Synthesis and characterization of microwave-assisted ring-opening polymerization of PLA-PEG-PLA triblock copolymers in the presence of Zn(Oct)<sub>2</sub> catalyst

Karabulut S. S., Bayyar S., Okur E., MÜFTÜLER A., DELİGÖZ H.

JOURNAL OF THE FACULTY OF ENGINEERING AND ARCHITECTURE OF GAZI UNIVERSITY, cilt.41, sa.1, ss.17-28, 2026 (SCI-Expanded, Scopus, TRDizin)

Özet

Purpose: This study aims to synthesize PLA-PEG-PLA triblock copolymers via microwave-assisted ring-opening polymerization (mROP) using Zn(Oct)(2) as a less toxic alternative to conventional catalysts. Theory and Methods: PLA-PEG-PLA triblock copolymers were synthesized via microwave-assisted ring-opening polymerization using L-lactide and PEG4000 as monomers and Zn(Oct)(2) as the catalyst. The monomer feed ratio was fixed at 70:30 (w/w, LA:PEG), while the catalyst amount was varied at 0.2%, 0.4%, 0.6%, 3%, and 6% by weight. Polymerizations were conducted in a closed vessel for 5 to 40 minutes under microwave irradiation. The resulting copolymers were characterized using FTIR, 1 1H NMR, DSC, GPC, and GC-MS to evaluate their structural, thermal, and molecular properties. Results: Polymerization time and yield showed a direct correlation with the amount of catalyst. Using 0.6% Zn(Oct)(2) resulted in a high polymerization conversion (99.5%) and a well-controlled molecular structure (M-n: 5,642 g/mol; M-w = 8,685 g/mol; PDI = 1.54) within 25 minutes. The microwave-assisted method dramatically shortened reaction time compared to conventional techniques, allowing high-conversion polymerization to be achieved in only 5 minutes with 3.0% catalyst. FTIR and H-1 NMR analyses confirmed the successful formation of the triblock structure, while DSC results indicated low glass transition temperatures (T-g = -19.9 degrees C) due to the presence of PEG segments. An optimal catalyst range was identified between 0.4-0.6% for balanced reactivity and structural control. Conclusion: The results indicate that Zn(Oct)(2) is a promising alternative to conventional Sn(Oct)(2) due to its high conversion efficiency, low polydispersity, and short reaction times. Moreover, microwave-assisted polymerization significantly reduced reaction times and enabled better control over molecular weight distribution compared to conventional heating.