ATRP总体速率与休眠物种激活速率之间的关系,Macromolecules

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ATRP总体速率与休眠物种激活速率之间的关系
Macromolecules ( IF 5.1 ) Pub Date : 2016-03-21 00:00:00 , DOI: 10.1021/acs.macromol.6b00058
Pawel Krys ₁ , Thomas G. Ribelli ₁ , Krzysztof Matyjaszewski ₁ , Armando Gennaro ₂

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原子转移自由基聚合（ATRP）的速率取决于传播的速率常数（k _p）和增长的自由基的浓度。后者与ATRP平衡常数（K _ATRP）和卤代烷，活化剂和减活化剂的浓度有关。Cu ^I / L活化卤代烷，X–Cu ^II活化自由基/ L是至关重要的过程，可在ATRP中提供良好的控制。这些反应的速率通常在整个聚合过程中是相同的，因为在基本上所有ATRP系统中都保持了ATRP平衡。有一些用ppm的铜催化剂进行的ATRP新工艺，例如通过电子转移再生的活化剂（ARGET），用于连续活化剂再生的引发剂（ICAR），补充活化剂和还原剂（SARA）以及电化学或光化学介导的ATRP（eATRP，photoATRP）。在这些过程中，如在常规自由基聚合中（或在RAFT中）一样，自由基的浓度是通过平衡自由基的产生速率（例如，来自热引发剂，还原速率或补充活化）和自由基终止（即达到稳态）来确定的。然而，在这些过程中，Cu ^I / L活化卤代烷的速率仍等于X–Cu ^II / L活化自由基的速率。烷基卤的活化率（通过Cu ^I或通过Cu ⁰）是否与ATRP的总体费用直接相关？该报告旨在阐明，Cu物种对卤代烷的活化速率不能直接与总聚合速率直接相关。许多案例具有相同的ATRP速率，但激活速率却大不相同，而案例具有相似的激活速率，但总体ATRP速率却大不相同。因此，分析方法和PREDICI模拟都清楚地表明，高催化剂负载量的正常ATRP速率以及低ppm ATRP体系（例如ICAR ATRP和SARA ATRP）的速率均不能与卤代烷的烷基卤化物活化速率直接相关。铜^我。在SARA ATRP中，Cu ^I的烷基卤化物活化总是比Cu ⁰快得多。

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Relation between Overall Rate of ATRP and Rates of Activation of Dormant Species

The rate of atom transfer radical polymerization (ATRP) depends on the rate constant of propagation (k_p) and concentration of growing radicals. The latter is related to the ATRP equilibrium constant (K_ATRP) and concentrations of alkyl halides, activators, and deactivators. Activation of alkyl halides by Cu^I/L and deactivation of radicals by X–Cu^II/L are vital processes providing good control in ATRP. Rates of these reactions are typically identical throughout polymerization, since the ATRP equilibrium is maintained in essentially all ATRP systems. There are new ATRP processes carried out with ppm of Cu catalysts, such as activators regenerated by electron transfer (ARGET), initiators for continuous activator regeneration (ICAR), supplemental activators and reducing agents (SARA), and electrochemically or photochemically mediated ATRP (eATRP, photoATRP). In these processes, as in conventional radical polymerization (or in RAFT), concentration of radicals is established by balancing rates of radical generation (e.g., from thermal initiators, reduction rate or supplemental activation) and radical termination (i.e., reaching steady state). However, in these processes, the rate of activation of alkyl halides by Cu^I/L is still equal to the rate of deactivation of radicals by X–Cu^II/L. Can the rates of activation of alkyl halides (by Cu^I or by Cu⁰) be directly related to the overall rate of ATRP? This report aims to clarify that rate of activation of alkyl halides by Cu species cannot be directly related to the overall rate of polymerization. There are many cases with the same rate of ATRP but dramatically different rates of activation and cases with similar activation rates but very different overall ATRP rates. Thus, both the analytical approach and PREDICI simulations clearly show that rates of normal ATRP with high catalyst loadings as well as rates of low ppm ATRP systems, such as ICAR ATRP and SARA ATRP, cannot be directly related with rates of activation of alkyl halides by Cu^I. In SARA ATRP, the activation of alkyl halides by Cu^I is always much faster than by Cu⁰.

更新日期：2016-03-21

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