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Values of Nc, the number of chain atoms between "entanglements", were obtained for 62 flexible, semiflexible, and rodlike polymers and plotted against the corresponding values of the characteristic ratio C" or the Kuhn step length A. It was found that the polymers are nicely divisible into the three groups above.Despite some scatter, the flexible polymers fall in a band about a line described by7Vc « CJ or Nc <* A2 and more specifically, Nc s IOC*2 or Nc s (2.5 Á"2)A2. In the case of rodlike polymers, the exponential dependence is less than 1.0, but the scatter prevents closer approximations. The semiflexible polymers fall in between the two extreme classes. When Lc, the chain length between "entanglements", is plotted against C* or A, again a Lc = C"2 or Lc = A2 relationship is obtained for flexible polymers. However, when fic, the spatial distance between "entanglements" of flexible chains, is plotted, then relationships of the form Rc C* or H0«A are obtained. The observations are discussed in terms of the "entanglements" being interferences to the translational and rotational mobility of whole rodlike molecules or whole or large parts of flexible macromolecules. The empirical relationships for flexible polymers indicated above are in excellent agreement with recent theoretical expectations in the literature.

The structure of nylon 6 fibers is analyzed by x‐ray diffraction. Our results suggest that only two forms of nylon 6, α and γ, along with lattice distortion and crystallite size, are sufficient to explain the whole range of crystalline structures observed in nylon 6. The γ phase is the preferred initial form in a number of nylon 6 samples. The lattice distortion of the γ form along the chain axis varies from 0.8 to 2.4%, depending on the processing conditions. Upon annealing nylon 6 fibers, the α form is produced primarily by γ‐to‐α conversion in high‐orientation fibers, while additional α form can also crystallize from the amorphous phase in low‐orientation fibers. Finally, we show that α crystallites are favored during conditioning of poorly crystallized fibers in a humid atmosphere, and therefore fibers with α as the major crystalline form are produced upon drawing these conditioned fibers. Fibers drawn without lag time contain primarily the γ phase.

It is shown that certain isocyanate polymers are mesogenic in concentrated solutions at ambient temperatures and in bulk at elevated temperatures. These polymers may be categorized into two classes:(1) alkylisocyanate homopolymers in which the alkyl side chains are long enough to facilitate concentrated solutions, yet short enough to prevent predominant side-chain interactions; and (2) copolymers of aralkyl and alkyl isocyanate where the aromatic residue is at least two (-CH2~) units removed from the backbone. Preliminary X-ray, IR, thermal analysis, dilute solution, and mechanical properties data are also presented.

ABSTRACT:Intrinsic viscosity-molecular weight relationships were determined for poly(hexyl isocyanate) in toluene and dichloromethane using a number of narrow-distribution samples covering ·a wide molecular weight range. The data were analyzed according to the YamakawaFujii-Y oshizaki theory of viscosity of wormlike cylinders, yielding the following values for the persistence length q and molar mass ML per unit contour length: q=41-34nm and ML =730-760 nm-1 in toluene between 10 and 40°C and q=2lnm and ML=750nm-1 in dichloromethane at 20°C. These parameter values are favorably compared with those reported for other solvent conditions for the same polymer.KEY WORDS Poly(hexyl isocyanate) / Wormlike Chain / Persistence Length/ Yamakawa-Fujii-Yoshizaki Theory/ Chain Stiffness/ Stiff Chain/ Intrinsic Viscosity /

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semicrystalline polymers poly (-caprolactam) (nylon-6) and poly (ethylene terephthalate) (PET).

A model rationalizing the curve of resistivity vs volume percent of a metal-powder component in a metal/polymer composite is considered. It shows the conductivity to be directly dependent on the surface area of the conducting particles and also shows a 2/3 power dependence on their volume. Comparison with experimental results shows a good fit.