Path-Dependent Preparation of Complex Micelle Packings of a Hydrated Diblock Oligomer
Path-Dependent Preparation of Complex Micelle Packings of a Hydrated Diblock Oligomer
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DOI：
10.1021/acscentsci.8b00903
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发表时间：
2019-04-24
影响因子：
18.2
通讯作者：
Mahanthappa, Mahesh K.
中科院分区：
文献类型：
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作者：
Jayaraman, Ashish;Zhang, Diana Y.;Mahanthappa, Mahesh K.
小角X射线散射分析表明，水合二嵌段低聚物n-C16 H23（OCH 2CH 2）（20）-OH（C16 E20或Brij 58）在30- 65wt%两亲物浓度范围内形成表现出面心立方（FCC）、体心立方（BCC）、Frank-Kasper（FK）A15和圆柱形（HI）形态的溶致液晶（LLC）。加热包含54- 59wt%C16E20的LLC驱动温度依赖性相变顺序：A15 -> BCC -> H-I。然而，将所得HI相从70 ° C快速淬火至25 ° C最初形成BCC相，其等温转变成包含30个准球形胶束的复杂的四氢FK s相。该胶束相的亚稳定性取决于样品的冷却速率，热淬火深度，和等温退火温度。我们合理化的A15结构在25摄氏度的最小化不利的水/疏水接触方面的偏好，同时最大限度地提高局部颗粒的球形度。在这些胶束LLC的对称性破缺过渡动力学显然源于温度依赖性的激活障碍相成核和生长，这是密切耦合到胶束重构的时间尺度由两亲物链交换和空间重排。这些发现突出了热处理如何影响本质上可重构的软球形颗粒的自组装形态的成核和生长。
Small-angle X-ray scattering analyses reveal that the hydrated diblock oligomer n-C16H23(OCH2CH2)(20)-OH (C16E20 or Brij 58) forms lyotropic liquid crystals (LLCs) exhibiting face-centered cubic (FCC), body-centered cubic (BCC), Frank-Kasper (FK) A15, and cylindrical (HI) morphologies over the concentration range 30-65 wt % amphiphile. Heating LLCs comprising 54-59 wt % C16E20 drives the temperature-dependent phase transition sequence: A15 -> BCC -> H-I. However, rapidly quenching the resulting HI phase from 70 to 25 degrees C initially forms a BCC phase that isothermally transforms into a complex, tetragonal FK s phase comprising 30 quasispherical micelles. The metastability of this micellar s phase is shown to depend on the sample cooling rate, thermal quench depth, and isothermal annealing temperature. We rationalize the preference for the A15 structure at 25 degrees C in terms of minimizing unfavorable water/hydrophobic contacts, while maximizing local particle sphericity. The symmetry breaking transition kinetics in these micellar LLCs apparently stem from the temperature-dependent activation barriers for phase nucleation and growth, which are intimately coupled to the time scales for micelle reconfiguration by amphiphile chain exchange and their spatial rearrangement. These findings highlight how thermal processing influences nucleation and growth of the self-assembled morphologies of intrinsically reconfigurable, soft spherical particles.