Relation of the correlation length to the size of the crystallites at the buried interface? A study of the in-plane structure of the TiO2-EPM6R8 liquid crystal system

We observed the changes that occur in the TiO2 – EPM6R8 system along the in-plane structure using grazing incidence x-ray scattering for concentrations of n = 7, 15 and 30 wt % of TiO2. The EPM6R8 has been electropolymerized with the TiO2 present, resulting in a structure where the hanging M6R8 monomers, and the monomers mixed with the TiO2 are mostly oriented along the in-plane direction. The region of q = 0.15 – 0.5 Ǻ^-1 covers the (002) and (003) peaks of the EPM6R8 polymer, and the (001) and (002) peaks of the M6R8 monomer, plus the monomer peak mixed with the TiO2. We observe that as a function of the wt % of TiO2, the polymer peaks in the in-plane direction disorder. This is marked by a crossover of peaks from a Gaussian (crystalline) shape to a Lorentzian (disordered) shape when crossing from 7 to 15 wt%. The peaks disappear completely in the in-plane direction for the 30 wt% sample. The peak mixed with the TiO2 sample, as well as the monomer (001) and (002) peaks remain crystalline. The peaks mixed with the TiO2 sample show a crystalline structure that varies between 20 to 30 nm, whereas the (001) and (002) monomer show a crystalline structure that varies between 61 to 69 nm. These in-plane values are smaller than the numbers calculated averaging over the three dimensions [1]. The sizes suggest that the in-plane structures may consist of nanowires [2,3].

[1] P. Romero-Hasler, et al., Liquid Crystals, 2020, 47, 423-432.

[2] C. J. Takacs, et al., ACS Nano, 2014, 8141-8152.

[3] M. Roders, et al., J. Phys. Chem. C, 2019, 27305-27316