Unexpected irregular structures of poly(itaconic acid) prepared in Deep Eutectic Solvents

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

“…Two cross‐peaks characteristic for methylene groups of poly(itaconic acid) (PIA) backbone are presented ( a + b and c + d ), and three additional signals can also be seen ( e , f , g ). In agreement with our previous findings, and based on results from NMR studies determining the structure of esterification products from IA–CC mixture (Figure S2–S21, Supporting Information), these cross‐peaks were assigned to choline ester group formed via esterification of the less sterically hindered carboxylic group of the itaconic unit. While detailed studies on stability of selected CC–carboxylic acid DESs indicate that choline undergoes esterification easily, even at room temperature, which can be a limitation in case of some DES applications, in our case, reaction between choline and carboxylic groups is a desired process leading to functionalization of the anionic polyelectrolyte (PIA).…”

“…The average degree of esterification of the polymers was estimated based on integration of appropriate resonance signals (Figure S15, Supporting Information), and shown to correspond to 1 esterified unit per 12 itaconic units. The degree of substitution is four times higher than reported before for polymers prepared by persulfate‐initiated radical polymerization of IA in IA–CC mixtures . Interestingly, we have found that the water solubility of the polymer PIAC3 is low at around pH 3 and increases sharply one pH unit away (Figure D).…”

“…The mixture shows no tendency to crystalize, presumably due to its high viscosity (13 000 mPa s at 21 °C, Table S1, Supporting Information). Instead it exhibits glass transition at about −60 °C . It has been demonstrated before that the IA–CC systems are physical mixtures of the starting materials and that the components undergo no undesired side‐reactions during preparation (heating at 110 °C for 1 h) .…”

“…The acid is also a well‐known low reactive vinyl monomer, and its free radical polymerization typically requires long reaction times and high amounts of an initiator . Based on our previous experience with persulphate‐initiated polymerization of the acid in aqueous media and in choline‐based DESs, we have asked ourselves whether it would be possible to prepare itaconic polymers via initiator‐free radical polymerization. It is well known that spontaneous thermal radical polymerization at temperature >100 °C is possible for several reactive vinyl monomers, including styrene and acrylic monomers .…”

“…Instead it exhibits glass transition at about −60 °C . It has been demonstrated before that the IA–CC systems are physical mixtures of the starting materials and that the components undergo no undesired side‐reactions during preparation (heating at 110 °C for 1 h) . To check if IA can exhibit thermal polymerization in IA–CC mixtures, we have analyzed compositions of IA–CC systems heated at 110 °C for 1 and 2 h, as well as at 110 °C for 20 h under reduced pressure (to limit oxidative degradation).…”