An investigation into the hexagonal phases formed in high-concentration dispersions of well-defined cylindrical block copolymer micelles

ABSTRACT

This paper presents a detailed analysis of the structure of the hexagonal phase of poly(ferrocenylsilane) (PFS)-based cylindrical micelles found at concentrations above ca. 5 wt. % in non-polar solvents such as decane. Small-angle X-ray scattering indicated that the hexagonal order is not long-range. In all samples, deviations in the lower order peak positions were observed with respect to those expected for a perfect hexagonal lattice, with the degree of deviation correlating with micelle length. Furthermore, analysis of the peak shapes and peak widths suggests that the phase possesses intermediate translational order similar. to the hexatic phase. The observed features can be reproduced by amending Hosemann’s paracrystal theory to include a distribution of lattice parameters to model well and poorly condensed regions. It is proposed that this distribution arises due to the bending and intertwining of individual micelles in a hexagonal lattice, resulting in a kinetically trapped phase that is initially neither perfectly hexagonal nor canonically hexatic but which anneals over time towards a perfect hexagonal lattice.

GRAPHICAL ABSTRACT

KEYWORDS:

• Block copolymer micelles
• small-angle X-ray scattering
• hexagonal phase
• paracrystalline lattice
• hexatic

Acknowledgements

The authors gratefully acknowledge the Diamond Light Source and MAX-Lab synchrotron facilities for the beamtime awards (SM6035) and (20140459) and the beamline staff for their help and support.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

Supplemental data for this article can be accessed here.

Additional information

Funding

DWH was supported by the Bristol Centre for Functional Nanomaterials under EPSRC doctoral training [grant number EP/G036780/1]; JBG is grateful to the NSERC of Canada for a postdoctoral fellowship; IM thanks the European Research Council for an Advanced Investigator Grant. The Ganesha X-ray scattering apparatus used for this research was purchased under EPSRC Grant Atoms to Applications [grant number EP/K035746/1].