Probes in polymers

The analysis viscoelasticity performed by David Roylance [25] is a nice outline about the mechanical response of polymer materials. This author consider that viscoelastic response is often used as a probe in polymer science, since it is sensitive to the material s chemistry and microstructure [25], While not all polymers are viscoelastic to any practical extent, even fewer are linearly viscoelastic [24,25], this theory provide a usable engineering approximation for many applications in polymer and composites engineering. Even in instances requiring more elaborate treatments, the linear viscoelastic theory is a useful starting point. 

A.M. Wasserman, A.L. Kovarsky, Spin marks and probes in polymers physical chemistry, Moscow Nauka (1986) (in Russian). 

A.M. Wasserman, Spin Labels and Spin Probes in Polymers. In Book Electron Spin resonance, 15, London The Royal Society of Chemistry (1996). 

Table 22. Nuclear properties of some important nuclei used as probes in polymer electrolytes and their comparison with protona (taken from Ref. 267)...

Table 4.3 Factors influencing diffusion of probes in polymer solutions...

Temperature dependence of emission in type B polymers has been discussed in Section III. In studies using type A probes in polymers, in general phosphorescence at low temperatures has been used. 

Berne and Pecora s text [16] is sometimes incorrectly cited as asserting that eq 12 is uniformly correct for light-scattering spectra. The analysis in Berne and Pecora [16] correctly obtains eq 12. However, this analysis refers the special case of a system in which particle displacements are governed by the simple Langevin equation. In these s tems, particle displacements in successive moments are uncorrelated. However, in a viscoelastic system, the polymer solution has a memory particle displacements in successive moments are no longer uncorrelated. With respect to probes in polymer solutions, Berne and Pecora s analysis is only applicable at times mtich longer than any viscoelastic relaxation times. 

In the above, virtually the entirety of the published literature on polymer self-diffusion and on the diffusion of chain probes in polymer solutions has been reviewed. Without exception the concentration dependences of Dg and Dp are described by stretched exponentials in polymer concentration. The measured molecular weight dependences compare favorably with the elaborated stretched exponential, eq. 16, except that, when P M or M P, there is a deviation from eq. 16, that deviation referring only to the molecular weight dependences. The deviation uniformly has the same form The elaborated stretched exponential overestimates the concentration dependence of Dp, so that at elevated c the predicted Dp/Do is less than the measured Dp/Dp. Contrarywise, almost without exception the experimental data on solutions is inconsistent with models that... 

The dynamics of spin probes in polymers is often characterized by Tsog, the temperature for which the extreme separation is 50 G, corresponding to AArei = 0.5 and Tc 3.5 ns. Below Tsog the nitroxide is in the slow tumbling regime and... 

Singh PK, Kumbhakar M, Pal H, Nath S (2008) Effect of electrostatic inteiactimi on the location of molecular probe in polymer-surfactant supramolecmar assembly a solvem relaxation study. J Phys Chem B 112 7771-7777... 

Abstract This chapter discusses the potential of fluorescence correlation spectroscopy (PCS) to study polymer systems. It introduces the technique and its variations, describes analysis methods, points out advantages and limitations, and summarizes PCS studies of molecular and macromolecular probes in polymer solutions, polymer gels, polymer nanoparticles, and polymeric micellar systems. In addition, a comparison with other experimental methods is presented and the potential of a combination with simulations discussed. 

Sixth, as observed at the beginning of the chapter, electrophoretic drift is affected by multiple local forces. The electrokinetic drag depends on events within the Debye layer, in ways that could be manipulated by changing the ionic strength of the solution. Systematic studies of the effect of solution ionic strength (and hence k) on electrophoretic mobility for probes in polymer solutions might clarify matters. 

Eor probes in polymer solutions, q may differ markedly from the macroscopically measured viscosity q. 

This equation may be inverted to give an apparent hydrodynamic radius r or a microviscosity rip. as determined by Dp and other parameters. For probes in polymer solutions, t]p often differs greatly from the directly-measured q, typically with Ppconcentration dependence of Dp will primarily be compared with... 

In general D q,t) has a nontrivial q -dependence, so it is equally generally incorrect to replace D q,t)t with a -independent F t), hence the closing inequality in the above equation. In a viscoelastic fluid, such as most polymer solutions, the elastic moduli are frequency-dependent. The fluctuation-dissipation theorem then substantially guarantees that the random thermal forces on probe particles have nonzero correlation times, so probe motions in polymer solutions are not described by Markoff processes. The mathematically correct discussion in Berne and Pecora on Brownian particles, including Eq. 9.5, therefore does not apply to probes in polymer solutions. 

Spin trapping, spin labels and spin probes in polymers and biological systems... 

Our objective in choosing to study these particular probes in polymer matrices is that the monomer lifetime of pyrene is over twenty times longer than that of the carhazolyl or the phenyl-anthryl group. The lifetime of the excited pyrene group is 184 ns in meso-DIPP and 235 ns in meso-BIPEE in a PB film at - 90°C, so that the two molecules are appropriate probes for investigation of the relaxation phenomena in the time range 10 - 10 s. 

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