Development And Properties Of Substitutes For Alkylphenol Ethoxylates Based On Vanillin

In order to ensure the eco-safety of surfactants at the source,developing and using natural non-toxic renewable raw materials,adopting green reaction process to synthesis non-toxic and easily biodegradable surfactants with high performance are the development direction of green surfactants.The molecular structure of cleavable surfactants contain a group that is easily decomposed under certain conditions,which can make the surfactant lose its surface activity after being discharged and is easily biodegradable,which is harmless to the environment.In order to replace the endocrine disrupter alkylphenol ethoxylates?APEO?,the natural edible spice vanillin is selected as the main raw material to react with 1,2-octanediol to produce the hydrophobic group containing acetal structure which was used to reacted with ethylene oxide to synthesize a decomposable nonionic surfactant-vanillin octanediol acetal polyoxyethylene ether?VAEO?.By adjusting the length of hydrophilic segments,a series of products VAEO_n with different hydrophilic and hydrophobic properties were synthesized.Their properties and structure-activity relationships were studied in detail,and their replacement of nonylphenol polyoxyethylene ether(NPEO₁₀)was evaluated.The optimized process for synthesizing the hydrophobic vanillin octanediol acetal was as follows:the molar ratio of vanillin to octanediol was 1:1.4,the amount of catalyst phosphoric acid was 3%of the mass of vanillin,the volume of n-hexane?mL?and vanillin mass?g?ratio was 3:1,reaction time was 8 h.The yield was about 85%and the purity after purification was 97%.The purified acetal was referred to as VA and the acetal containing a small amount of unreacted octanediol was referred to as OVA.VA and OVA reacted with ethylene oxide,respectively.The reaction conditions of vanillin acetal and ethylene oxide was as follows:the mass of the catalyst potassium hydroxide is 0.1%of the acetal mass,the reaction temperature was 150-160°C,and the pressure was?0.4 MPa.By adjusting the material ratio of acetal to ethylene oxide,nonionic surfactants with different degrees of ethoxylation VAEO_n?n=6,8,10,12,16,20,24,26?and OVAEO_n?n=4,6,8,10,12?were obtained,where n is the degree of EO polymerization.The molecular weights of VAEO and OVAEO were determined by time-of-flight mass spectrometry.The molecular weights distribution of VAEO and OVAEO was Poisson distribution.The pH stability and ecological safety of VAEO were tested.VAEO is easily decomposed under acidic conditions and is stable under neutral and alkaline conditions.The cumulative biodegradation rate of VAEO in 28 days is 92.32%,and it is less acutely toxic to fish,green algae and large alfalfa.The cytotoxicity of VAEO was significantly lower than that of NPEO and 4-NP,and no obvious genotoxicity was detected.In addition,VAEO has no estrogen-interfering effect,and its anti-androgen and anti-thyroid hormone effects are also significantly weaker than NPEO and 4-NP.This kind of surfactant has better ecological safety and meets EPA standards for green surfactants.Except of VAEO₆ with a cloud point lower than room temperature,the study of the gas-liquid interfacial properties of VAEO aqueous solution showed that the surface tension of VAEO increases,the surface saturation adsorption amount?_m and the adsorption efficiency decreases with the increase of hydrophilic base chain.The surfactant molecules form micelles more easily in the bulk phase.The?_cmc of NPEO₁₀ is between VAEO₆ and VAEO₈.The CMC of VAEO is about 10 times that of NPEO₁₀,and it is more difficult to form micelles than NPEO.This is because the molecular structure of VAEO is more complex than that of NPEO.The hydrophobic part of VAEO is composed of a five-membered cyclic acetal and a benzene ring with methoxy group,which makes it hydrophilic and bulky.VAEO contains a chiral carbon atom.The alkyl chains are oriented in different directions.These factors lead to a complicated arrangement of VAEO at the gas-liquid interface,and it was difficult to aggregate to form micelles.The study of the adsorption behavior at the gas-liquid interface and at the solid-liquid interface shows that the adsorption of VAEO conforms to the diffusion-controlled adsorption model at the initial stage and the hybrid control adsorption model at the late stage of adsorption.The adsorption of VAEO and NPEO₁₀ on the surface of quartz sand belongs to the Langmuir monolayer adsorption model.The study of aggregation behavior in aqueous solution showed that the longer the ethoxylate chain of VAEO was,the easier to form micelles in aqueous solution.NPEO₁₀ aggregated to form micelles more easily than VAEO.The morphology of the micelles of VAEO and NPEO₁₀ were mainly spherical,and the larger the concentration,the larger the aggregates.Computer simulation results showed that VAEO₈ can form spherical,layered aggregates and lamellar liquid crystal structures with increasing concentration.Different ethoxylated chains with 10%molar ratio of beads in solution,the aggregate morphology of VAEO was mainly spherical and layered aggregates,which was consistent with the observation of frozen transmission electron microscopy.Through the study of the structure-activity relationship of VAEO,the HLB value and cloud point increased with the increase of ethoxylate chain,the wettability decreases,the emulsifiability decreases,the washing and decontamination effect does not change much,and the foaming first decreases and then increases.Overall,the wettability of VAEO_n is worse than that of NPEO₁₀.The low degree of polymerization of VAEO_n is slightly better or equivalent than NPEO₁₀.VAEO_n has a washing and decontaminating effect on carbon black stained cloth which is equivalent to NPEO₁₀,and the decontamination effect on sebum stain is slightly worse than that of NPEO₁₀.The foaming property of VAEO_n?n?16?is lower than that of NPEO₁₀.Compared with various excellent NPEO₁₀,emulsification of VAEO has obvious advantages especially in emulsification and low foaming at high temperatures.The properties of VAEO_n with low degree of polymerization are comparable to those of NPEO₁₀ and can be used as a substitute for NPEO₁₀.The effect of VAEO emulsified ternary copolymerized amino silicone oil was comparable to that of NPEO₁₀.The effect of VAEO_n in cotton fabric pretreatment was comparable to that of NPEO₁₀.The stability of paraffin emulsified by VAEO_n and NPEO₁₀ was simulated by coarse granulation kinetics.It was found that the hydrophilic chain of VAEO_n grew,the aggregation rate of paraffin increased,the stability of emulsion decreased.The aggregation rate of paraffin wax was close to that of VAEO_20-24.Through the analysis of the total energy change of the system during emulsification,it is found that the lowest total energy value of paraffin system emulsified by VAEO_n decreases with the increase of ethoxy chain length,the tendency of paraffin aggregation increases,and the ethoxy chain is explained from the energy point of view.The reason why the length is negatively related to the emulsifying ability.Molecular dynamics simulation of the molecular conformation of VAEO₈ and NPEO₁₀ in aqueous solution,combined with analysis of dynamic surface tension,found that the cause of the foaming difference of VAEO and NPEO₁₀ is the aggregation tendency of the surfactant molecule,and the surfactant with a larger tendency to aggregate has a small decrease in the dynamic surface tension in the early stage,and has a large restoring force and a strong foaming property.In the later stage of bubble formation,the surfactant with low surface tension is balanced,and the interfacial film has a large restoring force,which enables more surfactant molecules to be arranged on the interface film.The film has good elasticity and good foam stability.Through the detailed study of the nature and structure-activity relationship of VAEO,the relationship between ethoxylate chain length and property properties was obtained.VAEO with low degree of polymerization can be used as a substitute for NPEO₁₀.This type of surfactant is expected to be a new generation of environmentally friendly surfactants with a great market potential.