Radical polymerization of vinyl monomers (styrene, methyl methacrylate, and vinyl acetate) was performed in various nanochannels of porous coordination polymers (PCPs), where relationships between the channel size and polymerization behaviors, such as monomer reactivity, molecular weight, and stereostructure, were studied. The capability for precise size tuning of nanospaces has afforded the first systematic study of radical polymerization in microporous channels based on PCPs. In this polymerization system, the polymer-growing radicals were remarkably stabilized by efficient suppression of termination reactions in the nanochannels, resulting in living radical polymerizations with relatively narrow molecular weight distributions. A significant nanochannel effect on the polymer stereoregularity was also seen, leading to a clear increase of isotacticity in the resulting polymers.

The first radical polymerisation of styrene in porous coordination polymers has been carried out, providing stable propagating radicals (living radicals), and a specific space effect of the host frameworks on the monomer reactivity is demonstrated.Since the early 1990s, the quest for porous coordination polymers (PCPs) composed of transition metal ions and bridging organic ligands has been the subject of intense research because of their potential applications in many areas, including molecular storage, separation, and exchange. PCPs is to utilize their regulated and tunable nanochannels in the field of polymerisation, which would not only allow multi-level control of polymerisation (control of stereoregularity, molecular weight, helicity, etc.), but also provide well-defined nanostructures permitting fabrication of next-generation materials. However, in spite of the potential advantages, successful attempts at polymerisation in the nanochannels of PCPs have not been reported to date. Molecules in confined nanospace have properties clearly different from those of the corresponding bulk fluids, which is called a space effect. Recently, our interest has also been focused on specific behaviours of guest molecules accommodated in the nanochannels of PCPs.2b,4 Such studies are essential for evaluation and understanding of the guest molecular properties (adsorption, reaction, conversion, alignment, etc.), and design of new functions based on PCPs. Nevertheless, little attention has been paid to guest behaviour in the nanochannels of PCPs, 5 and the relationship between the guest behaviour and its reactivity in the nanochannels has not been explored yet.[M 2 (1,4-benzenedicarboxylate) 2 (triethylenediamine)] n (1a; M 5 Zn , determined by thermogravimetric analysis (TGA). To induce polymerisation of the accommodated St, the adduct (1a[PSt) was heated with 2,29-azobis(isobutyronitrile) (AIBN) as a radical polymerisation initiator at 70 uC for 48 h (Scheme 1). The final polystyrene (PSt) composite (1a[PSt) was obtained after a thorough washing with MeOH and drying. We compare the X-ray powder diffraction (XRPD) pattern of 1a[PSt with that of 1a alone (Fig. 1). Although the peak positions of 1a[PSt were in good agreement with those of 1a, the relative peak intensities have obviously changed. Such a change in peak intensities is commonly observed for porous compounds when the pores are occupied by guest molecules, which is ascribed to the change of electron density in the pores. 2b,8 This result indicates that the channel structure of 1a was maintained during the polymerisation and the resultant PSt chain is encapsulated in the nanochannel. The TGA data of 1a[PSt show that conversion of the adsorbed St to PSt in the nanochannel of 1a is 71%. Quantitative recovery of the accommodated PSt from the host 1a was performed by decomposition of the 1a framework in 0.1 N NaOH. § Characterisation of the resultant product by solution 1 H and 13 C NMR measurements showed the typical characteristics of pure PSt.{ From the GPC measureme...

Molecules confined in nanospaces will have distinctly different properties to those in the bulk state because of the formation of specific molecular assemblies and conformations. We studied the chain conformation and dynamics of single polystyrene (PSt) chains confined in highly regular one-dimensional nanochannels of a porous coordination polymer [Zn 2(bdc) 2ted] n ( 1; bdc = 1,4-benzenedicarboxylate, ted = triethylenediamine). Characterization by two-dimensional (2D) heteronuclear (1)H- (13)C NMR gave a direct demonstration of the nanocomposite formation and the intimacy between the PSt and the pore surfaces of 1. Calorimetric analysis of the composite did not reveal any glass transition of PSt, which illustrates the different nature of the PSt encapsulated in the nanochannels compared with that of bulk PSt. From N 2 adsorption measurements, the apparent density of PSt in the nanochannel was estimated to be 0.55 g cm (-3), which is much lower than that of bulk PSt. Results of a solid-state (2)H NMR study of the composite showed the homogeneous mobility of phenyl flipping with significantly low activation energy, as a result of the encapsulation of single PSt chains in one-dimensional regular crystalline nanochannels. This is also supported by molecular dynamics (MD) simulations.