Preparation and Selected Applications of Functional Hydrogel Films Synthesized by Initiated Chemical Vapor Deposition (iCVD)
In this thesis, functional hydrogel films were synthesized using initiated Chemical Vapor Deposition (iCVD) for selected applications. Hydrogels possess various tailorable properties, such as softness or swellability while being highly biocompatible. Thus, they are an interesting material for a manifold of applications. iCVD is a solvent-free, all-dry surface polymerization technique performed under vacuum. It is able to deposit conformal, pinhole-free thin films of application-specific polymers in a single step onto complex and porous structures. In iCVD, an initiator is activated to form free radicals in the gas phase. Gaseous monomers adsorb onto a cooled substrate followed by surface reactions where the free radicals attach to multiple monomer units resulting in chain growth polymerization to form long polymer chains. Here, PHEMA films were investigated, crosslinked and copolymerized with EGDMA. Adapting the composition and properties of the hydrogel layers to the specific needs, a vast field of applications can be met. In this thesis, applications ranging from barrier layers used in drug delivery systems towards membranes suitable for an oil-water separation device were investigated. The all-dry and conformal coating behaviour of iCVD enables the creation of novel free-standing 3D biocompatible interconnected highly porous network structures promising for tissue engineering approaches. Due to the mild iCVD deposition conditions, temperature sensitive composite patches can be modified to enhance the viability and proliferation of human osteoblast cells enabling the usage as biomaterial in bone tissue engineering. In addition, different initiating molecules are investigated and their temperature responses are studied to select the respective initiator for specific applications. In this thesis, it will be demonstrated that synthesizing hydrogel films via iCVD offers great freedom to deposit polymeric thin films for a manifold of applications.
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