TY  - JOUR
A1  - Shkilnyy, Andriy
A1  - Brandt, Jessica
A1  - Mantion, Alexandre
A1  - Paris, Oskar
A1  - Schlaad, Helmut
A1  - Taubert, Andreas
T1  - Calcium phosphate with a channel-like morphology by polymer templating
N2  - Calcium phosphate mineralization from aqueous solution in the presence of organic growth modifiers has been intensely studied in the recent past. This is mostly due to potential applications of the resulting composites in the biomaterials field. Polymers in particular are efficient growth modifiers. As a result, there has been a large amount of work on polymeric growth modifiers. Interestingly, however, relatively little work has been done on polycationic additives. The current paper shows that poly(ethylene oxide)b-poly(L-lysine) block copolymers lead to an interesting morphology of calcium phosphate precipitated at room temperature and subjected to a mild heat treatment at 85 degrees C. Electron microscopy, synchrotron X-ray diffraction, and porosity analysis show that a (somewhat) porous material with channel-like features forms. Closer inspection using transmission electron microscopy shows that the channels are probably not real channels. Much rather the morphology is the result of the aggregation of ca. 100-nm-sized rodlike primary particles, which changes upon drying to exhibit the observed channel-like features. Comparison experiments conducted in the absence of polymer and with poly(ethylene oxide)-b-poly(L-glutamate) show that these features only form in the presence of the polycationic poly(L-lysine) block, suggesting a distinct interaction of the polycation with either the crystal or the phosphate ions prior to mineralization.
Y1  - 2009
UR  - http://pubs.acs.org/journal/cmatex
U6  - https://doi.org/10.1021/Cm803244z
SN  - 0897-4756
ER  - 
TY  - JOUR
A1  - Casse, Olivier
A1  - Shkilnyy, Andriy
A1  - Linders, Jürgen
A1  - Mayer, Christian
A1  - Häussinger, Daniel
A1  - Völkel, Antje
A1  - Thünemann, Andreas F.
A1  - Dimova, Rumiana
A1  - Cölfen, Helmut
A1  - Meier, Wolfgang P.
A1  - Schlaad, Helmut
A1  - Taubert, Andreas
T1  - Solution behavior of double-hydrophilic block copolymers in dilute aqueous solution
JF  - Macromolecules : a publication of the American Chemical Society
N2  - The self-assembly of double-hydrophilic poly(ethylene oxide)-poly(2-methyl-2-oxazoline) diblock copolymers in water has been studied. Isothermal titration calorimetry, small-angle X-ray scattering, and analytical ultracentrifugation suggest that only single polymer chains are present in solution. In contrast, light scattering and transmission electron microscopy detect aggregates with radii of ca. 100 nm. Pulsed field gradient NMR spectroscopy confirms the presence of aggregates, although only 2% of the polymer chains undergo aggregation. Water uptake experiments indicate differences in the hydrophilicity of the two blocks, which is believed to be the origin of the unexpected aggregation behavior (in accordance with an earlier study by Ke et al. [Macromolecules 2009, 42, 5339-5344]). The data therefore suggest that even in double-hydrophilic block copolymers, differences in hydrophilicity are sufficient to drive polymer aggregation, a phenomenon that has largely been overlooked or ignored so far.
Y1  - 2012
U6  - https://doi.org/10.1021/ma300621g
SN  - 0024-9297
VL  - 45
IS  - 11
SP  - 4772
EP  - 4777
PB  - American Chemical Society
CY  - Washington
ER  -