Self-assembly Of Blcok Copolymers Into Micellar Membranes:Structural Control And Process Investigations

In this dissertation,porous membranes with obviously self-organized structure were prepared by the self-assembly and non-solvent induced phase separation?SNIPS?method using polystyrene-b-polyacrylic acid?PS-b-PAA?as the membrane forming material.The additives were used to regulate and control the membrane structure.Firstly,small molecule additives?such as methanol,ethanol,1-propanol and water?were applied to control the membrane formation process and the microstructure.The influence of additives on polymer membrane diameter,porosity,and water flux was obtained.It was found that the dielectric constants of the additives showed significant effect on the diameter of the micelles:additives with smaller dielectric constants led to larger micelle diameters.The porosity of the copolymer membrane was related to the diameter of the micelle,and larger water flux was found on membranes composed of bigger micelles.In addition,the porosity was also related to the amount of solvent remaining in the cast film:the shorter the evaporation time,the less volatile the additive,and the greater the amount of residual solvent,resulting in greater porosity.In this experiment,the lysozyme adsorption to membranes prepared from different additives and evaporation time were investigated.The maximum amount of lysozyme adsorption to membranes was 188.8 mg/cm³,which was obviously higher than the results reported in previous literatures.Secondly,the effects of polyethylene glycol?PEG?on membrane formation were explored.The morphologies observed by scanning electron microscopy indicated that when the PEG molecular weight was increased to 8000 g/mol and 20000 g/mol,the self-assembly in membranes was largely hindered.It was proved by fourier infrared spectroscopy and nuclear magnetic resonance that the increased diameter of micelle was resulted from the high molecular weight PEG reserved in membranes.This section also explored the effect of additive PEG300 on membrane mechanical properties.It found that the porosity increased and mechanical strength decreased with the increase of the PEG300 concentrations.The reversible,pressure dependent CO₂-responsive was explored,and successful interception of gold nanoparticles was achieved with the aid of this property.