title: Differences in cationic and anionic charge densities dictate zwitterionic associations and stimuli responses.
abstract: Zwitterionic materials have shown their excellent performance in many biological and chemical applications. Zwitterionic materials possess moieties that own both cationic and anionic groups. The associations among zwitterionic moieties through electrostatic interactions play an important role in properties of zwitterionic materials. However, the relationship between the molecular structures and associations of zwitterionic moieties are still not well understood. This work compared thermal- and salt-responsive behaviors of sulfobetaine and carboxybetaine polymers by examining their rheological properties as a function of temperature and their hydrodynamic sizes as a function of salt concentration. Results showed that carboxybetaine polymers do not exhibit stimuli responses as expected from the antipolyelectrolyte behavior of zwitterionic polymers as observed in sulfobetaine polymers. We studied and compared the associations among zwitterionic moieties in these two zwitterionic polymers using molecular dynamic simulations. Simulation results show that the charge-density difference between cationic and anionic groups determines the associations among zwitterionic moieties, which are responsible for different stimuli responses of carboxybetaine and sulfobetaine polymers.
authors.affiliation: Department of Chemical Engineering, University of Washington , Seattle, Washington 98195, United States.
authors.forename: Qing
authors.initials: Q
authors.lastname: Shao
authors.forename: Luo
authors.initials: L
authors.lastname: Mi
authors.forename: Xia
authors.initials: X
authors.lastname: Han
authors.forename: Tao
authors.initials: T
authors.lastname: Bai
authors.forename: Sijun
authors.initials: S
authors.lastname: Liu
authors.forename: Yuting
authors.initials: Y
authors.lastname: Li
authors.forename: Shaoyi
authors.initials: S
authors.lastname: Jiang
mesh_terms: D000838:Anions / Q000737:chemistry; D001622:Betaine / Q000031:analogs & derivatives / Q000737:chemistry; D002412:Cations / Q000737:chemistry; D056004:Molecular Dynamics Simulation; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry*; D012212:Rheology; D014867:Water / Q000737:chemistry
chemical_list: D000838:Anions; D002412:Cations; D011108:Polymers; D014867:Water; D001622:Betaine; C483727:sulfobetaine