Chiroptical Properties of Terthiophene Chromophores Dispersed in Oriented and Unoriented Polyethylene Films
✍ Scribed by Andrea Pucci; Silvia Nannizzi; Gennaro Pescitelli; Lorenzo Di Bari; Giacomo Ruggeri
- Publisher
- John Wiley and Sons
- Year
- 2004
- Tongue
- English
- Weight
- 222 KB
- Volume
- 205
- Category
- Article
- ISSN
- 1022-1352
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✦ Synopsis
Abstract
Summary: Two new chiral terthiophene chromophores II and III were prepared with 99% enantiomeric excess. Chiroptical properties of these dyes dispersed in ultra high molecular weight polyethylene (UHMWPE) films were determined and compared with the same properties in solution. In the solid state, the optical activity strongly depends on the interaction mechanisms within small crystalline aggregates of chromophores. The film morphology and chromophore dispersion were also investigated by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The good correlation between chromophore aggregation and chiroptical activity of the binary films promotes circular dichroism (CD) as an effective technique for monitoring the phase dispersion behaviour of dichroic dyes into polymer matrices. By mechanical stretching of the film a linearly dichroic orientation of the chromophores is obtained which results in a high degree of linear dichroism. The influence of the uniaxial orientation of terthiophene molecules along the drawing direction of UHMWPE on the chiroptical properties of the films, and the possible application of the oriented devices as linear polarizers are discussed.
Absorption and CD spectra of unoriented UHMWPEII film at different rotation angles θ.
magnified imageAbsorption and CD spectra of unoriented UHMWPEII film at different rotation angles θ.