Tensile orientation behavior of alkoxy-substituted bis(phenylethynyl)benzene derivatives in polyolefin blend films

A series of new dichroic, photoluminescent alkoxy-substituted bis(phenyleth ynyl)benzene derivatives la-e, have been synthesized and characterized. All dyes are highly emissive and show bright-blue photoluminescence with quant um yields in solution ranging from 0.63 to 0.72. Oriented blend films compr ising these dyes were prepared with ultrahigh-molecular-weight polyethylene (UHMW PE) as the matrix material by solution-casting, and with linear low- density polyethylene (LLDPE) by melt-processing as well as guest diffusion. Despite the introduction of alkoxy substituents, not all dyes are compatib le with UHMW PE and large-scale phase segregation was observed during the p reparation of a number of UHMW PE blend films. In the case of the latter, f ilms with relatively good dichroic properties are only obtained if the melt ing point of the dye is lower than or equal to the deformation temperature. On the other hand, melt-processing of la-e with LLDPE produces homogeneous blends that, after tensile deformation, give rise to highly dichroic photo luminescent films. In this case, the melting temperature of the dye was fou nd to be less relevant for the orientation process. In view of a future app lication of these PL blends as photoluminescent polarizer, melt-processed b lends based on octyloxy- and dodecyloxy-substituted bis(phenyl-ethynyl)benz ene derivatives (1c,d) and LLDPE embody the optimal combination of good acc essibility, excellent luminescence characteristics and high polarization of the emitted light.