Understanding dispersity control in photo-atom transfer radical polymerization: Effect of degree of polymerization and kinetic evaluation
Understanding dispersity control in photo-atom transfer radical polymerization: Effect of degree of polymerization and kinetic evaluation
复制标题
DOI：
10.1002/pol.20210319
复制
发表时间：
2021-06-05
影响因子：
3.4
通讯作者：
Anastasaki, Athina
中科院分区：
文献类型：
--
作者：
Rolland, Manon;Lohmann, Victoria;Anastasaki, Athina
在光原子转移自由基聚合（ATRP）中，分散性可以通过改变失活剂浓度来有效地控制。在这项工作中，我们提供了一系列条件下进行详细的动力学分散控制的光ATRP机制的见解。对于较低分散性的聚合物，观察到常规的一级动力学曲线，伴随着数均分子量（M-n）随转化率的线性演变，而反应达到中等至高转化率（66%至93%）。然而，当目标是高分散性的聚合物时，M-n在整个聚合过程中保持相对恒定，并且反应在转化率小于50%时停止。特别是，对于= 1.84，理论和实验分子量之间的显着偏差是显而易见的。该偏差明确地归因于缓慢引发，如通过H-INMR所指示的，其中观察到显著百分比的未反应引发剂。重要的是，在聚合平台处添加配体重新引发聚合并导致未反应的引发剂的完全消耗，从而能够合成一锅法二嵌段共聚物。我们随后评估了当保持恒定的催化剂比率时聚合度（DP）对所获得的分散性的影响。根据这些实验结果的插值，我们可以预测任何理想的DP和色散的实验条件。
In photo-atom transfer radical polymerization (ATRP), dispersity can be efficiently controlled by varying the deactivator concentration. In this work, we provide mechanistic insight into dispersity-controlled photo-ATRP by conducting detailed kinetics under a range of conditions. For the lower dispersity polymers, a conventional first-order kinetic profile was observed accompanied by a linear evolution of number average molecular weight (M-n) with conversion while the reactions reached moderate to high conversions (between 66% and 93%). Whereas, when polymers of high dispersity were targeted, the M-n remained relatively constant throughout the polymerization and the reactions ceased at less than 50% of conversion. In particular, for = 1.84, a significant deviation between theoretical and experimental molecular weights was evident. This deviation was unambiguously attributed to slow initiation as indicated by H-1 NMR, where significant percentages of unreacted initiator were observed. Importantly, the addition of ligand at the polymerization plateau re-initiated the polymerization and led to the complete consumption of the unreacted initiator, thus enabling the synthesis of one-pot diblock copolymers. We subsequently evaluated the effect of the degree of polymerization (DP) on the obtained dispersity when a constant catalyst ratio was maintained. Based on the interpolation of those experiments results, we could predict experimental conditions for any desirable DPs and dispersities.