensile drawing at temperatures close to, but below, the melting temperature of the p~l y m e r ; l -~ dichroic chromophores are introduced in the oriented films either by chemical modification of the polymer or by incorporation of dichroic dyes in the films prior to or

action by mixing two micellar solutions containing the reactants. The coprecipitation takes place by mixing two micellar solutions having the same water content, w = [H 2 O]/[AOT]: 0.1 M Na(AOT) containing Na 2 Te and a mixed micellar solution containing Cd(AOT) 2 [46] and Na(AOT). An excess of cadmium ions is used in the synthesis (x = [Cd 2+ ]/[Te 2± ] = 2). The overall concentrations of Na 2 Te and Cd(AOT) 2 in micellar solution were 1.5 10 ±4 and 3´10 ±4 M, respectively. The relative volume of each solution varied. CdTe nanocrystals were formed a few seconds after these two degassed micellar solutions were mixed. The syntheses were performed with droplets of various sizes.Procedure I: On addition of dodecanethiol to the micellar solution, a selective surface reaction between the thio derivative and the cations took place. The coated particles were then extracted from the micellar solution and the surfactant used to form the colloidal dispersion was removed by addition of degassed ethanol. The coated particles precipitated. After centrifugation, the substrate was removed. The coated particles are in powder form and they are stable in air. The coated particles were then redispersed in a mixture of two solvents (isopentane/methylcyclohexane, 3V/V) forming an optically clear glass at low temperature. The coated particles dispersed in solution were stable for a short period (7 days). When they were kept for longer, the stability of the particles changed markedly. In contrast, in powder form, the particles are stable for several months.Procedure II. This was the same as procedure I except that after the two micellar solutions had been mixed, the particles were kept in micellar solution under nitrogen for 48 h. Then dodecanethiol was then added and the particles extracted as before.Remark: When syntheses were performed in the presence of excess telluride (x = [Cd 2+ ]/[Te 2± ] = 1/2), CdTe nanoparticles were formed. However, after dodecanethiol addition and during the washing process, a black precipitate appeared, due to the formation of tellurium oxide. It was then impossible to separate the CdTe nanoparticles from TeO 2 aggregates.

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