NMR研究溶液中正十四烷基硫酸钠/正十四烷基聚氧乙烯醚(3)表面活性剂之间的相互作用

采用¹HNMR弛豫、自扩散系数和二维相敏(2DNOESY)实验研究了正十四烷基硫酸钠[n-CH₃(CH₂)₁₃OSO₃Na(STS)]和正十四烷基聚氧乙烯醚(3)[n-CH₃(CH₂)₁₃O(C₂H₄O)₃H(C₁₄E₃)]在溶液中的自聚集以及二者混合后的相互作用.结果表明,STS与C₁₄E₃混合后存在相互作用,并形成混合胶束;弛豫实验表明,混合胶束中STS疏水链质子运动更加受阻,C₁₄E₃的α-(4″)和β-CH₂(3″)处链堆积紧密.C₁₄E₃的亲水端(CH₂CH₂0)₃链卷曲紧贴在疏水壳表面外链堆积较紧密处.自扩散系数测量表明,混合胶束比单一阴离子表面活性剂形成的胶束大.单一非离子型胶束和混合胶束的亲水端(CH₂CH₂0)₃(5″)链构成相应较软和松散的外壳.单一C₁₄E₃在极性溶剂氯仿溶液中,质子运动比在水中自由度大,但2DNOESY谱中出现了少量分子间的交叉峰,也可能形成了一些小的聚集体.     

光散射法研究氧化胺胶束与聚苯乙烯磺酸钠的相互作用

采用光散射法研究了十二烷基二甲基氧化胺(DDAO)胶束与聚苯乙烯磺酸钠(NaPSS)的相互作用,浊度滴定和激光光散射结果表明,DDAO胶束与NaPSS的相互作用受介质离子强度影响,但与胶束浓度无关,浊度滴定曲线出现一个转折点(β_c),而平均流体力学半径R_h对胶束离解度β的关系曲线出现2个转折点,在第一个转折点(β₁)时,胶束与NaPSS开始缔合,在第二个转折点(β₂)时,胶束与NaPSS的缔合达到饱和,β₂相当于浊度滴定曲线的转折β_c,β₂,和β₁不随离子强度而变化,采用β₁和β_c分别计算胶束与NaPSS发生缔合时的临界表面电荷密度,两者差距约为15％,电泳光散射也证实了β₁的存在.     

n-十二烷基-β-D-麦芽糖苷与十二烷基三甲基 氯化铵混合胶束的1H NMR研究

利用NMR技术的自扩散、自旋-自旋弛豫时间(T2)和自旋-晶格弛豫时间(T1)以及二维NOESY谱, 研究了n-十二烷基-β-D-麦芽糖苷(DM)与十二烷基三甲基氯化铵(DTAC)的二元混合体系中混合胶束的形成、大小变化、排列方式、复配比例和相互作用点等. NMR的自扩散系数表明了混合胶束的大小主要取决于DM分子, T2/T1显示混合胶束堆积的较紧密, 两分子的疏水链是以肩并肩的方式位于胶束核中, 2D NOESY 谱表明DTAC分子中与极头相连的亚甲基邻近DM分子中倒数第二个糖环, 产生分子间相互作用, 其相互作用和分子间距的大小随DM/DTAC比例的不同而变化, DM/DTAC在1∶4和1∶8之间是较好的复配比例范围, 并确定混合前后出现的变化T2值是混合胶束中产生相互作用的证椐.     

正离子Gemini表面活性剂/负离子聚电解质相互作用的研究

摘要 采用荧光探针法和电导法研究了正离子偶联表面活性剂(C₁₂H₂₅(CH₃)₂N-(CH₂)₆-N(CH₃)₂C₁₂H₂₅•2Br) (12-6-12• 2Br^－)和带相反电荷聚电解质聚丙烯酸钠(NaPA)的相互作用, 结果表明: 由于静电相互作用, 12-6-12•2Br^－和NaPA之间可以形成类胶束或复合物. 对比十二烷基三甲基溴化铵(DTMAB)与NaPA复配体系的荧光光谱, 发现偶联表面活性剂与NaPA的相互作用强于传统表面活性剂. 此外, 还研究了盐和醇对偶联表面活性剂/聚丙烯酸钠的复配体系微极性的影响, 发现盐和醇对表面活性剂在聚电解质上形成类胶束和复合物的溶解都有一定的促进作用.     

