Coordination polymers nanostructures

Nanostructures Based on Coordination Polymers 3.1 Thin Layer-by-Layer Films... 

We have reviewed recent advances in the development of hierarchical self-assembly structures on the basis of coordination polymers. The judicious combination of reversible coordination polymers with oppositely charged species allows us to fabricate a variety of nanometer-sized self-assembled structures. Formation of films, hollow spheres, micelles, microemulsions, and nanoribbons has been observed. These secondary nanostructures can be used as new functional materials. 

Supramolecular engineering gives access to the molecular information-controlled generation of nanostructures [38,39] and of polymolecular architectures and patterns in molecular assemblies, layers, films, membranes, micelles, gels, colloids, mesophases, and solids as well as in large inorganic entities, polymetallic coordination architectures, and coordination polymers. 

By thermal decomposition of the nano 2D MOCP precursors [Pb(2-pyc)(NCS)] and [Pb(3-pyc)(NCS)] (.Hpyc = pyridinecarboxylic acid) at 400°C, nanorods and nanoplates of PbS were obtained (Figure 3.4) [141]. The sizes and shapes of the nanostructures are related to the structure of the coordination polymers. An identical thermal processing on the [Pb(L4)(p3 3-NCS)(H20)] HL4 = lH-l,2,4-triazole-3-carboxylic acid) precursor has led to the formation of a mixture composed from PbS and Pb (S0 )0 nanoparticles [142]. This reveals that the composition or crystal packing of the initial MOCP may lead to different final products. 

Compared to block copolymers, there have been relatively fewer examples of using homopolymers for nanofabrication. Nevertheless, some polymers with amphiphilic properties were also used in the fabrication of nanostructures with various metal salts/complexes. For example, polyaniline (PANI) emeraldine base formed self-organized mesomorphic structures when mixed with Zn(DBS)2 by the coordination between Zn2+ and the imine nitrogen atoms on the polymer main chain.100 The resulting supramolecule PANI[Zn(DBS)2]0.5 had a comb-shaped... 

Electro-optic composite nanostructures or chiral nanostructures of conducting polymers have received great attention in the application of electro-optic nanodevices [100]. Coordination of micelle soft-template with functional dopant induced method is a simple and an efficient approach to prepare electro-optical... 

Inorganic nanoparticles such as metal/semiconductors (M/SC) immobilized in polymer matrices have attracted considerable interest in recent years due to their distinct individualistic and cooperative properties [84]. Although the control of size and shape of M/SC nanoparticles has been widely investigated, the fundamental mechanism of nanostructural formation and evolution is still poorly understood. A novel cryochemical solid-state synthesis technique has been developed to produce M/SC nanocomposites [85]. This method is based on the low-temperature cocondensation of M/SC and monomer vapors, followed by the low-temperature solid-state polymerization of the cocondensates. As a result of the method of stabilizing the metal particle without requiring any specific coordination bonds between the particle surface and the polymer matrix, generated nanoparticles (Ag-nanocrystal mean size 50 A) were embedded in the polymer matrix with well-controlled shapes and a narrow size distribution [86]. 

The fnnctionality present on the MNP surface also greatly impacts their assembly behavior. In most cases, the surface of the MNPs is passivated by an organic monolayer that protects them from aggregation and provides solubility in solvents. The particle surface also represents the interface at which the particle and polymer interact within the composite assembly. Self-assembly processes require favorable interactions between the MNP building blocks and the polymer, such that stable equilibrium (or near equilibrium) structures are formed. The types of intermolecular noncovalent interactions include hydrogen bonding, metal coordination, electrostatic, dipole-dipole, and hydrophobic interactions, as well as van der Waals forces, between MNPs and polymers. The successful self-assembly of MNPs into well-defined nanostructures not only depends on the ability to control precisely their composition, shape, and size but also on the modification of the MNP surface with the desired functionahty that mediates interactions with the polymer. 

Subsequent pyridine-assisted polymerization induced a solvophobic orthogonal interaction, based on phenyl-boron-phenyl jt-stacking, leading to dispersible nucleation. On aggregation, pyridine-coordinated boronate ester polymers are converted into planar structures via elimination of pyridine, because the trigonal planar state of the boronate ester is thermodynamically favoured over the pyridine-coordinated tetrahedral structure. As a result, spherical particles composed of lamellar nanostructures are produced, and their size depends on the minimization of interfacial free energy... 

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