Topologically Induced Heterogeneity in Gradient Copolymer Brush Particle Materials
Topologically Induced Heterogeneity in Gradient Copolymer Brush Particle Materials
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DOI：
10.1021/acs.macromol.2c01131
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发表时间：
2022-07
期刊：
影响因子：
5.5
通讯作者：
Yuqi Zhao;Zongyu Wang;Chenxi Yu;Hanshu Wu;Mateusz Olszewski;Rongguan Yin;Yue-Liang Zhai;Tong Liu;Amy Coronado;K. Matyjaszewski;M. Bockstaller
中科院分区：
文献类型：
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作者：
Yuqi Zhao;Zongyu Wang;Chenxi Yu;Hanshu Wu;Mateusz Olszewski;Rongguan Yin;Yue-Liang Zhai;Tong Liu;Amy Coronado;K. Matyjaszewski;M. Bockstaller
采用表面引发原子转移自由基聚合（SI-ATRP）技术，合成了丙烯酸丁酯（BA）和甲基丙烯酸甲酯（MMA）无规和梯度接枝的二氧化硅刷状粒子。研究了链结构对共聚物-栓系刷状颗粒膜的结构和热机械性能的影响，并与线性共聚物类似物进行了比较。无规共聚物刷系统显示出均匀和窄的玻璃化转变，和线性共聚物的玻璃化转变温度的依赖性遵循类似的趋势。与此相反，梯度刷材料的特点是分裂的玻璃化转变温度与MMA含量的增加沿着与一个台阶状的增加杨氏模量和延展性下降。结果进行了解释方面的刷架构上的微观结构的薄膜的效果。结果表明，在无规刷以及线性无规和线性梯度共聚物系统的膜中的“分子均匀”的微观结构。相比之下，梯度刷系统具有异质的微观结构，其中MMA丰富的区域作为“陷阱”，减少链的流动性。组成异质性的形成是合理的“规定的方向”的梯度共聚物链附近的颗粒界面，放大组成波动，因此局部隔离的重复单元。结果突出了需要更好地理解共聚物刷颗粒为基础的混合材料的物理性能的“几何约束”的作用，并通过控制除了整体组合物的链段分布的多重性能增强的机会。
A facile synthetic route toward silica brush particles with random and gradient copolymer grafts comprised ofn-butyl acrylate (BA) and methyl methacrylate (MMA) using surface-initiated atom transfer radical polymerization (SI-ATRP) was developed. The effect of chain architecture on the structure and thermomechanical properties of copolymer-tethered brush particle films was investigated and compared to linear copolymer analogues. Random copolymer brush systems displayed a uniform and narrow glass transition, and the dependence of the glass-transition temperature followed a similar trend as for linear copolymers. In contrast, gradient brush materials featured a splitting of the glass-transition temperature with increasing MMA content along with a step-like increase of Young’s modulus and a decrease in ductility. The results were interpreted in terms of the effect of brush architecture on the microstructure of films. The results suggested a “molecularly uniform” microstructure in films of the random brush as well as linear random and linear gradient copolymer systems. In contrast, gradient brush systems featured a heterogeneous microstructure in which MMA-rich regions acted as “traps” that reduced chain mobility. The formation of compositional heterogeneity was rationalized by the “prescribed orientation” of gradient copolymer chains near the particle interface that amplified composition fluctuations and hence local segregation of repeat units. The results highlight the need for a better understanding of the role of “geometric constraints” on the physical properties of copolymer brush particle-based hybrid materials and the opportunity for multiple property enhancement by control of segment distribution in addition to the overall composition.