Synthesis of poly(ethylene-co-acrylic acid) via a tandem hydrocarboxylation/hydrogenation of poly(butadiene)

A high molecular weight, linear poly(ethylene-co-acrylic acid) (pEAA) was synthesized via the tandem hydrocarboxylation/hydrogenation of cis-poly(butadiene) (cis-pBD). Treatment of cis-pBD (Mn = 160 kDa) with an N,N′-diamidocarbene afforded a polycyclopropanated intermediate that was subsequently hydrolyzed (Mn = 198 kDa). Catalytic hydrogenation of the resultant poly(butadiene-co-(ethylene-alt-acrylic acid)) (pBDEAA) generated a pEAA that contained 15 mol% of acrylic acid and was isolated in up to 75% overall yield from the cis-pBD starting material. Thermal analysis revealed that the pEAA displayed an increased glass transition temperature (Tg = −10 °C) and melting temperature (Tm = 80 °C) with respect to its poly(butadiene) precursor (Tg = −108 °C; Tm = 10 °C). Likewise, when compared to a poly(ethylene) homopolymer prepared by hydrogenating the cis-pBD starting material (H2-pBD), the pEAA exhibited increased tensile strength (2.61–3.97 MPa for pEAA vs. 0.91–1.46 MPa for H2-pBD) and elongation (223–507% for pEAA vs. 12–30% for H2-pBD) but a reduced storage modulus (200 MPa for pEAA vs. 801 MPa for H2-pBA), as determined by dynamic mechanical analysis. A pEAA with a relatively low acrylic acid content (6 mol%) was also synthesized using a similar methodology and found to display thermomechanical properties that were intermediate of those described above (Tm = 93 °C; tensile strength = 2.19–2.76 MPa; elongation = 101–324%; storage modulus = 378 MPa).