By studying the molecular weights of various solutions of cis‐1,4‐polyisoprene the authors arrived at the formula \documentclass{article}\pagestyle{empty}\begin{document}$$\left[ \eta \right] = \sqrt {2/c} \sqrt {\eta _{sp} - {\rm l}n\eta } _{rel} $$\end{document} which allowed the calculation of the intrinsic viscosity of the polymer solutions by a single viscosity determination. The formula was verified for different systems of polymer–solvent and the values are in accord with those obtained by extrapolation. An operating concentration of about 0.2% is recommended.

SynopsisThe properties of poly-N-vinylcaprolactam organic and aqueous solutions were studied.Aqueous solutions present a very accentuated diminishing of [ q ] from 10 to 30°C. Above 30°C. the polymer precipitates from ita aqueous solutions. The precipitation temperature does not depend on the concentration but on the molecular weight of the polymer. Some acid and basic agents have a marked inhence on [q] and the precipitation temperature of the aqueous solutions.Toluene solutions present an increasing [?] from 10 to 40°C.There are no studies about the behavior of poly-N-vinylcaprolactam solutions. It is only known that some poly-N-vinyllactams precipitate with heat from their aqueous solutions.The temperature at which the precipitation phenomenon appears is dependent on the number of C atoms of the lactamic ring: for po1y-Nvinylcaprolactam this temperature is about 35°C. and for poly-N-vinylpiperidone it is 64-65OC.lIn the case of poly-N-vinylpyrrolidone such a precipitation does not take place in the usual temperttture range (O--lOO°C.). It was admitted that this abnormal phenomenon is due to the colloidal nature of aqueous solutions of poly-N-vinyllactams,2 and it was supposed that the increasing temperature diminishes the polymer ~olvation.~ The object of the present work was the study of the behavior of po1y-Nvinylcaprolactam solutions from the viewpoint of their viscosity and of the factors that influence the temperature at which the polymer precipitates from its aqueous solutions.

The polymerization of large cyclic vinyl compounds is of considerable interest in the interpretation of the mechanism of action of complex organometallic catalysts. Numerous vinyl compounds have been investigated up to now but no study has been made of compounds containing large rings. Studies on the isotactic polymerization of vinylcarbazole have brought to light very important facts permitting of a number of inferences as to the mechanism of isotactic polymerization. Despite the large molecular volume of vinylcarbazole and the steric hindrances that should be expected due to this, a study of the polymerization kinetics has revealed reaction rates similar to those observed in the polymerization of other monomers. The study of the polymerization of vinylcarbazole and of other monomers showed that the butyllithium‐titanium chloride catalyst belongs to the class of organometallic complexes that act either by a stepwise or ionic mechanism. The specific features of complex organometallic catalysts in the polymerization of vinylcarbazole are evidently associated with preliminary activation of the active centers during which activation of the monomer also takes place. The formation of polymers with an isotactic microstructure is due to one of the possible mechanism of the catalysis, namely, to nonstepwise action. In the polymerization of vinylcarbazole in the presence of organolithium compounds and titanium tetrachloride the microstructure of the resultant polymer and the rate of polymerization depend upon the formation of other than primary complex compounds. The microstructure of isotactic polyvinylcarbazole shows a particular shape of spherulites, depending upon the nature of the catalyst.

No abstract

SynopsisBulk radical polymerization of N-vinylcaprolactam was studied at temperatures between 60 and 120'C. with different initiators. Satisfactory results were obtained with azobisisobutyronitrile, terl-butyl perbenzoate, and tert-butyl peroxide as initiators. The polymerization reaction of N-vinylcaprolectam with these initiators is first order witch respect to the monomer and 0.5 order with respect to the initiator. A linearity of the kinetic curves up to high conversions was observed. The cause of this behavior is a feeble gel effect, which also induces an increase of the molecular weight during polymerization.N-vinylcaprolactam polymerization was studied with HzOz and benzoyl peroxide as initiators at temperatures over 100°C. ; low molecular weight polymers were Satisfactory results were obtained with azobisisobutyronitrile as initiator13 but there are no published data on the kinetics of this reaction. ExperimentalThe monomer was obtained by vinylation of caprolactam with acetylene in the presence of caprolactyl N-Vinylcaprolactam was isolated from the reaction mass by distillation at reduced pressure (8-10 mm.) under argon; it then was purified by being distilled twice under argon at 8-10 mm. through a rectification column (4 = 30 mm., h = 700 mm.) filled with glass rings (4 = 4 mm., h = 5 mm.), the reflux ratio being SOTo; the fraction was collected directly in ampules at temperatures between 11O.S and 111.2"C. The ampules containing pure monomer were closed under argon. I n such conditions pure N-vinylcaprolactam (ng = 1.5057, freezing point 345°C.) may be conserved a long time at room temperature in the dark.The pure moiiomer was handled only uiider dry, inert atmosphere. The precautionary measures of purifying, conserving, and handling of the N-vinylcaprolactam were necessary because of the sensitivity of this monomer to the action of oxygen, which oxidizes rapidly to a brown-yellow compound. The presence of such compounds diminishes considerably the activity of N-vinylcaprolactam in the polymerization reaction, and the results of kinetic measurements became unreproducible. 1843