Polymer Chemistry in Coordination Nanospaces
Since 2005, our group has reported that nanochannels in porous coordination polymers (PCPs/MOFs) are desirable fields not only for precision synthesis of polymer materials, but also for exploring specific properties of polymer confinement. The ability to control the framework structures of PCPs makes us confident that polymer synthesis at our desire is no longer a dream for the future. In addition, construction of nanohybrids between PCPs and polymers will provide unprecedented material platforms to accomplish many nanoscale functions. Considering the characteristic features of PCPs, there are many fundamental and fascinating issues about polymer chemistry that can be performed in the nanochannels of PCPs.
Nano-information transcription polymerizations
One can program nanosized information, such as channel length and dimensionality, surface functionality, and pore size and shape, into the frameworks of PCPs, because of the infinite combinations between the metal ions and organic ligands. Incorporation of monomers into the host framework can allow their programmed arrangement to be polymerized. After the polymerization, the host PCPs can be removed in mild ambient conditions, thus resulting in the isolation of polymer materials with controlled structures directly related to the nano-information of PCPs. This methodology contributes not only to multiple controls of polymer primary structures, such as molecular weight, stereostructure, reaction position, and monomer composition and sequence, but also to a dimension-controlled polymerization in layered or 3-D intersecting channels of PCPs to produce anisotropic 2-D polymer objects or porous polymer materials.
Chain-confinement chemistry
The regulated and tailor-made pore characteristics of PCPs are also of key importance for achieving unique polymer encapsulation systems. We are now able to control precisely the following features within the designable nanochannels of PCPs: (1) the number of polymer chains, (2) the environments for polymers, and (3) the chain orientations. This concept leads to quantitative analysis of low-dimensional properties of polymer assemblies (single, double, triple, ··· chains) in specific porous environments and orientations, and to the preparation of a new class of materials based on PCP–polymer hybridization. Understanding and controlling the polymer properties within the 2 nm region will give valuable information for their future applications in nanosized molecular-based devices.
Reviews
T. Uemura, S. Horike, S. Kitagawa, Chem. Asian J. 1, 36 (2006); T. Uemura, N. Yanai, S. Kitagawa, Chem. Soc. Rev. 38, 1228 (2009); T. Uemura, S. Kitagawa, Top. Curr. Chem. 293, 155 (2010).