水溶性非离子大分子与烷基硫酸钠同系物团簇化的比饱和簇集量

研究了烷基硫酸钠同系物(ROSO₃Na)与聚乙二醇(PEG)及聚乙烯吡咯烷酮(PVP)的γ-lgc曲线的双拐点特征,根据拟双平台现象求得烷基硫酸钠同系物对大分子的饱和簇集量Γ_∞(mmol/L)和比饱和簇集量[Γ_∞].由Γ_∞-cP回归方程的斜率得到ROSO₃Na-PEG及ROSO₃Na-PVP体系的[Γ_∞]_reg分别为0.394和0.415m/n.[Γ_∞]随表面活性剂疏水基链长、大分子分子量及浓度的变化均很小,t检验结果表明回归值[Γ_∞]_reg与实验值[Γ_∞]_exp之间无明显差异,因此超分子相互作用参数[Γ_∞]可以被视为不变量.烷基硫酸钠同系物的类胶束与大分子形成软物质团簇的作用方式为静电超分子自组装.     

十四烷基芳基磺酸盐形成的分子有序组合体

以表面张力法、碘光谱法、水增溶法和相态图法研究了自制的三种十四烷基芳基磺酸盐在不同条件下形成的分子有序组合体(胶束、反胶束和微乳液),并考察了分子结构、溶剂、无机盐和短链醇等对其的影响.结果表明:增加十四烷基芳基磺酸盐分子亲油基支化度,不利于其在水溶液或混合极性溶剂(乙二醇-水)中形成胶束而有利于其在非极性溶剂正庚烷中形成反胶束;溶剂极性的降低,促使表面活性剂溶液由胶束溶液→单体溶液→反胶束溶液转变;无机盐或短链醇的加入促进了水溶液中胶束的形成,且反离子价态数或醇烷基碳原子数越大,越有利于胶束形成;无机盐浓度的增加导致表面活性剂/正丁醇/正辛烷/NaCl/水形成的微乳液体系在一定温度下发生由WinsorI→WinsorIII→WinsorII型的转变.     

利用光化学探针技术研究长链烷烃硫酸钠水溶液中预胶束的生成

罗丹明6G与罗丹明B之间的能量转移和吖啶橙形成聚态的现象用于研究长链烷基硫酸钠(C_nH_(2n+1)OSO_3Na,n=12,14和16)在水溶液中预胶束的生成.结果表明,烷基链的长度影响这些表面活性剂形成预胶束的能力,碳数的增加使预胶束形成浓度降低.     

十二烷基混合糖苷与其它表面活性剂二元体系表面吸附和胶束形成的顺序研究

摘要绿色表面活性剂烷基糖苷C₁₂G _1.46具有混合糖苷组成, 将其分别与十二烷基三氧乙烯磺酸钠C₁₂E₃S、 十二烷基三甲基氯化铵C₁₂TAC、 三硅氧烷非离子表面活性剂BE-6、 聚醚类表面活性剂 TMN-6复配, 在25 ℃下测定它们在0.1 mol/L NaCl溶液中的表面活性, 通过其混合表面层和混合胶束的分子交换能(ε, ε_m)的计算得出如下结论: (1) C₁₂G_1.46的活性高于C₁₂G₁和C₁₂G₂, 即烷基混合糖苷的活性高于相同烷基的纯糖苷的结论得到了进一步证实. 利用MM2分子力场计算的能量数据可合理地解释这种混合产品活性提高的原因. (2) 在该烷基混合糖苷的二元体系溶液中, 对其表面吸附和胶束化两个过程的顺序问题进行探讨, 一种情况是先建立表面吸附, 再形成胶束(C₁₂G_1.46/BE-6 和 C₁₂G_1.46/TMN-6 体系); 另一种情况是表面吸附和胶束化同时进行(C₁₂G_1.46/C₁₂TAC和C₁₂G_1.46/C₁₂E₃S体系).     

