A bis(alkoxy-imine-phenoxy) titanium(IV) complex was synthesized and characterized by IR, 1H NMR, elemental analysis and single crystal X-ray diffraction method. The crystal of titanium(IV) complex belongs to triclinic system with space group, P , a＝14.294(9) ?, b＝16.206(10) ?, c＝18.458(12) ?, V＝3911(4) ?3, Dc＝1.098 g•cm－3, μ＝0.262 mm－1, F(000)＝1589, Z＝2, R1＝0.081, wR2＝0.240. The ring-opening polymerization (ROP) of D,L-lactide catalyzed by the titanium(IV) complex could take place over 130 ℃ and the maximum number-averaged molecular weight (Mn) of poly(D,L-lactic acid) (PDLLA) was 8.8×104 g/mol. Kinetics experiments indicate that the polymerization shows second-order kinetics in D,L-lactide monomer concentration and first-order kinetics in catalyst concentration. The apparent activation energy (Ea) and frequency factor (A) amount to 76.63 kJ/mol and 2.91×1011, respectively. 1H NMR spectroscopy of polymer terminated by benzyl group suggests that the polymerization proceeds via a conventional coordination-insertion mechanism and Ti—O active centers initiate the cleavage of acyl-oxygen bond of D,L-lactide monomer.
HU Cheng-Bo
,
FU Ya
,
XIANG Hong-Zhao
,
SUN Jiao-Xia
,
RUAN Chang-Shun
,
LI Xiang
,
XIANG Yan
,
PENG Qin
,
WANG Yuan-Liang
. ROP of D,L-Lactide Catalyzed by Bis(alkoxy-imine-phenoxy) Titanium(IV) Complex: Kinetic and Mechanism[J]. Acta Chimica Sinica, 2011
, 69(21)
: 2574
-2582
.
DOI: 10.6023/A1012234D
