ACS Macro Letters

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ISSN / EISSN : 2161-1653 / 2161-1653
Published by: American Chemical Society (ACS) (10.1021)
Total articles ≅ 2,801
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Lei Ma, Weixing Xiong, Kaiwen Yu, Xiyu Wang, Ying Cao, Xinhua Lu,
ACS Macro Letters pp 1410-1415;

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Stanislaw Penczek, Julia Pretula
ACS Macro Letters pp 1377-1397;

The origin of the activated monomer mechanism (AMM) in cationic ring-opening polymerization (CROP) is described first. Then, conditions leading to the active chain end (ACE) mechanism and AMM are compared, as well as methods allowing to distinguish between these two mechanisms. These methods are based on the “ion trapping” of the active ionic species using highly basic phosphines or by comparing ACE and AMM kinetics of polymerization. The major factors deciding on the actual mechanism include: basicity of the monomers, ring strain, and the presence of the protic additives in the reaction system. These factors are tabulated for major cyclic ethers and cyclic esters. The historically evolved subsequent steps of AMM in the polymerization of cyclic esters are described: from the first experiments with trialkyloxonium salts, precursors of protonic acids, and added alcohols, via HCl as catalyst, and then CF3S(═O)2OH (polymerizing lactides) to the most popular derivatives of phosphoric acid, like diphenyl phosphate. Conditions allowing to synthesize poly(ε-caprolactone) (PCL), according to AMM-CROP, with molar mass up to 105 g·mol–1, are described as well as methods to polymerize CL with a protic initiator and acidic catalyst in one molecule. Then various methods enhancing the activity of the polymerizing systems are compared, based predominantly on hydrogen bonding, either to the polymer active end group (usually the hydroxyl group) or to the acid anion. Finally, kinetic equations for ACE and AMM are compared, and it is shown that the majority of the AMM-CROP systems, mostly studied for CL and lactides, proceed as living/controlled polymerizations. Since polymer end groups are hydroxyl groups, then, as it was shown in several papers, any initiator with one or many hydroxyl groups provides macromolecules with the corresponding architecture. The papers on synthetic methods are not discussed in detail.
Zixin Yu, Jie Wang, Zhen Hu, Chuanqun Hu, Dachuan Ding, Bin Yang, Tao Hu, Xinghou Gong, , Masanori Hara
ACS Macro Letters, Volume 10, pp 1326-1326;

Manisha Singh, Ivan Solic,
ACS Macro Letters pp 1353-1358;

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Akash Arora, Tzyy-Shyang Lin, Nathan J. Rebello, Sarah H. M. Av-Ron, Hidenobu Mochigase,
ACS Macro Letters pp 1339-1345;

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Yanyao Zhang, Yusheng Tang, Junliang Zhang,
ACS Macro Letters pp 1346-1352;

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