利用光化学探针技术研究长链烷烃硫酸钠水溶液中预胶束的生成

罗丹明6G与罗丹明B之间的能量转移和吖啶橙形成聚态的现象用于研究长链烷基硫酸钠(C~nH~2~n~+~1OSO~3Na,n=12,14和16)在水溶液中预胶束的生成。结果表明,烷基链的长度影响这些表面活性剂形成预胶束的能力,碳数的增加使预胶束形成浓度降低。     

阴离子磺酸盐型Gemini表面活性剂与PEO-PPO-PEO嵌段共聚物相互作用的研究

用差示扫描微量热、等温滴定微量量热、动态光散射和核磁共振(NOESY,弛豫时间)技术,研究了在pH＝9时阴离子磺酸盐型Gemini表面活性剂12-3-12(SO₃)₂与PEO-PPO-PEO嵌段共聚物F127 (EO₉₇PO₆₉EO₉₇)和P123 (EO₂₀PO₇₀EO₂₀)之间的相互作用. 研究发现,随着12-3-12(SO₃)₂浓度的增大,聚合物的临界胶束温度(CMT)降低. 与传统的单链离子表面活性剂相比,12-3-12(SO₃)₂具有更强的降低共聚物CMT的能力. 此外,在低于聚合物的CMT时,12-3-12(SO₃)₂与聚合物单体可以形成聚合物/表面活性剂胶束聚集体;在高于聚合物的CMT时,12-3-12(SO₃)₂的加入首先与聚合物单体和胶束的混合物或聚合物胶束形成聚合物/12-3-12(SO₃)₂混合胶束,然后随着12-3-12(SO₃)₂浓度的增大,混合胶束逐步解离为小的聚集体,但是,即使在很高的12-3-12(SO₃)₂浓度时,混合胶束也未完全解离.     

Effect of alkyl chain length and size of the headgroups of the surfactant on solvent and rotational relaxation of Coumarin 480 in micelles and mixed micelles

The effect of alkyl chain length and size of the headgroups of the surfactant on the solvation dynamics and rotational relaxation of Coumarin 480 (C-480) has been investigated using dynamic Stokes' shift of C-480 in different types of alkyltrimethylammonium bromide micelles and mixed micelles. The rotational relaxation time increases with increase in alkyl chain length of the surfactant. The increase in the number of alkyl chains of the surfactant leads to the more close packed micelles, hence the microviscosity of the micelles increases and consequently rotational relaxation time increases. Solvation time also increases due to the increase in number of alkyl chains of the surfactant. The change in solvation and rotational relaxation time is more prominent in micelles compared to mixed micelles. The solvation and rotational relaxation time also increase with the increase in size of the headgroup of the surfactant.     

Mixed micelles of polyethylene glycol (23) lauryl ether with ionic surfactants studied by proton 1D and 2D NMR

(1)H NMR chemical shift, spin-lattice relaxation time, spin-spin relaxation time, self-diffusion coefficient, and two-dimensional nuclear Overhauser enhancement (2D NOESY) measurements have been used to study the nonionic-ionic surfactant mixed micelles. Cetyl trimethyl ammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) were used as the ionic surfactants and polyethylene glycol (23) lauryl ether (Brij-35) as the nonionic surfactant. The two systems are both with varying molar ratios of CTAB/Brij-35 (C/B) and SDS/Brij-35 (S/B) ranging from 0.5 to 2, respectively, at a constant concentration of 6 mM for Brij-35 in aqueous solutions. Results give information about the relative arrangement of the surfactant molecules in the mixed micelles. In the former system, the trimethyl groups attached to the polar heads of the CTAB molecules are located between the first oxy-ethylene groups next to the hydrophobic chains of Brij-35 molecules. These oxy-ethylene groups gradually move outward from the hydrophobic core of the mixed micelle with an increase in C/B in the mixed solution. In contrast to the case of the CTAB/Triton X-100 system, the long flexible hydrophilic poly oxy-ethylene chains, which are in the exterior part of the mixed micelles, remain coiled, but looser, surrounding the hydrophobic core. There is almost no variation in conformation of the hydrophilic chains of Brij-35 molecules in the mixed micelles of the SDS/Brij-35 system as the S/B increases. The hydrophobic chains of both CTAB and SDS are co-aggregated with Brij-35, respectively, in their mixed micellar cores.     

