A-bond polymers

Metal-carbon a-bonds, polymers characteristics, 12, 364 examples, 12, 378... 

At a hrst glance, a bonded polymers may be considered as being characteristically different from n bonded polymers. However, there are several systems which truly behave very much like Jt polymers. Characteristic examples include polysilanes, whose backbone is a <7 bonded silicon zig-zag chain with alkylic side groups (Rabolt et al., 1986). The similarity to the Ji-.systems results from the fact that there is an efficient overlap of adjacent orbitals leading to conjugated [Pg.381]

However, EVAL as a monolithic film is quite unsatisfactory what is required, ideally, is a multi-layer, composite film. One excellent composite, for example, is a five layer film ABCBA in which A is branched polyethylene (35 /tm), B is a bonding polymer (5 /im), and C is EVAL (8 to 12 pm). Another barrier component widely used is nylon for example, for a wide range of food packaging a typical combination is ABCBD, in which A is branched polyethylene, B is bonding polymer, C is nylon 6, and D is ethylene-vinyl... 

Ethylenediamine Formation of a bonded polymer on the surface of the electrode [382]... 

Muller M 1999 Misoibility behavior and single ohain properties in polymer blends a bond fluotuation model study Macromol. Theory Simul. 8 343... 

All the double bonds in rubber have the Z (or cis) con figuration A different polymer of isoprene called gutta-percha has shorter polymer chains and E (or trans) double bonds Gutta percha is a tough horn like substance once used as a material for golf ball covers ... 

The leader of DuPont s effort was Wallace H Carothers who reasoned that he could reproduce the properties of silk by constructing a polymer chain held together as is silk by amide bonds The neces sary amide bonds were formed by heating a dicar boxylic acid with a diamine Hexanedioic acid adipic acid) and 1 6 hexanediamme hexamethylenedi-amine) react to give a salt that when heated gives a polyamide called nylon 66 The amide bonds form by a condensation reaction and nylon 66 is an example of a condensation polymer... 

Monomer (Section 6 21) The simplest stable molecule from which a particular polymer may be prepared Monosaccharide (Section 25 1) A carbohydrate that cannot be hydrolyzed further to yield a simpler carbohydrate Monosubstituted alkene (Section 5 6) An alkene of the type RCH=CH2 in which there is only one carbon directly bonded to the carbons of the double bond Multiplicity (Section 13 7) The number of peaks into which a signal IS split in nuclear magnetic resonance spectroscopy Signals are described as singlets doublets triplets and so on according to the number of peaks into which they are split... 

Gutta percha is a natural polymer of isoprene (3-methyl-l,3-butadiene) in which the configuration around each double bond is trans. It is hard and horny and has the following formula ... 

Figure 1.10 Helical conformations in polymer molecules, (a) A vinyl polymer with R substituents has three repeat units per turn, (b) The a helix of the protein molecule is stabilized by hydrogen bonding. [From R. B. Corey and L. Pauling,/ end. Inst. Lombardo Sci. 89 10 (1955).]...

The presence of carbon—fluorine bonds in organic polymers is known to characteristically impart polymer stabiUty and solvent resistance. The poly(fluorosibcones) are siloxane polymers with fluorinated organic substituents bonded to siUcon. Poly(fluorosibcones) have unique appHcations resulting from the combination provided by fluorine substitution into a siloxane polymer stmcture (see Silicon compounds, silicones). 

Free mono- and multilayer films may be adhesive- or extmsion-bonded in the laminating process. The bonding adhesive may be water- or solvent-based. Alternatively, a temperature-dependent polymer-based adhesive without solvent may be heated and set by cooling. In extmsion lamination, a film of a thermoplastic such as polyethylene is extmded as a bond between the two flat materials, which are brought together between a chilled and backup roU. 

Because of the rotation of the N—N bond, X-500 is considerably more flexible than the polyamides discussed above. A higher polymer volume fraction is required for an anisotropic phase to appear. In solution, the X-500 polymer is not anisotropic at rest but becomes so when sheared. The characteristic viscosity anomaly which occurs at the onset of Hquid crystal formation appears only at higher shear rates for X-500. The critical volume fraction ( ) shifts to lower polymer concentrations under conditions of greater shear (32). The mechanical orientation that is necessary for Hquid crystal formation must occur during the spinning process which enhances the alignment of the macromolecules. 

The wide range of soHd lubricants can generally be classified as either inorganic compounds or organic polymers, both commonly used in a bonded coating on a matching substrate, plus chemical conversion coatings and metal films. Since solid-film lubricants often suffer from poor wear resistance and inabihty to self-heal any breaks in the film, search continues for improved compositions. 

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