Chain structure polymeric networks

The silver(I) complexes with the tetrakis(methylthio)tetrathiafulvalene ligand have been reported, the nitrate salt presents a 3D structure with an unprecedented 4.16-net porous inorganic layer of silver nitrate,1160 the triflate salt presents a two interwoven polymeric chain structure.1161 The latter behaves as a semiconductor when doped with iodine. With a similar ligand, 2,5-bis-(5,5,-bis(methylthio)-l,3,-dithiol-2 -ylidene)-l,3,4,6-tetrathiapentalene, a 3D supramolecular network is constructed via coordination bonds and S"-S contacts. The iodine-doped compound is highly conductive.1162 (Methylthio)methyl-substituted calix[4]arenes have been used as silver-selective chemically modified field effect transistors and as potential extractants for Ag1.1163,1164... 

Figure 8. Part of a tetrafunctional network formed from an RA t and RBi polymerization corresponding to Mc°, the molar mass between junction points of the perfect network (a). Detail of the chain structure defining Mc° for HDl reacting with an OPPE, n is the number-average degree of polymerization of each arm with respect to oxypropylene units, (b). Part of the chain structure defining v, the number of bonds in the chain forming the smallest ring structure (C), for the reaction system in (b) (29). Reproduced, with permission, from Ref. 21. Copyright 1980, Stein-...

Most network structures involving crown ethers are simple hydrogen bonded chains where the crown forms second sphere coordination interactions with a complex ion. These are known for [18]crown-6, [15]crown-5 and [12]crown-4 hosts with a variety of metal complexes [17-25]. For instance when combined with the small [12] crown-4, the perchlorate salts of Mn(II), Ni(II) and Zn(II) form polymeric chain structures with alternating crown ethers and [M(H20)6]2+ cations [19]. Similarly the larger [18]crown-6 forms simple linear chains with metal complexes and cations such as fra s-[Pt(NH3)2Cl2] [20], [Cu(NH3)4(H20)]2+ (Fig.2) [21],and [Mg(H20)5(N03)] + [22],... 

Most of the isolated borate anions shown above may polymerize in a variety of ways to form extended chains, sheets, and networks. Polymerization occurs by either sharing an exocyclic oxygen atom or by sharing an intracyclic tetrahedral boron atom. These are exemplified by the structures of the important industrial minerals colemanite [29], Ca[6304(0H)3] H2O... 

According to the theory of rubber elasticity, the elastic response of molecular networks is characterized by two mechanisms. The first one is connected with the deformation of the network, and the free energy change is determined by the conformational changes of the elastically active network chains. In the early theories, the free energy change on deformation of polymeric networks has been completely identified with the change of conformational entropy of chains. The molecular structure of the chains... 

This review was devoted to tridimensional polymeric networks of well-defined structure, called for that reason model networks. These networks are synthesized by endlinking processes, whereby well-characterized linear precursor chains become elastically effective network chains. The model network can be considered close to... 

Taking into consideration the Si—O bonds within the glass surface, the difference between a strongly reacted layer and a highly polymerized network is difficult to define. However, with the above model the siloxane layer also contains partially polymerized structural units and/or hydrolysed remnants of the three-dimensional layer which would be expected from the random deposition of the hydrolysed APS. Consequently, some fragments may arise from pendant chains. Thus, the actual struture of the deposit will consist of a poly-siloxane probably chemically bonded to the glass surface every third silicon atom. 

When considering structural aspects of polymeric systems, solutions wherein partial polymer association occurs, must also be taken into consideration. In concentrated or semi-dilute solutions, long polymer chains can form networks through the association of short segments randomly distributed along the chains the physical association may arise from charge transfer or from hydrophobic interactions networks may also result from the presence of chains which both enter in the formation of small aggregates and connect them to one another. 

There are also carboxylates15 (Section 17-E-10), phosphates, catecholates, and oxalates. Most of the divalent iron oxalato compounds have a chain structure but the product of photoreduction of mononuclear [bipyH] [Feni(ojc)2(H20)2] gives a three-dimensional anionic polymeric network of [Fe2I(ox)3]2 1 and [Fen(bipy)3]2+ ions.16 Magnetic exchange typically occurs through the oxalate bridges.17 Six-coordinate iron(II) a-amino acid complexes are readily obtained from the reaction of the 4-coordinate Fe(mes)2(phen) and the protic amino add, AH, in THF 18... 

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