Glassy state structural components

Glassy state structural components distinction defines their behavior distinctions in both deformation [46] and relaxation [47] processes. It is known [48, 49], that in its turn polymers glassy state includes a substates number, differing by mechanical properties temperature dependences. A breaking (bend) on the corresponding parameter dependence, for example, of yield stress on temperature, is a typical indication of transition from one substate to another. At present unequivocal structural identification of these states is... 

In this section we will discuss the molecular structure of this polymer based on our results mainly from the solid-state 13C NMR, paying particular attention to the phase structure [24]. This polymer has somewhat different character when compared to the crystalline polymers such as polyethylene and poly(tetrameth-ylene) oxide discussed previously. Isotactic polypropylene has a helical molecular chain conformation as the most stable conformation and its amorphous component is in a glassy state at room temperature, while the most stable molecular chain conformation of the polymers examined in the previous sections is planar zig-zag form and their amorphous phase is in the rubbery state at room temperature. This difference will reflect on their phase structure. 

On the other hand, in the solid-state high resolution 13C NMR, elementary line shape of each phase could be plausibly determined using magnetic relaxation phenomenon generally for crystalline polymers. When the amorphous phase is in a glassy state, such as isotactic or syndiotactic polypropylene at room temperature, the determination of the elementary line shapes of the amorphous and crystalline-amorphous interphases was not so easy because of the very broad line width of both the elementary line shapes. However, the line-decomposition analysis could plausibly be carried out referring to that at higher temperatures where the amorphous phase is in the rubbery state. Thus, the component analysis of the spectrum could be performed and the information about each phase structure such as the mass fraction, molecular conformation and mobility could be obtained for various polymers, whose character differs widely. 

The glassy state of materials refers to a nonequilibrium, solid state, such as is typical of inorganic glasses, synthetic noncrystalline polymers and food components. Characteristics of the glassy state include transparency, solid appearance and brittleness (White and Cakebread 1966 Sperling 1992). In such systems, molecules have no ordered structure and the volume of the system is larger than that of crystalline systems with the same composition. These systems are often referred to as amorphous (i.e., disordered) solids (e.g., glass) or supercooled liquids (e.g., rubber, leather, syrup) (Slade and Levine 1991 Roos 1995 Slade and Levine 1995). 

One of the blends whose aging properties have been extensively studied is PMMA/ PEO (Shimada and Isogai 1996 Vemeletal. 1999 Slobodian etal.2(X)6a,b Rihaetal. 2007). The blend consists of a fuUy amorphous polymer (PMMA) and a ciystallizable component (PEO). Miscibility in the melt state occurs when the PMMA content is above 70-80 %, but phase separation in the glassy state has been reported as indicated by the appearance of heterogeneous structures with domain sizes of 20-70 nm. 

Hence, the cluster model of polymers amorphous state structure allows to identify structural relaxation mechanisms in them. In the case of glassy loosely packed matrix relaxation process is realized by conformational reorganizations in this structural component (mechanism I) and in the case of its devitrification - clusters mutual motions (mechanism II). 

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