Cui Shuquan, Murphy Elizabeth A, Santra Subrata, Bates Frank S, Lodge Timothy P
Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States.
Materials Research Laboratory and Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, United States.
ACS Nano. 2025 Jan 14;19(1):1211-1221. doi: 10.1021/acsnano.4c13416. Epub 2025 Jan 6.
Bottlebrush block polymers, characterized by densely grafted side chains extending from a backbone, have recently garnered significant attention. A particularly attractive feature is the accessibility of ordered morphologies with domain spacings exceeding several hundred nanometers, a capability that is challenging to achieve with linear polymers. These large morphologies make bottlebrush block polymers promising for various applications, such as photonic crystals. However, the structures observed in AB diblock bottlebrushes are generally limited to simple lamellae and cylindrical phases, which restricts their use in many applications. In this study, we synthesized a library of 50 ABC bottlebrush triblock terpolymers, poly(DL-lactide)--poly(ethylene--propylene)--polystyrene (PLA-PEP-PS), spanning a wide range of compositions using ring-opening metathesis polymerization (ROMP) of norbornene-functionalized macromonomers. This constitutes a frustrated system, in that the mandatory internal interfaces (PLA/PEP and PEP/PS) have larger interfacial energies than PLA/PS. We systematically explored phase behavior using small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Morphological characterization revealed a series of intriguing mesoscopic structures, including layered microstructures, core-shell hexagonally packed cylinders (CSHEX, plane group 6), alternating tetragonally packed cylinders (ATET, plane group 4), and rectangular centered cylinders-in-undulating-lamellae (RCCUL, plane group 2). Adjustments in molecular weight resulted in a wide range of unit cell dimensions (exemplified by RCCUL), from 40 nm to over 130 nm. This work demonstrates that multiblock bottlebrushes offer promising opportunities for developing materials with diverse structures and a broad range of domain dimensions.
瓶刷状嵌段聚合物的特征是从主链延伸出密集接枝的侧链，最近受到了广泛关注。一个特别吸引人的特点是能够形成有序形态，其域间距超过几百纳米，这是线性聚合物难以实现的。这些大尺寸形态使瓶刷状嵌段聚合物在诸如光子晶体等各种应用中具有广阔前景。然而，在AB二嵌段瓶刷中观察到的结构通常仅限于简单的片层和圆柱相，这限制了它们在许多应用中的使用。在本研究中，我们使用降冰片烯官能化大分子单体的开环易位聚合（ROMP）合成了50种ABC瓶刷状三嵌段三元共聚物，聚（DL-丙交酯）-聚（乙烯-丙烯）-聚苯乙烯（PLA-PEP-PS），涵盖了广泛的组成范围。这构成了一个受挫体系，因为强制的内部界面（PLA/PEP和PEP/PS）的界面能比PLA/PS大。我们使用小角X射线散射（SAXS）和透射电子显微镜（TEM）系统地探索了相行为。形态表征揭示了一系列有趣的介观结构，包括层状微结构、核壳六方堆积圆柱（CSHEX，平面群6）、交替四方堆积圆柱（ATET，平面群4）和矩形中心圆柱在起伏片层中（RCCUL，平面群2）。分子量的调整导致了从40纳米到超过130纳米的广泛的晶胞尺寸范围（以RCCUL为例）。这项工作表明，多嵌段瓶刷为开发具有多样结构和广泛域尺寸的材料提供了广阔的机会。
