Incommensurate structures investigated by X-ray studies of electropolymerised methacrylic monomer with TiO₂ nanoparticles

ABSTRACT

We explore the possibility of producing polymer nanocomposites with an ordered distribution of nanoparticles by using an electropolymerizable liquid crystal (LC) monomer. The nanoparticles are added to the monomer before polymerizing it. We study the polymer derived from the LC (E)-6-(3-hydroxy-4-(((4-octyloxy)phenyl)imino)methyl)phenoxy)hexyl methacrylate (M6R8) both pure and in the presence of 3.4 nm TiO₂ nanoparticles, at 30 wt%. This particular system is chosen since (1) the LC polymers we work with have the added advantage of having a specific orientation and structure which allows us to study its effect in the nanoparticles and (2) when considering the nanocomposite, it is polymerized with the nanoparticles included. The system is studied using grazing incidence small angle X-ray scattering and in-plane direction X-ray scattering. The polymer obtained alone appears to be tilted with respect to the surface of the substrate. The structure adopted by the nanoparticles in the nanocomposite is layered and apparently incommensurate with the polymer. It is formed through the association of the nanoparticles with the M6R8 aromatic cores during the process of electropolymerisation. This interpretation of the data is supported by the nanoparticle structures formed when the related, non-polymerizable LC, (E)-6-(3-hydroxy-4-(((4-octyloxy)phenyl)imino)methyl)phenoxy)hexyl isobutyrate (I6R8), is analysed. We find that for both, the pure polymer poly-((E)-6-(3-hydroxy-4-(((4-octyloxy)phenyl)imino)methyl)phenoxy)hexyl) methacrylate (EPM6R8) as well as the polymer with nanoparticles (EPM6R830TO), the electropolymerisation imposes a preferred growth direction of the polymer side chains, and therefore for the nanoparticle arrangement in the polymer.

Graphical Abstract

KEYWORDS:

• Nanoparticles
• methacrylic LC monomers
• electropolymerisation
• grazing incidence X-ray scattering
• incommensurate structures

Acknowledgements

P. Romero Hasler and A. Meneses-Franco acknowledge CONICYT scholarships 21130413 and 21090713, respectively, for doctoral studies. E. A. Soto-Bustamante thanks Fondecyt Project 1130187. L. J. Martínez-Miranda thanks partial support by NSF grant NSF-OISE-1157589. We thank M.Sc. Dennys Reis of the Complex Fluids Group, Physics Institute, University of São Paulo, Brazil, for helping in the GISAXS measurement on the pure polymer.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

P. Romero Hasler and A. Meneses-Franco acknowledge CONICYT scholarships 21130413 and 21090713, respectively, for doctoral studies. E. A. Soto-Bustamante thanks Fondecyt Project 1130187. L. J. Martínez-Miranda thanks partial support by NSF grant NSF-OISE-1157589.