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Molecular recognition is of paramount importance for modern chemical processes and has now been achieved for small molecules using well-established host-guest chemistry and adsorption-science principles. In contrast, technologies for recognizing polymer structure are relatively undeveloped. Conventional polymer separation methods, which are mostly limited in practice to size-exclusion chromatography and reprecipitation, find it difficult to recognize minute structural differences in polymer structures as such small structural alterations barely influence the polymer characteristics, including molecular size, polarity, and solubility. Therefore, most of the polymeric products being used today contain mixtures of polymers with different structures as it is challenging to completely control polymer structures during synthesis even with state-of-the-art substitution and polymerization techniques. In this context, development of novel techniques that can resolve the challenges of polymer recognition and separation is in great demand, as these techniques hold the promise of a new paradigm in polymer synthesis, impacting not only materials chemistry but also analytical and biological chemistry.In biological systems, precise recognition and translation of base monomer sequences of mRNA are achieved by threading them through small ribosome tunnels. This principle of introducing polymers into nanosized channels can possibly help us design powerful polymer recognition and separation technologies using metal-organic frameworks (MOFs) as ideal and highly designable recognition media. MOFs are porous materials comprising organic ligands and metal ions and have been extensively studied as porous beds for gas separation and storage. Recently, we found that MOFs can accommodate large polymeric chains in their nanopores. Polymer chains can spontaneously infiltrate MOFs from neat molten and solution phases by threading their terminals into MOF nanochannels. Polymer structures can be recognized and differentiated due to such insertion processes, resulting in the selective adsorption of polymers on MOFs. This enables the precise recognition of the polymer terminus structure, resulting in the perfect separation of a variety of terminal-functionalized polymers that are otherwise difficult to separate by conventional polymer separation methods. Furthermore, the MOFs can recognize polymer shapes, thus enabling the large-scale separation of high purity cyclic polymers from the complex crude mixtures of linear polymers, which are used as precursor materials in common cyclization reactions. In solution-phase adsorption, many factors, including molecular weight, terminal groups, polymer shape, polymer-MOF interaction, and coexisting solvent molecules, influence the selective adsorption behavior; this yields a new liquid chromatography-based polymer separation technology using an MOF as the stationary phase. MOF-packed columns, in which a novel separation mode based on polymer insertion into the MOF operates under a dynamic insertion/rejection equilibrium at the liquid/solid interface, exhibited excellent polymer separation capability. The polymer recognition principle described in this study thus has a high probability for realizing previously unfeasible polymer separations based on monomer composition and sequences, stereoregularity, regioregularity, helicity, and block sequences in synthetic polymers and biomacromolecules.

Metal–organic frameworks (MOFs) composed of metal ions and organic ligands have been extensively studied over the last few decades owing to their versatile porous structures with controllable sizes...

Summary Selective molecular adsorption using metal-organic frameworks (MOFs) has been firmly established as an effective technique in modern separation science. However, polymer insertion into MOFs remains inadequately investigated, probably owing to the large conformational disadvantages commonly associated with spontaneous intercalation processes. Meanwhile, it has been demonstrated that in situ formation of polymers is possible in well-designed nanochannels of MOFs. Being able to take full advantage of the polymer intercalation mechanism would help us devise powerful macromolecular recognition and separation technologies with unprecedented selectivity. Here, we discuss the prospects of polymer recognition using programmed MOF nanospaces, which can be realized via selective intercalation of polymer chains in MOF hosts. Designing nanosized porous MOFs with a regular arrangement of reactive/interactive/responsive entities offers the possibility of universal polymer recognition that cannot be accomplished by conventional methods.

Polymers with two-dimensional (2D) network topologies are currently gaining significant attention due to their unique properties that originate from their regulated conformations. However, in contrast to conventional 1D- and 3D-networked macromolecules, the synthesis of such 2D networks provides challenges for polymer chemists because of the nature of the networking polymerisation reaction, which occurs in a spatially random fashion when conventional solution-phase synthesis is performed. Here we report a versatile synthesis of polymeric monosheets with unimolecularly thick networking architectures by exploiting the 2D nanospaces of metal–organic frameworks (MOFs) as reaction templates. Crosslinking radical polymerisation in the 2D nanospaces of pillared-layer-type MOFs affords monosheets of typical vinyl polymers and can be carried out on the gram scale. Remarkably, the prepared polymer monosheets are highly soluble in organic solvents and show atypical thermal and rheological properties that result from their 2D-regulated conformations that cannot be adopted by their 1D or 3D analogues., Unlike 1D and 3D-networked macromolecules, the synthesis of 2D molecular networks is challenging because of the nature of the polymerisation reaction. Here the authors report the synthesis of polymeric monosheets with unimolecularly thick networks by exploiting the 2D nanospaces of metal–organic frameworks as reaction templates.

