DSC Kinetics Analysis for the Synthesis of Three-Arms Poly(ε-caprolactone) Using Aluminum Tri-sec-Butoxide as Initiator

Abstract

© 2015 Wiley Periodicals, Inc. The kinetics of the ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) initiated by soluble aluminum tri-sec-butoxide (Al(OsecBu)<inf>3</inf>) has been investigated by the differential scanning calorimetry (DSC). The DSC polymerizations were carried out under nonisothermal and isothermal conditions to obtain three-arms poly(ε-caprolactone) (PCL). From nonisothermal DSC, the polymerization rate (dα/dt) increased with increasing heating rates. The values of E<inf>a</inf> were determined from Kissinger (63±2 kJ mol^-1), Friedman (31.0 - 63.0 kJ mol^-1), and Starink (64.0 - 71.0 kJ mol^-1) methods. From isothermal DSC, the dα/dt and the apparent rate constant (k<inf>app</inf>) increased with increasing polymerization temperatures. The ROP of ε-CL initiated by Al(OsecBu)<inf>3</inf> occurred via the coordination insertion mechanism. The number average molecular weight (M¯n) and percent yield of the synthesized PCL was enhanced by increasing polymerization temperature. The synthesized PCL with M¯n of 2.4 × 10⁴ was obtained using a molar ratio of monomer to Al-O active center ([M]/[Al-O]) of 400 at 150°C for 24 h. Al(OsecBu)<inf>3</inf> is one of the promising initiator due to its solubility, low transesterification reaction, and high efficiency in ε-CL polymerization.