Research On The Antifouling Surface Structure Of Amphipbilic Fluorinated Copolymers

Protein adsorption at solid surfaces plays a critical role in many biologicalphenomena and has aroused a wide range of interest for researchers. Nonspecificadsorption for protein and associated bioadhesion is one of the most significantlimitations to the end point utility of many infrastructures and devices like biomedicalimplants, marine ship hulls, water purification and textile industry areas. Recently, anexcellent coating material, fluorinated amphiphilic polymer exhibits better antifoulingperformance than its homopolymer independently for owning the double superioritybelonging to traditional hydrophilic materials and low-energy materials, respectively.Most researches focused on the design of molecular structure for antifouling, whichresulting in little knowledge for the antifouling mechanism, even though more andmore attentions have been paid to this issue. Generally, the novel fouling-resistanceperformance was attributed to surface composition, topography and phase segregationand so on. Building appropriate surface structure consist of micro nanostructure,chemical composition, which weakens and inhibits organism bonding and adsorptionabilities for antifouling, is critical. Therefore, it’s necessary to develop antifoulingpolymer surfaces with optimum surface structures for the purpose of preventingunwanted accumulation of bioadhesion and protein adsorption at surfaces andinterfaces.In this thesis, two series of fluorinated amphiphilic copolymers with differentcomposition comprised of random and ABC type triblock copolymers have beendesigned and synthesized. FT-IR, NMR, GPC, elemental analysis, AFM, XPS wasemployed to characterize the polymers structure. With bovine serum albumin (BSA)and human fibrinogen (HFg) as protein models, the antifouling performance wasanalyzed by detecting atom of N1s%by XPS as an indication of HFg or BSA. Theconclusions obtained are followed below as a systematical study on the antifoulingsurface. (1) Hydroxyethylmethacrylate (HEMA) and2-perfluorooctylethyl methacrylate(FMA) were chosen and used for synthesizing a series of random copolymersPHEMA-r-PFMA, on which surfaces the behavior of BSA and HFg were investigated.When the FMA mol%is2.45%and7.56%separately, HFg and BSA proteinadsorption reached the least level. In addition, all the fluorinated random copolymersexhibited excellent E.coil adhesion-resist property. It was found that the copolymersexhibited better antifouling properties than the corresponding homopolymers did,when the percentage of hydrophilic hydroxyl groups is from4%to7%and thepercentage of hydrophobic fluorinated moieties is from4%to14%on the surface,neither BSA nor HFg can easily deposit. Simultaneously, the surface energy is about20~30mN/m, which lying in the range defined by the Baier curve, suggesting that thehydrophily or hydrophobicity is not the crucial factor for fluorinated amphiphiliccopolymer surfaces against the protein adsorption. Further research showed that, thesurface compositional heterogeneities on the molecular size scale with special contentof hydrophilic and fluorinated moieties play a significant role in antifouling properties.The protein molecular size scale and the pattern of microphase segregation domainson the support surface strongly affect the adsorption behaviors of proteins.(2) A series of amphiphilic fluorinated ABC-type triblock copolymersmPEG-b-PMMA-b-PFMA have been synthesized by atom transfer radicalpolymerization and characterized. The surface compositions of amphiphiliccopolymer coatings and the atoms of nitrogen content after Human fibrinogen (HFg)adsorption on these surfaces were measured by X-ray photoelectron spectroscopy, andthe relationship of surface structure and proteins adsorption behavior was furtherinvestigated. It was found that these amphiphilic fluorinated copolymer coatingexhibited excellent antifouling performance when5.98mol%fluorinated units, only0.7%nitrogen content on surface which was almost negligible compared to PMMAafter protein adsorption experiment. The results demonstrated that protein adsorptioncan be seriously disrupted by such surfaces where the content of hydrophilic groupswas at the range of around8-12%and fluorinated content was at10-30%. The effectof PMMA block for mPEG44-PMMAm-PFMA1on surface properties and HFg adsorption behavior was investigated. The result showed that the hydrophilicweakened while no obvious fluorinated moieties change on the surface, and theamount of HFg protein adsorbed have increased eventually.