合成了双(烷氧-亚胺芳氧)基钛(IV)配合物, 通过IR, 1H NMR和元素分析对其进行表征, X射线单晶衍射测定了其晶体结构. 单晶结构分析表明, 该晶体属于三斜晶系, 空间群为P , a＝14.294(9) Å, b＝16.206(10) Å, c＝18.458(12) Å, V＝3911(4) Å3, Dc＝1.098 g•cm－3, μ＝0.262 mm－1, F(000)＝1589, Z＝2, R1＝0.081, wR2＝0.240. 实验结果表明该配合物在130 ℃以上能引发D,L-丙交酯单体开环聚合, 可得数均分子量(Mn)为8.8×104 g/mol的聚(D,L-乳酸)(PDLLA). 动力学研究表明该聚合反应对D,L-丙交酯单体浓度和催化剂浓度分别呈2级和1级, 表观活化能和频率因子分别为76.63 kJ/mol和2.91×1011. 通过苄基封端聚合物1H NMR谱的研究, 表明钛配合物引发D,L-丙交酯开环聚合是基于以Ti—O键为活性中心引发D,L-丙交酯单体酰氧键断裂开环聚合的“配位-插入”机理.
胡承波
,
傅亚
,
向鸿照
,
孙娇霞
,
阮长顺
,
李香
,
向燕
,
彭琴
,
王远亮
. 双(烷氧-亚胺芳氧)基钛(IV)配合物催化D,L-丙交酯开环聚合、动力学及机理[J]. 化学学报, 2011
, 69(21)
: 2574
-2582
.
DOI: 10.6023/A1012234D
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.
