Polymer complexation crystal

Structural arrangements in polymers can be exceedingly complex. Crystals are rare, but not unknown. By first growing monomer crystals of diacetylene molecules, and then photo-polymerizing them, large optical-quality polydi-acety-lene crystals can be made, for example. 

An investigation of lithium diisopropyl amide (LDA) by solid state NMR led to the observation of dramatic differences between the spectra of the solid polymer and the complex crystallized from THF. Li as well as "C and "N MAS spectra showed large sideband patterns in the former case and only a few sidebands in the latter. For both materials X-ray data are available and establish a helix structure for the polymeric material, which is insoluble in hydrocarbon or ethereal solvents, and a dimer structure of the THF complex (25, 26, Scheme 4). The obvious difference between both structures, apart from the solvent coordination in the THF complex, is the magnitude of the structural N-Li-N angle, which is close to 180° in the first case and close to 90° in the second (176° and 107°, respectively). Thus, a large difference for the electric field gradient around the Li cation is expected for the different bonding situations. 

Monodisperse spherical colloids and most of the applications derived from these materials are still in an early stage of technical development. Many issues still need to be addressed before these materials can reach their potential in industrial applications. For example, the diversity of materials must be greatly expanded to include every major class of functional materials. At the moment, only silica and a few organic polymers (e.g., polystyrene and polymethylmethacrylate) can be prepared as truly monodispersed spherical colloids. These materials, unfortunately, do not exhibit any particularly interesting optical, nonlinear optical or electro-optical functionality. In this regard, it is necessary to develop new methods to either dope currently existing spherical colloids with functional components or to directly deal with the synthesis of other functional materials. Second, formation of complex crystal structures other than closely packed lattices has been met with limited success. As a major limitation to the self-assembly procedures described in this chapter, all of them seem to lack the ability to form 3D lattices with arbitrary structures. Recent demonstrations based on optical trapping method may provide a potential solution to this problem, albeit this approach seems to be too slow to be useful in practice.181-184 Third, the density of defects in the crystalline lattices of spherical colloids must be well-characterized and kept below... 

In spite of hundreds of papers describing the phenomenology of TXN homopolymerization and TXN-DXL copolymerization (rates, Mn) on polymerization variables (cf. for example Refs. 24"48-58)), little is known as to the elementary reactions involved. Progress was hampered by the insolubility of the polymer and crystallization that occurs during polymerization. Another difficulty is the complexity of thermodynamics of TXN polymerization. 

Time-resolved luminescence of europium complexes with organic ligands is investigated in several nonpolar organic solvents, xerogel, porous glass, and opal-polymer photonic crystals. Possible explanations of nonexponential luminescence decays of Eu ions in nanostmsctured dielectric environments are discussed. 

---