Block copolymers (BCP) self-assemble into a variety of microstructures and controlling the orientation of these structures relative to the substrate surface allows for their use in lithographic techniques. Control over the orientation is non-trivial and requires chemical treatment of the substrate or external fields that can interact and orient these BCP microstructure domains. With this research we highlight a facile thin film casting methodology that produces and orients diblock copolymer microstructure perpendicular to the substrate in the casting process itself. The films are cast from a solvent mixture with a block selective Ionic Liquid (IL) that plasticizes the BCP, enhances repulsive interactions between blocks, and screens preferential interactions between the BCP and the substrate. With a well-developed and fully perpendicular microstructure these films can find applications in sub-20nm lithography processes and as ultrafiltration membranes after selectively etching out the assembled domains.
Marianne Prévôt, Leah Bergquist, Anshul Sharma, Taizo Mori, Yungxiang Gao, Tanmay Bera, Chenhui Zhu, Michelle Leslie, Richard Cukelj, LaShanda T. J. Korley, Ernest Freeman, Jennifer McDonough, Robert Clements, Elda Hegmann
We report here on cell growth and proliferation within a 3D architecture created using smectic liquid crystal elastomers (LCEs) leading to a responsive scaffold for tissue engineering. The investigated LCE scaffolds exhibit biocompatibility, controlled degradability, with mechanical properties and morphologies that can match development of the extracellular matrix. Moreover, the synthetic pathway and scaffold design offer a versatility of processing, allowing modifications of the surface such as adjusting the hydrophilic/hydrophobic balance and the mobility of the LC moieties to enhance the biomaterial performance. First, we succeeded in generating LCEs whose mechanical properties mimic muscle tissue. In films, our LCEs showed cell adhesion, proliferation, and alignment. We also achieved creating 3D LCE structures using either metallic template or microsphere scaffolds. Finally, we recorded a four times higher cell proliferation capability in comparison to conventional porous films and, most importantly, anisotropic cell growth that highlights the tremendous effect of liquid crystal moieties within LCEs on the cell environment.
The helical nanofilament (HNF) liquid crystal (LC) phase of bent core mesogens (also commonly termed the B4 phase) is among the most unique and exotic LC phases known. The structure involves a spontaneous hierarchical self assembly of molecules leading to a supramolecular twisted rod structure with a square cross section approximately 30 nm on a side, with the length of the filaments unconstrained.
Based upon solid state NMR data, we have proposed that the helical nanofilaments actually represents an unusual assembly of organic crystalline nanoparticles, which form an LC phase, in the case of NOBOW existing in the temperature range between about 150°C and 110°C, which becomes a glass at temperatures below 110°C. That is, the HMF phase is not a typical molecular LC, but an LC of nanocrystals.
Descriptions of the structure of these nanoparticles, their LC phases, and approaches to alignment will be given. Also, the fascinating and potentially useful behavior of the HNF phase as a host for other materials (LC and non-LC) in nanostructured composites will be presented.
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