High-Molecular-Weight Polyampholytes Synthesized via Daylight-Induced, Initiator-Free Radical Polymerization of Renewable Itaconic Acid.

Herein, it is reported for the first time that when mixed with choline chloride, itaconic acid (IA), normally a low-reactive vinyl monomer, undergoes initiator-free radical polymerization under normal daylight. Furthermore, the process results in the formation of abnormally high-molecular-weight poly(itaconic acid) derivatives with Mw greater than ≈800 000 g mol-1 . Detailed 1D/2D NMR studies indicate that the polymers have two types of ionizable moieties, that is, anionic carboxylic and cationic choline ester groups in an average molar ratio of 12:1. Potentiometric titration shows polyampholyte behavior of the polymers. Tentative mechanistic studies reveal that the daylight-induced polymerization is initiated by species generated via interactions of near UV light with IA. However, EPR findings show that choline also participates in secondary radical reactions. The obtained polyampholytes are useful bio-based materials for fast and straightforward fabrication of polymer-clay nanocomposite hydrogels with excellent mechanical properties.