1. The role of tri-n-butyltin(IV) n-butoxide/aluminum(III) tri-s-butoxide mixed initiators in the non-isothermal ring-opening polymerization of ε-caprolactone: from small-scale to larger-scale polymerization.
- Author
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Limwanich, Wanich, Punyodom, Winita, and Meepowpan, Puttinan
- Subjects
RING-opening polymerization ,NUCLEAR magnetic resonance spectroscopy ,DIFFERENTIAL scanning calorimetry ,POLYMERIZATION ,MOLECULAR weights ,ACTIVATION energy - Abstract
The solvent-free ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) with the tri-n-butyltin(IV) n-butoxide/aluminum(III) tri-s-butoxide mixed initiators [nBu
3 SnOnBu/Al(OsBu)3 ] was successfully studied by the non-isothermal differential scanning calorimetry for the first time. The nBu3 SnOnBu/Al(OsBu)3 mixed initiators were completely dissolved in ε-CL and could be utilized to produce high molecular weight poly(ε-caprolactone) (PCL). The presence of the Al(OsBu)3 in the mixed initiators did not interfere with the initiation temperature and could increase the propagation rate of ε-CL. The activation energies (Ea ) obtained from the peak methods of Kissinger and Ozawa for the ROP of ε-CL initiated by the nBu3 SnOnBu/Al(OsBu)3 (1.0:2.0 mol%) (74.2–78.6 kJ/mol) were lower than nBu3 SnOnBu/Al(OsBu)3 (1.0:1.0 mol%) (75.8–80.3 kJ/mol) and the single nBu3 SnOnBu initiator (78.3–82.8 kJ/mol), respectively. From the proton-nuclear magnetic resonance spectroscopy (1 H-NMR), the polymerization mechanism was proposed through the classic coordination–insertion mechanism that comprised: (i) the coordination of ε-CL and nBu3 SnOnBu with Al(OsBu)3 and (ii) the nucleophilic attacked of n-butoxy group (–OnBu) from nBu3 SnOnBu to the carbonyl carbon of ε-CL. From the small-scale synthesis (4 g) of PCL, our nBu3 SnOnBu/Al(OsBu)3 mixed initiators could control the polymerization of ε-CL by adjusting the concentration of Al(OsBu)3 . The number and weight average molecular weights (Mn and Mw ) of PCL increased with decreasing concentration of mixed initiator. The nBu3 SnOnBu/Al(OsBu)3 mixed initiators produced PCL with Mn , Mw , dispersity (Đ), and %yield in the range of 1.3 × 104 –4.0 × 104 g/mol, 2.9 × 104 –6.5 × 104 g/mol, 1.65–2.26 and 50–95%, respectively. The larger-scale polymerization (250 g) of ε-CL with the nBu3 SnOnBu/Al(OsBu)3 mixed initiators was preliminary conducted at 150 °C for 48 h. PCL with higher Mn (7.3 × 104 g/mol) and Mw (1.2 × 105 g/mol) was synthesized. The nBu3 SnOnBu/Al(OsBu)3 mixed initiators acted as an effective candidate for the production of the high molecular weight PCL via solvent-free polymerization. [ABSTRACT FROM AUTHOR]- Published
- 2024
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