Enhanced Poly(propylene carbonate) with Thermoplastic Networks: A Cross-Linking Role of Maleic Anhydride Oligomer in CO2/PO Copolymerization

Poly(propylene carbonate) networks with excellent properties: Terpolymerization of carbon dioxide, propylene oxide, and 4,4ʹ-(hexafluoroisopropylidene) diphthalic anhydride

Poly(propylene carbonate) (PPC) is an emerging low-cost biodegradable plastic with potential application in many fields. However, compared with polyolefin plastics, the major limitations of PPC are its poor mechanical and thermal properties. Herein, a thermoplastic PPC containing cross-linked networks, one-pot synthesized by the copolymerization of carbon dioxide, propylene oxide, and 4,4ʹ-(hexafluoroisopropylidene) diphthalic anhydride, had excellent thermal and mechanical properties and dimensional stability. The weight-average molecular weight and the polymer yield of the PPC5 were up to 212 kg mol−1 and 104 gpolym gcat −1, respectively. The 5% thermal weight loss temperature reached 320°C, and it could withstand a tensile force of 52 MPa. This cross-linked PPC has excellent properties and is expected to be used under extreme conditions, as the material can withstand strong tension and will not deform.

Cross-Linked Networks in Poly(propylene carbonate) by Incorporating (Maleic Anhydride/cis-1,2,3,6-Tetrahydrophthalic Anhydride) Oligomer in CO2/Propylene Oxide Copolymerization: Improving and Tailoring Thermal, Mechanical, and Dimensional Properties

Poly(propylene carbonate) (PPC) from CO₂ and propylene oxide (PO) has wide potential applications as a degradable "plastic". However, the thermal stability and mechanical properties of PPC cannot meet most of the application requirements. Herein, we focus on improving these properties. A (maleic anhydride/cis-1,2,3,6-tetrahydrophthalic anhydride) (MA/THPA) oligomer containing several cyclocarboxylic anhydride groups, which can copolymerize with PO, has been readily synthesized and used as the third comonomer to prepare PPC with cross-linked networks. The gel contents increase from 16 to 42% with increasing MA/THPA oligomer feed contents from 0.5 to 4 wt % of PO. The formation of cross-linked networks in PPC greatly improves the thermal, mechanical, and dimensional properties. The 5% weight-loss degradation temperature increases from 217 °C to nearly 290 °C before and after cross-linking, which ensures that PPC does not decompose in melt processing. The tensile strength of the copolymer is in the range of 22.2-44.3 MPa with elongation at break of 11-312%. The maximum tensile strength is improved by 143% compared to that of PPC. When the MA/THPA oligomer feed is above 3 wt % of PO, the hot-set elongation of the copolymer at 65 °C decreases more than 10 times when compared with that of PPC, and the permanent deformation is close to 0, while it is 145% for PPC. The dimensional stability is improved sharply. It can overcome the cold flow phenomenon of PPC. The improvement of the above comprehensive properties is of great significance to the practical application of PPC in various fields.