Synthesis and characterization of cleavable cationic surfactants with a 1,3-dioxane ring

A series of cationic cleavable surfactants was prepared by condensation of 2-alkyl-1,3-propanediols with 3-bromopropanal, followed by reaction with triethylamine. Each surfactant is a mixture of two diastereomers, and their precursors’ stereochemical assignments were based on¹H nuclear magnetic resonance spectra and melting points. The critical micelle concentrations, Krafft points and destructibility of these surfactants were determined.     

Synthesis and properties of bis(sodium sulfonated ester) types of cleavable surfactants derived from 1-O-alkylglycerols

Novel sulfonated ester types of cleavable surfactants were easily prepared by acid-catalyzed esterification of 1-O-alkylglycerols with bromocarboxylic acids, followed by the Strecker reaction. These surfactants have good solubility in water. Though this series of cleavable surfactants are divalent in type, they show good micelle formation and the ability to lower surface tension. The solubility of these surfactants in hard water was more than 10 times higher than sodium 1-dodecanesulfonate. They decompose quickly and completely in 0.5 M NaOD. Their biodegradabilities were higher or almost the same as that of sodium 1-dodecanesulfonate.     

Preparation and properties of sulfonate salt-type cleavable surfactants with a 1,3-dioxane ring

A series of di-anionic cleavable surfactants were prepared by the condensation of aldehydes with 2,2-bis(hydroxymethyl)-1,3-propanediol, followed by reaction with 1,3-propanesultone in the presence of sodium hydride. Surfactant 5a had a different¹H nuclear magnetic resonance spectrum in D₂O than products 5b−d. This was rationalized by its different conformation, which originates from the self-coiling of its alkyl chain. The critical micelle concentrations, Krafft points and hydrolysis properties of these surfactants were determined.     

Preparation and properties of cleavable dianionic surfactants with a 1,3-dioxane ring

Some cleavable dianionic surfactants were prepared by the reaction of aldehydes with diethylbis(hydroxymethyl)-malonate, followed by saponification with sodium hydroxide. The critical micelle concentrations of the surfactants were determined.     

Synthesis and Properties of New Cleavable Cationic Surfactants Containing Carbonate Groups

A novel series of cleavable alkyltrimethylammonium surfactants with different hydrocarbon chain lengths (C8–16) were synthesized. A carbonate break site inserted between the polar head and the hydrocarbon chain makes these compounds hydrolyzable. The reagents used are renewable, (bio)degradable, or reusable. The hydrolysis of these cleavable surfactants will lead to the generation of fatty alcohols and choline, which is an essential biological nutrient. The surface activities in aqueous solution of the synthesized carbonates fulfill the requirement of being good surfactants. In addition, the cleavable compounds containing n-decyl and n-dodecyl chains showed similar or higher antimicrobial activities when compared to a non-cleavable analog.     

Biodegradation of different carboxylate types of cleavable surfactants bearing a 1,3-dioxolane ring

The biodegradability of new carboxylate types of “acid-sensitive” cleavable surfactants bearing a 1,3-dioxolane ring was measured by the biochemical oxygen demand (BOD) method in the presence of activated sludge. The result for sodium dodecanoate, measured under the same conditions, was used as a standard for evaluating the biodegradability of these cleavable surfactants. For cleavable surfactants derived from epoxides and oxocarboxylates, the biodegradation was considerably influenced by the length of the lipophilic alkyl chain, the presence of the oxymethyl moiety in the lipophilic group, and the number of methylene units between the dioxolane ring and the carboxylate group. For another type of cleavable surfactant, 2-(long-chain alkyl)-1,3-dioxolane-4,5-dicarboxylate, the biodegradation rate for the compound, bearing a proton at position 2 in the dioxolane ring, is faster than that for the corresponding compound bearing a methyl group at position 2.     