Recent developments in controlling polymer assemblies using metal–organic frameworks (MOFs) are covered in this highlight review. The characteristic features of MOFs are their highly tailorable and...

Here, we report an unprecedented chirality transfer from a metal-organic framework (MOF) to a polymer. In this work, unsubstituted polythiophene (PTh) was prepared in the nanochannels of a chiral MOF. Circular dichroism spectroscopy revealed that nanoconfinement of the polymer chains could endow optically inactive PTh with a chiral nature. The thickness of polymer chain assemblies could be controlled by tuning the loading amount of PTh, which resulted in a drastic change in the chiroptical properties. Note that PTh liberated from the host still exhibited chirality even without the chiral support. Remarkably, the recovered PTh presented high thermal stability of chirality up to 250 °C. Our findings show that the encapsulation of the polymer chains in chiral MOFs is a simple and effective methodology not only to express the chirality of polymers but also to elucidate the inter- and intrachain chirality in polymer assemblies.

Metal–organic frameworks (MOFs) have recently emerged as a new class of porous materials. Highly ordered and tunable structures of MOFs can serve as a universal platform for controlled polymer synthesis as well as high-precision polymer recognition. In addition, the integration of MOFs and polymers can achieve host–guest synergies, leading to the emergence of intriguing composites with tailored architectures. The integration of MOFs and polymers has provided new aspects for both MOF and polymer chemistry. In this chapter, we highlight recent advances in the hybridization of MOFs and polymers.

The preparation of metal-organic structures with a controlled degree of disorder is currently one of the most promising fields of materials science. Here, we describe the effect of guest polymer chains on the transformation of a metal-organic framework (MOF). Heating a pillared MOF at a controlled temperature resulted in the exclusive removal of the pillar ligands, while the connectivity of the metal-organic square-grid layers was maintained. In the absence of a polymer, 2D-layers rearranged to form a new crystalline phase. In contrast, the presence of a polymer in the MOF inhibited totally the recrystallization, leading to a turbostratic phase with layers threaded and maintained apart by the polymer chains. This work demonstrates a new synthetic approach toward the preparation of anisotropic metal-organic materials with controlled disorder. It also reveals how guests can dramatically modify the conversion of host MOFs, even though no chemical reaction occurs between them.

Conjugated organic frameworks are an interesting class of functional porous organic materials having a π-conjugated backbone with permanent porosity. These materials are potential candidates for optoelectronic applications. Although there are several reports on the structure–property relationship between π-conjugated building blocks and optoelectronic performance, the influence of the linker position is hitherto unknown. We report two novel imine-linked 2D π-conjugated polymers which are positional isomers of each other consisting of pyrene and anthracene units. The polymers exhibited similar optical and electronic properties under ambient conditions. Upon I2 doping, one of the isomers exhibited high radical density and enhanced conductivity due to energetically favoured chemical oxidation. The linker position dramatically affects the optoelectronic performance of these polymers even though they have the same π-conjugated backbone.

The purification step in the manufacturing of cyclic polymers is difficult as complete fractionation to eliminate linear impurities requires considerable effort. Here, we report a new polymer separation methodology that uses metal-organic frameworks (MOFs) to discriminate between linear and cyclic polyethylene glycols (PEGs) via selective polymer insertion into the MOF nanopores. Preparation of a MOF-packed column allowed analytical and preparative chromatographic separation of these topologically distinct pairs. In addition, gram-scale PEGs with only cyclic structures were successfully obtained from a crude reaction mixture by using MOF as an adsorbent.

Unlike commonly used molecular recognition techniques, recognition of polymer structures requires an additional aspect of extremely high recognition ability, by which marginal structural differences can be identified in a large polymer chain. Herein we show that metal–organic frameworks (MOFs) can recognize polymer terminal structures, thus enabling the first reported chromatographic separation of polymers. End-functionalized polyethylene glycols (PEGs) are selectively inserted into the MOF channel, the insertion kinetics being dependent on the projection size of the PEG terminus. This size-selective insertion mechanism facilitates precise discrimination of end-functionalized PEGs using liquid chromatography (LC). An MOF-packed column thus provides an efficient and easily accessible method for the separation of such end-functionalized polymers using conventional LC systems.

