title: On the supramacromolecular structure of core-shell amphiphilic macromolecules derived from hyperbranched polyethyleneimine.
abstract: The supramacromolecular structure of core-shell amphiphilic macromolecules (CAMs) with hyperbranched polyethyleneimine (HPEI) cores and fatty acid chain shells (HPEI-Cn) for different chain lengths was investigated both, in colloidal suspension, solid phase and at the air-water interface using Small Angle X-ray Scattering (SAXS), Wide Angle X-ray Scattering (WAXS), X-ray Reflectometry (XRR) and Langmuir isotherms. At low temperatures colloidal toluene suspensions of the HPEI-Cn polymers form, as evidenced by peaks arising in the structure factor of the system showing mean particle-to-particle distances correlated with the length of the aliphatic chains forming the shells of HPEI-Cn unimicelles. The CAM sizes as found from the SAXS experiments also display a clear dependence on shell thickness suggesting that the aliphatic chains adopt a brush-like configuration. After solvent extraction, HPEI-Cn adopts ordered structures with hexagonal packing of the aliphatic chains. Submitted to lateral pressure Π at the air-water interface, HPEI-Cn undergoes a disorder-order transition with increasing transition pressure for increasing chain lengths. The CAMs show different behaviors in-plane and out-of-plane. While out-of-plane the aliphatic chains behave as a brush remaining almost fully unfolded, whereas parallel to the air-water interface the chains fold down in a mushroom way with increasing lateral pressure Π.
authors.affiliation: Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Universidad Nacional de La Plata, CONICET, CC 16, Suc. 4, 1900 La Plata, Argentina.
authors.forename: Agustin
authors.initials: A
authors.lastname: Picco
authors.affiliation: Institute of Condensed Matter Physics, Technische Universität Darmstadt, Hochschulstraße 8, D-64289 Darmstadt, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Kraska
authors.affiliation: Institute of Condensed Matter Physics, Technische Universität Darmstadt, Hochschulstraße 8, D-64289 Darmstadt, Germany.
authors.forename: Haiko
authors.initials: H
authors.lastname: Didzoleit
authors.affiliation: Institute of Condensed Matter Physics, Technische Universität Darmstadt, Hochschulstraße 8, D-64289 Darmstadt, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Appel
authors.affiliation: INQUISUR, Departamento de Química, Universidad Nacional del Sur, Avenida Alem 1253, B8000CPB Bahía Blanca, Argentina.
authors.forename: Gustavo
authors.initials: G
authors.lastname: Silbestri
authors.affiliation: Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Universidad Nacional de La Plata, CONICET, CC 16, Suc. 4, 1900 La Plata, Argentina.
authors.forename: Omar
authors.initials: O
authors.lastname: Azzaroni
authors.affiliation: Institute of Condensed Matter Physics, Technische Universität Darmstadt, Hochschulstraße 8, D-64289 Darmstadt, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Stühn
authors.affiliation: Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Universidad Nacional de La Plata, CONICET, CC 16, Suc. 4, 1900 La Plata, Argentina. Electronic address: mceolin@inifta.unlp.edu.ar.
authors.forename: Marcelo
authors.initials: M
authors.lastname: Ceolin
keywords: Core–shell amphiphilic macromolecules; Hyperbranched polymers; X-ray Reflectometry; X-ray Scattering