Fabrication Of Fluorinated Amphiphilic Polymer Brushes And Their Protein-resistant Performance

Protein adsorption on the material surface is believed to be the ubiquitous event when a material comes into contact with the biological environment. Understanding and controlling the interaction between proteins and material surfaces is of great significance in some fields such as biomedical materials and marine antibiofouling. Larger microorganisms as well as proteins are inherently amphiphilic. They operate by different attachment mechanisms, with some having higher affinity to hydrophobic surfaces and others to hydrophilic. Either hydrophilic or hydrophobic surface is often inadequate in resisting fouling upon prolonged exposure to complex environments such as blood. Polymer brushes provide an effective approach to achieve ultrathin antibiofouling coatings with well-defined polymeric structures. Therefore, it is of little surprise that significant attention has been directed toward development of amphiphilic polymer brushes.(1) The V-shaped fluorinated amphiphilic copolymer brushes were prepared by the “grafting-to” method. Fluorinated amphiphilic copolymers m PEGm-b-PAAm-b-PMMAx-b-PFMAy were synthesized by atom transfer radical polymerization(ATRP), and then attached to modified Si O2 substrate by the covalent bonds formed between the carboxyl group of PAA segment and the epoxy on the modified substrate surface. Two kinds of V-shaped fluorinated amphiphilic copolymer brushes were synthetized. One was the amphiphilic copolymer brushes with the same length of hydrophilic chain(PEG) and hydrophobic chain(PMMA-b-PFMA) and the other was that with the non-identical length of hydrophilic chain(PEG) and hydrophobic chain(PMMA-b-PFMA).(2) The surface structures and their relationship with the protein-resistant performance of the copolymer brushes with the same length of hydrophilic chain(PEG) and hydrophobic chain(PMMA-b-PFMA) were studied. Fluorinated amphiphilic surfaces with different chemical compositions were obtained by changing the polymerization degree of PFMA. The hydrophobicity and lipophobicity were enhanced with the increasing of the polymerization degree of PFMA. Fluorinated amphiphilic surfaces exhibited much better protein resistance compared to the pure hydrophilic surface. When the polymerization degree(PD) of PFMA was 8 and the ratio of the content of fluoride components to the content of hydrophilic components was 2.43, the amphiphilic surface had the optimal protein-resistant performance. The phase segregation and surface reconstruction behavior of the fluorinated amphiphilic brushes were researched. Results showed that it exhibited the pronounced compositional heterogeneity when the PD of PFMA was 8. This surface undergone the greatest degree of reconstruction. The reconstruction behavior was related to the protein-resisitant performance of the amphiphilic surface. It was found that the protein-resisitant performance improved with increasing of △θ and △(F1s/C1s) which could be a measure of the degree of surface reconstruction after being immersed into the water. The improved protein repellent property of fluorinated amphiphilic polymer brush with 8 FMA units was attributed to(i) the synergistic effect of hydrophilic composition and hydrophobic composition, and(ii) the morphological and compositional complexities of nanostructured amphiphilic surfaces, generated due to the phase segregation of two incompatible monomer precursors, which weaken the interactions between the biomolecule surface and the substrates.(3) The surface structures and its relationship with the protein-resistant performance of the copolymer brushes with non-identical length of hydrophilic chain(PEG) and hydrophobic chain(PMMA-b-PFMA) were investigated. Fluorinated amphiphilic surfaces with different chemical compositions were obtained by changing the polymerization degree of PMMA. The hydrophobicity and lipophobicity weakened with the increasing of the polymerization degree of PMMA. The amphiphilic surface with 15 MMA units which had the greatest degree of surface reconstruction achieved the optimal protein-resisitant performance. It was found that the protein-resisitant performance improved with increasing of △θ and △(F1s/C1s) which could be a measure of the degree of surface reconstruction. This phenomenon maybe was related to the structure of the polymer brush. When the hydrophilic chain was much longer than the hydrophobic one, the long PEG segment with the greater mobility could be easily taken from a dry to a hydrated state. The highly-hydrated hydrophilic chain can reach protein-resistant performance. While the short fluorinated hydrophobic chain among the hydrophilic chains with low surface energy can release foulings. Therefore, the combination of highly-hydrated hydrophilic chain and fouling-released fluorinated hydrophobic chain could improve its protein-resistant performance.