Phase behavior and local dynamics of concentrated triblock copolymer micelles

We report a neutron-scattering study to characterize the ordering and local dynamics of spherical micelles formed by the triblock copolymer polyethylene oxide (PEO)--polypropylene oxide (PPO)--polyethylene oxide (Pluronic) in aqueous solution. The study focuses on two Pluronic species, F68 and F108, that have the same weight fraction of PEO but that differ in chain length by approximately a factor of 2. At sufficiently high concentration, both species undergo a sequence of phase changes with increasing temperature from dissolved chains to micelles with liquid-like order to a cubic crystal phase and finally back to a micelle liquid phase. A comparison of the phase diagrams constructed from small-angle neutron scattering indicates that crystallization is suppressed for shorter chain micelles due to fluctuation effects. The intermediate scattering function I(Q,t)I(Q,0) determined by neutron spin echo displays a line shape with two distinct relaxations. Comparisons between I(Q,t)I(Q,0) for fully hydrogenated F68 chains in D2O and for F68 with deuterated PEO blocks reveal that the slower relaxation corresponds to Rouse modes of the PPO segments in the concentrated micelle cores. The faster relaxation is identified with longitudinal diffusive modes in the PEO corona characteristic of a polymer brush.     

Conformation and dynamics of polyoxyethylene lauryl ether (Brij-35) chains in aqueous micellar solution studied by 2D NOESY and 1H NMR relaxation

Spin-lattice relaxation time, spin-spin relaxation time and two-dimensional nuclear Overhauser enhancement spectroscopy (2D NOESY) experiments of polyoxyethylene lauryl ether (Brij-35) micelles in aqueous solutions at a concentration of 100 times the critical micellar concentration (cmc) give direct evidence that the hydrophilic polyoxyethylene chains, staying in the exterior of the micellar core, are coiled, bent and aligned around the micellar core with a certain number of water molecules included. This hydrophilic layer is in contact with the solvent, water, keeping the micellar solution stable. 1H NMR relaxation time measurements show that the first oxyethylene group next to the alkyl chain participates in the formation of the surface area of the micellar core. The motion of the hydrophilic polyoxyethylene chains is less restricted as compared with the hy-drophobic alkyl chains.     

Conformation and dynamics of polyoxyethylene lauryl ether (Brij- 35) chains in aqueous micellar solution studied by 2D NOESY and <Superscript>1</Superscript>H NMR relaxation

Spin-lattice relaxation time, spin-spin relaxation time and two-dimensional nuclear Overhauser enhancement spectroscopy (2D NOESY) experiments of polyoxyethylene lauryl ether (Brij-35) micelles in aqueous solutions at a concentration of 100 times the critical micellar concentration (cmc) give direct evidence that the hydrophilic polyoxyethylene chains, staying in the exterior of the micellar core, are coiled, bent and aligned around the micellar core with a certain number of water molecules included. This hydrophilic layer is in contact with the solvent, water, keeping the micellar solution stable. ¹H NMR relaxation time measurements show that the first oxyethylene group next to the alkyl chain participates in the formation of the surface area of the micellar core. The motion of the hydrophilic polyoxyethylene chains is less restricted as compared with the hydrophobic alkyl chains.     

