Directing block copolymer self-assembly with permanent magnets: photopatterning microdomain alignment and generating oriented nanopores†,Molecular Systems Design & Engineering

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Directing block copolymer self-assembly with permanent magnets: photopatterning microdomain alignment and generating oriented nanopores†
Molecular Systems Design & Engineering ( IF 3.2 ) Pub Date : 2017-10-23 00:00:00 , DOI: 10.1039/c7me00070g
Manesh Gopinadhan _{1,

2,

3,

4} , Youngwoo Choo _{1,

2,

3,

4} , Lalit H. Mahajan _{4,

5,

6,

7} , Dennis Ndaya _{4,

5,

6,

7} , Gilad Kaufman _{1,

2,

3,

4} , Yekaterina Rokhlenko _{1,

2,

3,

4} , Rajeswari M. Kasi _{4,

5,

6,

7,

8} , Chinedum O. Osuji _{1,

2,

3,

4}

Affiliation

Magnetic fields are useful for directing block copolymer (BCP) self-assembly, but to date such a field alignment has required large fields (>5 T) necessitating the use of superconducting magnets. We report an approach that circumvents this limitation by introducing labile reactive mesogens into a liquid crystalline (LC) BCP based on a norbornene backbone with a poly(lactide) minority block that forms hexagonally packed cylinders. The free mesogens co-assemble with the smectic A mesophase of the BCP and enable alignment at fields as low as 0.5 T. The remarkable field response originates from the combined effects of enhanced mobility and decreased segregation strength, and the presence of large micron-scale grains in the system. We demonstrate a robust alignment of mesogen-blended samples using simple permanent magnets. The etching of poly(lactide) yields nanoporous films, while the spatially selective microdomain immobilization by UV-induced crosslinking through a photomask provides a versatile mechanism for creating alignment patterns. We anticipate that the nanoporous materials as generated here may find application in membrane fabrication or BCP lithography, while the ability to spatially pattern alignment is promising for the design of mechanical metamaterials exploiting the shape memory effect of LC elastomers.

中文翻译：

指导嵌段共聚物与永磁体的自组装：光图案化微区排列并生成取向的纳米孔†

磁场可用于指导嵌段共聚物（BCP）的自组装，但是迄今为止，这种磁场对准需要大磁场（> 5 T），因此必须使用超导磁体。我们报告了一种方法，该方法通过将不稳定的反应性液晶元引入基于降冰片烯骨架的液晶（LC）BCP中，该降冰片烯骨架具有形成六边形填充圆柱体的聚丙交酯少数嵌段，从而避免了这种局限性。游离的液晶元与BCP的近晶A中间相共组装，并能够在低至0.5 T的磁场中对齐。出色的磁场响应源自增强的迁移率和降低的偏析强度以及大微米级存在的综合作用系统中的谷物。我们展示了使用简单的永磁体对混合型介晶样品的鲁棒对准。聚丙交酯的蚀刻产生纳米多孔膜，而通过紫外线诱导的通过光掩模的交联进行的空间选择性微区固定化提供了用于创建对准图案的通用机制。我们预计，此处生成的纳米多孔材料可能会在膜制造或BCP光刻中找到应用，而空间图案对齐的能力对于利用LC弹性体的形状记忆效应的机械超材料的设计很有前途。

更新日期：2017-10-23

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