A set of best values for t he te mperatures a nd enthalpies of fusion alld transition for the n-paraffins is presented. From a n a nalysis of these data a general qualitative t heory of the phase behavior of the n-paraffins is developed. Four di stinct. crystal structures-h exagonal, t riclinic, monoclinic, and orthorhombic-describe t he solid phases of all n-paraffins with more than nine carbon atoms in the cha in. The la tter t wo structures beco me equivalent at longer chain lengt hs. Odd-even d ifferences are resolved in terms of reasonable diffet'ences in end group packing, a nd t he smooth in crease in melting a nd transition t emperature " 'ith increasing chain length is attributed to a dec rease in t he r atio of end groups to ch ain gro ups. Double t ransitions a re predicted for several pure n-paraffins a bove n-C34H 70 • Impurity effec ts are isolated from the pure n-para ffin properties a nd disc ussed. The equat ion, TM (O K ) = 414.3 (n-1. 5) ! (n + 5.0) is presented as a correct d escript ion of the m elting te mperatures (T M ) of all n-paraffins above n-C44H IlO • Suffi cient data t o p ermit an acc urate extrapolation of the enthalpie and entropies of fu sion to the infinite-c bain limit are not avail a ble.

The antipolar crystal form of poly(vinylidene fluoride) can be made piezoelectric and pyroelecric by the temporary application of electric fields in excess of 1 MV/cm at room temperature. Infrared and x-ray diffraction data reveal that the polarization occurs in two stages. At fields near 1 MV/cm, a phase transition to a polar form II occurs with presumably no change in chain conformation. Fields near 5 MV/cm cause a change in conformation to produce form I. Our results indicate that at least a portion of the residual polarization occurs within the crystal phase of the polymer.

A description is given of the molecular and morphological structure of polyvinylidene fluoride and from this description a classical model is proposed for calculating the piezoelectric and pyroelectric properties. The model consists of an array of crystal lamellae with a net moment from aligned dipoles in the crystals and compensating space charge on the crystal surfaces. The results for no compensation and complete compensation essentially bracket experimentally observed results and indicate that the largest contribution to the activity of this polymer arises from bulk dimensional changes rather than from changes in molecular dipole moments.

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flections. In a fiber diagram from a sample having cylindrical symmetry, one could imagine this pattern being spun about the central spot.