Separation of high-molecular-weight polymers differing just by one monomeric unit remains a challenging task. Here, we describe a protocol using metal-organic frameworks (MOFs) for the efficient separation and purification of mixtures of polymers that differ only by their terminal groups. In this process, polymer chains are inserted by threading one of their extremities through a series of MOF nanowindows. Selected termini can be adjusted by tuning the MOF structure, and the insertion methodology. Accordingly, MOFs with permanently opened pores allow for the complete separation of poly(ethylene glycol) (PEG) based on steric hindrance of the terminal groups. Excellent separation is achieved, even for high molecular weights (20 kDa). Furthermore, the dynamic character of a flexible MOF is used to separate PEG mixtures with very similar terminal moieties, such as OH, OMe, and OEt, as the slight difference of polarity in these groups significantly changes the pore opening kinetics., The separation of high molecular weight polymers composed of the same number of monomeric units remains highly challenging. Here, the authors show that efficient separation and purification of mixtures of polymers that differ only by their terminal groups can be achieved through polymer threading in metal-organic framework channels.

The design of monomer sequences in polymers has been a challenging research subject, especially in making vinyl copolymers by free-radical polymerization. Here, we report a strategy to obtain sequence-regulated vinyl copolymers, utilizing the periodic structure of a porous coordination polymer (PCP) as a template. Mixing of Cu2+ ion and styrene-3, 5-dicarboxylic acid (S) produces a PCP, [Cu(styrene-3, 5-dicarboxylate)] n , with the styryl groups periodically immobilized along the one-dimensional channels. After the introduction of acrylonitrile (A) into the host PCP, radical copolymerization between A and the immobilized S is performed inside the channel, followed by decomposing the PCP to isolate the resulting copolymer. The predominant repetitive SAAA sequence in the copolymer is confirmed by monomer composition, NMR spectroscopy and theoretical calculations. Copolymerization using methyl vinyl ketone also provides the same type of sequence-regulated copolymer, showing that this methodology has a versatility to control the copolymer sequence via transcription of PCP periodicity at the molecular level., 連結分子の並びを巧みに制御できる高分子合成法を開発 --DNAのように分子情報を転写--. 京都大学プレスリリース. 2018-01-24.

The development of highly porous metal–organic frameworks (MOFs) is greatly sought after, due to their wide range of applications. As an alternative to the development of new structures, we propose to obtain new stable configurations for flexible MOFs by insertion of polymeric guests. The guests prevent the otherwise spontaneous closing of the host frameworks and result in stable opened forms. Introduced at a fraction of the maximal capacity, polymer chains cause an opening of the occupied nanochannels, and because of the MOF reticular stiffness, this opening is propagated to the neighboring nanochannels that become accessible for adsorption. Composites were obtained by in situ polymerization of vinyl monomers in the nanochannels of an otherwise nonporous MOF, resulting in homogeneously loaded materials with a significant increase of porosity (SBET = 920 m2/g). In addition, by limiting the accessible configurations for the framework and forbidding the formation of a reactive intermediate, the polymeric gu...

Polymerization of monosaccharide monomers usually suffers from the production of polysaccharides with ill-defined structures because of the uncontrolled random reactions among many reactive hydroxyl groups on saccharide monomers. In particular, rational synthesis of polysaccharides with porosity approximating molecular dimensions is still in its infancy, despite their usefulness as drug carriers. Here, we disclose an efficient synthetic methodology for the preparation of polysaccharides with controllable mesoporosity in the structure, utilizing [Cu3(benzene-1,3,5-tricarboxylate)]n (HKUST-1; 1) as templates. Cationic ring-opening polymerization of 1,6-anhydro glucose was performed in nanochannels of 1, followed by removal of the host frameworks, giving polysaccharide particles as replicas of the original molds. Nitrogen adsorption measurement revealed that the obtained polysaccharide particles contained high mesoporosity in the structure, which could be controlled systematically depending on the polymeriza...

The properties of polymeric materials can be amplified by macromolecular alignment. The highly ordered chain alignment of unsubstituted polythiophene, an unprocessable polymer, has been achieved using a porous coordination polymer (PCP) as a template. Due to the extended conjugation system, the obtained anisotropic polymer particles exhibit higher conductivity than that of polythiophene prepared by solution polymerization.

