Wang Zongyu, Lee Jaejun, Wang Zhenhua, Zhao Yuqi, Yan Jiajun, Lin Yu, Li Sipei, Liu Tong, Olszewski Mateusz, Pietrasik Joanna, Bockstaller Michael R, Matyjaszewski Krzysztof
Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States.
Department of Materials Science & Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213, United States.
ACS Macro Lett. 2020 Jun 16;9(6):806-812. doi: 10.1021/acsmacrolett.0c00158. Epub 2020 May 19.
A strategy to synthesize SiO--PMMA/PMMA--PS mono- and bimodal block copolymer particle brushes by surface-initiated atom transfer radical polymerization (SI-ATRP) from silica particles is presented. First, PMMA blocks were prepared by normal ATRP with controlled degree of polymerizations and grafting density. In a second step, the PS block was synthesized through a chain extension using low parts per million of Cu catalyst. Variation of the SiO--PMMA-Br macroinitiator concentration had a pronounced effect on the modality of the chain extension product. In the limit of small concentration, partial termination resulted in bimodal brush architectures, while more uniform brush architectures were observed with increasing concentration of macroinitiator. Brush nanoparticles with bimodal architectures assembled into string-like aggregates that bore a resemblance to structures found in systems comprised of sparse (homopolymer) brush particles. The unexpected effect of modality on structure formation points to opportunities in controlling microstructures in brush particle materials.
提出了一种通过二氧化硅颗粒表面引发的原子转移自由基聚合（SI-ATRP）合成SiO--PMMA/PMMA--PS单峰和双峰嵌段共聚物颗粒刷的策略。首先，通过具有可控聚合度和接枝密度的常规ATRP制备PMMA嵌段。在第二步中，使用百万分之几的铜催化剂通过链延伸合成PS嵌段。SiO--PMMA-Br大分子引发剂浓度的变化对链延伸产物的模态有显著影响。在低浓度极限下，部分终止导致双峰刷结构，而随着大分子引发剂浓度的增加，观察到更均匀的刷结构。具有双峰结构的刷状纳米颗粒组装成串状聚集体，类似于由稀疏（均聚物）刷状颗粒组成的系统中发现的结构。模态对结构形成的意外影响为控制刷状颗粒材料的微观结构提供了机会。
