Interaction Between Nonionic Oligomeric Surfactant Tyloxapol And Amphiphiles

Oligomeric surfactants are a new class of amphiphiles including dimeric(gemini), trimeric,and tetrameric,etc.These surfactants are made up of two amphiphilic moieties connected at the level of the head groups or very close to the head groups by a spacer group. Oligomeric surfactants have more excellent physico-chemical properties than conventional surfactants,such as higher surface activity,special phase behavior and rheologial property. The molecular weight of oligomeric surfactants is between that of conventional and macromolecular surfactants,so they have filled the gap between conventional and macromolecular surfactant.Oligomeric surfactants are the most likely to be used in 21st century.People have paid much attention to the study on Gemini surfactants,especially on quaternary ammonium Gemini surfactants.However,a few studies on poly(ethylene oxide) nonionic oligomeric surfactants are reported.In this thesis,it is focused on the study of the nonionic oligomeric surfactant Tyloxapol,which can be considered as an oligomer of the non-ionic polyoxyethylene tert-octylphenyl ether(Triton X-100,TX-100),with a polymerization degree below 7.The physicochemical property of Tyloxapol and its interactions with hexadecyltrimethylammonium bromide(CTAB),polymer [(PEO₉₉PPO₆₅PEO₉₉,F127) and(poly ethylene glycol,PEG)]and partially hydrolytic polyacrylamide(HPAM)/CTAB are investigated via surface tension,surface dilational rheology,steady-state fluorescence,UV-vis spectrum,DLS(dynamic light scattering), computer simulation and high-resolution transmission electron microscopy(HRTEM) method.For comparison,parallel measurement on TX-100 is made.The thesis aims to provide basic data and theoretical basis for developing Tyloxapol's widely use in different areas.This thesis consists of five parts.In the first section,the importance and the progress of studies on oligomeric surfactant are summarized.The second section consists of two parts.In part one,surface tension and dilational viscoelasticity of water in the presence of surfactants Tyloxapol and TX-100 with CTAB are investigated.The surfactant interactions in the micelles and monolayers have been analyzed using the theories of Clint,Rubingh,Rosen,and Maeda with the aim to reveal the comparative performance of these mixtures.The results show that the surface tension reduction efficiency of Tyloxapol is higher than that of TX-100,however,the surface tension reduction effectiveness of the former is lower than that of the latter.The aberrant behavior of Tyloxapol is attributed to its "U" or "V" conformation at the air/water surface. It is noticeable that cmc andγ_cmc of the Tyloxapol/CTAB mixture is even lower than those of Tyloxapol at higher mole fraction of nonionic surfactant,indicating synergism in surface tension reduction effectiveness and efficiency.However,the TX-100/CTAB mixture only shows the synergism in surface tension reduction effectiveness.According to the Rubingh and Rosen theory,the results indicate that both interaction parameters for mixed micelle formation in an aqueous solutionβ^m and interaction parameters for mixed monolayersβ^s at the air/water interface are negative,predicting non-ideal mixing and attractive interaction between the constituent surfactants in the mixed micelle and layer.β^m is less negative thanβ^s in the Tyloxapol/CTAB mixed system,bothβ^m andβ^s are more or less the same for the TX-100/CTAB system.Furthermore,bothβ^m andβ^s are more negative for the Tyloxapol/CTAB mixture than that for the TX-100/CTAB one,indicating stronger attractive interaction between Tyloxapol and CTAB.The chain-chain interaction parameter B₁ is less negative thanβ^m andβ^s.The mixed micelles and monolayer are predominated by nonionic surfactants.The surface dilational viscoelasticity results show that the adsorption layer of Tyloxapol has the highest dilational modulus value among three single surfactants.Also,it indicates the surface dilational modulus maximum values of surfactant mixtures are usually between that of the single surfactant.Moreover,it is worth noting that the dilational modulus maximum values of Tyloxapol/CTAB mixtures are always higher than those of TX-100/CTAB ones.In part two,the solubility of pyrene in Tyloxapol and TX-100 with CTAB are investigated.For three single surfactants,the solubilization power increases in the order of TX-100＜CTAB＜Tyloxapol.Tyloxapol/CTAB has higher solubilization power than TX-100/CTAB.In addition,Tyloxapol/CTAB mixture has the highest solubilization power when the mole ratio of Tyloxapol to CTAB is 5:1.In the third section,interfacial tension(IFT) between Tyloxapol and TX-100 with CTAB in the presence of HPAM is investigated by spinning drop technology at high salinities and temperature.Effects of different