Metal-organic frameworks (MOFs) have received much attention because of their attractive properties. They show great potential applications in many fields. An emerging trend in MOF research is hybridization with flexible materials, which is the subject of this review. Polymers possess a variety of unique attributes, such as softness, thermal and chemical stability, and optoelectrical properties that can be integrated with MOFs to make hybrids with sophisticated architectures. Hybridization of MOFs and polymers is producing new and versatile materials that exhibit peculiar properties hard to realize with the individual components. This review article focuses on the methodology for hybridization of MOFs and polymers, as well as the intriguing functions of hybrid materials.

Controlled synthesis and assembly of polymer chains is highly important to tune or enhance the properties of the polymeric materials. Kinetic approach using host–guest chemistry can allow rational design of chain assemblies with many functional properties. Metal-organic frameworks (MOFs), composed of metal ions and organic ligands, have nanopores that can be tuned in terms of pore size, shape, surface, and flexibility. Thus, employing the nanochannels of MOFs for controlled polymerizations is an attractive idea, which allows multilevel controls of primary structures of resulting polymers by efficient through-space inductions and specific host–monomer interactions. Use of MOFs as removable templates can also give polymer specific assemblies with highly aligned or intimately blended structure.

The mechanical strength of metal-organic frameworks (MOFs) is highly relevant for their practical applications. In this research, we show that encapsulation of polymer chains into MOF nanochannels can effectively restrain the breakage of coordination bonding in MOFs and inhibit the amorphization under high physical pressure. The hardness of single MOF crystals was greatly improved, which depended on the direction of the inserted polymers, as revealed by nanoindentation analysis. Insertion of polymer chains did not influence the crystal structure of MOFs, which indicates that this approach should be highly promising for improving the mechanical properties of MOFs.

Strong interchain interactions render unsubstituted polythiophene un-fusible, non-melting, and insoluble. Therefore, control of the packing structure, which has a profound effect on the optical and electronic properties of the polymer, has never been achieved. Unsubstituted polythiophene was prepared in the one-dimensional channels of [La(1,3,5-benzenetrisbenzoate)]n, where polymer chains form unprecedented assembly structures mediated by the host framework. It is noteworthy that the emission and carrier transport properties were drastically changed by varying the number of chains within a particular assembly. The response of the composite to additional guests is also examined as a method to use the composites as low-concentration sensors. Our findings show that the encapsulation of polymer chains in host materials is a facile method for understanding the intrinsic properties of conjugated polymers, along with controlling and enhancing their functions.

Insertion of polymers into microporous metal–organic frameworks (MOFs) appeared recently as a powerful strategy to accomplish very difficult separations. However, the dynamics of their insertion remains to be fully unravelled. In this article, we describe the spontaneous insertion of poly(ethylene glycol) (PEG) into a flexible MOF. Thanks to the structural changes upon PEG insertion, in situ powder X-ray diffraction (PXRD) analysis could be performed. For PEGs with identical main chains, the insertion speed was strongly dependent on the nature of the terminus. Furthermore, a concentration dependence for terminal groups was observed, providing insight into the pore-opening mechanism, and suggesting a mildly cooperative terminus-first insertion. This establishes polymers as very valuable tools to study MOF dynamics, as their extended size allows domains with clearly different properties within the same macromolecule.

The quest for porous coordination polymers (PCPs) has been the subject of intense research because of their unique porous functions. Although considerable attention has been paid to the behavior of gases and low-molecular-weight compounds in PCPs, the study of adsorption, diffusion, and interaction of macromolecules, including oligomers and polymers, in PCPs at the molecular level has been limited to date. Here, we have studied the dynamic behavior of oligomeric chain molecules, both theoretically and experimentally, in [Zn2(bdc)2(ted)]n (1; bdc = 1,4-benzenedicarboxylate, ted = triethylenediamine). Molecular dynamics simulations revealed that the motion of linear oligomeric chains, such as oligo(ethylene glycols) or paraffins, is composed of smooth transfer along the large channels and slow transfer to the adjacent channels by penetrating the narrow apertures of 1. Moreover, this anisotropic behavior depends on the polarity of the guest chains because of the Coulomb interactions with the polarized apertu...

Thermal ring-opening polymerization of the unsymmetrically substituted [1]ferrocenophane was performed in one-dimensional nanochannels of porous coordination polymers (PCPs). In contrast to conventional thermal polymerization in bulk, formation of cyclic polymer was inhibited in the channels. In addition, the tacticity of the resulting polymer was dependent on the pore size of PCPs.

