Dynamic mechanical properties of poly‐α‐olefins containing ring structures in side chains

Dynamic loss modulus curves have been determined over a temperature range beginning at liquid nitrogen temperature for poly‐α‐olefin polymers containing various ring structures, i.e., phenyl, cyclohexyl, cyclopentyl, and naphthyl, in the side chain. Glass transition and appropriate secondary relaxation temperatures were observed for each polymer. Separation of each pendant ring structure from the main backbone chain by successive additions of methylene units results in lower glass‐transition temperatures. Comparison of polymers with similar side chains and different ring structures shows that the respective glass‐transition temperatures decrease in the order naphthyl > cyclohexyl > phenyl > cyclopentyl. Secondary relaxation peaks were obtained at about −150°C for polymers containing the cyclohexyl and cyclopentyl rings. A similar peak was observed for the polymer possessing a phenyl ring separated from the main chain backbone by two methylene units. The comparable polymer containing the naphthyl ring structure exhibited a broad secondary relaxation peak centered at −20°C. The polymers possessing cyclohexyl rings separated from the main chain backbone by one or two methylene units had an additional low temperature peak at −80°C. The molecular mechanism associated with this relaxation may be related to intramolecular transformations of the cyclohexyl ring between its “chair–chair” conformations.