title: Monolayers of an amphiphilic para-carboxy-calix[4]arene act as templates for the crystallization of acetaminophen.
abstract: The title compound, 5,11,17,23-tetra-carboxy-25,26,27,28-tetradodecyloxy-calix[4]arene, 1, has been studied at the air-water interface, self-assembled as Langmuir monolayers, for its ability to interact with an active pharmaceutical ingredient (API), acetaminophen (APAP), and to initiate its crystallization. The Π/A isotherm study shows that there is a clear interaction between 1 and APAP causing an expansion of the monolayer. In addition to the known phase transition occurring at a surface tension of 38 mN m(-1), an additional kink is observed in the compression isotherm for concentrations of APAP above 40 mM suggesting that this API is causing an additional phase transition of the monolayer. Interface-initiated crystallization studies show that the presence of a monolayer spread on a supersaturated solution of APAP (26 g L(-1)) triggers this API crystal growth from the interface. The transfer of 1-based monolayers on glass surfaces has been carried out using the Langmuir-Blodgett technique. The so-produced monolayers have been shown to template the crystallization of APAP. LB films of 1 have characterized using imaging and spectroscopic ellipsometry. The results suggest that each monolayer has an average thickness of 18 Å, which is consistent with the molecular structure of 1 self-organized parallel to the interface with the alkyl chains pointing out parallel to the axis of the macrocycle and without interdigitation of the alkyl chains. The presence of APAP in the subphase during the LB transfer causes a limited but relevant increase in the layer thickness. The study of the capabilities of the LB films to initiate crystallization of APAP is also demonstrated showing the influence of the monolayer packing on the quantity of formed crystals.
authors.affiliation: School of Life Sciences, Institute for Chemistry and Bioanalytics, University of Applied Sciences Northwestern Switzerland, Gründenstrasse 40, Muttenz CH-4132, Switzerland.
authors.forename: Negar
authors.initials: N
authors.lastname: Moridi
authors.forename: Oksana
authors.initials: O
authors.lastname: Danylyuk
authors.forename: Kinga
authors.initials: K
authors.lastname: Suwinska
authors.forename: Patrick
authors.initials: P
authors.lastname: Shahgaldian
mesh_terms: D000082:Acetaminophen / Q000737:chemistry*; D000388:Air; D047250:Calixarenes / Q000737:chemistry*; D003460:Crystallization; D008567:Membranes, Artificial; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: C555692:5,11,17,23-tetra-carboxy-25,26,27,28-tetradodecyloxycalix(4)arene; D008567:Membranes, Artificial; D013501:Surface-Active Agents; D014867:Water; D047250:Calixarenes; D000082:Acetaminophen