Radical cyclopolymerization of difunctional monomers based on 1,6-diene components was performed in one-dimensional channels of porous coordination polymers (PCPs). Although bulk or solution polymerization of the monomers usually gives cross-linked insoluble polymers, the unfavorable interpolymer reactions were effectively suppressed in the narrow nanochannels of PCPs to provide soluble linear polymers. The pore matrices and functionality of PCPs can be readily designed by changing the organic ligands, so that polymerization of the diene monomers in different sized pores was examined. The primary structures of the resulting polymers, such as branching, cyclic structure, and stereoregularity, were changed, depending on the pore characteristics of the PCPs.

Controlled organization of polymer chains into ordered structures is highly important to tune or enhance the properties of the polymeric materials. A supramolecular approach using host-guest chemistry has allowed rational design of chain assemblies with many functional properties. Nanoporous materials with ordered channel structures are particularly useful for attaining precise assemblies of polymer chains through nanoconfinement.

Nonspherical polymer particles have been efficiently prepared in different morphological crystals of porous coordination polymers (PCPs) by in situ radical polymerization of styrene and methylmethacrylate, followed by removal of the host PCP frameworks in aqueous tetrasodium ethylenediaminetetraacetate (Na-EDTA) solution. In this replication process, the isolated vinyl polymer particles retained the size and morphologies of the original PCP particles, although the polymer chains were not stabilized by cross-linking. This morphological retention of vinyl polymers after the isolation from the PCP matrixes was ensured by the rigidity and porosity of the polymers, which was confirmed by DSC and adsorption measurements. The unconventional assembly of polymer chains in the particles is of interest from the viewpoints of functional properties of the polymer particles.

Chain alignment can significantly influence the macroscopic properties of a polymeric material, but no general and versatile methodology has yet been reported to obtain highly ordered crystalline packing of polymer chains, with high stability. Here, we disclose a strategy that relies on 'ordered crosslinks' to produce polymeric materials that exhibit a crystalline arrangement. Divinyl crosslinkers (2,5-divinyl-terephthalate) were first embedded, as substitutional ligands, into the structure of a porous coordination polymer (PCP), [Cu(terephthalate)triethylenediamine0.5]n. A representative vinyl monomer, styrene, was subsequently polymerized inside the channels of the host PCP. The polystyrene chains that form within the PCP channels also crosslink with the divinyl species. This bridges together the polymer chains of adjacent channels and ensures that, on selective removal of the PCP, the polymer chains remain aligned. Indeed, the resulting material exhibits long-range order and is stable to thermal and solvent treatments, as demonstrated by X-ray powder diffraction and transmission electron microscopy.

Controlling the condensed state of multiple guests in nanoporous media is critical to many applications, but an understanding of this phenomenon in pores smaller than a few nanometers is still unavailable. In this work, we investigate the aggregation state of binary guests, poly(ethylene glycol) (PEG), and long-chain normal alkanes, in subnanometer channels of a porous coordination polymer (PCP) by monitoring their thermal transition behaviors. PEG and alkanes are immiscible in the bulk and their melting transitions are not affected by each other. Meanwhile, in the PCP nanochannels, the transition temperature and the heat of the binary–guest system were significantly different from when PEG or an alkane was individually included. This suggests the formation of microscopically segregated domain structures of PEG and alkane in the host crystal. The transition behaviors gradually varied by changing the introduction ratio between PEG and alkane, and thus the aggregation states of the two guests were successfu...

Porous coordination polymers (PCPs) have been recently highlighted because of their high synthetic designability in structure and functions. Because of their ordered nanoporous structures with a large surface area and tunable pore surface functionality, PCPs have emerged as a significant class of nanoporous materials with potential applications in gas storage, separation, catalysis, and chemical sensing. Recent research has shown the utility of PCPs as host materials for the confinement of nanoparticles of inorganic polymers (IPs), such as metals, metal oxides, and metal chalcogenides. The fabrication of IP nanoparticles in PCPs (PCP⊃IP) has been studied for manifesting specific nanosized-dependent properties and host-guest synergistic functions. In this review, we describe the recent progress in the accommodation of IPs in the nanochannels of PCPs and the remarkable functions of the composite materials.