Nonionic cleavable ortho ester surfactants

A new class of cleavable surfactants based on the ortho ester link is described. Ortho ester surfactants were synthesized from a short-chain ortho ester, a fatty alcohol, and a poly(ethylene glycol) monomethyl ether. The triple functionality of the ortho ester link results in a mixture of surface-active and nonsurface-active species. Structures were confirmed by ¹H and ¹³C nuclear magnetic resonance. Hydrolysis characteristics at pH values ranging from 2 to 8 were determined. It was shown that, after a steep rise, hydrolysis curves flattened out before complete hydrolysis was reached. Ortho ester surfactants hydrolyze more rapidly than corresponding acetal surfactants. Hydrolysis rates are higher for purified samples and at higher temeprature, while plateau levels are higher for the purified surfactant mixtures and at lower pH. The origin of these results is discussed. Data also indicate that the hydrolysis mechanism changes with pH. A test of the loss of emulsification capacity for an ortho ester surfactant with time at pH values from 2 to 11.5 and at 22 or 50°C was carried out, showing rapid breaking of the emulsion at mild acid conditions and a requirement of pH≥10 for long-term stability. Surface tension and critical micelle concentration were determined for some of the surfactant mixtures. It was demonstrated that ortho ester surfactants possess excellent biodegradation properties. The new surfactants are promising candidates for use in industrial processes where temporary surfactant action is required.     

绿色表面活性剂的研究进展

从表面活性剂的分类、性能以及对人体和环境产生的影响等方面介绍了目前国内外绿色表面活性剂的研究热点。根据绿色表面活性剂在反应中降解方式的不同,概述了生物表面活性剂、可降解表面活性剂及反应型表面活性剂的定义、性能以及相关应用。同时,对表面活性剂的发展方向及绿色表面活性剂的应用前景进行了展望。     

Preparation and Properties of New Ester-Linked Cleavable Gemini Surfactants

We have prepared a series of novel gemini surfactants having ester bonds in their structures. These surfactants possess two identical hydrophilic polyethylene glycol moieties, two hydrophobic alkyl group moieties, and an anionic spacer. The structures of these compounds were confirmed through infrared and nuclear magnetic resonance spectroscopic and elemental analyses. The novel gemini surfactants exhibit excellent surface activity in terms of their surface tension, low-foaming, wetting power, and fluorescence properties. The presence of the ester linkages made these structures cleavable surfactants.     

Surface Activity and Cleavability of Gemini Surfactants Featuring Hydrophilic Spacer Groups

In this study we prepared and characterized a series of novel ester-linked gemini surfactants, featuring ester bonds in their structures, through the reactions of polyethylene glycol (PEG400) with various fatty acids (C8?CC18). These gemini surfactants exhibit excellent surface activities, as evidenced by their surface tension, wetting power, and low-foaming and buffer abilities. We examine the influence of the concentrations of the ester-linked gemini surfactants on the surface tension, from which we obtain the critical micelle concentrations. Under basic conditions, each of these cleavable surfactants decomposes into a water-insoluble fatty acid and two water-soluble products; in contrast, they are stable under neutral and acidic conditions.     

Preparation,surface-active properties and acid decomposition profiles of a new “soap” bearing a 1,3-dioxolane ring

New soap-type surfactants bearing a 1,3-dioxolane ring were prepared in good yields by the acid-catalyzed condensation of 1-O-alkylglycerols (alkyl: decyl, dodecyl, tetradecyl, heptadecyl, octadecyl, orcis-9-octadecenyl) with oxocarboxylic acid esters, followed by alkaline hydrolysis without any expensive reagent and special equipment. These surfactants were soluble in alkaline water at room temperature. Their critical micelle concentrations were much smaller than that of sodium dodecanoate. An alkaline solution of the octadecyl homologue was nonfoaming, but the other homologues, including thecis-9-octadecenyl derivative, showed high foaming ability in alkaline solutions. The structural effect of these compounds on the area per molecule at the surface is also discussed. Because these surfactants contain a 1,3-dioxolane ring, they can be utilized as a new acid-decomposable type of cleavable surfactant. At pH 1, they decompose almost completely into nonsurface-active species after 80 min.     

