Talk given by Doreen Hentrich Institute of Chemistry University of Potsdam Abstract: The phase behavior of an amphiphilic block copolymer based on a poly(aspartic acid) hydrophilic block and a poly(n-butyl acrylate) hydrophobic block was investigated at the air-water and air-buffer interface. The polymer forms stable monomolecular films on both subphases. At low pH, the isotherms exhibit a plateau. Compression-expansion experiments and infrared reflection absorption spectroscopy suggest that the plateau is likely due to the formation of polymer bi- or multilayers. At high pH the films remain intact upon compression and no multilayer formation is observed. Furthermore, the mineralization of calcium phosphate beneath the monolayer was studied at different pH. The pH of the subphase and thus the polymer charge strongly affects the phase behavior of the film and the mineral formation. After 4 h of mineralization at low pH, atomic force microscopy shows smooth mineral films with a low roughness. With increasing pH the mineral films become inhomogeneous and the roughness increases. Transmission electron microscopy confirms this: at low pH a few small but uniform particles form whereas particles grown at higher pH are larger and highly agglomerated. Energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy confirm the formation of calcium phosphate. The levels of mineralization are higher in samples grown at high pH. In the second study the phase behavior of a dendritic amphiphile containing a Newkome type dendron as the hydrophilic moiety and a cholesterol unit as the hydrophobic segment was investigated at the air-water interface. Newkome dendrons provide a pH-responsive hydrophilic head group, which is interesting for controlling electrostatic interactions, for example to model calcium phosphate (CP) biomineralization. The amphiphile forms stable monomolecular films at the air-water interface on different subphases. The subphase temperature has a strong influence on the phase behavior of the amphiphile, whereas the subphase pH between 5 and 8 shows a less significant influence. Furthermore, the mineralization of CP beneath the monolayer at different calcium and phosphate concentrations (2 and 20 mM) vs. mineralization time (3, 4 and 5 h) shows that needles, flakes and spheres were formed.

This event is part of the eventgroup INT Talks

Homepage
https://www.int.kit.edu/events.php

Speaker
Doreen Hentrich

University of Potsdam
Institute of Chemistry, Taubert Lab

Organizer
Dr. Christian Kübel
Institute of Nanotechnology (INT)
Karlsruhe Institute of Technology (KIT)
Eggenstein-Leopoldshafen
Mail: christian kuebel ∂does-not-exist.kit edu

Targetgroup
Interested / Everyone