Towards completely miscible PMMA nanocomposites reinforced by shear-stiff, nano-mica.
Optimizing the reinforcement of polymers with nanoplatelets requires optimization of the aspect ratio and the moduli of the filler while providing a complete stress transfer. Employing a novel shear-stiff, nano-mica with large aspect ratio, we focus on maximizing the interfacial interaction between filler and matrix. External surfaces of the nano-mica were selectively modified by a polycationic macro-initiator and two PMMA-polymer brushes of length below and above critical entanglement length, respectively, and the mechanical properties of the three PMMA nanocomposites were measured. The multiple electrostatic anchoring groups of the macro-initiator not only provide reliable adhesion but at the same time allow the variation of the degree of protonation providing a local match between the charge densities of the clay surface and the adsorbed macro-initiator. PMMA coating of the nano-mica via surface initiated polymerization yielded long-term stable suspensions in THF that showed birefringence of a nematic phase. Solution blending of the PMMA coated nano-mica allows for dispersing single clay tactoids in the translucent PMMA nanocomposites at 5 wt% clay loading as determined by transmission electron microscopy (TEM). Although significantly improved mechanical properties could be achieved as compared to nanocomposites made with conventional clay fillers, the full potential - as expressed by Halpin-Tsai equations - of the PMMA coated nano-mica can still not be completely utilized. This is attributed to the non-wetting character of the densely packed PMMA brushes attached to planar nanoplatelets.
Lehrstuhl für Anorganische Chemie I, Universität Bayreuth, Universitätstrasse 30, 95440 Bayreuth, Germany.
Mazen
M
Ziadeh
Lehrstuhl für Makromolekulare Chemie II, Universität Bayreuth, Universitätstrasse 30, 95440 Bayreuth, Germany.
Stephan
S
Weiss
Lehrstuhl für Polymere Werkstoffe, Universität Bayreuth, Universitätstrasse 30, 95447 Bayreuth, Germany.
Bianca
B
Fischer
Lehrstuhl für Physikalische Chemie I, Universität Bayreuth, Universitätstrasse 30, 95440 Bayreuth, Germany.
Stephan
S
Förster
Lehrstuhl für Polymere Werkstoffe, Universität Bayreuth, Universitätstrasse 30, 95447 Bayreuth, Germany.
Volker
V
Altstädt
Institute of Organic Chemistry, Johannes Gutenberg University Mainz, 55099 Mainz, Germany.
Axel H E
AH
Müller
Lehrstuhl für Anorganische Chemie I, Universität Bayreuth, Universitätstrasse 30, 95440 Bayreuth, Germany. Electronic address: josef.breu@uni-bayreuth.de.
Josef
J
Breu
Colloidal stability; Nano-mica; Nematic phase; Non-wetting; PMMA nanocomposites; SI-ATRP