Sánchez-Leija Regina J, Mysona Joshua A, de Pablo Juan J, Nealey Paul F
Materials Science Division, Argonne National Laboratory, 9700 S Cass Avenue, Lemont, Illinois 60439, United States.
Pritzker School of Molecular Engineering, the University of Chicago, 5640 S Ellis Avenue, Chicago, Illinois 60637, United States.
Macromolecules. 2024 Feb 20;57(5):2019-2029. doi: 10.1021/acs.macromol.3c02180. eCollection 2024 Mar 12.
This study explores how conformational asymmetry influences the bulk phase behavior of linear-brush block copolymers. We synthesized 60 diblock copolymers composed of poly(trifluoroethyl methacrylate) as the linear block and poly[oligo(ethylene glycol) methyl ether methacrylate] as the brush block, varying the molecular weight, composition, and side-chain length to introduce different degrees of conformational asymmetry. Using small-angle X-ray scattering, we determined the morphology and phase diagrams for three different side-chain length systems, mainly observing lamellar and cylindrical phases. Increasing the side-chain length of the brush block from three to nine ethylene oxide units introduces sufficient asymmetry between the blocks to alter the phase behavior, shifting the lamellar-to-cylindrical transitions toward lower brush block compositions and transitioning the brush block from the dense comb-like regime to the bottlebrush regime. Coarse-grained simulations support our experimental observations and provide a mapping between the composition and conformational asymmetry. A comparison of our findings to strong stretching theory across multiple phase boundary predictions confirms the transition between the dense comb-like regime and the bottlebrush regime.
本研究探索了构象不对称性如何影响线性刷状嵌段共聚物的本体相行为。我们合成了60种由聚（甲基丙烯酸三氟乙酯）作为线性嵌段和聚[聚（乙二醇）甲醚甲基丙烯酸酯]作为刷状嵌段组成的二嵌段共聚物，通过改变分子量、组成和侧链长度来引入不同程度的构象不对称性。利用小角X射线散射，我们确定了三种不同侧链长度体系的形态和相图，主要观察到层状相和柱状相。将刷状嵌段的侧链长度从三个环氧乙烷单元增加到九个环氧乙烷单元，会在嵌段之间引入足够的不对称性，从而改变相行为，使层状到柱状的转变朝着更低的刷状嵌段组成方向移动，并使刷状嵌段从致密梳状状态转变为瓶刷状状态。粗粒化模拟支持了我们的实验观察结果，并提供了组成与构象不对称性之间的映射关系。将我们的研究结果与跨越多个相边界预测的强拉伸理论进行比较，证实了致密梳状状态和瓶刷状状态之间的转变。