Porous coordination polymers (PCPs) have been recently highlighted because of their high synthetic designability in structure and functions. Because of their ordered nanoporous structures with a large surface area and tunable pore surface functionality, PCPs have emerged as a significant class of nanoporous materials with potential applications in gas storage, separation, catalysis, and chemical sensing. Recent research has shown the utility of PCPs as host materials for the confinement of nanoparticles of inorganic polymers (IPs), such as metals, metal oxides, and metal chalcogenides. The fabrication of IP nanoparticles in PCPs (PCP⊃IP) has been studied for manifesting specific nanosized-dependent properties and host-guest synergistic functions. In this review, we describe the recent progress in the accommodation of IPs in the nanochannels of PCPs and the remarkable functions of the composite materials.

We report on the formation of single poly(N-vinylcarbazole) (PVCz) chains in one-dimensional channels of [La(1,3,5-benzenetrisbenzoate)](n), where the side carbazolyl groups of the confined PVCz are effectively π-stacked. This ideal conformation of PVCz chains in the coordination nanochannels contributed to a drastic increase in hole mobility, which was 5 orders of magnitude higher than that in the bulk state. It is also noteworthy that PVCz isolated from the nanchannels still had a high hole mobility.

Recently, Metal-Organic Frameworks (MOFs) or Porous Coordination Polymers (PCPs) composed of transition metal ions and bridging organic ligands have been extensively studied. The characteristic features of PCPs are highly regular channel structures, controllable channel sizes approximating molecular dimensions, designable surface potentials and functionality, and flexible frameworks responsive to guest molecules. Owing to these advantages, successful applications of PCPs range from molecular storage/separation to heterogeneous catalysts. In particular, use of their regulated and tunable nanochannels for a field of polymerization has allowed multi-level controls of polymerization (controls of stereoregularlity, molecular weight, etc.). Here I report on recent progress in polymerization utilizing the nanochannels of PCPs, and demonstrate why this polymerization system is attractive and promising, from the viewpoints of precision controls of polymer structures.

In nature, biopolymers are efficiently synthesized by multilevel arrangements of monomers within constrained molecular-level spaces. These biological systems produce regio- and stereoregular polyme...

The development of a new methodology for visualizing and detecting gases is imperative for various applications. Here, we report a novel strategy in which gas molecules are detected by signals from a reporter guest that can read out a host structural transformation. A composite between a flexible porous coordination polymer and fluorescent reporter distyrylbenzene (DSB) selectively adsorbed CO₂ over other atmospheric gases. This adsorption induced a host transformation, which was accompanied by conformational variations of the included DSB. This read-out process resulted in a critical change in DSB fluorescence at a specific threshold pressure. The composite shows different fluorescence responses to CO₂ and acetylene, compounds that have similar physicochemical properties. Our system showed, for the first time, that fluorescent molecules can detect gases without any chemical interaction or energy transfer. The host-guest coupled transformations play a pivotal role in converting the gas adsorption events into detectable output signals.

Radical polymerization of vinyl monomers was performed in nanochannels of porous coordination polymers with unsaturated metal sites, [M(1,3,5-benzenetrisbenzoate)] (1Al, M = Al3+; 1Eu, M = Eu3+; 1Nd, M = Nd3+; 1Y, M = Y3+; 1La, M = La3+; and 1Tb, M = Tb3+). In this system, the polymerization behaviors are strongly dependent on the Lewis acidity of the metal sites. For example, polymerizability of monomers was influenced by the metal sites because of the interaction with the monomers. From the viewpoint of streteoregularity, composition of isotactic unit in the resulting poly(methyl methacrylate) (PMMA) increased as the Lewis acidity of the hosts becomes higher. Although discrete Tb3+ ions are not effective for changing the stereoregularity of PMMA in solution polymerization system, nanochannels of 1Tb gave PMMA with the increase in the isotactic unit, showing that the metal ions embedded in the pore walls of PCPs are useful for controlling stereoregularity of polymers.

1 / 1 Institute for Integrated Cell-Material Sciences (iCeMS), Kyoto University Title: Fabrication of Two-Dimensional Polymer Arrays: Template Synthesis of Polypyrrole between Redox-Active Coordination Nanoslits Author: N. Yanai, T. Uemura, M. Ohba, Y. Kadowaki, M. Maesato, M. Takenaka, S. Nishitsuji, H. Hasegawa, and S. Kitagawa Journal: Angew. Chem. Int. Ed., Vol. 47, No. 51, 9883-9886 (2008) Abstract: Oxidative and intercalative polymerization of pyrrole was conducted within the nanoslits of a layered coordination open framework containing redox-active sites. Isolation of polypyrrole from the host framework led to stacked sheet polymer objects whose orientation and morphology are directly related to the original coordination polymer template.

