Solids-like polymers

While well-established for liquid-like samples such as macromolecules in solutions [7], the applications of NMR to solid or solid-like polymers is more demanding because of the presence of anisotropic interactions that complicate the analysis of the results. Several techniques for the removal of these interactions have thus been developed and are nowadays in a state where they can be routinely applied. Non-averaged anisotropic interactions on the other hand provide valuable information that is lost in the solution state. Thus, while it is often necessary to remove the anisotropic interactions, in many cases one would simultaneously like to preserve them in order to exploit their information content. 

Molecular solids like polymers present greater problems since the creation of surfaces may involve the severence of primary (intra-molecular) or secondary (inter-molecular) bonds, or, more likely, both simultaneously. In thermoplastics it is possible to envisage molecular pull-out in which no molecules are broken but are simply separated from one another against the frictional secondary bonding forces. 

The application of temperature-dependent line shapes and the measurements of second moments in more complex organic solids like polymers followed soon after. Even nowadays, this simple method still has its place in the characterization of materials like solid polymer electrolytes where the line widths and Ti relaxation of the charge carriers provide information about their mobility that can be correlated with the electrical conductivity of the material. More detailed information can be obtained from cases in which the interaction is well defined, i.e., when an anisotropic single-spin interaction dominates the spectrum. Typical cases are the chemical shielding anisotropy (CSA) and quadrupolar interaction for which the theory is well developed. 

The temperature at which the spin-spin relaxation of protons begins to involve the Lorentzian relaxation process due to liquid-like polymer protons in addition to the Gaussian-type relaxation process due to solid-like polymer protons is considered to be a glass/rubber transition temperature. Basically, this is a critical temperature of molecular mobility as determined by NMR relaxation measurements, and is analogous to the glass transition temperature (Tg) determined by DSC. This critieal mobility temperature is referred as T- c-... 

Nonlinear Viscoelastic Response of Solid-like Polymers. The study of the nonlinear viscoelastic response of solid or solid-like polymers is one that has... 

Natural fractals, such as clouds, polymers, aerogels, porous media, dendrites, cracks, solid fracture surfaces and so on, possess only statistical self-similarity, which takes place only in the restricted range of the spatial scales [1-3, 14]. For solid-like polymers it has been experimentally shown [20] that such a range spreads from several angstroms up to several tens of angstroms. 

The obligatory use of, as a minimum, two parameters (for example, d and d at fixed d) is the key condition, following from fractality of macromolecular networks of glassy (solid-like) polymers [29]. 

Nonlinear Viscoelastic Response of Solid-like Polymers. The study of the nonlinear viscoelastic response of solid or solid-like polymers is one that has been relatively neglected. One reason is that there is no real molecular framework for the description of these materials, particularly when they are amorphous. The other reason is that many workers in the field have adopted the framework of metal plasticity and then made modifications to try to adapt it to, for example, the fact that amorphous polymers do not readily admit to treatment with the physics of dislocations. In the case of semicrystalline polymers, the... 

For solids like polymers, a number of methods are available for making the sample sufficiently transparent for transmission measurements. 

The aim of this chapter is to give a state-of-the-art report on the plastic solar cells based on conjugated polymers. Results from other organic solar cells like pristine fullerene cells [7, 8], dye-sensitized liquid electrolyte [9], or solid state polymer electrolyte cells [10], pure dye cells [11, 12], or small molecule cells [13], mostly based on heterojunctions between phthaocyanines and perylenes [14], will not be discussed. Extensive literature exists on the fabrication of solar cells based on small molecular dyes with donor-acceptor systems (see for example [2, 3] and references therein). 

It is generally thought that the ER effect happens only in nonconducting oils. Here an ER effect in solid-like matrices such as polymer gels will be discussed. The nature of the ER effect in polymer gels will be explained using the point dipole model in [44],... 

Galgali and his colleagues [46] have also shown that the typical rheological response in nanocomposites arises from frictional interactions between the silicate layers and not from the immobilization of confined polymer chains between the silicate layers. They have also shown a dramatic decrease in the creep compliance for the PP-based nanocomposite with 9 wt% MMT. They showed a dramatic three orders of magnitude drop in the zero shear viscosity beyond the apparent yield stress, suggesting that the solid-like behavior in the quiescent state is a result of the percolated structure of the layered silicate. 

The final main category of non-Newtonian behaviour is viscoelasticity. As the name implies, viscoelastic fluids exhibit a combination of ordinary liquid-like (viscous) and solid-like (elastic) behaviour. The most important viscoelastic fluids are molten polymers but other materials containing macromolecules or long flexible particles, such as fibre suspensions, are viscoelastic. An everyday example of purely viscous and viscoelastic behaviour can be seen with different types of soup. When a thin , watery soup is stirred in a bowl and the stirring then stopped, the soup continues to flow round the bowl and gradually comes to rest. This is an example of purely viscous behaviour. In contrast, with certain thick soups, on cessation of stirring the soup rapidly slows down and then recoils slightly. 

The structural chemistry of the organotin halides is dominated by their Lewis acid properties and their propensity to form five- and six-coordinate complexes. Self-association may give oligomers or polymers in the solid state, which usually dissociate in solution. The structure of tricyclohexyltin chloride in the crystal is temperature-dependent. At 108 K, it has the form of a rod-like polymer with distorted trigonal-bipyramidal tin and Sn-Cl separations of 245.6(7) and 300.77(7) pm, but at 298 K, the structure is best regarded as consisting of near-tetrahedral discrete molecules.3... 

It is possible that microbubble shell may be shattered during the interaction with an ultrasound pulse. Indeed, drastic variation of microbubble size, up to several-fold in less than a microsecond, has been reported [33], with linear speeds of the wall motion of microbubble approaching hundreds of meters per second in certain conditions. At these rates, it is easy to shatter the materials that would otherwise flow under slow deformation conditions. In some cases (e.g., lipid monolayer shells, which are held together solely by the hydrophobic interaction of the adjacent molecules), after such shattering the re-formation of the shell maybe possible in other cases - e.g., with a solid crosslinked polymer or a denatured protein shells - the detached iceberg-like pieces of the microbubble shell coat would probably not re-form and anneal, and the acoustic response of microbubbles to the subsequent ultrasound pulses would be different [34]. 

Various diverse systems qualify as gels if one assumes that in these systems the common features are the solid-like behavior and the presence of a continuous structure of macroscopic nature (6,7). For the purpose of the discussion in this paper, we describe a gel as a colloidal system comprised of a dispersed component and a dispersion medium both of which the junction points are formed by covalent bonds, secondary valence bonds, or long range attractive forces that cause association between segments of polymer chains or formation of crystalline regions which have essentially infinite life time (8). 

Table II highlights the 3C NMR relaxation times that reflect molecular motions and help define the physical properties of the cutin polymer. For those solid-like carbons that cross polarized, considerable motional freedom was evidenced for (CH2)n and CH2OCOR groups, on both MHz and kHz timescales, by the short values of Tj(C) and Tip(C), respectively. By contrast, the CHOCOR moiety was more restricted dynamically as judged from its long value of TX(C) low-frequency motions in particular were implicated by the strong dependence of Tip(C) on Bi. These latter groups...

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