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 copolymerization of N-vinyl-E-caprolactam (VCL) with maleic anhydride (MA) in homogeneous solution of N,N-dimethylformamide at 70°C, initiated by benzoyl peroxide, is studied. VCL and MA form a 1:l charge-transfer complex which is confirmed by spectroscopic analysis. The complex is decisive in the copolymerization reaction and has an equilibrium constant of 0,2 I/mol. The reactivity ratios of the VCL-MA pair are determined as follows: rvcL = 0,006 rAM = 0,17
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