Polymeric sheets

ASTM D5019, Standard Specification for Reinforced Non-Vulcanized Polymeric Sheet Used in Roofing Membrane, ASTM, Philadelphia, Pa. 

CuBr and Cu(Et2[Pg.110]

A compound with an unusual polymeric sheet structure of [Cp2PbCp(TFIF)Na]3 rings is obtained from the... 

Lieb WR, Stein WD (1969) Biological membranes behave as non-porous polymeric sheets with respect to the diffusion of non-electrolytes. Nature 224 240-243. 

This problem has also been more durably addressed by modifying the surface properties of the polyolefin materials used to form polymeric sheets, by graft-copolymerizing to those surfaces a monomeric substance which, after copolymerization, confers hydrophilic properties and, in some cases, ion exchange properties. This technique has been found to be practical when the porous substrate is formed from PE, which has been found to lend itself well to a graft-copolymerization reaction of this kind. However, it has been found that when such a reaction is... 

Many ceramics are partially polymeric in structure. These include the new superconductive materials that exist as polymeric sheets connected by metal ions similar to many of the silicate sheets. 

The compounds M(NH3)2Ni(CN)4 (M = Zn or Cd), which consist of two-dimensional polymeric sheets of tetracyanonickelate ions bridged by coordinating diamminemetal(II) cations, function as host lattices for clathration of small aromatic molecules such as thiophene, furan, pyrrole or pyridine IR studies indicate the presence of hydrogen bonding between the host lattice ammonia and the aromatic guest molecules.132,133 A crystal structure determination of the related clathrate Cd(en)Ni(CN)4(pyrrole)2 has been reported.134 Similarly, the complex Cd(py)2Ni(CN)4 consists of polymeric [Cd—Ni(CN)4] layers held together by Cd-bound pyridine.135... 

The reaction of Cu(II) halides with Cu(R2Dtc)2 complexes was reported to give polymeric materials (270). At a later date the exact nature of these products was probed and, by means of the reaction of Cu(PipDtc)2 with CuBr2, complexes of the type Cu(PipDtc)2(CuBr) (n = 4, and 6) were isolated. The structures of these molecules have been determined and consist of polymeric sheets of individual Cu(PipDtc)2 molecules linked to polymeric CuBr chains by way of Cu-S bonds (Table IX). The Cu(PipDtc)2(CuG)4 homologue is x-ray isomorphous and probably isostructural with the corresponding bromo compound. 

The polymers which have been used to illustrate problems of inorganic polymer formation have been lieteroatomic. that is, their chains are built from different atoms alternating with each other. The other structure mentioned has been homoatomic—all the atoms in the chain are the same. There aie only a few homoatomic polymers of airy promise. Most elements will form only cyclic materials of low molecular weight if they polymerize at all. In addition to the silane polymers, black phosphorus, a high-pressure modification of the element, forms in polymeric sheets. 

Fig. 14. A portion of the layer network of OnlGeCt CHaCC H). The alkyl carboxylate groups, which have been omitted for clarity, alternate above and below the polymeric sheet.

FIGURE 70. Unit cell contents of (323tet)2(PbBr2)3 down a, showing the polymeric sheet note also the quasi-anti-square-prismatic environment of cationic Pb(2). Reproduced by permission of the Australian Academy of Science and CSIRO from Reference 130... 

A two-dimensional polymeric sheet-like structure was reported for Me2Sn(S03F)2305 and a polymeric zigzag chain for chlorotris(j2-methylsulphonylphenyl)tin, ISnCldVdLt-S02CH3-p)31 (142)306. In 142, the tin atoms are pentacoordinated as a result of a weak intermolecular Sn—O interaction of 3.046(5) A. Only one out of the three p-methyl-sulphonylphenyl groups is involved in coordinative oxygen-tin bonds. 

As already indicated, a feature common to all clay minerals is the two-dimensional polymeric sheet which is composed of interlinked Si04 tetrahedra. These siloxane, O—Si—O, hexagonal (or tetrahedral ) sheets are constructed from three of the four available oxygen atoms at the comers of the tetrahedra. The spare apical oxygens are directed away (upwards or downwards) from each sheet. 

Vaginal films are produced with polymers such as polyacrylates, polyethylene glycol, polyvinyl alcohol, and cellulose derivatives. Proper combination of these polymer is essential to achieve adequate mucoadhesion and optimal drug release profiles. Vaginal films can be produced by casting [132], in which polymer solutions containing the active substance(s) are poured into adequate molds and dried until a thin, solid, and flexible polymeric sheet is formed. Afterward, the sheet is cut in small pieces (individual films) and peeled off. 

The complexes Q[Sb4F13] (Q = K, Rb, Cs, Tl, NH4) form an isomor-phous series (98,99) in which the [E4F13] unit is present as a tetramer of SbF3 units, with a central fluoride anion in the center of the Sb4 square and weaker Sb-F-Sb bridging interactions between the tetra-mers, giving rise to an infinite two-dimensional polymeric sheet. The structure of the potassium salt (93) is shown in Fig. 31. 

The coordination environment of germanium in Me2Ge(CN)2 is close to tetrahedral however, the intermolecular N Ge distances of 3.84 A indicate a weak association . An analogous tin dicyanide Me2Sn(CN)2 forms infinite polymeric sheets as a result of intermolecular N Sn interactions of 2.68 A. The tin atom has a strongly distorted octahedral environment as is illustrated by the C—Sn—C angles of 148.7° for the trans-Me2Sn moiety and of 85.3° for the cA-Sn(CN)2 moiety. 

Figure 100 Portion of the polymeric sheets formed from association of (LiCl)3(TMEDA)2.

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