Nanobowls from Amphiphilic Core–Shell Cyclic Bottlebrush Polymers
Nanobowls from Amphiphilic Core–Shell Cyclic Bottlebrush Polymers
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DOI：
10.1021/acs.macromol.2c01232
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发表时间：
2022-08
期刊：
影响因子：
5.5
通讯作者：
Digvijayee Pal;John B. Garrison;Zhihui Miao;Lily E. Diodati;A. Veige;B. Sumerlin
中科院分区：
文献类型：
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作者：
Digvijayee Pal;John B. Garrison;Zhihui Miao;Lily E. Diodati;A. Veige;B. Sumerlin
环状瓶刷聚合物是大环，几乎每个重复单元上都含有侧链聚合物。我们利用一种方法，利用扩环聚合(REP)和随后的原子转移自由基聚合(ATRP)接枝制备了环状瓶刷聚合物，并研究了它们在水中的自组装行为。瓶刷聚合物由环状主链和侧链组成，侧链由疏水性聚苯乙烯嵌段和亲水性聚丙烯酸嵌段组成。从四氢呋喃到水的溶剂交换过程中，观察到了从球体到多孔球到纳米鸟(具有单个大孔的球)的两步形态转变。相反，在相同的实验条件下，具有相似主链和侧链聚合度的相似线性瓶刷聚合物不会聚集成纳米猫头鹰，而是表现出多孔球的形态。这些不寻常的形态和它们的转化倾向可以归因于在溶剂交换过程中聚集体的内部粘度的变化。此外，研究还发现，溶剂交换速率会影响形状转变的倾向。
Cyclic bottlebrush polymers are macrocycles that contain pendent side-chain polymers on nearly every repeat unit. We leveraged a method to generate cyclic bottlebrush polymers utilizing ring-expansion polymerization (REP) followed by subsequent grafting-from via atom-transfer radical polymerization (ATRP) to produce core–shell cyclic bottlebrush polymers and investigated their self-assembly behavior in water. The bottlebrush polymers were comprised of a cyclic backbone with side chains composed of a hydrophobic polystyrene block and a hydrophilic poly(acrylic acid) block. A two-step morphological transformation from spheres to porous spheres to nanobowls (spheres with a single large pore) was observed with solvent exchange from tetrahydrofuran to water. In contrast, under identical experimental conditions, an analogous linear bottlebrush polymer with a similar backbone and side chain degrees of polymerizations did not aggregate into nanobowls but rather exhibited a porous sphere morphology. These unusual morphologies and their propensities to transform can be attributed to changes in the internal viscosity of the aggregates during the solvent exchange process. Additionally, the rate of solvent exchange was found to influence the propensity for shape transformation to occur.