Temperature Responsive Nanopore Based On Functional Nanoporous Polycarbonate Membranes

Functional stimulus responsive nanopore membranes have attracted great attention because of their comprehensive applications including smart separation, chemo/bio sensing and controlled drug release. In this thesis, nanoporous polycarbonate membranes were functionally modified with different methods, and then the properties and differences of these functional temperature responsive membranes were investigated. The research works of this dissertation are summarized as follows:1. Nanopore membranes with gold along the porewalls and surface were prepared by chemic aggradation, and then poly(N-isopropylacrylamide) (PNIPAm) brushes were grafted onto these gold coated nanoporous track-etched polycarbonate membranes. The permeabilities of the resulting pore-filled membranes were determined by total internal reflection fluorescence microscopy. And the influence of different grafting yield of PNIPAm were also investigated. The results showed that, the change of permeability related to the temperature is distinct at different grafting yield. At low grafting yield, the response of permeability to environmental temperature is due to the change of effective membrane pore size induced by the conformation (expand or shrink) change of the grafted PNIPAm chains, so the permeability of thermoresponsive membranes was higher at temprature above the lower critical solution temperature (LCST); In contrast, at high grafting yield, the response of permeability to environmental temperature is due to the hydrophilic or hydrophobic change of the grafted PNIPAm chains.The permeability of thermoresponsive membranes was higher at temperature below the LCST. A drug permeation model was proposed using doxorubicin as a probe, and the results were consistent with the above. Therefore, this kind of controllable thermoresponsive membrane can be applied in practical controlled drug release, and may have a unique potential application in the field of life process simulation and so on.2. Nanopore membranes with single side gold coated were prepared by vacuum sputter coating, which is a relatively simple method. Temperature responsive nanopore membranes were prepared by modifying the resulting membranes with PNIPAm. The thermally switchable transport properties of the PNIPAm modified membranes with different grafting yield were also investigated. The results confirm that the permeability was higher at temperature above the LCST both at low and high grafting yield. Because the pore walls of these nanoporous membranes were not grafted with PNIP Am and the permeability was dominated by the surface pore coverage rather than the hydrophilic or hydrophobic property of polymer brushes. Therefore, this research developed a new type of temperature responsive nanopore membranes, which may be applied to micro-valves and controlled drug release.3. A novel kind of temperature responsive nanopore membranes without gold coating were obtained through modifying membranes with PNIPAm in terms of vacuum filtration. This method based on polyallylamine hydrochloride (PAH) electrostatic interaction with nanoporous track-etched polycarbonate membranes. Field emission scanning electron microscopy, attenuated total reflectance Fourier transform infrared spectroscopy, and drop shape analyzer were used to characterize the chemical composition, surface morphologies and thermoresponsive properties of the modified membranes. In addition, the permeabilities of the resulting membranes were investigated by total internal reflection fluorescence microscopy. The results showed that this is an economical, simple and convenient method to construct temperature responsive nanopore membrane with notable thermoresponsive property and favorable reversibility.