Microwave Assisted Synthesis of Poly(Trimethylene Ether Glycol) with Novel ATR-FTIR Reaction Monitoring

Polytrimethylene ether glycol (PO3G) oligomers, valued for their renewable origin and alignment with Green Chemistry principles, represent a growing market with broad industrial applications. This work reports, for the first time, the microwave-assisted (MW) synthesis of PO3G via Step-Growth polymerization optimized through design of experiments (DoE). Reaction time and catalyst amount were identified as the most influential parameters for both synthetic conversion and oligomer growth, whereas MW power had minimal effect-allowing energy savings without compromising performance. Under optimal conditions, 81.6% conversion of 1,3-propanediol (1,3-PDO) to PO3G was achieved in just 10 min, with a weighted molecular size (WMS) of 7.2. In addition, a reagent-free attenuated total reflectance Fourier transformed infrared (ATR-FTIR) monitoring method was developed, providing a relative conversion degree (RCD) that correlates strongly (coefficient of determination (R²) = 0.99) with 1,3-PDO content determined by gas chromatography with flame ion detector (GC-FID). This approach enables tenfold faster analysis and real-time reaction tracking without sample preparation. The integration of MW-assisted synthesis, DoE optimization, and rapid ATR-FTIR monitoring advances both the efficiency and sustainability of PO3G production, supporting its application in high-value sectors such as cosmetics and pharmaceuticals.