Hydrophobically Functionalized Chitosan Particles

Abstract

Particles of chitosan have a very polar surface, and thus they are easily wetted by water and also dissolve in acidic media. The hydroxyl and amino groups offer a high potential for grafting reactions. Aldehydes and carbonic acid derivatives were covalently grafted, preferably onto the amino groups. The reactions were carried out in solution as homogeneous phase reactions as well as on the particle surfaces as heterogeneous phase reactions. Covalently bonded alkyl chains impart the chitosan molecules with hydrophobic properties. We employed different methods such as NMR, XPS, elemental analysis and FT-IR spectroscopy to study the reactions and to estimate the degree of functionalization. The wetting behavior of the particles was investigated by a modified Wilhelmy technique, where an adhesive tape completely coated with the particles was dipped in water. Some of the samples having a high degree of functionalization showed super-hydrophobic surface properties. The observed super-hydrophobic effect results from a combination of the hydrophobic properties of the modified particles and the roughness of the particle coating.

Superhydrophobic Alumina Surfaces Based on Polymer‐Stabilized Oxide Layers

“…Model reactions previously carried out on CHS microparticles, showed that the grafting of bifunctional copolymers is more effective than the grafting of single molecules. [14,15] POMA was found to be the most convenient copolymer in comparison with other maleic anhydride copolymers and polymers bearing epoxy or sulfonic acid groups. [16] The anhydride groups of POMA are highly reactive to the amino groups of CHS and the long alkyl chains are able to form a closely packed hydrocarbon layer with terminal methyl groups lowering the surface polarity substantially.…”

In Metalloberflächen verankerte Polymere zur Herstellung ultrahydrophober Metalloberflächen

“…Für Pfropfreaktionen erscheinen wegen ihrer hohen Reaktivität gegenüber Carbonylverbindungen insbesondere die primären Aminogruppen des Chitosans geeignet [8]. Die Aminogruppen wurden aber auch genutzt, um über partielle Vernetzungsreaktionen mit bifunktionellen organischen Molekülen (z.…”

“…B. Säurechloride und -anhydride) an. An Modellreaktionen konnte mittels 13 C-CP-MAS-NMR-Spektroskopie gezeigt werden, dass eine Anbindung der Carbonsäuren an die Aminogruppen unter Ausbildung kovalenter Amidbindungen stattfand [8]. Die Umsatzgrade waren auch unter Verwendung von N,N'-Dicyclohexylcarbodiimid und Dimethylaminopyridin so gering, dass keine der so hergestellten Kompositoberflächen ultrahydrophobe Eigenschaften zeigte.…”

“…Key words: Superhydrophobic surface, Self-cleaning, Aluminium/Aluminium oxide, Anodic oxidation, Chitosan, Surface reactions [7,8].…”

“…B. Aldehyde oder Carbonsäu-rederivate) [8], oder durch das Umsetzen der Aminogruppen mit polymeren Maleinsäureanhydridcopolymeren, deren Alkylensequenzen ebenfalls längere Alkylreste trugen [7,9]. Die Maleinsäureanhydridcopolymere erschienen als Funktionalisierungsagens besonders geeignet, da sie das Vernetzen des Chitosans und das Hydrophobieren der Oberflächen in einem Schritt ermöglichten.…”