Synthesis Of Random Copolymer Surfactant And Effects Of Its Structure On The Properties Of Conductive Fiber

On the basis of the molecular structure characterization ofamphiphilic random copolymer surfactant, a series of amphiphiliccopolymers containing different hydrophilic segments and hydrophobicsegments could be prepared, by controlling types, amount and ratio ofraw materials and synthesized conditions. The synthetic copolymershave some properties of the polymeric surfactant through the moleculardesign and structure control, which is mainly reflected in the decreaseof surface tension of solution and the aggregate behavior of amphiphiliccopolymer in the aqueous solution. This work is to get novelamphiphilic random copolymer with ethylenic monomer containinghydrophobic group and hydrophilic group as raw materials. Moreover,the obtained copoplymers exhibit higher surface activity and othersolution properties in water solution, due to the introduction of thereactive group and the molecular weight control of copolymer. Thecationic groups, such as amino groups, located in the synthetic cationicrandom copolymer molecular chain could pull electronics from apyrrole ring and then suppress the generation of the irregularpolypyrrole chain. Therefore, the synthetic cationic random copolymersurfactant could be used as the dopant for polypyrrole/natural fiberconductive fiber. Simultaneously, the different aggregate micellesformed by the cationic random copolymer surfactant and natural fibercould be used as soft templates for polypyrrole, and then thepolypyrrole/natural fiber conductive fiber is obtained containingvarious microstructure. Meanwhile, the cationic random copolymersurfactant can be doped in polypyrrole/natural fiber conductive fiberfirmly thanks to its long chain structure， thereby improving the mechanical properties and stability of conductive fiber. In addition, thecationic random copolymer surfactant also can ameliorate theflocculation of conductive fiber, as a result of the good dispersion ofcationic random copolymer. The main research of this work was asfollows:1. Two series of cationic random copolymer surfactant （CPSD andCPSDA） were synthesized by free radical solution copolymerization,using styrene （St）, butyl acrylate （BA） as lipophilic monomers, anddimethylaminoethyl methacrylate （DMAM） and acrylamide （AM） ashydrophilic monomers. The obtained cationic random copolymer hadhigher surface activity via molecular design and structure control ofcopolymer chain. The study showed that the category and content ofhydrophilic group had a significant impact on the structures of CPSDand CPSDA copolymers and their solution properties, such as surfacetension, specific viscosity, aggregate behaviors and steady staterheological property.The FTIR results demonstrated that the benzene ring content ashydrophobic group in the CPSD copolymers decreased with the increaseof the dosage of DMAM, and the content of-CONH2group of CPSDAcopolymers increased with the increase of the dosage of AM. This resultwas in coincidence with the change of the number of hydrophobicgroups and hydrophiphilic groups of CPSD and CPSDA copolymers,calculated by molecular weight measured with GPC.There was complex relationship between specific viscosity ofCPSD and CPSDA copolymers solution and their concentration, due tothe self-assembly aggregate behavior of CPSD and CPSDA copolymersin water solution.The result of surface tension and solution surface adsorptionparameter calculated suggested that CPSD and CPSDA copolymers hadhigher surface activity. However, the surface tension of solution couldonly be reduced to40mN.m^-1, because the hydrophobic segments in thecopolymer chain （-C4H9and benzene ring） was too short and theadsorption layer was thin. Steady-state fluorescence technique, aggregate micelle particle testand transmission electron microscopy technique were used to study theaggregation behaviors of CPSD and CPSDA copolymers. The resultsdisplayed that the critical aggregate concentration （cac） of CPSDcopolymers increased with the increase of DMAM, and the cac ofCPSDA copolymers also increased with the increase of AM. The size ofCPSD and CPSDA copolymer aggregate micelles mainly distributed intwo ranges: the smaller aggregate size was located in20³0nm,whereas, the larger aggregate size was in150²00nm. The aggregatemicelles in smaller partice size were unicore multipolymer micelles（intra-and/or inter-polymer aggregate） in CPSD and CPSDAcopolymers solution; whereas, the aggregate micelles in larger particesize were polycore multipolymer micelles. And the aggregate micellesmainly exhibited spherical shape.The steady state rheological tests implied that the viscosity ofCPSD and CPSDA copolymers solution decreased with the increase ofshear rate, when shear rate was in0.001⁰.1s^-1, presenting shear-thinning phenomenon. However, the viscosity of CPSD and CPSDAcopolymers solution was almost constant, when shear rate was in0.1¹00s^-1, showing the Newtonian fluid behavior. Besides, theviscosity of the CPSD and CPSDA copolymers gradually increased asthe content of hydrophilic group of CPSD and CPSDA copolymersincreased at lower range of shear rate.2. Two series of anionic random copolymer surfactant （APSA andAPSAA） were synthesized by free radical solution copolymerization,using styrene （St）, butyl acrylate （BA） as lipophilic monomers, and2-acrylamide-2-methyl-propanesulfonic acid （AMPS） and acrylamide（AM） as hydrophilic monomers. The obtained anionic randomcopolymer had higher surface activity via molecular design andstructure control of copolymer chain. The study showed that thecategory and content of hydrophilic group had a significant impact onthe structures of APSA and APSAA copolymers and their solutionproperties, such as surface tension, specific viscosity, aggregate behaviors and steady state rheological property.The FTIR results demonstrated that the content of-SO₃H group inthe APSA copolymers increased with the increase of the dosage ofAMPS, and the content of-CONH2group of APSAA copolymersincreased with the increase of the dosage of AM. This result wascosistent with the change of the number of hydrophobic groups andhydrophiphilic groups of APSA and APSAA copolymers, calculated bymolecular weight measured with GPC.There was complex relationship between specific viscosity ofAPSA and APSAA copolymers solution and their concentration, due tothe self-assembly aggregate behavior of APSA and APSAA copolymersin water solution.The result of surface tension and solution surface adsorptionparameter calculated suggested that APSA and APSAA copolymers hadhigher surface activity. The hydrophobic segments in the copolymerchain （-C4H9and benzene ring） was too short and the adsorption layerwas thin. Moreover, the entropy of APSA and APSAA copolymersreduced because of the strong hydration caused by-SO₃H group.Therefore, the capacity and efficiency of APSA copolymers to decreasethe surface tension of solution were declined. APSA4copolymer onlyreduced the surface tension to46.72mN.m^-1. However, the introductionof AM could improve the capacity of APSAA copolymers to decreasethe surface tension, and APSAA3copolymer could reduce the surfacetension to40.90mN.m^-1.Steady-state fluorescence technique, aggregate micelle particle testand transmission electron microscopy technique were used to study theaggregation behaviors of APSA and APSAA copolymers. The resultsdisplayed that the critical aggregate concentration （cac） of APSAcopolymers increased with the increase of AMPS, and the cac ofAPSAA copolymers decreased with the increase of AM. The size ofAPSA and APSAA copolymer aggregate micelles mainly distributed intwo ranges: the smaller aggregate size was situated in20³0nm,whereas, the larger aggregate size of APSA and APSAA copolymer aggregate micelles mainly located in150²00nm and100nm,respectively. The aggregate micelles in smaller partice size wereunicore multipolymer micelles （intra-and/or inter-polymer aggregate）in APSA and APSAA copolymers solution; whereas, the aggregatemicelles in larger partice size were polycore multipolymer micelles.And the aggregate micelles mainly exhibited spherical shape.The steady state rheological tests implied that the viscosity ofAPSA and APSAA copolymers solution decreased with the increase ofshear rate, when shear rate was in0.001⁰.1s^-1, presenting shear-thinning phenomenon. However, the viscosity of APSA and APSAAcopolymers solution was almost constant, when shear rate was in0.1¹00s^-1, showing the Newtonian fluid behavior. Besides, theviscosity of the APSA and APSAA copolymers gradually increased asthe content of hydrophilic group of APSA and APSAA copolymersincreased at lower range of shear rate.3. The polypyrrole （PPy）/natural fiber composite conductive fiberwas prepared using in-situ chemical oxidation polymerization process,using self-made CPSD and CPSDA copolymers as dopants and FeCl3asoxidant. Then, a series of conductive paper （CF） were obtained througha converntianl papermaking process. Fourier-transform infrared （FTIR）,elemental analysis, and X-ray photoelectron spectroscopy （XPS） wereperformed on the resultant conductive composites. Scanning trans-mission electron microscope （SEM） was used to investigate fibersurface morphology of NF, CF3and CF7. Finally, the mechanicalproperty, thermal stability and electrical conductivity of CF conductivepaper were tested. The main results were as follows:FTIR, elemental analysis and XPS proved that CPSD3andCPSDA3coplymers had been doped in polypyrrole adsorbed in CFconductive fiber. The retention of both polyrrole and CPSD3on CF3，and it of both polyrrole and CPSDA3on CF7were calculated, and theywere30.45%and32.36%, respectively. XPS results illustrated that a lotof N elements aggregated on the surface of CF3and CF7conductivefibers, suggesting that polypyrrole aggregated on the surface of fibers. Photogroph and SEM images of NF paper and CF conductive paperexhibited that the surface of conductive fiber were completely coated bypolypyrrole.The electrical conductivity test displayed that CF conductive paperhad good conductive property, and the lowest surface resistivity of12k/square was obtained from CF7conductive paper. The electricalresistivity of CF conductive paper increased with the increase of thestorage time, revealing that the electrical conductivity of CF conductivepaper declined.TG anylysis demonstrated that polypyrrole adsorbed on the fiberhad an impact on the thermal stability of CF conductive fiber. Comparedto the NF, the main degradation peak of CF3and CF7shifts to lowertemperature, and the main degradation rates reduced, however, theresidue char of CF3and CF7was higher.The mechanical property of conductive paper was declined aftermodification, the tension index was decreased from40kN·m·kg^-1ofunmodified paper to21kN·m·kg^-1of CF7.