Microgel/SiO2 Hybrid Colloids with Different Architectures

Agrawal, Garima; Pich, Andrij (Thesis advisor); Möller, Martin (Thesis advisor)

Aachen : Publikationsserver der RWTH Aachen University (2015)
Dissertation / PhD Thesis

Aachen, Techn. Hochsch., Diss., 2014


This dissertation deals with the development and characterization of microgel/silica hybrid colloids of different complexity based on different derivatives of hyperbranched polyalkoxysiloxanes (PAOS) as functional silica precursor polymers.Microgels are porous polymeric crosslinked particles which are swollen in a solvent like water. Additionally, these soft colloids provide an opportunity to combine different functionalities in a confined space. Taking advantage of this, a water based method for the formation of microgel/silica hybrid colloids is shown. Here, functional polymer microgels act as smart self-catalyzing systems e.g. inducing controlled formation of silica nanoparticles inside the polymer network. A water soluble silica precursor polyethyleneglycol (PEG) substituted PAOS has been developed to load microgels with silica particles in aqueous medium. Furthermore, a controlled in-situ reductive process for the site specific gold formation with no additional reducing agent inside microgel network is also presented. This is a new phenomenon and not so much work has been reported on it. The catalytic activity of these hybrid colloids can be tuned depending on the amount of gold loaded inside the microgels. The hybrid particles can easily be isolated after catalysis via centrifugation and re-used with retention of the catalytic activity.The properties of microgels can be tuned based on the type of crosslinker used during the synthesis. A series of PAOS containing vinyl and PEG groups (Cross-PAOS) have been used as crosslinker for synthesis of degradable microgels with tunable size and temperature sensitive properties.Cross-PAOS has been further used for coating of hematite nanoparticles with simultaneous surface functionalization in a water based chemical approach. At last, the preparation of adaptive hybrid capsules with microgel/silica composite walls is described. The capsules with controlled size, morphology and shell permeability are fabricated by using the combination of Pickering emulsion and sol-gel process at the interface. Responsive microgels present in the capsule wall act as transportation channels for different encapsulated substances. Similarly, formation of temperature sensitive silica capsules with encapsulated wax has also been investigated.