Layer-by-layer (LBL) self-assembled ultrathin films were prepared via consecutively alternating immersion of substrates into solutions of electron donor, poly(dithiafulvene) (PDF), and electron acceptor, poly(hexanyl viologen) (6-VP). The charge transfer (CT) interaction formed at solid–liquid interfaces between the backbones of the electron acceptor and donor polymers was the driving force of the alternative deposition. The sandwich heterostructure of the LBL film led to electrical anisotropy in the directions parallel and perpendicular to the film surfaces. Incorporation of gold nanoparticles into the LBL films was investigated by reducing gold ions with the PDF layers already deposited on the film surfaces, or depositing PDF-protected gold colloidal solution as the electron donor layers directly. The influence of the gold nanoparticles on the electrical anisotropy of the LBL films was also illustrated in this research. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1608–1615, 2007

The establishment of methodologies for the mixing of immiscible substances is highly desirable to facilitate the development of fundamental science and materials technology. Herein we describe a new protocol for the compatibilization of immiscible polymers at the molecular level using porous coordination polymers (PCPs) as removable templates. In this process, the typical immiscible polymer pair of polystyrene (PSt) and poly(methyl methacrylate) (PMMA) was prepared via the successive homopolymerizations of their monomers in a PCP to distribute the polymers inside the PCP particles. Subsequent dissolution of the PCP frameworks in a chelator solution affords a PSt/PMMA blend that is homogeneous in the range of several nanometers. Due to the unusual compatibilization, the thermal properties of the polymer blend are remarkably improved compared with the conventional solvent-cast blend. This method is also applicable to the compatibilization of PSt and polyacrylonitrile, which have very different solubility parameters., The intimate mixing of immiscible polymers is desirable both to aid understanding of the fundamental science and for the development of new materials. Here, the authors successfully compatibilize polystyrene and poly(methyl methacrylate) using a porous coordination polymer as a removable template.

Radical polymerization of unpolymerizable sterically hindered butadiene was successfully performed in the nanochannels of porous coordination polymers because of the effective suppression of unfavourable termination reactions. Microstructures of the resulting polymer could also be tuned depending on the structure of the porous hosts.

Inspired by elegant polymerizations in biological systems, polymer synthesis in confined artificial nanospaces is a key challenge in the control of polymer structures and the design of well-defined nanostructures. In this regard, porous coordination polymers (PCPs) have a wide range of advantages, such as regular channel structures, controllable pore size, dynamic and flexible pores, and unique surface potentials and functionality, which can be utilized for precisely controlled polymerization and polymer arrangement. This Focus Review describes recent progress in polymerization in the nanochannels of PCPs and demonstrates why this polymerization system is so attractive and promising, from the viewpoints of three essential polymerization processes in PCPs, that is, monomer arrangement, polymerization methods, and control of polymer structure.

This review highlights the recent progress of nanosize crystals based on coordination polymers (CP). Development of synthetic method with controllable size and shape in nanometer regime as well as ...

Prussian blue (PB) nanoparticles protected by organic polymers such as poly(vinylpyrrolidone) (PVP) and poly(diallyldimethylammonium chloride) (PDDA) were prepared. Different experimental conditions (concentrations of Fe ions and feed ratios of Fe to the polymers) have been investigated to control the size of the PB nanoparticles. For example, the averaged dimensions of the PB nanoparticles were tuned from 12 to 27 nm by use of PVP in the different conditions. Addition of PDDA produced the PB nanoparticles with very small dimensions (5-8 nm) by an effective electrostatic interaction. We found that the surface environments of the PB nanoparticles affect the inherent properties of PB. The shifts of charge transfer (CT) absorptions from Fe(2+) to Fe(3+) in the PB nanoparticles resulted from the surface-protecting polymers. Especially, the PB nanoparticles with the PVP protection show high solubility in a variety of organic solvents and a solvent-dependent CT absorption. Measurement of the magnetic properties of the PB nanoparticles showed unprecedented size-dependency, surface effect, and superparamagnetic properties.

