Selective Synthesis of 7-/14-membered Cyclic Carbonates by Temperature Gradient-Assisted Depolymerization and...

Area of Science:

• Polymer Chemistry
• Materials Science

Background:

• Aliphatic polycarbonates (APCs) with 2- or 3-carbon spacers are synthesized via CO2/epoxide copolymerization or 6-membered cyclic carbonate ROP.
• APCs with longer (≥4-carbon) aliphatic spacers are typically made by step-growth polycondensation, facing harsh conditions and poor molecular control.

Purpose of the Study:

• To develop a new method for synthesizing APCs with longer in-chain aliphatic spacers.
• To prepare and characterize poly(1,4-butylene carbonate) (PBC) with controlled molecular weights.

Main Methods:

• A "temperature gradient-assisted" depolymerization strategy was employed for selective synthesis of 7-membered cyclic 1,4-butylene carbonate (7-CBC) and its dimer.
• Ring-opening polymerization (ROP) of 7-CBC and its dimer was catalyzed by an (amidoalkyl)pyridine-phenolate aluminum complex.

Main Results:

• The ROP yielded poly(1,4-butylene carbonate) (PBC) with tunable molecular weights ranging from 27.3 kDa to 208.4 kDa.
• PBC demonstrated significantly enhanced mechanical strength and gas barrier properties compared to HDPE, LDPE, and PCL.
• The study systematically investigated the impact of molecular weight on PBC's crystallinity, thermal, mechanical, and rheological characteristics.

Conclusions:

• The developed temperature gradient-assisted depolymerization and ROP strategy overcomes synthetic challenges associated with traditional polycondensation methods.
• This approach provides a versatile route for producing high-performance aliphatic polycarbonates with long in-chain spacers.