title: Temperature effect on the build-up of exponentially growing polyelectrolyte multilayers. An exponential-to-linear transition point.
abstract: In this study, the effect of temperature on the build-up of exponentially growing polyelectrolyte multilayer films was investigated. It aims at understanding the multilayer growth mechanism as crucially important for the fabrication of tailor-made multilayer films. Model poly(L-lysine)/hyaluronic acid (PLL/HA) multilayers were assembled in the temperature range of 25-85 °C by layer-by-layer deposition using a dipping method. The film growth switches from the exponential to the linear regime at the transition point as a result of limited polymer diffusion into the film. With the increase of the build-up temperature the film growth rate is enhanced in both regimes; the position of the transition point shifts to a higher number of deposition steps confirming the diffusion-mediated growth mechanism. Not only the faster polymer diffusion into the film but also more porous/permeable film structure are responsible for faster film growth at higher preparation temperature. The latter mechanism is assumed from analysis of the film growth rate upon switching of the preparation temperature during the film growth. Interestingly, the as-prepared films are equilibrated and remain intact (no swelling or shrinking) during temperature variation in the range of 25-45 °C. The average activation energy for complexation between PLL and HA in the multilayers calculated from the Arrhenius plot has been found to be about 0.3 kJ mol(-1) for monomers of PLL. Finally, the following processes known to be dependent on temperature are discussed with respect to the multilayer growth: (i) polymer diffusion, (ii) polymer conformational changes, and (iii) inter-polymer interactions.
authors.affiliation: School of Science and Technology, Nottingham Trent University, Clifton Lane, Nottingham NG11 8NS, UK. dmitry.volodkin@ntu.ac.uk and Fraunhofer IZI-BB, Am Mühlenberg 13, 14424, Potsdam, Germany. vladimir.prokopovic@izi-bb.fraunhofer claus.duschl@izi-bb.fraunhofer.de katja.uhlig@izi-bb.fraunhofer.de and The Faculty of Fundamental Medicine, Laboratory of Medical Biophysics, Lomonosov Moscow State University, Moscow, 119991, Russia. vikulina.msu@gmail.com.
authors.forename: Anna S
authors.initials: AS
authors.lastname: Vikulina
authors.affiliation: School of Natural Sciences and Micro and Nano Technology Centre, Griffith University, Australia. y.anissimov@griffith.edu.au.
authors.forename: Yuri G
authors.initials: YG
authors.lastname: Anissimov
authors.affiliation: Fraunhofer IZI-BB, Am Mühlenberg 13, 14424, Potsdam, Germany. vladimir.prokopovic@izi-bb.fraunhofer claus.duschl@izi-bb.fraunhofer.de katja.uhlig@izi-bb.fraunhofer.de and Laboratory of Developmental Biology, Department of Medical Biochemistry and Molecular Biology, Institute of Biomedicine, University of Oulu, PO Box 5000, 90014 Oulu, Finland. psingh@mail.student.oulu.fi.
authors.forename: Prateek
authors.initials: P
authors.lastname: Singh
authors.affiliation: Fraunhofer IZI-BB, Am Mühlenberg 13, 14424, Potsdam, Germany. vladimir.prokopovic@izi-bb.fraunhofer claus.duschl@izi-bb.fraunhofer.de katja.uhlig@izi-bb.fraunhofer.de.
authors.forename: Vladimir Z
authors.initials: VZ
authors.lastname: Prokopović
authors.affiliation: Fraunhofer IZI-BB, Am Mühlenberg 13, 14424, Potsdam, Germany. vladimir.prokopovic@izi-bb.fraunhofer claus.duschl@izi-bb.fraunhofer.de katja.uhlig@izi-bb.fraunhofer.de.
authors.forename: Katja
authors.initials: K
authors.lastname: Uhlig
authors.affiliation: Fraunhofer IZI-BB, Am Mühlenberg 13, 14424, Potsdam, Germany. vladimir.prokopovic@izi-bb.fraunhofer claus.duschl@izi-bb.fraunhofer.de katja.uhlig@izi-bb.fraunhofer.de and Federal Institute for Risk Assessment (BfR), Max-Dohrn-Strasse 8-10, 10589 Berlin, Germany. magnus.jaeger@bfr.bund.de.
authors.forename: Magnus S
authors.initials: MS
authors.lastname: Jaeger
authors.affiliation: Stranski-Laboratorium für Physikalische und Theoretische Chemie, Technische Universität Berlin, Strasse des 17. Juni 124, D-10623 Berlin, Germany. klitzing@mailbox.tu-berlin.de.
authors.forename: Regine
authors.initials: R
authors.lastname: von Klitzing
authors.affiliation: Fraunhofer IZI-BB, Am Mühlenberg 13, 14424, Potsdam, Germany. vladimir.prokopovic@izi-bb.fraunhofer claus.duschl@izi-bb.fraunhofer.de katja.uhlig@izi-bb.fraunhofer.de.
authors.forename: Claus
authors.initials: C
authors.lastname: Duschl
authors.affiliation: School of Science and Technology, Nottingham Trent University, Clifton Lane, Nottingham NG11 8NS, UK. dmitry.volodkin@ntu.ac.uk and Fraunhofer IZI-BB, Am Mühlenberg 13, 14424, Potsdam, Germany. vladimir.prokopovic@izi-bb.fraunhofer claus.duschl@izi-bb.fraunhofer.de katja.uhlig@izi-bb.fraunhofer.de.
authors.forename: Dmitry
authors.initials: D
authors.lastname: Volodkin