Materials World Network to Study Liquid Precursor Formation and Crystallization at Interfaces: Fundamentals towards Applications
Final Report Abstract
The overall goal of the project was to investigate fundamental thermodynamic and kinetic aspects of Polymer Induced Liquid Precursor (PILP) formation. We were able to reach the main goals of the initial project proposal. Cölfen group: 1. demonstrated that the PILP concept is not universally applicable to every mineralizing system in a straightforward way. PILP formation could be observed for acidic or basic amino acid systems with the counter charged polyelectrolyte additive. 2. determined the phase diagram for the DL-Glutamic acid / poly(ethylene imine) system. PILP precursors are found only in a very small part of the phase diagram. In larger regions in the phase diagram, direct crystallization of DL- Glu from homogeneous solution is observed or coacervates were formed, which are thermodynamically stable liquids with comparable appearance to PILPs. In addition, the volume of the obtained PILPs was always very small (<< 1 vol.-%) regardless of the experimental conditions. 3. investigated PILP growth by time resolved SAXS and SANS investigations. 4. investigated the time dependent PILP formation process for CaCO3 in presence of poly(aspartic acid) quantitatively confirming earlier reports by the Gower group. The solubility product of the PILP phase could be quantitatively detected as well as its changing composition. Also, PILP formation was for the first time discovered for a low molar mass additive (sodium tripolyphosphate). 5. demonstrated the liquid character of the PILP phase by coalescence of microdroplets. In addition to the solution of main questions formulated in the initial grant proposal, we achieved several interesting preparative aspects of PILP precursor phases. All of them concern the straightforward preparation of complex nanoparticle superstructures from PILP precursors. These are namely: 1. Hierarchical microspheres from PILP by crystallization within the PILP droplets. 2. Hierarchical thin films with at least five hierarchy levels on a hydrophilic glass surface by a simple solvent evaporation process from PILP. 3. Patterned and crack free thin films by a simple dip coating process from PILP. These examples demonstrate that PILP precursors are very interesting starting phases for the preparation of complex materials. Not only complex morphologies but also hierarchy can be induced by simple preparation reactions. However, the downside of this approach is the very limited range of experimental conditions under which a PILP phase can be found as well as the associated very low amount of this phase. Volkmer group: 1. Investigations on PILP formation underneath charged and non-charged monolayers for a range of structurally different monolayers indicate that the chemical nature of the monolayer has little influence on the PILP. We could not find experimental evidence for a structure (=orientation) directing influence of the surface onto which the PILP is deposited. PILPS formed from supersaturated CaCO3 solutions always lead to calcitic thin films upon PILP-to-crystal transformation. Quantitative birefringence microscopy (AbrioTM), and electron backscattering (EBSD) techniques have been established as valuable analytical tools to characterize PILP-to-crystal transformation processes in general. 2. Experimental coating procedures have been developed for depositing PILP materials onto surfaces. These include a Layer-by-Layer (LbL) deposition technique, employing layers of PS-b-PAA block copolymer/PILP. Thus manufactured multilayered thin films bear a striking resemblance to biogenic nacre, albeit their mechanical properties deserve further improvements. 3. Reactive spray-coating could be established as a second thin film deposition technique, in which different types of functional groups, stemming from low molecular weight hyperbranched polyglycidols, lead to different CaCO3 crystal polymorphs during the preparation of mechanically robust calcium carbonate thin films. For the latter approach, however, experimental evidence pointing at an intermediate metastable PILP phase could not be found, which is presumably due to the fact that the conc. ranges under which CaCO3 PILPs form are too narrow for this particular application. Future work can profit from the PILP process to generate materials with adjustable / moldable morphologies as well as crystalline thin films. Further material applications could be functional crystalline coatings.
Publications
- Multilayered CaCO3/block-copolymer materials via amorphous precursor to crystal transformation. Coll. Surf. A 354, 279 (2010)
H. Gong, M. Pluntke, O. Marti, P. Walther, L. Gower, H. Cölfen, D. Volkmer
- Precursor Phases in Non Classical Crystallization. PhD Thesis, Universität Potsdam (2010)
Y. Jiang
- Hierarchical DL-Glutamic Acid Microspheres from Polymer-Induced Liquid Precursors. Cryst. Growth Des. 11, 3243 (2011)
Y. Jiang, L. B. Gower, D. Volkmer, H. Cölfen
- How to control the scaling of CaCO3: A "Fingerprinting Technique" to classify additives. Phys. Chem. Chem. Phys. 13, 16811 (2011)
A. Verch, D. Gebauer, M. Antonietti, H. Cölfen
- Preparation of Hierarchical Mesocrystalline DL-Lysine_HCl-Poly(acrylic acid) Hybrid Thin Films. Adv. Mater. 23, 3548 (2011)
Y. Jiang, H. F. Gong, D. Volkmer, L. B. Gower, H. Cölfen
- Biomimetic Approaches for the Preparation of Nacre-type Composites with Microtextured Surfaces. PhD Thesis, Augsburg University (2012)
K. Malinova
