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available, to relate the observed strong dependence of HF solubility on solvent composition with the relative stabilities of some of the alkali metal acid fluorides noted previously a t lower temperatures. l 3Since LiF 4 forms quite unstable b i f l~o r i d e s~.~~ it might be predicted that the solubility of HF in LiF-ZrF4 mixtures would be smaller and less dependent on the composition of the solvent than in the corresponding NaF-ZrR mixtures.Number average molecular weight-intrinsic viscosity relationships have been determined for atactic polypropylene in three solvents. High temperature light scattering studies of olypropylene in 1-chloronaphthalene at 125' have provided weight average molecular weight-intrinsic viscosity relationskps for atactic and isotactic polypropylene. I n a thermodynamically good solvent the "K" and "a" constants from the Mark-Houwink expression are found identical for these geometrical isomers. The root-mean-square-end-to-end-distances for atactic and isotactic polypropylene in l-chloronaphthalene a t 125' were found to have experimental values in reasonable agreement with hydrodynamical theory. The calculated values of the universal hydrodynamic interaction constant (a) were in good agreement with those reported for other atactic polymers. The second virial coefficients for atactic polypro ylene differed from those of the isotactic polymer reflecting differences in thermodynamic interaction between polymer anasolvent and possibly molecular size.

Methyl α‐cyanoacrylate, when suitably inhibited by Lewis acids against anionic polymerization, can be polymerized readily with free‐radical initiators to form hard, clear, high molecular weight polymers. The ratio of kp2/kt is approximately 0.021 at 60°C. if 100% efficiency of initiation by azobisisobutyronitrile is assumed. Acceleration occurs at very low conversion to polymer during bulk polymerizations. The homopolymer is thermally unstable at temperatures only slightly above the glass temperature (estimated to be 165–170°C.). Degradation of the polymer under gamma irradiation is pronounced, only 18 e.v. being required per main‐chain scission.

synopsisCopolymerization of methyl a-cyanoacrylate with five reference monomers gave values e = +2.1 and of log Q = 0.65, with much scatter in the latter value. Alternating copolymers are formed by copolymerization with monomers of e = -0.8 or less. Bulk copolymerization with such monomers could not be accomplished, aa a rapid noncatalyzed polymerization occurred upon mixing even at 0°C. Random copolymers with methyl methacrylate could be prepared in bulk; those with ca. 10% methyl methacrylate had physical properties similar to the homopolymer of methyl a-cyanoacrylate, except that the heat distortion temperature was lowered 10-15°C. The alternating copolymers were more thermally stable than the random copolymers. Glass temperature values for alternating copolymers do not appear to agree with values predicted from equations for random copolymers.In the first paper of this series,' we discussed the free radical-initiated homopolymerization of methyl a-cyanoacrylate (MCyA) and compared its behavior with that of vinylidene cyanide. Gilbert and co-workers2 have reported an extensive study of the free radical-initiated copolymerization of vinylidene cyanide with a variety of monomers and have determined the Q and e parameters. The present study was undertaken to compare the reactivity of MCyA in similar copolymerizations arid also to determine some properties of the copolymers formed, as it was hoped that certain deficiencies in poly(methy1 a-cyanoacrylate) could be corrected in this manner. Although difficulties were encountered in the quantitative determination of reactivity ratios, the qualitative observations on the preparation and properties of these copolymers should be of interest.