Linear long alkyl chain substituted POSS cages: the effect of alkyl chain length on the self-assembled packing morphology

Heeley, Ellen L.; Hughes, Darren J.; El Aziz, Youssef; Taylor, Peter and Bassindale, Alan R. (2013). Linear long alkyl chain substituted POSS cages: the effect of alkyl chain length on the self-assembled packing morphology. Macromolecules, 46(12) pp. 4944–4954.

DOI: https://doi.org/10.1021/ma400635e

URL: http://pubs.acs.org/doi/abs/10.1021/ma400635e

Abstract

The self-assembled long-range ordering, packing morphology and thermal behavior of a series of polyhedral oligomeric silsesquioxanes (POSS) T₈ cage systems with long n-alkyl chain pendant groups is presented. State-of-the-art time-resolved small- and wide-angle X-ray scattering (SAXS/WAXS), thermal and optical techniques were used to elucidate their morphology. X-ray scattering showed long-range crystalline ordering where the alkyl chains align in an axial disposition from the POSS core giving a “rod-like” self-assembled packing morphology with a length-scale correlating to the overall molecular dimensions. Phase transitions observed by thermal methods were comparable to those seen in the crystallization of bulk n-alkanes. Optical measurements and crystallization kinetics confirmed a lamellar macromorphology again being similar to the crystal structure of bulk n-alkanes. This study reveals for the first time, the direct effect that the alkyl chain length has on the self-assembled crystalline packing morphology of this novel and potentially commercially relevant, series of POSS systems.

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