Synthesis,Structural Characterization And Protein Resistance Of Amphiphilic Block Copolymers Based On Polydimethylsiloxanes

The protein adsorption on material surfaces often results in bio-fouling and degradation,and thus protein resistant materials have been increasingly studied for medical devices,marine anti-fouling,membrane separation,etc.Zwitterionic polymers have showed exceptional performance in a number of studies concerning protein resistance due to their formation of ?hydration layer? barriers.However,their highly hydrophilic nature tends to prevent them from aggregating to hydrophobic surfaces which are usually susceptible to protein adsorption and bio-fouling,and the applicability of zwitterionic polymers in aqueous solution is thus limited.In order to enable the zwitterionic groups with anti-fouling properties to function on hydrophobic surfaces properly,a hydrophobic block is introduced to zwitterionic polydimethylsiloxanes grafted with cysteine groups and a series of amphiphilic diblock copolymers based on PDMS [referred as PDMS-b-(PDMS-g-Cysteine)] are prepared.The solution behavior and protein resistance of PDMS-b-(PDMS-g-Cys)are further investigated.The main contents of this thesis are as follows:(1)A series of PDMS-b-PVMS backbones with controllable molecular weight and narrow distribution of each block are synthesized through anionic ring-opening polymerization.N-acetyl-L-cysteine side groups are then grafted to the backbones via thiol-ene ?click reaction?,after which the N-acetyl group are removed by hydrolysis in acid solutions and PDMS-b-(PDMS-g-Cys)s are obtained.The synthesis route is controllable and efficient,which only involves three steps of mild reactions.(2)The solution behavior of PDMS-b-(PDMS-g-Cys)s indicates its amphiphilicity as typical surfactants.The critical micelle concentrations for PDMS-b-(PDMS-g-Cys)s decreases with the length of hydrophobic PDMS block increasing.Moreover,for a certain structure of hydrophilic block,an overlong hydrophobic block could result poor solubility of the copolymer,thus hindering its application in solution.(3)Quartz crystal microbalance with dissipation(QCM-D)measurement is utilized to characterize the adsorption of PDMS-b-(PDMS-g-Cys)and its protein resistance.The results indicate that the predominant force involved in the adsorption of amphiphilic block copolymers onto surfaces is the hydrophobicity of their backbones.An increased length of PDMS backbone is able to promoting the adsorption remarkably.The zwitterionic density assembled on the surface is found to have a fundamental and direct influence on the protein resistance.The TEM photos and the dynamic surface tension studies show that the hydrophobic interaction induced adsorption is effective to assemble zwitterionic polymers onto surfaces,especially in salts solution.The cytotoxity test shows the non-toxity of PDMS-b-(PDMS-g-Cys)s.