Layer-by-layer assemblies of chitosan and heparin: effect of solution ionic strength and pH
2011 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, no 12, 7537-7548 p.Article in journal (Refereed) Published
The growth of polysaccharide multilayers consisting of positively charged chitosan (CH) and negatively charged heparin (HEP) was monitored in situ by employing a quartz crystal microbalance (QCM-D) and dual-polarization interferometry (DPI). The main focus was on how the physicochemical properties of the solution affect the growth and structure of the resulting multilayer film These results showed that when increasing the ionic strength of the polysaccharide solutions at a fixed pH, both the "dry" (optical) (DPI) mass and wet (QCM) mass of the adsorbed multilayer film increased. The same effect was found when increasing the pH while keeping the ionic strength constant. Furthermore, the growth of multilayers showed an exponential-like behavior independent of the solution conditions that were used in this study. It was also established that chitosan was the predominant species present in the chitosan heparin multilayer film. We discuss the viscoelastic properties of the adsorbed layers and their variation during the multilayer buildup. Interestingly and contrary to common interpretation of the QCM-D results, we found that under one particular solution condition (pH 4.2 and 30 mM NaCl) the increase in the dissipation of oscillation energy from the adsorbed layer was a consequence of layer stiffening rather than indicating a more hydrated and viscous film. On the basis of the widely used Voigt viscoelastic model for an adsorbed layer, we show that it is the film viscosity and shear that define the layer viscoelasticity (structure) of the film and not the absolute value of energy dissipation, which in fact can be very misleading.
Place, publisher, year, edition, pages
American Chemical Society (ACS) , 2011. Vol. 27, no 12, 7537-7548 p.
QUARTZ-CRYSTAL MICROBALANCE, POLYELECTROLYTE MULTILAYER FILMS, EXPONENTIAL-GROWTH, VISCOELASTIC PROPERTIES, ELECTROLYTE-SOLUTIONS, DISSIPATION, ADSORPTION, SURFACES, WATER, ELLIPSOMETRY
Chemical Sciences Physical Chemistry
IdentifiersURN: urn:nbn:se:kth:diva-14274DOI: 10.1021/la200441uISI: 000291500700029ScopusID: 2-s2.0-79959202077OAI: oai:DiVA.org:kth-14274DiVA: diva2:331990
FunderSwedish Research Council
Updated from manuscript to article in journal. Previous title: Layer-by-layer assemblies of chitosan and heparin: effect of ionic strength and pH.2010-07-292010-07-292016-04-29Bibliographically approved