Functional polyethylene with regularly distributed ester pendants via ring-opening metathesis polymerization of ester functionalized cyclopentene: Synthesis and characterization

•Functionalized cyclopentenes carrying −COOR (R = C1−C16 alkyl) were synthesized.•ROMP of the cyclopentene monomers with ruthenium-based HG-II catalyst were conducted.•Hydrogenation of the ROMP polymer gave PE with −COOR on every five main chain carbons.•The polymers have higher side chain Xc than polyacrylates with the same side alkyl.•The PEs present crystal lamella thickness close to length of the extended side groups.

A new series of functional polyethylene (PE) with ester pendant (−COOR, R = methyl, ethyl, n-propyl, n-butyl, n-octyl, n-dodecyl, n-tetradecyl and n-hexadecyl) on every five main chain carbons were prepared via ring-opening metathesis polymerization (ROMP) of COOR functionalized cyclopentene catalyzed by a ruthenium-based catalyst and subsequent hydrogenation of the ROMP products. High monomer conversions (70-80%) were achieved in all the ROMP reactions. Chain structure, molecular weight and molecular weight distribution (MWD) of the ROMP products and hydrogenated polymers were characterized by 1H, 13C NMR and GPC, which showed regular distribution of the COOR pendants along the main chain, moderate molecular weight and narrow MWD. Thermal properties and side chain crystallization behaviors of the functional PEs were investigated by differential scanning calorimetry (DSC). Glass transition temperature (Tg) of the polymer decreased for nearly 30 °C when R of the pendant COOR was enlarged from methyl to n-octyl, and the new polymers showed lower melting temperature (Tm), higher side chain crystallinity (Xc) and more precise side chain lamellar crystal thickness (lc) as compared with corresponding polyacrylates carrying the same side alkyl. The new polymers exhibited moderate thermal stability.

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