Eco-friendly synthesis of ionic helical polymers and their chemical properties and reactivity

• Published in: RSC advances Vol. 8; no. 52; pp. 29988 - 29994
• Main Authors: Yamaguchi, Isao, Tanaka, Yuki, Wang, Aohan
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 01.01.2018; The Royal Society of Chemistry
• Subjects: Anion exchanging; Chains (polymeric); Chemical properties; Chemical synthesis; Chemistry; Conjugation; Depolymerization; Dichroism; Electrochemical oxidation; Molecular conformation; Molecular weight; Nitrogen atoms; Organic chemistry; Phenylenediamine; Polymers; Pyridinium chlorides; Ring opening; Sodium
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/c8ra05686b

Reaction of -(2,4-dinitrophenyl)pyridinium chloride (salt(Cl )) with sodium dicyanamide (Na(CN) N) resulted in anion exchange between Cl and (CN) N to yield a new Zincke salt, salt((CN) N ). Reactions of salt((CN) N ) with piperazine, specifically ( )-(-)- or ( )-(+)-2-methylpiperazine under eco-friendly conditions, such as in aqueous solution, in the absence of a catalyst, and at room temperature, resulted in pyridinium ring opening to yield ionic high-molecular-weight polymers with 5-2,4-dienylideneammonium dicyanamide units or chiral 5-(2-methylpiperazinium)-2,4-dienylideneammonium dicyanamide units, namely, polymer(H;(CN) N ), polymer( -Me;(CN) N ), and polymer( -Me;(CN) N ). UV-Vis measurements revealed that the π-conjugation system expanded along the polymer chain due to the orbital interaction between the electrons on the two nitrogen atoms of the piperazinium ring. Circular dichroism (CD) measurements revealed a helical conformation of the main chain in polymer( -Me;(CN) N ) and polymer( -Me;(CN) N ). The reaction of polymer(H;(CN) N ) with -phenylenediamine (PDA) caused recyclization of the 2,4-dienylideneammonium unit and resulted in depolymerization to yield -(4-aminophenyl)pyridinium dicyanamide. Cyclic voltammetry analysis suggested that the polymers obtained in this study undergo electrochemical oxidation and reduction.