Effect of the dispersion of the chromophore on the optical performances of polarizers from polyethylene and 5”-thio- (3-butyl)nonyl-2,2’:5’,2”-terthiophene

Abstract

Abstract:A new polyethylene-compatible terthiophene chromophore, 5"-thio-(3-butyl)nonyl-2,2':5',2"-terthiophene, with melting point lower than 0°C was prepared and used for linear polarizers based on ultra-high-molecular-weight polyethylene (UHMWPE). Differential scanning calorimetry and scanning electron microscopy indicate that the new chromophore is dispersed uniformly in films of UHMWPE obtained by casting from solution. The films show excellent dichroic properties (dichroic ratio 30) at rather low drawing ratio (≈ 20) . Moreover, qualitative agreement is observed with the Ward pseudo-affine deformation scheme.

Absorption and Emission Dichroism of Polyethylene Films with Molecularly Dispersed Push‐Pull Terthiophenes

“…On the other hand, the melting points of the former result significantly lower (63–64 °C for Y3 and 116–118 °C for Y1; 110–111 °C for V2 and 135–136 °C for V) as expected. Indeed in alkyl terthiophenes a decreasing of the melting point of about 90 °C was observed by substituting the linear octadecyl with the branched 3‐butylnonyl alkyl functionalization 12…”

“…A commonly accepted point is that high polarizing efficiency is obtained by orienting anisotropic and strongly absorbing dyes through tensile action (according to a pseudo‐affine deformation scheme)1,7 on ultradrawable polyolefins, such as Ultra High Molecular Weight Poly(Ethylene) (UHMWPE),7,8 Linear Low density PE (LLDPE) and High Density PE (HDPE) 9. We have recently studied absorption polarizers based on guest terthiophene chromophores dispersed in oriented polyethylene (PE) host matrices 10–14. These chromophores were chosen due to the linear and easy‐to‐functionalize structure; moreover, the slight non‐coplanarity of the aromatic rings in the solid state (torsion angles of 171–174° between 2 molecules of thiophene)15 helps in keeping low intermolecular interactions based on π ‐stacking and, at the same time, does not reduce the π ‐orbital overlap, responsible for the conjugation 16.…”

“…A model study of dispersion based on different alkyl functionalized terthiophene molecules evidenced the strong influence of the dye crystallization degree on the phase dispersion behaviour into solution‐casted UHMWPE films 12,14. In particular, linear and long alkyl lateral chains (number of carbon atoms composing the chain > 10) appeared able to confer the guest molecule the best affinity with PE, but at the same time the high packing tendency increased the dye crystallinity favouring the phase segregation by the generation of aggregates and affecting the dichroic behaviour of the oriented devices 14.…”

“…In particular, linear and long alkyl lateral chains (number of carbon atoms composing the chain > 10) appeared able to confer the guest molecule the best affinity with PE, but at the same time the high packing tendency increased the dye crystallinity favouring the phase segregation by the generation of aggregates and affecting the dichroic behaviour of the oriented devices 14. On the other hand, the introduction of branched alkyl functionalization on the terthiophene nuclei reduced the temperature and tendency to crystallize of the dye favouring its dispersion in the PE apolar matrix and increasing its orientation sensibility to the mechanical stretching of the macromolecular fibres 12. Also films prepared from melt‐processable LLDPE and HDPE and terthiophene derivatives showed a high degree of homogeneity and potentially interesting optical anisotropy 11,13…”

New Cyclic Olefin Copolymer for the Preparation of Thermally Responsive Luminescent Films

“…It is actually reported in the literature [24][25][26] that the phase-segregation process of small chromophoric molecules dispersed in polymers occurs favourably by increase in their concentration with a process which strictly depends on the chemical nature of both dye molecules and polymer matrix. Accordingly, no aggregation phenomenon (see Supporting Information) was detected both in absorption and in emission for the FDC7BBS_0.03 film containing the 0.03 wt.-% of BBS in the temperature range investigated, suggesting that in these films the chromophore concentration is below the solubility limit of the mixture FDC7/BBS.…”