The Physicochemical Properties Of Water-soluble Polymer And Its Interaction With Carboxylate Surfactant

Nowadays,water-soluble polymer is one of the most important polymers because of their biocompatibility and environmently friendly.Moreover.surfactants and water-soluble polymers can interaction with each other to form complexs,they usually displays intriguing and fascinating features,which is different from polymer or surfactant.Thus,the studies on the physicochemical properties of water-soluble polymer and its interaction with surfactant have attracted increasing attention because of their complex behaviors and potential applications in detergents,paints,cosmetics. food,pharmaceuticals,coatings and enhanced oil recovery,etc.In the past decades,a number of studies have focused on the physicochemical properties of water-soluble neutral polymers like poly(ethylene oxide)(PEO). Polyethylene glycol(PEG),poly-(vinylpyrrolidone)(PVP)and polyacrylamine(PAM) and their interactions with surfactant.In this thesis,the interaction between a star-like amphiphilic block copolymer(denoted as AP432,which was synthesized via anionic polymerization in our lab)and carboxylate surfactant sodium oleate(C₁₇H₃₃COONa) is studied by surface tension,oscillating barrier,steady-state fluorescence measurements and transmission electron microscopy(TEM).etc.For comparision. parallel measurements have also been made on the interaction between PVP and sodium oleate.Moreover,in order to finish the programme of oil field,the interaction between HPAM and C₁₇H₃₃COONa.sodium stearate(C₁₇H₃₅COONa)were investigated by rheological measurements.The rheological properties of HPAM/C₁₇H₃₃COONa as a function of concentration and the heat and salt tolerances of HPAM/C₁₇H₃₅COONa system were studied.This thesis is divided into five parts:In the first section,the properties and applications of water-soluble polymers and surfactants and the study progress on the interaction between surfactant and water-soluble polymer are summarized.In the second section,the interface properties and the aggregation behavior of AP432,in aqueous solutions were investigated by surface tension,steady-state fluorescence,dynamic light scattering(DLS)and TEM.For comparison.a commercially available linear amphiphilic PEO-PPO-PEO block copolymer, Pluronics L64,which has a similar PEO fraction to AP432,was also studied.It is found that both the efficiency and the effectiveness of AP432 to lower the surface tension of water are higher than those of L64,theΓ_maxvalue of AP432 is higher and the A_minvalue of AP432 is lower than that of L64.From fluorescence measurement,it can be conclude that the I₁/I₃ value of AP432 is much lower than that of L64 at high concentration,indicating that the micelles formed by AP432 are more compact than that of L64.TEM observations reveal that the molecules of AP432 are inclined to aggregate more compact and more molecules can aggegated to form one micelle when the concentration is increased.But for L64.once the micelles are formed,more molecules can form another micelle or combined together with increasing of L64 concentration.In the third section,the ability of dispersing carbon nanotubes(CNTs)in aqueous solutions by AP432 was investigated in detail by UV-vis-NIR,Raman spectra,TEM and HRTEM observations.For comparison,two commercially available linear amphiphilic PEO-PPO-PEO tri-block copolymers,Pluronics L64 and F127 were also studied.From the experiments,it was found that AP432 and F127 can get good CNTs dispersions stable for months while it was not the case for L64.The star-like AP432 with five branches could disperse CNTs efficiently at much lower concentration and has advantages to disperse CNTs in individuals or smaller bundles compared with the linear F127,although it has a smaller molecular weight and shorter terminal EO groups.Increasing concentration of AP432 or F127 would disperse more CNTs,but the flocculation of dispersed CNTs was observed at high copolymer concentrations,which may be related to the free micelles formed by AP432 or F127 around CNTs.At high concentration of AP432.free