Ortho ester-based cleavable cationic surfactants

A new type of cleavable cationic surfactant, based on the ortho ester link, is described. Ortho ester amines with alkyl chain lengths from C₈ to C₁₆ were synthesized from a short-chain ortho ester, a fatty alcohol, and an amino acohol. The ortho ester amine was subsequently quaternized with methyl chloride, yielding a cationic surfactant. The structures were confirmed by ¹H and ¹³C nuclear magnetic resonance and the surface chemical properties were investigated by measuring both static and dynamic surface tensions. The results were compared to standard n-alkyl trimethyl ammonium bromides. The critical micelle concentrations were found to vary rather widely, whereas the surface tensions in some cases were comparatively low. The short alkyl chain ortho ester quaternaries were found to have low surface tensions at short surface ages and to induce rapid wetting of a hydrophobic surface in dynamic tests. Additionally, the new surfactants were found to hydrolyze rapidly under mild acidic conditions, as measured by both titation and monitoring of the dynamic surface tension. Further, they showed excellent long-term stability at pH 10 in dilute aqueous solutions. The effect of added electrolyte on rate of hydrolysis was also investigated. A marked enhancement in the hydrolysis rate was found when NaBr was added, whereas NaCl did not have the same effect. The new surfactants could potentially be used to provide temporary surfactant action in application areas such as disinfection, fabric care, personal care, chain lubrication, and mineral flotation as well as in textile processes such as dyeing or scouring.     

New cleavable surfactants derived from glucono-1,5-lactone

New amido nonionic cleavable surfactants were synthesized in good yields by the acetalization of glucono-1,5-lactone with octanal, 2-octanone or 2-undecanone, followed by amidation with monoethanolamine, diethanolamine or morpholine. These compounds possessed good water solubilities. The compounds derived from 2-octanone showed higher critical micelle concentrations than the compounds from octanal. For the same hydrophobic chain, both the micelle-forming property and the ability to lower surface tension increased with the change in the terminal amide group in the order diethanolamide<morpholide<monoethanolamide. Interestingly, in spite of their relatively short hydrophobic chains, these compounds showed greater ability to lower surface tension than conventional nonionic surfactants, such as alcohol ethoxylates. Furthermore, their acid-decomposition properties were determined. Their decomposition rates were also compared with that of the corresponding carboxylate type of compound derived from glucono-1,5-lactone.     

缩醛型可分解表面活性剂的合成

在对甲苯磺酸的催化下,庚醛、癸醛分别与3-氯-1,2-丙二醇通过缩合反应制备了氯代缩醛2-烷基-4-氯甲基-1,3-二氧杂环戊烷;再分别与亚硫酸钠进行磺化反应,合成了缩醛型可分解表面活性剂(2-烷基-1,3-二氧杂环-4)甲烷-1-磺酸钠盐,磺化产率分别为87.9%和87.3%;所得中间体和产物的结构经IR、1HNMR表征。对缩合反应的物料摩尔比、催化剂用量、反应时间等进行了优化,结果表明:n(庚醛)∶n(3-氯-1,2-丙二醇)=1∶1.2,对甲苯磺酸0.4g,反应时间20h为较佳合成条件,产率达66.51%～68.70%。测试了可分解表面活性剂Ⅱa、Ⅱb在盐酸溶液中的分解率,结果显示:分别在1.5、3h,分解率就可达100%。     

Synthesis of Cleavable Aryl Sulfonate Anionic Surfactants and a Study of their Surface Activity

A series of cleavable aryl sulfonate anionic surfactants were synthesized from cyanuric chloride, aliphatic amine and H-acid mono sodium salt. Their structures were identified by ¹H NMR, Infrared Spectrum (IR) and Elementary Analysis (EA). Their critical micelle concentrations (CMC) in aqueous solutions at 25 °C were determined by a steady-state fluorescence probe method and a surface-tension method. With the increasing length of the carbon chain, the value of their CMCs and surface tensions under CMC (γ _CMC) initially decreased and then reached a minimum (respectively 2.63 × 10⁻⁵ mol L⁻¹ and 28.29 mN m⁻¹) when the carbon number was 10. The CMC and γ _CMC then increased when the carbon number was increased to 12. The results showed that, compared with sodium dodecyl benzene sulfonate (SDBS), such kinds of surfactants have much lower surface adsorption amounts and greater molecular areas on the aqueous surface.

Cleavable Surfactants: A Comparison between Ester,Amide, and Carbonate as the Weak Bond

Cleavable surfactants, i.e., surfactants in which a weak bond has deliberately been inserted into the molecule, are of interest when remaining surface-active material at a surface can cause problems. Ester and amide bonds are established as week linkages in surfactants but these generate an acid when they hydrolyze. For some applications, acidic degradation products are unwanted. Surfactants with a carbonate bond between the polar headgroup and the hydrophobic tail are of interest for such purposes. In this article, we compare the physical–chemical properties of nonionic carbonate surfactants with those of the corresponding ester and amide surfactants. The half-lives of the different cleavable surfactants are also compared and it was found that a carbonate bond is slightly more stable to alkaline hydrolysis than an ester bond when present in otherwise identical structures. A nonionic Gemini surfactant with a carbonate bond in the spacer, which on hydrolysis decomposes into two identical single-tailed nonionic amphiphiles, is also presented. The hydrolysis kinetics for this surfactant was studied in some detail and it was found that it degrades much faster at low temperature than at higher temperature. This anti-Arrhenius type of hydrolysis kinetics is proposed to be due to the reverse solubility versus temperature behavior of ethoxylated surfactants.     

