Mechanism and kinetics of iodide-mediated polymerization of styrene

被引:135
作者
Goto, A [1 ]
Ohno, K [1 ]
Fukuda, T [1 ]
机构
[1] Kyoto Univ, Inst Chem Res, Uji, Kyoto 6110011, Japan
关键词
D O I
10.1021/ma9712007
中图分类号
O63 [高分子化学(高聚物)];
学科分类号
070305 ; 080501 ; 081704 ;
摘要
The kinetics of the bulk polymerization of styrene in the presence of a model omega-polystyryl iodide (M-n approximate to 2000, and M-w/M-n approximate to 1.26) as mediator and benzoyl peroxide as initiator was studied. The rate of polymerization, R-p, was found to be independent of the iodide concentration, showing that the stationary concentration of polymer radicals, [P*], is determined by the balance of initiation and termination rates, as in the conventional (iodide-free) system. The pseudo-first-order activation rate constant k(act) of the model iodide was determined as a function of BPO concentration and temperature (50-80 degrees C) by both the GPC curve-resolution and polydispersity-analysis methods. The results showed that k(act) is directly proportional to [P*], which means that degenerative transfer (active species-exchanging transfer) is the only important mechanism of activation in this system. The activation energy for the transfer rate constant k(ex) was found to be 27.8 kJ mol(-1), somewhat smaller than the known activation energy for the styrene propagation rate constant k(p) of 32.5 kJ mol(-1). This indicates that lowering, rather than raising, the reaction temperature will be more effective in preparing polystyrenes with a narrower polydispersity by the iodide-mediated polymerization. This is because the most important parameter for determining the polydispersity of a degenerative-transfer-type system is the k(ex)/k(p) ratio, as has been known for some time.
引用
收藏
页码:2809 / 2814
页数:6
相关论文
共 45 条
[11]   NARROW MOLECULAR-WEIGHT RESINS BY A FREE-RADICAL POLYMERIZATION PROCESS [J].
GEORGES, MK ;
VEREGIN, RPN ;
KAZMAIER, PM ;
HAMER, GK .
MACROMOLECULES, 1993, 26 (11) :2987-2988
[12]  
GEORGES MK, 1994, TRENDS POLYM SCI, V2, P66
[13]   Critically-evaluated propagation rate coefficients in free radical polymerizations .1. Styrene and methyl methacrylate [J].
Gilbert, RG .
PURE AND APPLIED CHEMISTRY, 1996, 68 (07) :1491-1494
[14]   Mechanism and kinetics of activation processes in a nitroxyl-mediated polymerization of styrene [J].
Goto, A ;
Fukuda, T .
MACROMOLECULES, 1997, 30 (17) :5183-5186
[15]   Mechanism of controlled/''living'' radical polymerization of styrene in the presence of nitroxyl radicals. Kinetics and simulations [J].
Greszta, D ;
Matyjaszewski, K .
MACROMOLECULES, 1996, 29 (24) :7661-7670
[16]   LIVING RADICAL POLYMERIZATION .1. POSSIBILITIES AND LIMITATIONS [J].
GRESZTA, D ;
MARDARE, D ;
MATYJASZEWSKI, K .
MACROMOLECULES, 1994, 27 (03) :638-644
[17]   Controlled/''living'' radical polymerization of methyl methacrylate by atom transfer radical polymerization [J].
Grimaud, T ;
Matyjaszewski, K .
MACROMOLECULES, 1997, 30 (07) :2216-2218
[18]   MOLECULAR-WEIGHT CONTROL BY A LIVING FREE-RADICAL POLYMERIZATION PROCESS [J].
HAWKER, CJ .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1994, 116 (24) :11185-11186
[19]  
Hawker CJ, 1996, TRENDS POLYM SCI, V4, P183
[20]   Synthesis and properties of 2,2,6,6-tetramethyl-1(1-phenethyloxy)piperidine, an initiator for living free radical styrene polymerization [J].
Howell, BA ;
Priddy, DB ;
Li, IQ ;
Smith, PB ;
Kastl, PE .
POLYMER BULLETIN, 1996, 37 (04) :451-456