Well-Defined Polymer-Brush-Coated Rod-Shaped Particles: Synthesis and Formation of Liquid Crystals

• Published in: Macromolecules 2016-11, Vol.49 (22), p.8430-8439
• Main Authors: Huang, Yun, Sasano, Tatsuya, Tsujii, Yoshinobu, Ohno, Kohji
• Format: Article
• Language: English
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/acs.macromol.6b02266

The surface of hematite rods (α-Fe2O3 rods; aspect ratio = 6, semimajor axis = 600 nm) was modified by surface-initiated atom transfer radical polymerization (SI-ATRP). The copper-catalyzed SI-ATRP of methyl methacrylate (MMA) was conducted on the surface of the initiator-fixed α-Fe2O3 rods using a free (sacrificial) initiator, ethyl 2-bromo­isobutyrate. Well-defined poly­(MMA) (PMMA) brushes were densely grafted on the rods with a chain density of up to 0.7 chains/nm2. These hybrids composed of a rod-shaped particle as the core and a PMMA brush as the shell were highly dispersed in any of “good solvents” for PMMA. Double-layer (organic layer/inorganic layer)-coated α-Fe2O3 rods were also fabricated by grafting PMMA brushes on the surface of silica-coated α-Fe2O3 rods. The α-Fe2O3 cores of the hybrid rods were etched with hydrochloric acid, affording hollow hybrid rods. Polarized optical microscopy confirmed the formation of lyotropic liquid crystals by the rods grafted with polymer chains of a proper length.