| The structure of substance determines its properties.The structure-property relationship is the general law of the relationship between substance and structure.Although many laws of surfactants?structure-property relationships have been summarized,the known structure-property relationships of surfactants are not enough to design surfactants according to specific needs.At present,the research on structure-property relationships of surfactants is mostly focused on the categories of surfactant hydrophilic group and hydrophobic chain length,there is also a small amount of research on surfactant isomerism.However,from three different angles of hydrophilic group,hydrophobic group and isomer,systematically examining the structure-activity relationship between surfactant molecules and their properties is rare.Therefore,in order to further supplement the research on the structure-property relationships of surfactants,we designed and synthesized salt monoester alkyl alcohol phthalate?PASn?,salt monoester alkyl alcohol isophthalate?IASn?and salt monoester alkyl alcohol terephthalate?TASn?,where n is 12,14 and 16,respectively;then,we systematically investigated the structure-property relationships between surfactants and their surface?interfacial?properties;We prepared worm-like micelles by PASn and investigated the salt tolerance of the worm-like micelle.Within the scope of this article,the main research contents and conclusions involved are summarized as follows:?1?Synthesis and characterization of salt monoester alkyl alcohol?iso,tere?phthalate with alkyl alcohol(C12,C14,C16)and phthalic anhydride as raw materials,PASn were synthesized through esterification reaction;with alkyl alcohol(C12,C14,C16),isophthaloyl chloride and terephthaloyl chloride as raw materials,IASn and TASn were synthesized by esterification,and the molecular structure was verified by means of nuclear magnetic resonance hydrogen spectroscopy?1H NMR?and electrospray mass spectrometry?ESI-MS?.The purity was98.00±0.50%.?2?Structure-property relationship of salt alkyl alcohol?iso,tere?phthalateWe explore structure-property relationship of surfactans with Krafft temperature?KT?,surface?interfacial?tension,foam properties,emulsion properties and alkali hydrolysis properties from three angles?hydrophilic group,hydrophobic group,isomers?.The results show that:?1?Compared with KT?25.0 oC?of sodium laurate?SL?,KT?PAS12?is lower by 8.6 oC,KT?IAS12?is lower by 4.3 oC,and TAS12 has a higher KT?KT?TAS12?=32.3 oC?;as the alkyl alcohol chain length?n?increases,the KT of PASn,IASn and TASn gradually increase,satisfying the relationship of KT=an+b;when n is the same,KT?PASn?<KT?IASn?<KT?TASn?.?2?Compared with SL,cmc?PAS12?<cmc?SL?,?cmc?PAS12?<?cmc?SL?,?cmc?PAS12?<?cmc?SL?;with the increase of n,cmc and n of isomers satisfy the empirical formula lg?cmc?=A-Bn,and?cmc and?cmc gradually decrease with the increase of n;when n is the same,cmc,?cmc and?cmcmc also decrease in the order of PASn-IASn-TASn between isomers.?3?PAS12 has better foaming ability and foam stability than SL;as n increases,the foaming ability of PASn,IASn and TASn gradually decreases,and the initial foam height?h0?and n satisfy the relationship of h0=m-kn,but the foam stability gradually increases with the increase of n;when n is the same,the foaming power gradually increases in the order of PASn-IASn-TASn between isomers.?4?After the emulsions stabilized by PAS12 and SL of the same mass concentration were allowed to stand for5 days,the emulsion stabilized by PAS12 had better stability;the stability of the emulsion based on PASn,IASn,and TASn gradually increased as n increased.?5?salt dodecyl alcohol phthalate that the concentration is slightly higher than cmc can be hydrolyzed at pH=13.00,and the time for alkali hydrolysis micelles to disintegrate gradually increases in order of PAS12-IAS12-TAS12.?3?Preparation of PASn worm-like micelle system and its salt toleranceWe selected the PASn with the best salt tolerance among the isomers,and explore the effect of n on the worm-like micelles constructed by PASn from the perspective of the hydrophobic group?alkyl alcohol chain length n?.The results show that the viscosity of PAS12 system is unchanged with the increase of concentration,showing the characteristics of low viscosity Newtonian fluid,while the viscosity of PAS14 and PAS16 systems increases gradually with the increase of concentration,especially the viscosity of PAS16 system is the largest;As the pH decreases,the viscosity of the PAS14 and PAS16 systems gradually increases,and the worm-like micelle viscosity reaches the maximum when the pH is 7.02 and 7.66,respectively.As n increases,comparing the high viscosity p H range of PAS14?6.89-7.66?and PAS16?6.76-10.20?,it can be found that the high viscosity pH range of PASn gradually widens.When pH=12.00,the ester bond in PAS16 was found to hydrolyse.Through Cryo-TEM,the structure of worm-like micelles formed by PAS16?100 mmol/L,pH=7.66?is fibrous,with a cross-sectional diameter of about 6nm,and a length of about 700 nm-2?m.The tolerance of the PAS16 system to salts was also explored.The results show that PAS16 has a tolerance to NaCl,CaCl2 and FeCl3,and all are better than SL.The tolerance to NaCl is the best,and it can tolerate 26 times its own concentration of NaCl?about half the concentration of saturated NaCl solution?. |
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