Enzymatic Polymerization Of Arylamines And Its Application

Enzymatic polymerizations under mild conditions in aqueous solution are an attractive alternative to chemical polymerizations.Particularly challenging is the use of oxidative enzymes which only oxidize the monomers without direct influence on the actual polymerization,leading to the formation of ill-defined products.To nevertheless exert some control on the selectivity of the nonenzymatic coupling reactions,the presence of dispersed soft interfaces as templates,e.g.polymers,micelles or vesicles,is often extremely useful.By using soft templates during the polymerization of aniline with laccase or horseradish peroxidase?HRP?and O₂/H₂O₂ as oxidant in aqueous solution,the green emeraldine salt form of polyaniline?PANI-ES?in its polaron state was obtained as a stable suspension.In clear contrast,without soft templates,a brown product precipitated.The main aim of the work presented was the multi-functionalization of fabrics,e.g.,electromagnetic protection performance,conduction,reversible color change,hydrophobic property,based on enzymatic polymerization of aniline with different soft templates,and the detailed investigation of the role of the sodium bis?2-ethylhexyl?sulfosuccinate?AOT?vesicles as template for the polymerization of aniline and aniline derivatives,i.e.,p-aminodiphenylamine?PADPA?,p-phenylenediamine?PPD?,o-phenylenediamine?OPD?.In the end,the oligomerization of PPD was applied for monitoring the activity of HRP inside lipid vesicles?liposomes?.From chapter 2 to chapter 4,functionalized cotton were prepared based on laccase-catalyzed synthesis of PANI-ES in the presence of sodium dodecylbenzenesulfonate?SDBS?,lignosulfonate?LGS?and perfluorooctanesulfonate acid potassium salt?PFOS?as templates,respectively.In chapter 2,fabric induction electrostatic test and far-field EMC shielding effectiveness test confirmed that the electromagnetic protection performance of the functionalized cotton were improved by PANI-ES products.In chapter 3,variable optoelectronic properties of the functionalized cotton were confirmed by cyclic voltammetry and color strength test.In this chapter,a comparison of laccase-catalyzed polymerization of aniline in SDBS and LGS template systems was made to check the influences of different templates on the kinetics of the polymerization and the characteristics of the complexes obtained.It was found that,PANI-ES obtained with LGS template had a higher degree of oxidation with a higher amount of benzene rings compared with PANI-ES obtained in SDBS emulsion,and the doping effect of LGS-doped PANI-ES was thus better than that of SDBS-doped one.Cyclic voltammetry and thermal analysis confirmed relatively higher electrochemical activity and better thermal stability of LGS-doped PANI-ES.In chapter 4,utilizing the doping/dedoping process of PANI,the wettability of the functionalized cotton underwent a reversible change fromhydrophilic to hydrophobic.Zeta potential measurements and color test were served as auxiliary evidence to explain the mechanism of the wettability switch of the functionalized cotton:the different attachment status of PFOS during PANI doping/dedoping process led to the reversible change of wettability of functionalized cotton.These researches are the first use of enzymatic synthesized PANI-ES in the modification of natural fabrics and will allow further exploration on the use of natural fabrics in the fields of electromagnetic shielding,color changing textiles and gas detection.In chapter 5 and chapter 6,we took AOT vesicles as an example to explore the role of templates in the polymerization of arylamines.In chapter 5,the reaction of PADPA was improved by introducing aniline to get a mixture system.The PANI-ES products obtained from the copolymerization of the mixture system had less phenazine side products,more aniline hexamer and higher electroactivity,compared with the PANI-ES products obtained from the oligomerization of PADPA alone.Based on the analysis of HPLC-DAD/MS and the reaction with deuteroaniline,a reasonable reaction mechanism was proposed:the fast formation and variation of aniline trimer.The final PANI-ES products were a mixture of aniline trimer,tetramer and hexamer.In chapter 6,instead of aniline,easy oxidazed PPD and OPD were used as alternative monomers for the synthesis of PANI-ES.It was found that,PANI-ES products cannot be obtained from enzymatic polymerization of PPD or OPD,no matter with or without templates.For PPD,in the presene of AOT vesicles,the rate of PPD PPD radical formation influences follow-up coupling reactions,i.e.,the chemical structure of the products.Although PANI-ES cannot be obtained from the polymerization of PPD or OPD,we didin?t abandon these active substrates immediately.In chapter 7,it was found that trace amounts of HRP?10-100 pM?can be determined by following the formation of PPD trimer,under conditions,i.e.,1.5 mM PPD,80?M H₂O₂,pH 7.0,25°C,10 min reaction time.The assay was applied for monitoring the activity of HRP inside lipid vesicles?liposomes?,prepared from POPC?1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine?and purified by size exclusion chromatography.PPD can be used to assess encapsulated HRP without destroying the vesicles chemically,which is not possible for ABTS^2-,since ABTS^2-is impermeable to lipsomes,i.e.,selective oxidation and trimerization of PPD inside the vesicles to yield Bandrowski?s base.Therefore,using PPD and ABTS^2-in separate assays allows distinguishing between vesicle-trapped HRP and HRP in the external bulk solution.It was found that pH 7.0 suspensions of POPC vesicles?2.2 mM POPC?containing on average about12 HRP molecules per vesicle are stable for at least 1 month without any significant HRP leakage,if stored at 4°C.Different from organic chemistry,which generally focus on the design of reactions,enzymatic reactions,coming from nature,are kind of radical polymerization and are always much more complicated.In this work,with the help of structure-controlling templates and some chemical analyses,we successfully learnt something about the mechanism and the application of enzymatic catalyzed oxidation and polymerization of arylamins,which definitely benefit the research on enzymatic reactions.