Triblock Copolymers from CO2, Propylene Oxide, and p-Tosyl Isocyanate of Higher Toughness than Polyethylenes

In this report, a series of ABA triblock copolymers composed of a poly(propylene carbonate-co-propylene oxide)s (PPPC) middle block flanked by two poly(N-tosyl propylene urethane) (PTPU) outer blocks were synthesized in one-pot, using a difunctional initiator in the presence of triethyl borane (TEB). In the first step, the central PPPC block was obtained through the copolymerization of propylene oxide (PO) with CO2. Varying the polymerization pressure of CO2, the carbonate content in the PPPC central block could be adjusted, giving access to PPPC blocks with different glass transition temperatures. In the second step, p-tosyl isocyanate (TSI) was subsequently added and copolymerized with the remaining PO, affording the growth of two outer PTPU blocks without any incorporation of polyether or polycarbonate and the formation of well-defined ABA triblock copolymers as confirmed by 1H NMR and size exclusion chromatography (SEC). Their thermal and mechanical properties were measured using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and universal testing machine (UTM). PTPU-b-PPPC-b-PTPU (U-PC-U) triblock copolymers with PTPU (hard blocks) weight fraction of 28% and 80–85 wt % of carbonate content in the middle PPPC block show higher toughness than commercial polyolefins.