Nanocylindrical confinement imparts highest structural order in molecular self-assembly of organophosphonates on aluminum oxideElectronic supplementary information (ESI) available: Nine figures, one table, and three explanatory paragraphs. See DOI: 10.1039/c7nr02420g

We report the impact of geometrical constraint on intramolecular interactions in self-assembled monolayers (SAMs) of alkylphosphonates grown on anodically oxidized aluminum (AAO). Molecular order in these films was determined by sum frequency generation (SFG) spectroscopy, a more sensitive measure of order than infrared absorption spectroscopy. Using SFG we show that films grown on AAO are, within detection limits, nearly perfectly ordered in an all- trans alkyl chain configuration. In marked contrast, films formed on planar, plasma-oxidized aluminum oxide or α-Al 2 O 3 (0001) are replete with gauche defects. We attribute these differences to the nanocylindrical structure of AAO, which enforces molecular confinement. Sum frequency generation measurements show that self-assembled monolayers in alumina nanopores are nearly perfectly ordered due to spatial confinement effects.