可裂解的表面活性剂(英)(待续)

可裂解的表面活性剂值得关注有几方面的原因。首先,弱键联接的表面活性剂分子结构迎合了改善两亲性物质生物降解能力的发展趋势。裂解可以被酶催化,其生物降解作用可能与污水处理的一般发机理相符合。另外,这些表面活性剂也可以妥,例如,用酸、碱、此一（ＵＶ）、热或臭氧诱发降解反应,对酸、碱不稳定的表面活性剂已引起特别关注,因为在初始步骤所需的稳定性与其在后续步骤中应易裂解并不冲突。综述了制可裂解性表面活性剂的主     

Cleavable surfactants

Cleavable surfactants are of interest for several reasons. Above all, the development of surfactants with weak bonds deliberately built into the structure is driven by the need for improved biodegradability of amphiphiles. The breakdown may be catalyzed by enzymes, and biodegradation would be the normal mechanism in sewage plants. Alternatively, the surfactant may degrade by chemical means, e.g., induced by acid, alkali, ultraviolet (UV) light, heat, or ozone. Acid- and alkali-labile surfactants have attracted particular attention, and there is often a compromise between required stability at one stage and ease of breakdown at a subsequent stage. The paper reviews the main routes used to prepare cleavable surfactants and points out advantages and disadvantages of the different approaches. Emphasis is placed on the development during recent years. Cyclic and acyclic acetals, ketals, and ortho esters are the most important types of bonds for the preparation of acid-labile surfactants, whereas alkali-labile amphiphiles usually are based on ester bonds. The ester bond approach has been particularly important for cationic surfactants, and so-called ester quats have rapidly taken a large share of the traditional market for quats. Betaine esters constitute a special class of ester with very pronounced pH dependence. UV-labile surfactants based, for instance, on an azo bond, offer promise for the future.     

可断键均三嗪脂肪磺酸盐表面活性剂的泡沫性能研究

采用改进的Ross-Miles法研究了4种不同烷基链长的可断键均三嗪脂肪磺酸盐表面活性剂(OSEAT、DSEAT、TSEAT、HSEAT)的泡沫性能,考察了质量浓度、温度、Ca2+浓度对它们泡沫性能的影响。结果表明,OSEAT的抗钙能力最强,其起泡性和稳泡性几乎不受Ca2+浓度的影响;DSEAT的起泡性最好,在0.46 g/L时达到最大发泡力185 mm,且抗温能力强,当Ca2+浓度小于200 mg/L时,其抗钙能力比较强;TSEAT的起泡性较好,且具有一定的抗温、抗钙能力;HSEAT在水溶液中稳泡性最优,其发泡力随温度的升高而增大,55℃时达到最大值144 mm。与普通表面活性剂C12-LAS的泡沫性能比较,DSEAT发泡能力比C12-LAS强,泡沫稳定与C12-LAS接近。     

Synthesis,Characterization, and Computational Study of New Ferrocene-Based Schiff Bases as Potential Nonionic Surfactants

Ferrocene-based nonionic surfactants were synthesized by reacting ferrocenylcarboxyaldehyde with different long-chain amines. Nonionic surfactants were characterized using Fourier transform infrared spectra (FT-IR), ¹HNMR, and ¹³CNMR spectroscopy. The ferrocene-based surfactants were characterized using ultraviolet (UV)–visible spectroscopy and surface tension measurements to determine the critical micelle concentration (CMC). The CMC values indicate high aggregation ability of the synthesized surfactants in ethanol. Dominance of their hydrophilic character was ensured from hydrophilic–lipophilic balance in the 10–15 range. Voltammetric response of all surfactants showed well-defined and stable redox signals. Computational studies further revealed their physicochemical characteristics. Results of the study confirm the multifunctionality of the surfactants and suggest utilization in various fields.