Amides dielectric behavior

A second type of study that corroborates the basic assumption is any measurement which specifically shows that the H bonded species are cyclic. Infrared data can offer such evidence, provided the only important species over a wide concentration range are monomers and dimers. For such a system the peak intensities of absorption by the monomer (Im) and dimer (Id) are simply related the ratio IdIIm is a constant. Such behavior has been observed and cited in favor of cyclic dimers of S-valerolactam and of -caprolactam by Tsuboi (2050), and of y-bu-tyrolactam by Klemperer et al. (1117). However, no such deduction can be made for other amides (e.g., see 1117), phenols (e.g., see 411), or alcohols (e.g., see 1375 and 1150). There is much evidence in favor of cyclic dimers of carboxylic acids in the gas phase (1081), and some referring to solutions (1652 and 445). On the other hand, the IR data for liquid formic acid are more complicated. Ghapman (373) concludes that the liquid contains a mixture of cyclic dimers and chain polymers. Dielectric data have been interpreted to show that formic acid is not entirely dimeric (1046). By use of thermo-electric osmometry Davies and Thomas have measured AH of dimerization of several amides and have concluded that trichloroacetamide and A -methyltrichloroacet-amide form cyclic dimers, whereeis iV-methylaceteunide, iV-methylform-... 

The spectroscopic analysis and various physical, dielectric, and electrical properties of odd-numbered nylons have been sumtxtarized. Odd-numbered nylons sb polymorphism. Nylon-11 shows at least live different crystal forms. The y form seems to be the most common polymorph in many odd-numbered nylons. The piezoelectric and ferroelectric behaviors fA odd-numbered nylons such as nylon-7 and nykm-11 are comparable or belter than for PVDF and depend on the crystal form. The desired stability of the piezoelectric response in odd-munbered nylons is related to the ferroelectric reorientation of the amide group dipoles followed by densely packed hydrogen-bonded sheets in the crystalline regions induced by poling and annealing. 

As in S-PS solutions in polar solvent, a polyelectrolyte behavior was evidenced [59,69,70]. In alcoholic solutions, the effect was found to decrease with increasing solvent chain length due to the decrease of the dielectric constant [70]. The most important effect was found in dimethylacetamide solutions (a = 38), but it was surprising to find only a small effect in water solutions and no effect at all in amide solvents of dielectric constants larger than 100. Such a result was also evidenced in S-PS solutions [35]. Two explanations can be proposed either the effect occurs at lower concentration or the extension in such solvent is already maximum. 

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