Electronic and steric effects of methyl substituent in samarium (III) phenolates on their initiation activities in polymerization of ε-caprolactone

被引:10
作者
Peng, Fei [1 ]
Shen, Zhiquan [1 ]
机构
[1] Zhejiang Univ, Inst Polymer Sci, Hangzhou 310027, Peoples R China
关键词
ring opening polymerization; calculations; epsilon-caprolactone; samarium (III) phenolate;
D O I
10.1002/app.26842
中图分类号
O63 [高分子化学(高聚物)];
学科分类号
070305 ; 080501 ; 081704 ;
摘要
Seven phenols with methyls substituting ortho or para hydrogens are firstly reported as ligands for Samarium (111) complexes. The resultant Samarium (111) phenolates were used as single component initiators for ring-opening polymerization (ROP) of E-caprolactone (CL). The results were in good order and met well with structural changes in phenol ligands. To explain the ordered correlation between ROP results and ligand structures of these phenolates, quantum chemical (QC) method was applied to optimize the most stable conformations for substituted phenols. QC data indicated that changes in charge distribution and geometric parameters of phenol ligands also followed certain order, which could be attributed to electronic and steric effects caused by methyl substituents. It was found that: methyl in phenol, especially single ortho one, would induce more space around metal center and easier nucleophilic attack from phenol oxygen to CL monomer, which means positive electronic effect and could induce increased initiation activity of corresponding phenolate. Meanwhile, two ortho methyls will take up considerable space around the metal center and bring along un-ignorable negative steric effect, which surpasses positive electronic effect also introduced by these two ortho methyls and finally leads to decreased activity in phenolates. This study revealed that there is correlation between the initiation characteristics of phenolates and the structures of their phenol ligands; QC calculation is a convenient, cheap, and helpful method to aid study on it. (C) 2007 Wiley Periodicals, Inc.
引用
收藏
页码:1828 / 1835
页数:8
相关论文
共 35 条
[1]  
Albertsson AC, 2002, ADV POLYM SCI, V157, P1
[2]   Recent developments in ring opening polymerization of lactones for biomedical applications [J].
Albertsson, AC ;
Varma, IK .
BIOMACROMOLECULES, 2003, 4 (06) :1466-1486
[3]   Quantitative comparison of selectivities in the polymerization of cyclic esters [J].
Baran, J ;
Duda, A ;
Kowalski, A ;
Szymanski, R ;
Penczek, S .
MACROMOLECULAR SYMPOSIA, 1997, 123 :93-101
[4]   Intermolecular chain transfer to polymer with chain scission: General treatment and determination of k(p)/k(tr) in L,L-lactide polymerization [J].
Baran, J ;
Duda, A ;
Kowalski, A ;
Szymanski, R ;
Penczek, S .
MACROMOLECULAR RAPID COMMUNICATIONS, 1997, 18 (04) :325-333
[5]  
Biela T, 2002, MACROMOL SYMP, V183, P1, DOI 10.1002/1521-3900(200207)183:1<1::AID-MASY1>3.0.CO
[6]  
2-Q
[7]  
Deng XM, 1997, J APPL POLYM SCI, V64, P1295, DOI 10.1002/(SICI)1097-4628(19970516)64:7<1295::AID-APP8>3.0.CO
[8]  
2-E
[9]   MACROMOLECULAR ENGINEERING OF POLYLACTONES AND POLYLACTIDES .4. MECHANISM AND KINETICS OF LACTIDE HOMOPOLYMERIZATION BY ALUMINUM ISOPROPOXIDE [J].
DUBOIS, P ;
JACOBS, C ;
JEROME, R ;
TEYSSIE, P .
MACROMOLECULES, 1991, 24 (09) :2266-2270
[10]   Reaction chemistry of sterically crowded tris(pentamethylcyclopentadienyl)samarium [J].
Evans, WJ ;
Forrestal, KJ ;
Ziller, JW .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1998, 120 (36) :9273-9282