nonionic surfactants,HPAM concentration and mass ratios of nonionic surfactant/CTAB on the dynamic IFT between crude oil and aqueous solution are studied in detail.For single surfactant systems,it is found that the ability of lowering IFT for CTAB is better than that for nonionic surfactant,while the IFT between Tyloxapol and crude oil is higher than that that between TX-100 and crude oil, which is attributed to the aberrant aggregation behavior of Tyloxapol at the crude oil/water interface.The IFTs between mixed surfactants systems and crude oil are always higher than that between CTAB and crude oil.However,IFTs between both single and mixed surfactants systems and crued oil can't reach ultra-low level.Interestingly,the ultra-low IFT is obtained for all surfactant mixtures in the presence of appropriate HPAM,which is ascribed to the formation of polymer-surfactant complexes PS_γwith high surface-activity at interface by nonionic surfactant/CTAB and HPAM.Mass ratios of nonionic surfactant/CTAB in aqueous phase also have effect on IFT.Only proper mass ratios of nonionic surfactant/CTAB in aqueous phase could yield ultra-low IFT values,which are 1:1, 3:1 and 5:1.The time to reach ultra-low level for Tyloxapol/CTAB/HPAM mixed system is much longer than TX-100/CTAB/HPAM,but the time to reach ultra-low level for polyoxyethylene nonylphenyl ether NP-10/CTAB/HPAM and TX-100/CTAB/HPAM mixed system is almost the same.The time to reach ultra-low level for polyoxyethylene nonylphenyl ether dimer bis-(NP-10)/CTAB/HPAM mixed system is shorter than NP-10/CTAB/HPAM,this is because that the transport of bis-(NP-10) molecules to interface is slower,but it has high surface activity than NP-10.In the fourth section,the interaction between Tyloxapol and F127(PEO₉₉PPO₆₅PEO₉₉) is investigated via the surface tension,dynamic surface dilational viscoelasticity, steady-state fluorescence,DLS measurement and computer simulation method.For comparison,PEG and TX-100 are also selected.The results of both surface tension and dynamic surface dilational viscoelasticity testify that the interaction mechanism between Tyloxapol and TX-100 with F127 is the same.There is formation of mixed adsorption layer between Tyloxapol and TX-100 with F127 mixtures,while the surfactant molecules mainly adsorb on the surface for Tyloxapol and TX-100 with PEG mixtures.The I₁/I₃ value in Tyloxapol/F127 mixed micelle is smaller than in single Tyloxapol and F127 micelle.The I₁/I₃ value becomes smaller with increasing F127 concentration,indicating the packing of molecules in mixed micelle is denser.However,The I₁/I₃ value in Tyloxapol/PEG mixed micelle is higher than in single Tyloxapol micelle,which is due to penetration of PEG molecules into Tyloxapol micelle making the mixed micelle looser.The results of DLS measurement also show that there is formation of mixed micelle for surfactant and F127, while surfactant and PEG forms surfactant/PEG complex by the penetration of PEG molecules into surfactant micelle.The structure of aggregate is related to the ratio and concentration of surfactant and polymer.The results of dissipative particle dynamics(DPD) simulation and DLS measurement show that there is interaction between hydrophilic chains for and F127 mixture at low F127 concentration.However,there is interaction between hydrophilic and hydrophobic chain for Tyloxapol and F127 mixture at high F127 concentration.Compared to the interaction between TX-100 and F127,the interaction between Tloxapol and F127 is weaker due to Tyloxapol's steric effect and the interaction between its monomers.When the PEG concentration is low,the molecule will wrap around the Tyloxapol and TX-100 micelle.When the PEG concentration is increased,the PEG molecules will act as a "bridge" between micelles.In the fifth section,the ability of dispersing carbon nanotubes(CNTs) in aqueous solutions by Tyloxapol is investigated in detail by UV-vis-NIR,Raman spectra and HRTEM observations.For comparison,TX-100 is also selected.The results show that the amount of the CNTs in surfactant solution first increases and then decreases with increasing surfactant concentration.Tyloxapol could disperse CNTs at rather low concentration compared with TX-100.The maximum dispersing amount of the CNTs in Tyloxapol solution is a little higher than in TX-100 solution.On one hand,this is because that some chains of Tyloxapol will adsorb on the CNTs,while the others can stretch into water phase and hence create steric repulsion effect,which is favorable to disperse CNTs;on the other hand,it is not easy for Tyloxapol to adsorb on the CNTs due to its steric repulsion effect,Tyloxapol will self-aggregate to form micelle in solution,which is unfavorable to disperse CNTs.As a result,the maximum dispersing amount of the CNTs in Tyloxapol solution is just a little higher than in TX-100 solution.