A stable colloidal form of novel π-conjugated polydithiafulvene (PDF)-protected PbS nanoparticles was first prepared in a nonaqueous solution at room temperature. The results of X-ray diffraction (XRD) and transmission electron microscopy (TEM) images demonstrated that the synthesized PbS nanoparticles of stable colloidal form were of cubic rock-salt structure with narrow size distribution. The average diameters of PDF-protected PbS nanoparticles were controllable by varying the initial concentrations of the lead and sulfur sources in the reaction systems. The absorption spectra and electrochemical properties of the protected PbS nanoparticles have been investigated. It was found that the PDF influenced strongly the excitonic absorption peaks of the protected PbS nanoparticles.

New π-conjugated polymers (2) with the thioketene dimer unit were prepared by cycloaddition polymerization of bis(thioketene) derived from bis(triphenylphosphonium chloride) (1). The structures of the polymers were compared with that of 2,4-dibenzylidene-1,3-dithietane (3), which was prepared by dimerization of phenylthioketene derived from benzyltriphenylphosphonium chloride, by use of IR and 1 H NMR. The lower energy absorption edges of 2 were located at longer wavelengths than that of the model compound 3, due to developments of π-conjugations in 2. The cyclic voltammogram of 3 showed irreversible two-step oxidation peaks at 0.25 and 0.61 V vs Ag/Ag', indicating that the electron-donating ability of 3 is stronger than that of tetrathiafulvalene (TTF). The electron-donating properties of the polymers 2 were also confirmed by cyclic voltammetry and were found to depend on aromatic structures in 2. The polymer 2 formed charge-transfer (CT) complexes with TCNQ (1:1 ratio of the repeating unit in 2 to TCNQ) in DMSO. The degrees of CT in the complex were investigated by UV and IR measurements. In the solid state, the complex of 2b contained partially charge-transferred TCNQ (degree of CT = 0.59), resulting in higher conductivity than that of 2a.

New polymers containing an intramolecular charge-transfer (ICT) structure (pyridinium–dithiafulvene–pyridinium) in the main chain were prepared. UV–vis measurements of the polymers suggested that conjugative effects occur through saturated polymethylene chains, and that such effects are enhanced as the length of the spacer polymethylene chain decreases. Polyviologens showed small but similar conjugations in their UV–vis measurements. A PM3 calculation of 1,1′-(1,2-ethanediyl)bis(pyridinium) suggested that low-lying LUMO resulting from an interaction between the σ* of the ethylene unit and π* of the pyridinium moiety affords the conjugative effect. The PM3 calculations and the UV–vis results show that the incorporation of the ICT moiety in the polymeric framework increases the conjugative effect through the polymethylene chains. The redox and conducting properties of the ICT polymers were also investigated. Both studies gave some implications of the conjugative effects of the polymers.

Electron-donating π-conjugated polymers with dithiafulvene moiety (4) or with diselenafulvene moiety (5) were prepared by cycloaddition polymerization of chalcogenoketenes derived from aromatic diy...

Controlled organization of polymer chains into ordered structures is highly important to tune or enhance the properties of the polymeric materials. A supramolecular approach using host-guest chemistry has allowed rational design of chain assemblies with many functional properties. Nanoporous materials with ordered channel structures are particularly useful for attaining precise assemblies of polymer chains through nanoconfinement.

Polymerization by cycloaddition between aldothioketene and its alkynethiol tautomer (derived in situ from a diyne) leading to the formation of dithiafulvene unit-linked polymers has been studied. Two aromatic diynes [bis(4-ethynyldiphenyl)methane (1a) and 4,4′-diethynyldiphenyl ether) (1b)] were used as starting materials with the aim of obtaining non-π-conjugated methylene- and oxygen-bridged aromatic poly(dithiafulvene)s. The poly(dithiafulvene) derived from bis(4-ethynyldiphenyl)methane can be considered as an interesting precursor to a small band-gap polymer having alternating aromatic and quinonoid moieties. Further, two aliphatic diynes [1,7-octadiyne (3a) and 1,9-decadiyne (3b)] were subjected to cycloaddition polymerization to obtain aliphatic poly(dithiafulvene)s containing localized electron-rich dithiafulvene units. The polymers obtained were characterized by IR, 1H NMR, gel permeation chromatography, and cyclic voltammetry. The electron-donating property of the polymers was evident from the charge-transfer (CT) complex formation with an electron acceptor 7,7,8,8-teracyanoquinodimethane. The CT complexes were characterized by IR, 1H NMR, and ultraviolet–visible spectroscopies. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3593–3603, 2001