Polymer glass

In the foregoing we have described the glassy state as being a very disordered state of high modulus with neither complete internal rotational nor translational motions taking place. We now look at this in more detail. 

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Nagasawa Y, Passino S A, Joo T and Fleming G R 1997 Temperature dependence of optical dephasing in an organic polymer glass J. Chem. Phys. 106 4840-52... 

Organic polymer glass Organic sequestrants Organic sulfides Organic sulfur... 

Properties. One of the characteristic properties of the polyphosphazene backbone is high chain dexibility which allows mobility of the chains even at quite low temperatures. Glass-transition temperatures down to —105° C are known with some alkoxy substituents. Symmetrically substituted alkoxy and aryloxy polymers often exhibit melting transitions if the substituents allow packing of the chains, but mixed-substituent polymers are amorphous. Thus the mixed substitution pattern is deUberately used for the synthesis of various phosphazene elastomers. On the other hand, as with many other flexible-chain polymers, glass-transition temperatures above 100°C can be obtained with bulky substituents on the phosphazene backbone. 

Other immobilization methods are based on chemical and physical binding to soHd supports, eg, polysaccharides, polymers, glass, and other chemically and physically stable materials, which are usually modified with functional groups such as amine, carboxy, epoxy, phenyl, or alkane to enable covalent coupling to amino acid side chains on the enzyme surface. These supports may be macroporous, with pore diameters in the range 30—300 nm, to facihtate accommodation of enzyme within a support particle. Ionic and nonionic adsorption to macroporous supports is a gentle, simple, and often efficient method. Use of powdered enzyme, or enzyme precipitated on inert supports, may be adequate for use in nonaqueous media. Entrapment in polysaccharide/polymer gels is used for both cells and isolated enzymes. 

It is necessary to consider the micro-mechanical processes of polymer glasses and elastomers separately as their mechanical properties are so different. In addition, cross-linking profoundly affects the deformation processes in glasses but very little is known about the micro-mechanical processe.s that occur in single phase cross-linked glasses so the latter materials will not be discussed further. 

Just as many small-molecule materials, polymers also form glasses [4]. Actually, most polymeric materials of everyday use are made of polymer glasses, polystyrene (PS) cups or compact discs made of polycarbonates, for instance. In many respects polymer glasses are very similar to small-molecule glasses, and there is nothing special about them. However, on the other hand, the special aspects of polymer materials allow specific studies beyond characteristic studies on small-molecule glasses. 

Polymer Glass transition temp., Tg( C) Melting temp., Tm(°C)... 

In another smdy, the introduction of an adamantyl group to the poly(etherimide) structure caused polymer glass transition temperature, Tg, and solubility enhancements in some solvents like chloroform and other aprotic solvents [92]. 

This behavior shows that the dimensions of these polymers are independent of pH, ionic strength (in the ranges studied) and presence or absence of Tergitol or polyethyleneoxide. This result is of considerable help in interpretation of GPC behavior since in the absence of polymer-glass substrate interactions, the molecular weight calibration curves (log MW vs. elution volume) should be independent of pH, ionic strength or the two nonionic surfactants investigated. 

OS 76] [R 3] [P 56] After 500 h, total conversion was achieved for the micro reactor [3]. Polymer/glass rods and crushed rods were considerably less active, by a factor of 4—5 (Figure 4.86). 

Probably the best understood and most commonly used property of polymers, glass transition temperatures are important in virtually... 

Mechanical Heterogeneities in Model Polymer Glasses at Small Length Scales. 

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