Polymers glass state

In contrast, the flexibility of amorphous polymers above the glass state is decreased when stiffening groups (structures 2.10 through 2.13) are present in the polymer backbone ... 

Polymer glasses are formed best when the macromolecular chains are irregular in structure (atactic, branched, crosslinked) so that crystallization is prevented. Regular (isotactic, syndiotactic unbranched) polymer chains form glasses only if they are cooled down so fast that crystallization is prevented such a quenching procedure freezes the material in the glassy state even if the polymer is able to crystallize. 

In the melt of a two-component system, polymer-plasticizer, the segments of a macromolecule and the molecules of the plasticizer are arranged in such a way that almost no holes exist (Figure 3a). In the glass state such an arrangement is no... 

The model of Condo permits the determination of the limiting pressure at which the glass state exists, on the basis of a reduced number of parameters (only the glass transition temperature of the pure polymer is needed to calibrate the energy parameter) for this reason, it seems particularly useful for the prediction of the plasticizing effects. 

The essential part of an ISE is the ion-selective membrane that contains fixed or mobile sites that interact with ions in the solution. The membrane is commonly based on a plasticized polymer, glass, single crystal, or a sparingly soluble salt. The back-side of the membrane is in contact with a liquid- or solid-state ion-to-electron transducer that completes the ISE. New materials, such... 

Some of the most important early experimental observations were of transitions from the quasi-brittle crazing deformation mode to the ductile shear deformation mechanisms with changes in the experimental conditions, such as temperature and strain rate, as well as in polymer variables, such as polymer backbone architecture, blend composition, crosslinking and physical aging state of the polymer glass. One of the strengths of the model of craze growth outlined above is that it allows one to make sense out of some experimentally observed craze-to-shear transitions that had previously defied explanation . The idea behind this explanation is quite simple One writes an expression for the shear yield stress, viz ... 

The development of membranes that exhibit both sensitivity and selectivity for species of interest is paramount in the application of ISEs. Between these two properties, selectivity is by far the more difficult one to achieve. Three basic types of membranes have been developed, because of their selectivity, for ISEs. These are liquid and polymer, solid state, and glass membranes. Electrodes are commercially available for numerous inorganic ions such as Na , Ag , Cu , ... 

Some orientation was retained on thermal polymerization of p-benz-amidostyrene when polymerization was carried out below the polymer glass transition temp>erature 66). Again the monomer crystal has a layer structure separating reactive radicals. The reaction proceeded in successive layers of the monomer crystal form the outside to the inside without induction period. However, the retained orientation detected by optical microscopy and infrared dichroism disappeared above the glass transition temperature of the polymer. Again no path to a polymer crystal structure seems to be available in this reaction. The polymer produced is slightly less dense than the monomer crystal since it is amorphous (6K5). Similar orientation in the amorphous state was found on polymerization of terephthalonitril oxide aystals 67). 

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