micelles began to form which caused a subsequent of the dispersed tubes.Under the HRTEM analysis and other observations used in our measurements,the mechanism of dispersing CNTs by different copolymers can be rationalized,that is.when mixed with CNTs,the PO groups would interact with the sidewall of CNTs while the EO groups extend into water and hence create a so-called steric repulsion. The fourth section divides into two parts.In part one,the interaction between AP432 and an anionic surfactantC₁₇H₃₃COONa in aqueous solutions was investigated by surface tension,oscillating barrier,steady-state fluorescence measurements and TEM.For comparison,the interaction between Pluronics L64 and C₁₇H₃₃COONa was also studied.AP432 and C₁₇H₃₃COONa could form mixed micelles in aqueous solutions and the cmc values were between that of individual AP432(L64)and C₁₇H₃₃COONa,as revealed by surface tension measurements.TEM observations also reveal that both AP432/C₁₇H₃₃COONa and L64/C₁₇H₃₃COONa systems form mixed spherical micelles.Moreover,the dilational modulus increases gradually with the increase of dilational frequency and the dilational moduli pass through the maximum values with increasing concentration not only for the pure AP432,L64 and C₁₇H₃₃COONa solutions,but also for AP432/C₁₇H₃₃COONa and L64/C₁₇H₃₃COONa systems.In second part,the study of the interaction between PVP and C₁₇H₃₃COONa in aqueous solution in the presence of sodium halide(NaX:X=Cl,I)is investigated by surface tension and the oscillating barriers measurements.It can be seen that two inflection points were observed when PVP is added,implying the interaction between C₁₇H₃₃COONa and PVP occurs.An increase of PVP concentration shifts T₂ values toward higher C₁₇H₃₃COONa concentration,indicating that more C₁₇H₃₃COONa molecules bind on the PVP chains to form PVP/C₁₇H₃₃COONa complexes.It also can be concluded that the addition of NaX can decrease the CMC of C₁₇H₃₃COONa solutions and NaCl has more effect than NaI on decreasing the CMC of C₁₇H₃₃COONa solutions.An addition of NaX also affects the binding cooperativity between C₁₇H₃₃COONa and PVP,and the higher NaX concentration corresponds to the higher binding cooperativity.Moreover,NaCl is more efficient than NaI in promoting the interaction between C₁₇H₃₃COONa and PVP.The fifth section also divides into two parts.In part one.the interaction between HPAM and C₁₇H₃₃COONa was investigated by rheological measurements and the influences of the concentrations of HPAM and C₁₇H₃₃COONa on the rheological properties of mixed systems were also studied.With increasing amount of C₁₇H₃₃COONa.the shear viscosity of the system first shows an increase due to interpolymer cross-linking through hydrogen bonding between C₁₇H₃₃COONa and HPAM.It can be noted that the concentration of C₁₇H₃₃COONa needed to get the maximum viscosity increases for the higher HPAM concentration systems.With further increase of C₁₇H₃₃COONa concentration,a drastic decrease of viscosity is induced by the breakdown of the cross-linking network due to an increasing of ionic strength,which would make the coil of HPAM shrink.Also,to lower the viscosity of the sample to similar extent,higher concentration of C₁₇H₃₃COONa is required to make HPAM molecule shrink for higher concentration of HPAM.In second part.the effects of CaCl₂,temperature and pH on the HPAM/C₁₇H₃₅COONa systems were investigated via steady-flow and oscillatory experiments.The results reveal that addition of CaCl₂ causes the double layer of HPAM to collapse,resulting in loss of structure and a corresponding loss of viscosity and shear thinning behavior.Moreover. the increasing of temperature can give rise to crimple of HPAM molecules due to its dehydrating and destruction of the associational structure.As a consequence,the viscosities of systems also decrease.With pH increasing,carboxyl groups of the HPAM and C₁₇H₃₅COONa molecular chains ionize much more and the resultant electrostatic repulsion cause stretching of the chains,resulting in the decrease of intra-molecular associations of HPAM and the increase of interaction between HPAM and C₁₇H₃₅COONa.