Glassy state polymer

At the beginning of the polymerization reaction, the viscosity of the medium is low, and efficient rotation (about the ethylenic double bond and the single bond linking ethylene to the phenyl ring) accounts for the low fluorescence quantum yield. After a lag period, when approaching the polymer glassy state, the fluorescence intensity increases rapidly as a result of the sharp increase in... 

As alternative the authors of Ref. [28] assumed, that besides the indicated above binary hooking netwoik in polymers glassy state another entanglements type was available, nodes of whieh by their structure were similar... 

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... 

The phenomenon observed here, which is common to most polymerization reactions, demonstrates that polymers can interfere sterically with processes involving movement of parts of the guest molecules (fluorescent probes). As the polymer glassy state is approached, the relative free volume diminishes sharply, and the medium viscosity increases rapidly mobility becomes restricted and the deactivation rate of the probe becomes controlled by the microscopic free volume provided by the polymer. This accounts for the abrupt increase in fluorescence until the limiting conversion is reached, at which point fluorescence levels off. 

Let us first consider two identical polymers, one deuterated and the other not, in a melt or a glassy state. The two polymers (degree of polymerization d) differ from each other only by scadermg lengths and b. If the total number of molecules is N, x is the volume fraction of the deuterated species x = N- / N, with Aq -t = A). According to equation (B1.9.116), we obtain... 

The average polymer Enjoys a glassy state, but cools, forgets To slump, and clouds in closely patterned minuets. 

New photochromic dyes with electrocycHc reactions have been proposed on the basis of 1,5-electtocycHzation of heterogenous pentadienyl—anions (124). StiH newer are investigations into the photocycHzation of 2,4,6-tri-isoptopylbenzophenones for vinyl polymers ia the glassy state (133). 

Fig. 19. Generalized modulus—temperature curves for polymeric materials showing the high modulus glassy state, glass-transition regions for cured and uncured polymers, plateau regions for cross-linked polymers, and the dropoff in modulus for a linear polymer.

The Metravib Micromecanalyser is an inverted torsional pendulum, but unlike the torsional pendulums described eadier, it can be operated as a forced-vibration instmment. It is fully computerized and automatically determines G, and tan 5 as a function of temperature at low frequencies (10 1 Hz). Stress relaxation and creep measurements are also possible. The temperature range is —170 to 400°C. The Micromecanalyser probably has been used more for the characterization of glasses and metals than for polymers, but has proved useful for determining glassy-state relaxations and microstmctures of polymer blends (285) and latex films (286). 

Transition region or state in which an amorphous polymer changed from (or to) a viscous or rubbery condition to (or from) a hard and relatively brittle one. Transition occurs over a narrow temperature region similar to solidification of a glassy state. This transformation causes hardness, brittleness, thermal expansibility, specific heat and other properties to change dramatically. 

Fig. 29. Observed and calculated 2H NMR spectra for the mesogenic groups of a) the nematic (m = 2), b) the smectic (m = 6) liquid crystalline polymer in the glassy state, showing the line shape changes due to the freezing of the jump motion of the labelled phenyl ring. The exchange frequency corresponds to the centre of the distribution of correlation times. Note that the order parameters are different, S = 0.65 in the frozen nematic, and S = 0.85 in the frozen smectic system, respectively...

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