Polymérisation radicalaire du pentadiène‐1,3. I. Copolymérisation des cis et trans pentadiènes‐1,3 avec l'acrylonitrile. Détermination des rapports de réactivité

Cis (CP) and trans (TP) isomers of 1,3‐pentadiene (piperylene) were homo and copolymerized with acrylonitrile (A) in bulk and emulsion, at 50°C, using azobisisobutyronitrile and potassium persulfate as free radical initiators. The cis isomer reacts more rapidly than the trans monomer. The copolymer compositions were determined from nitrogen analysis, 100‐MHz 1H‐NMR and 25‐MHz 13C‐NMR spectra. The results thus obtained show that both the bulk and emulsion processes yield copolymers characterized by a very similar composition. Data plotted according to the Kelen‐Tüdös method indicate that the terminal‐unit model is applicable to the piperylene‐acrylonitrile system. Reactivity ratios for bulk copolymerization were as follows: rA = 0.079, rTP = 0.114, and rA = 0.033, rCP = 0.188. These values are very small and hence suggest a strong alternating tendency for acrylonitrile and 1,3‐pentadiene in both comonomer systems. This latter conclusion is corroborated by the comparison of the NMR spectra of the synthesized copolymers with that of a standard alternating sample. The reactivity (Q) and electronegativity (e) of the 1,3‐pentadiene isomers calculated from the reactivity ratios by the Alfrey—Price equations were QTP = 0.56, eTP = −0.97 and QCP = 1.215, eCP = −1.055 for trans and cis dienes, respectively.