Block and Gradient Copoly(2-oxazoline) Micelles: Strikingly Different on the Inside
Block and Gradient Copoly(2-oxazoline) Micelles: Strikingly Different on the Inside
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DOI：
10.1021/acs.jpclett.7b01588
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发表时间：
2017-08-17
影响因子：
5.7
通讯作者：
Hoogenboom, Richard
中科院分区：
文献类型：
--
作者：
Filippov, Sergey K.;Verbraeken, Bart;Hoogenboom, Richard
在这里，我们提供了一个直接的证据，在两亲性的两嵌段和梯度共聚物的胶束结构的差异，从而明确地证明了单体分布沿着聚合物链上的胶束化行为的影响。采用小角X射线散射（SAXS）、小角中子散射（SANS）、静态和动态光散射（SLS/DLS）和核磁共振氢谱（H-1 NMR）研究了亲水性聚（2-甲基-2-恶唑啉）（PMeOx）和疏水性聚（2-苯基-2-恶唑啉）（PPhOx）两亲性嵌段和梯度共聚2-恶唑啉在水和水-乙醇混合溶剂中的内部结构.对比度匹配SANS实验表明，嵌段共聚物形成胶束具有均匀的密度分布的核心。与普遍的假设相反，梯度共聚物胶束的核的外部部分具有比核的中间部分明显更高的密度。我们将后者的发现归因于亲水性和疏水性相互作用导致的链的回折，从而导致一种新型的胶束，我们称之为具有“球芯”结构的胶束。
Herein, we provide a direct proof for differences in the micellar structure of amphiphilic diblock and gradient copolymers, thereby unambiguously demonstrating the influence of monomer distribution along the polymer chains on the micellization behavior. The internal structure of amphiphilic block and gradient co poly(2-oxazolines) based on the hydrophilic poly(2-methyl-2-oxazoline) (PMeOx) and the hydrophobic poly(2-phenyl-2-oxazoline) (PPhOx) was studied in water and water ethanol mixtures by small-angle X-ray scattering (SAXS), small angle neutron scattering (SANS), static and dynamic light scattering (SLS/DLS), and H-1 NMR spectroscopy. Contrast matching SANS experiments revealed that block copolymers form micelles with a uniform density profile of the core. In contrast to popular assumption, the outer part of the core of the gradient copolymer micelles has a distinctly higher density than the middle of the core. We attribute the latter finding to back-folding of chains resulting from hydrophilic hydrophobic interactions, leading to a new type of micelles that we refer to as micelles with a "bitterball-core" structure.