High solid polymer-hectorite composites

• Hochfestkörper Polymer-Hektorit-Verbundwerkstoffe

Kensbock, Philip; Möller, Martin (Thesis advisor); Pich, Andrij (Thesis advisor)

Aachen : RWTH Aachen University (2022)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2022

Abstract

Interactive applications for Nanocomposites are a research field with long history and success and increasing focus in the scientific community. The use of high-solid composites with anisotropic nanoparticles like hectorites is a recent development, necessitated by the use of systems without organic solvents and with increasing demands to the material itself. Hectorites play an important role as rheology modifiers, for composite materials or catalytic substrates. For these applications, the microscopic interactions of hectorites have a crucial influence on the properties of the resulting material. Controlling these interactions lead to phase transitions from isotropic liquid over nematic to crystal-like columnar. Hereby, new ways of using this building block via self-assembly are possible. Consequently, in this thesis, materials with a defined degree of order or disorder were developed in the following applications: For one, the development of a barrier-material with properties like high mechanical strength, inswellability, high transparency and gas tightness for the perfect protection of sensitive materials like electronic components as LEDs or perishable food is presented. In this regards, nacre-mimetics have shown potential as functional materials with great mechanical performance. In contrast to artificial nacre, mussel shells show impeccable water resistance due to mineral bridges and have outstandingly high inorganic solid content between 95 and 99 %. This inorganic content was achieved for the first time and represents a significant improvement of the previous nacre mimetics (10-90 %). The brick-and-mortar structure produced via a biomimetic self-assembly of phosphoprotein casein and hectorites was the essential step towards better barrier properties (99.998% inhibited gas diffusion with 90% light transmission). The second successful application of the high solid nanoparticle-polymer combination is the development of a new artificial muscle. The material shown here is based on self-assembling, liquid crystalline, high aspect ratio fluoro hectorites inside a thermoresponsive poly-NIPAm matrix and mark a crucial step in the development of actuators. Building on factors like nanostructure formation, anisotropic deformation mechanisms and mechanical properties, highly anisotropic hydrogels (88% of the platelets in perfect orientation) were obtained and new insight in the mechanism behind the anisotropic movement was shown. Those hydrogels exhibit extraordinarily high anisotropic volume phase transitions (40% elongation with super fast 10 %/s elongation rate), previously only reachable for complex particle-alignment methods. The new facile and robust synthesis of muscle mimetic materials enables the production of bigger structures necessary for artificial actuating functions in the growing field of robotics.

Institutions

• Department of Chemistry [150000]
• Chair of Macromolecular Chemistry [154610]