Solid-state polymerization layered structures

Later, Tieke reported the UV- and y-irradiation polymerization of butadiene derivatives crystallized in perovskite-type layer structures [21,22]. He reported the solid-state polymerization of butadienes containing aminomethyl groups as pendant substituents that form layered perovskite halide salts to yield erythro-diisotactic 1,4-trans polymers. Interestingly, Tieke and his coworker determined the crystal structure of the polymerized compounds of some derivatives by X-ray diffraction [23,24]. From comparative X-ray studies of monomeric and polymeric crystals, a contraction of the lattice constant parallel to the polymer chain direction by approximately 8% is evident. Both the carboxylic acid and aminomethyl substituent groups are in an isotactic arrangement, resulting in diisotactic polymer chains. He also referred to the y-radiation polymerization of molecular crystals of the sorbic acid derivatives with a long alkyl chain as the N-substituent [25]. More recently, Schlitter and Beck reported the solid-state polymerization of lithium sorbate [26]. However, the details of topochemical polymerization of 1,3-diene monomers were not revealed until very recently. 

Solid-State Polymerization of 1,4-Disubstituted Butadienes in Layered Structures... 

This article describes the solid state polymerization of 1,i-disubstituted butadiene derivatives in perovskite-type layer structures, in layered structures of organic ammonium halide salts, and in lipid layer structures. Recent investigations by spectroscopic methods and x-ray structure analyses are described. The studies clearly indicate that the photolysis in the crystalline state leads to the formation of 1,i-trans-polymers exclusively. Crystal structure analyses of monomeric and polymeric layer perovskites demonstrate that upon y-irradiation a stereoregular polymer is obtained in a lattice controlled polymerization. 

Lauher and Fowler et al. have proposed an elegant strategy for the control of topochemical polymerization based on the host-guest cocrystal concept. They used the ureylene and oxalamide functionality to form layered supramolecu-lar structures for the topochemically controlled polymerization of diacetylenes and 1,3-butadienes in the solid state [62,63]. 

There is an ill-defined boundary between molecular and polymeric covalent substances. It is often possible to recognise discrete molecules in a solid-state structure, but closer scrutiny may reveal intermolecular attractions which are rather stronger than would be consistent with Van der Waals interactions. For example, in crystalline iodine each I atom has as its nearest neighbour another I atom at a distance of 272 pm, a little longer than the I-I distance in the gas-phase molecule (267 pm). However, each I atom has two next-nearest neighbours at 350 and 397 pm. The Van der Waals radius of the I atom is about 215 pm at 430 pm, the optimum balance is struck between the London attraction between two I atoms and their mutual repulsion, in the absence of any other source of bonding. There is therefore some reason to believe that the intermolecular interaction amounts to a degree of polymerisation, and the structure can be viewed as a two-dimensional layer lattice. The shortest I-I distance between layers is 427 pm, consistent with the Van der Waals radius. Elemental iodine behaves in most respects - in its volatility and solubility, for example - as a molecular solid, but it does exhibit incipient metallic properties. 

We now turn to the 3d series elements. The dihalides and trihalides can be treated as ionic solids, although the chlorides, bromides and iodides adopt layer structures which might be better viewed as polymeric covalent crystals. In Fig. 5.2 the third ionisation energies of the 3d atoms are plotted alongside those of the lanthanides. These all involve the removal of an electron from a 3d orbital from Fe onwards, the orbital concerned is doubly occupied so that spin-pairing energy assists the ionisation. This accounts for the break between Mn and Fe, as previously discussed (Section 4.3). The increase from Sc to Mn, and from Fe to Zn, is much sharper than the corresponding increases in the lanthanide series. However, the break at the half-filled shell is less abrupt for the 3d series. This explains why the II oxidation state - which is... 

All aluminum halides can be made by direct reaction, but A1F3 is best produced by reaction with anhydrous HF. It has a structure based on corner-sharing A1F6 octahedra (similar to Re03 see Topic D3). Solid A1C13 has a polymeric layer structure, but in the gas phase or nonpolar solvents is molecular and dimeric A12C16 (see Topic C9. Structure 1). The bromine and iodide have the molecular dimeric form in the solid state. Aluminum halides are strong Lewis acids (see Topic C9)... 

A rather complicated solid-state structure is observed for the donor-free deprotonation product 4. Two independent molecular units (Fig. 3, left) are connected via polyagostic contacts between the potassium cations and trimethylsilyl carbon atoms. Two free coordination sides (indicated by dotted arrows in Fig. 3, right) are used for a further linkage, thus resulting in a polymeric layer structure. In contrast to the structure of 3a, the two independent molecular units in 4 show an average Ln-C-K angle of 90°. 

The incorporation of metals in multilayer thin films significantly extends the scope of useful characteristics associated with these films. By employing, for instance, polymeric Ru(II) complexes as polycationic species and poly(sodium acrylate) as polyanions in the layer-by-layer deposition process, efficient fight-emitting solid-state devices could be fabricated [91]. In another example, a ferrocene-containing redox-active polycation was combined with an enzyme to produce electrocatalyticaUy active enzyme/mediator multilayer structures [92]. Multilayers composed of poly(4-vinylpyridine) complexed with [Os(bpy)2Cl] / and poly(sodium 4-styrenesulfonate), for example, were used to accomplish the electrocatalytic reduction of nitrite [93]. 

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