Polymer solubility in ionic liquids: dominated by hydrogen bonding

• Published in: Physical chemistry chemical physics : PCCP 2021-10, Vol.23 (38), p.21893-219
• Main Authors: Yuan, Ya-Fei, Zhang, Jin-Ming, Zhang, Bao-Qing, Liu, Jia-Jian, Zhou, Yan, Du, Ming-Xuan, Han, Lin-Xue, Xu, Kuang-Jie, Qiao, Xin, Liu, Chen-Yang
• Format: Article
• Language: English
• Subjects: Basicity; Chemical bonds; Hydrogen; Hydrogen bonding; Ionic liquids; Ions; Polymer solubility; Polymers; Solubility parameters
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/d1cp03193g

Polymer solubility in ionic liquids (ILs) cannot be predicted by the solubility parameter approach based on the "like dissolves like" principle. According to the Kamlet-Abraham-Taft (KAT) multi-parameter polarity scale, ILs can be categorized on the basis of hydrogen-bond acidity or basicity ones. The experimental observations, that acidic ILs easily dissolve basic polymers and basic ILs dissolve acidic polymers, reflect the complementary nature of hydrogen-bonding interactions. A quantitative hydrogen-bonding analysis is proposed for predicting the solubility by taking the product of Δ α Δ β as an indicator of the competition between cross-association and self-association hydrogen bonding (H-bonding), where Δ α is the difference of acidity parameters between the polymer and IL, and Δ β is the difference of basicity. This solubility criterion has been validated by the solubility data of 19 polymers (11 acidic and 8 basic) in 11 ILs (7 acidic and 4 basic). These principles based on KAT parameters can be applied to other systems dominated by hydrogen bonding. The product of H-bond acidity ( α ) and basicity parameter ( β ) reflects the complementary nature of the H-bonding interactions. Strong cross-association and weak self-association favor the solubility of polymer in ILs, therefore the product of Δ α Δ β < 0.