Article

Chiral Optical Films Based on Achiral Chromophore Guests

Università degli Studi di Salerno, Fisciano, Campania, Italy
Journal of the American Chemical Society (Impact Factor: 11.44). 06/2011; 133(25):9872-7. DOI: 10.1021/ja2021087
Source: PubMed

ABSTRACT Films constituted by an achiral host polymer and an achiral guest chromophore, which exhibit intense chiral optical responses for both host and guest peaks in the infrared as well as in the UV-visible regions, have been obtained. Such films can have any thickness from the nanoscale up to the macroscopic scale. This unexpected chiral optical behavior is easily achieved by crystallization of a robust commercial stereoregular host polymer (syndiotactic polystyrene, s-PS) from the amorphous phase as induced by a nonracemic guest, followed by exchange of the nonracemic guest with the achiral guest, leading to the formation of polymer-host/chromophore-guest cocrystalline phases. This finding opens the possibility to achieve s-PS-based films with chiral optical response at selected wavelengths. It has been also found that the chiral optical cocrystalline phase of s-PS with azulene exhibits a monoclinic δ-clathrate form with equal proportions of left- and right-handed helices. This confirms that the observed chiral optical behavior arises by the nonracemic native morphology of the crystalline regions, which has been induced by the temporary nonracemic guest.

2 Followers
 · 
104 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: A facile method is reported to prepare new polymer composites by introducing functional polymer (poly(3,4-ethylenedioxythiophene)) into a melt-processed film of a thermoplastic polymer matrix with a high melting-temperature (syndiotactic polystyrene), which benefits the applications of functional polymers which are difficult to process and vulnerable to high temperatures.
    RSC Advances 07/2014; 4(60). DOI:10.1039/C4RA04468A · 3.71 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The degree of circular polarization (g-value) of infrared and UV–vis bands of melt-extruded syndiotactic polystyrene (s-PS) films of different thickness, as induced by cocrystallization with a nonracemic guest ((R)-(−) or (S)-(+) carvone), and of their nonracemic and achiral guests has been studied. The induced circular dichroism (CD) phenomena, both for polymer host and for chromophore guests, are maximized for films with thickness of few micrometers. Surprisingly, for all the examined thicknesses and spectral ranges, the chiral response of the considered achiral guests (azulene and 4-nitroaniline) is definitely higher than for the chirality-inducing nonracemic guest (carvone). This clearly indicates that the origin of the chiral optical response is extrinsic to the site of photon absorption. In agreement with this extrinsic nature, a comparison of g-value for host and guest peaks of melt-extruded and spin-coated s-PS films indicates that the observed chiral response is an extensive property. The reported results also confirm that the intense chiral responses of s-PS films are associated with a nonracemic helical morphology of crystallites, as induced by the nonracemic guest.
    Macromolecules 04/2014; 47(8):2616–2624. DOI:10.1021/ma5000514 · 5.93 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: This review is mainly devoted to the chiral-optical behavior in the solid state of racemic synthetic polymers, which are able to form co-crystalline phases with low molecular mass guest molecules and whose chirality is induced by non-racemic (also temporary) guest molecules. The article starts with the description of chiral features relevant for the synthesis of stereoregular polymers. Subsequently, the chirality of chain helicity and the related phenomena of macromolecular amplification of chirality, both in solution and in the solid state, are discussed. The final part of the article describes the recent achievement of robust chiral-optical films being constituted by a racemic commercial host polymer and achiral guest chromophores.
    Rendiconti Lincei. Scienze Fisiche e Naturali 09/2013; 24(3):217-226. DOI:10.1007/s12210-013-0238-0 · 0.76 Impact Factor