2,5-双取代烷基苯磺酸钠胶束微结构的1H NMR研究

利用核磁共振化学位移变化, 自旋-自旋弛豫和2D NOESY(two-dimensional nuclear Overhauser enhancement spectroscopy)研究了一系列新合成的双取代烷基苯磺酸盐的胶束化. 结果表明, 邻位取代的是正烷烃链, 间位取代的是支烷烃链. 而且, 邻位取代的烷烃链越长, 参与形成胶束疏水核表面层的亚甲基个数越多. 因此, 每个分子在饱和吸附的油水界面上的面积越大. 间位取代的分支链在胶束疏水核中堆积得没有邻位取代的正烷烃链紧密. 分支链越短, 堆积得越不紧密. 描述了胶束中分子的相对排列.     

表面活性剂胶束形状随浓度转变的核磁共振研究

运用核磁共振一维氢谱和自扩散实验方法研究了聚乙烯乙二醇异辛酚醚(TX-100)、十二烷基苯磺酸钠(SDBS)和十四烷基三甲基溴化铵(TTAB)三种不同类型的表面活性剂在重水溶液中的胶束形状转变, 发现它们在临界胶束浓度以上的各自相应浓度都有胶束形状的变化(由球状转变为椭球状或棒状). 在常温常压和没有其他添加剂的情况下, 表面活性剂溶液浓度高于其临界胶束浓度时, 球状胶束开始形成. 核磁共振一维氢谱和自扩散实验的结果显示, 当溶液浓度继续增加到一定程度时, 溶液中表面活性剂分子的化学位移和自扩散系数的变化速率都有明显的转折, 这说明溶液中球状胶束开始发生转变. 进一步通过仔细分析对比核磁共振一维氢谱中各基团谱峰, 发现表面活性剂胶束亲水表面上的质子的化学位移变化速率要远高于其疏水内核中的质子, 据此推测胶束形状很可能由球状转变为椭球状或棒状.     

Difference in micellar properties of sodium dodecyl sulfonate from sodium 4-decyl naphthalene sulfonate in D2O solution studied by 1H NMR relaxation and 2D NOESY

¹H chemical shift changes of sodium 4-decyl naphthalene sulfonate (SDNS) at 313 K show that its critical micellar concentration lies between 0.82 and 0.92 mmol/dm³, which is in the same range as that of the previous study at 298 K. The spin–lattice relaxation time, spin–spin relaxation time and two-dimensional nuclear Overhauser enhancement spectroscopy experiments give information about the structure of the SDNS micelle and the dynamics of the molecules in the micelle. The size of the SDNS micelle remains almost unchanged in the temperature range from 298 to 313 K as deduced by analyzing the self-diffusion coefficient. Special arrangement of the naphthyl rings of SDNS in the micelles affects the packing of these hydrophobic chains. The methylene groups of the alkyl chain nearest the naphthalene groups penetrate into the aromatic region, which results in a more tightly packed hydrophobic micellar core than that of sodium dodecyl sulfonate.     

Microstructure of N,N′-bis(cetyldimethyl)-α,ω-propanediammonium dibromide micelle and its dynamics in solution studied by 1H NMR

The characteristics of N,N′-bis(cetyldimethyl)-α,ω-alkane (propane and butane) diammonium dibromide (16-3-16 and 16-4-16) aqueous solutions were studied by one- and two-dimensional ¹H nuclear magnetic resonance (NMR). The measurements of self-diffusion coefficient and inter-proton distance at 318 K suggest that 16-3-16 spherical micelles are formed in the dilute solution at a concentration of 0.26 mmol/l and the polar head groups of the surfactant are in a saw-toothed form staying at the surface of the micelle to overcome the strong electrostatic repulsion force. Relaxation measurements obviously show that the spacer chain is rigid in the surface layer of the hydrophobic micellar core, and the side alkyl chains of 16-3-16 are packed more tightly than those of 16-4-16 in the micellar core. The line-shape analysis of the methyl protons at the end of the side alkyl chain of 16-3-16 and 16-4-16 suggests that two possible momentary morphologies of their side alkyl chains are situated in the micelle, respectively.