Various examples are reported of chromogenic materials composed of a functional dye covalently linked to the polymer chains or physically dispersed in the continuous macromolecular matrix, the latter appears to be a more sustainable route for the industrial scale-up of these materials. In this study, a mechanochromic elastomer was prepared by physically dispersing dye materials into a rubber matrix by solution mixing technique. The employed rubber is natural rubber (NR). The NR was chosen because of its ability of strain-induced crystallization. Perylene diimide I is selected after considering its aggregachromic nature and affinity with rubber matrix. The optimum composition of dye in rubber composites was determined based on the mechanochromic performance characterized with ultraviolet/visible (UV/Vis) spectrometer, x-ray diffraction (XRD) and spectrofluorometer (FL). The UV/Vis spectrometer and FL monitor the optical responses, such as absorbance and emission property, under tensile deformation due to the breakage of dye aggregates. Spectroscopic analysis with polarization monitors the breakage of dye aggregates and anisotropic property of the sample. The XRD monitors the change in size of dye aggregates. With polarization filtering, the breakage of dye aggregates are clearly observed and anisotropic property of the sample is also confirmed. The XRD results indicate that dye aggregates were broken during stretching because the shear force is applied to dye aggregates.
A novel mechanochromic elastomer based on silicone rubber and coumarin 6 dye have been prepared with various concentrations of the dye ranges from 2wt.% to a maximum of 5wt.% by solution mixing technique. After evaporating the solvent, cured samples were prepared as thin films using compression molding at 170° C. The optimum composition of the dye in rubber composites was determined based on the mechanochromic performance characterized with ultraviolet/visible (UV/Vis) spectrometer, x-ray diffraction (XRD) and spectrofluorometer (FL). The UV/Vis spectrometer monitors the dye aggregation in polymer film during the tensile deformation. The XRD monitors the change in size of dye aggregates. The FL monitors the optical response during tensile deformation due to the re-arrangement of dyes. As increasing a mechanical deformation to the polymeric composite film, UV/Vis absorption intensity was decreased and the FL emission wavelength was moved to decrease wavelength because of breaking dye aggregations. Also, XRD intensity peak was decreased, which dye aggregations were broken after mechanical deformation.
Lyotropic chromonic liquid crystals (LCLCs) form a columnar discotic liquid crystalline (LC) phase in aqueous solution
due to the disc-like or plank-like molecular shape of chromonic dyes and their ionic peripheries. Such columnar
structures in the chromonic columnar N phase can be coated on a glass substrate, and aligned in one direction by
applying external forces. The resulting thin crystalline film (TCF) can absorb a polarized light parallel to the molecular
axis while transmitting a polarized light parallel to the columnar axis, which constructs an E-polarizer. Although the
concept of the coatable polarizer known, it has not been commercially successful due to numerous problems mainly
originated from the use of aqueous solution. It is extremely difficult to coat the aqueous solution on most of substrates,
especially on plastic substrates. Large volume shrinkage occurs during the crystallization process generating unfavorable
defects. Also, weak adhesion becomes an important issue when a TCF is applied to a flexible substrate.
In this presentation, we demonstrate a novel preparation method of coatable polarizer from a photo-curable organicbased
LCLC solution. Lyotropic LC solutions were prepared by dissolving amino-functional chromonic dye in acrylic
acid containing photoinitiator and crosslinking agents. The solution was shear-coated with subsequent UV irradiation to
provide a thin film polarizer. The coating processibility of this organic-based solution was outstanding, particularly on a
plastic substrate. The maximum polarization efficiency was measured to be > 98 %. The resulting thin film polarizer
showed excellent film characteristics, such as good adhesion strength to various substrates, superior surface hardness,
good solvent resistance and decent thermal stability.