Department of Chemical Sciences, University of Padova , Via Marzolo 1, 35131 Padova, Italy.
Center for Molecular Engineering, Department of Chemistry, Carnegie Mellon University , 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States.
J Am Chem Soc. 2016 Jun 15;138(23):7216-9. doi: 10.1021/jacs.6b01935. Epub 2016 May 31.
Polymerization of acidic monomers is one of the biggest challenges for atom transfer radical polymerization (ATRP). An intramolecular cyclization reaction leading to the loss of the C-X chain-end functionality was found to be the main reason for the partial termination of the growing polymer chains. Three approaches were used to overcome this problem: using Cl as the chain-end halogen, lowering the pH (to 0.9), and increasing polymerization rate. Methacrylic acid (MAA) was polymerized by both electrochemically mediated ATRP and supplemental activator and reducing agent ATRP up to high conversion (>90%), in t ≤ 4 h at 25 °C, using inexpensive and nontoxic reagents (NaCl, diluted HCl, water). Control over molecular weight (MW) dispersity was satisfactory, and MWs were in agreement with theoretical values. The "livingness" of the process was confirmed by an electrochemical switch, used to repeatedly and periodically deactivate/reactivate growing chains.
酸性单体的聚合是原子转移自由基聚合（ATRP）面临的最大挑战之一。人们发现，导致 C-X 链末端官能团损失的分子内环化反应是导致聚合链部分终止的主要原因。为了克服这个问题，人们采用了三种方法：使用 Cl 作为链末端卤素、降低 pH 值（至 0.9）以及提高聚合速率。使用廉价且无毒的试剂（NaCl、稀释的 HCl、水），通过电化学介导 ATRP 和补充引发剂和还原剂 ATRP，在 25°C 下 t ≤ 4 小时内，就可以将甲基丙烯酸（MAA）聚合到高转化率（>90%）。对分子量分散度的控制令人满意，分子量与理论值相符。通过电化学开关来确认聚合过程的“活性”，该开关可用于反复和周期性地使聚合链失活/再激活。
