Ampholyte microgels with controlled distribution of ionizable groups

  • Ampholyte Mikrogele mit kontrollierter Verteilung ionisierbarer Gruppen

Schröder, Ricarda; Pich, Andrij (Thesis advisor); Richtering, Walter (Thesis advisor)

Aachen (2016)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen, 2016

Abstract

The aim of this work is the understanding of how the distribution of functional groups (i.e. basic and acid moieties added through copolymerization) within the polymer network of environmentally responsive microgels influences the microgels’ properties. Applications of microgels are manifold and range from encapsulation/controlled release of drugs and genes and chemical sensing and/or filtration in membranes to coating for non-biofouling and protein-repellent surfaces. With regard to each application, the microgel architecture plays a crucial role. Zwitterionic and ampholyte microgels based on poly(N-vinylcaprolactam) (PVCL) and poly(N-isopropylacrylamide) (PNIPAm) with various distributions of basic and acid moieties within the microgel particle are synthesized and characterized in the first part of the work. The functional groups are incorporated either statistically, as core-shell or Janus. The influence of the distribution of ionizable groups as well as their amount in the microgel on the microgels’ properties such as particle size distribution, hydrodynamic radius, temperature- and pH-sensitivity, and softness is looked at. The second part looks closely at the influence of different microgel architecture on the uptake and release of charged species. Cytochrome c is used as a model protein and its release using various triggers such as temperature, the addition of salt and a change in pH is studied. Here, the focus is on how different distributions of ionizable groups lead to different uptake and release mechanisms. Hybrid materials of the above discussed microgels are studied in the third part of the work. First, ionizable microgels are used as nano-containers for biomineralization of CaCO3 and for bone substitution with β-TCP. Furthermore, zwitterionic microgels are deposited on surfaces to study the influence of the betaine amount on the surface’s hydrophilicity, protein-repellency, and self-healing properties.