Advanced Functional Thin Films and Networks towards Biological Applications

Abstract: Functional polymeric scaffolds have been employed in biological applications as several utilities, from nano-sized drug delivery systems to concrete implants. The progression in biological fields essentially relies on finding an appropriate material to fulfil the critical requirements for various types of applications with great potential for tuning functionality and mechanical properties. Therefore, the generation of new materials in extensive libraries is desirable for researchers. In this thesis, two main varieties of functional scaffolds have been constructed; these include i) periodic structure isoporous membranes and ii) three dimension (3D) crosslinked networks with programmable functionalities and mechanical properties. In the first case, a library of linear dendritic (LD) block copolymers was synthesised from biocompatible 2,2-bis(methylol)propionic acid (bis-MPA) dendrons and 2- hydroxyethyl methacrylate (HEMA) derivatives. These materials were successfully employed for the fabrication of isoporous membranes via the facile Breath Figure (BF) method. The dendritic periphery end groups control the manipulation of film morphology, as well as introduction of desired functionalities, either pre- or post- film formation. The introduction of azide functional group along the polymer backbone allows crosslinking reaction, which enhances the stability of the isoporous films. The stability towards temperature was improved from around its glass transition temperature (Tg) to 400 °C after crosslinking; simultaneously the porosity is maintained after immersion in the whole range of pH (1-14). These materials show great potential use as high performance isoporous membranes in futuristic applications such as micro-reactors, sensors and cell patterning platforms. In the second case, the facile fabrication of functional networks employs off-stoichiometric crosslinking, which resulted in residual reactive functional groups after film formation and networks with different crosslinking density. This straightforward off-stoichiometric concept is applied with commercially available materials and well-controlled dendritic-linear-dendritic (DLD) hybrid polymers, generating functional networks with different properties from high stiffness film to soft hydrogels. The network post-modification can be performed topologically and throughout the scaffold. Several crosslinking chemistries were employed for construction of hydrogels from DLD hybrid polymers. The Copper(I) Catalysed Azide-Alkyne Cycloaddition (CuAAC) click reaction results in hydrogels with higher compressive modulus compared to other hydrogels constructed from thiol-ene, thiol-yne and amine-N-hydroxysuccinimide (NHS) esters coupling methods with similar building blocks. These functional crosslinked networks are suitable for numerous applications including fabrication of microfluidic devices, cell culture platforms and bone adhesives.