Ether linkage in poly(1,2-propylene carbonate), a key structure factor to tune its performances

As an alternating copolymer of CO₂ and propylene oxide, poly(1,2-propylene carbonate) (PPC) should be composed of fully carbonate structure, whereas it generally contains certain ether linkage due to the existence of competitive formation of ether linkage by consecutive epoxide enchainment. Though the ether linkage was not always the dominant structure in PPC, a new understanding was provided in that the ether linkage was crucial structure factor on the PPC performances, especially for oxygen barrier property, transparency, thermal and mechanical properties. The gas barrier properties and transparency of PPC film became worse with increasing ether linkages, the oxygen, nitrogen and carbon dioxide permeability of PPC with ether linkage of 0.6 % were 14 cm³/m²/24 h/0.1 MPa, 11 cm³/m²/24 h/0.1 MPa and 220 cm³/m²/24 h/0.1 MPa, respectively, while for PPC with ether linkage of 54.1 %, they became 116 cm³/m²/24 h/0.1 MPa, 108 cm³/m²/24 h/0.1 MPa and 599 cm³/m²/24 h/0.1 MPa, respectively. When the ether linkage in PPC increased from 0.6 % to 54.1 %, the thermal decomposition temperature at 5 wt% loss(T _d-5% ) increased from 218.6 °C to 241.0 °C, while the glass-transition temperature(T _g ) decreased from 45.2 °C to 11.1 °C, meanwhile, the room temperature tensile strength decreased from 55.4 MPa to 2.3 MPa, and the elongation at break increased from 8.5 % to 1558.2 %.