Preparation, characterization and application of functional surfaces based on porous polymethacrylates

Porous polymethacrylates have numerous important applications in different research and industrial fields. These materials have been used as stationary phases for separation and catalysis, as substrates for thin layer chromatography, as materials for solid-phase extraction or filtration, or for making valves in microfluidic devices. The main advantage of porous polymethacrylates is that their physical and chemical properties, such as porosity, pore and polymer globule size, stiffness, hydrophobicity or hydrophilicity, as well as surface functional groups can be conveniently controlled by adjusting the composition of the polymerization mixtures. Porous polymethacrylate can be also functionalized using available surface modification strategies. This unique ability to control properties of porous polymethacrylates makes them suitable for the design and synthesis of novel functional materials. Surprisingly, most of the applications of porous polymethacrylates have been limited to their use inside columns, capillaries or microfluidic channels and their applications as open surfaces remained to a great extent unexplored. The goals of my PhD thesis were to: (1) develop methods for the preparation of (bio)functional porous polymethacrylate surfaces with well-defined surface properties; (2) characterize produced surfaces; (3) explore their unique properties in different biological applications. Surfaces with gradient properties have been widely used in many cell-surface interaction studies because these gradient surfaces offer the possibility to avoid the difficulties associated with the one-sample-for-one-measurement approach as well as the problems with sample variations. However, up to now, there are only a few methods for the preparation of surfaces with gradient properties. Taking advantage of the tunable porous properties of polymethacrylates, porous poly(butyl methacrylate-co-ethylene dimethacrylate) (BMA-EDMA) surfaces with gradient surface morphologies were prepared using a PDMS microfluidic chip designed and produced for this study. The produced BMA-EDMA surface possessed a gradient polymer globule size ranging from ~ 0.1 µm to ~ 0.5 µm. The surface with the globule size gradient in this range is useful for cell studies such as investigation of the effect of surface morphology on cell behavior. Porous polymethacrylate surfaces with a gradient in density of functional groups were also prepared via photografting by gradually varying the UV dosage along one direction on the surface during surface modification. The formation of the gradient was confirmed with X-ray photoelectron spectroscopy and water contact angle measurements. To show the potential of using the surface with a gradient density of functional groups, the behavior of human fibrosarcoma HT-1080 cells was studied on the surface. Recently, bio-inspired slippery liquid infused porous surfaces have attracted much attention due to their unique liquid repellent and self-cleaning properties. In this thesis, stable slippery surfaces were prepared by infusing the porous BMA-EDMA surface with water immiscible hydrophobic poly(hexafluoropropylene oxide) or perfluorotripentylamine. The antibacterial and anti-marine fouling properties of the slippery BMA-EDMA surfaces were carefully investigated. Our results demonstrated that the slippery BMA-EDMA surfaces had good antibacterial and anti-marine fouling properties. However, the results also revealed that the antibacterial property of the slippery BMA-EDMA surface was bacterial strain dependent. In addition, Ulva sporelings (young plants) were able to firmly attach to the slippery surface although the surface is able to resist Ulva spore adhesion. The ability to transform a superhydrophobic surface to a superhydrophilic one is essential for many applications such as creating superhydrophobic-superhydrophilic micropatterns or microarrays. Most of the existing methods for this transformation are time consuming or require harsh conditions. In this thesis, a new facile method to transform the superhydrophobic BMA-EDMA surface to a superhydrophilic one was developed. This method is based on the physisorption of an amphiphilic phospholipid on the hydrophobic surface of porous BMA-EDMA through hydrophobic-hydrophobic interactions. Using this method, superhydrophobic-superhydrophilic micropatterns could be fabricated simply by printing the phospholipid “ink” on the superhydrophobic BMA-EDMA surface with a contact printer