Specific Anion Effects on Charged-Neutral Random Copolymers: Interplay between Different Anion-Polymer Interactions.

The study of ion specificities of charged-neutral random copolymers is of great importance for understanding specific ion effects on natural macromolecules. In the present work, we have investigated the specific anion effects on the thermoresponsive behavior of poly([2-(methacryloyloxy)ethyl trimethylammonium chloride]---isopropylacrylamide) [P(METAC--NIPAM)] random copolymers. Our study demonstrates that the anion specificities of the P(METAC--NIPAM) copolymers are dependent on their chemical compositions.

Modulation of the Binding Affinity of Polyzwitterion-Conjugated Protein by Ion-Specific Effects in Crowded Environments.

Macromolecular crowding could influence the binding affinity of the polyzwitterion-conjugated proteins. Herein, the hydrolysis of N-succinyl-Ala-Ala-Pro-Phe p-nitroanilide by the poly(carboxybetaine) conjugated α-chymotrypsin (PCT) was employed as a model system to investigate the modulation of the binding affinity of the polyzwitterion-conjugated proteins by the ion-specific effects in the crowded environments. In comparison with the bare α-chymotrypsin (BCT), the binding affinity of the PCT to the peptide is stronger in the dilute solutions but becomes weaker in the crowded environments.

Ion specificities of artificial macromolecules.

Artificial macromolecules are well-defined synthetic polymers, with a relatively simple structure as compared to naturally occurring macromolecules. This review focuses on the ion specificities of artifical macromolecules. Ion specificities are influenced by solvent-mediated indirect ion-macromolecule interactions and also by direct ion-macromolecule interactions.

Cleaning with Bulk Nanobubbles.

The electrolysis of aqueous solutions produces solutions that are supersaturated in oxygen and hydrogen gas. This results in the formation of gas bubbles, including nanobubbles ∼100 nm in size that are stable for ∼24 h. These aqueous solutions containing bubbles have been evaluated for cleaning efficacy in the removal of model contaminants bovine serum albumin and lysozyme from surfaces and in the prevention of the fouling of surfaces by these same proteins.

Anion Specificity of Polyzwitterionic Brushes with Different Carbon Spacer Lengths and Its Application for Controlling Protein Adsorption.

Both ion-specific interaction and carbon spacer length have strong effects on the properties of polyzwitterions. In this work, we have investigated the anion specificity of poly(sulfobetaine methacrylamide) (PSBMAm) brushes with different carbon spacer lengths. The effectiveness of anions to enhance the hydration of the PSBMAm brushes increases from kosmotropic to chaotropic anions.

Ion specificity of macromolecules in crowded environments.

Macromolecular crowding plays a significant role in the solubility and stability of biomacromolecules. In this work, the thermo-sensitive poly(N-isopropylacrylamide) (PNIPAM) has been employed as a model system to study the specific ion effects on the solubility of macromolecules in crowded environments of dextran and polyethylene glycol (PEG). Our study demonstrates that crowding agents can interact with either anions or PNIPAM chains.

Cation-specific conformational behavior of polyelectrolyte brushes: from aqueous to nonaqueous solvent.

We have investigated changes in the cation-specific conformational behavior of poly(sodium styrenesulfonate) (PSS) brushes as the solvent changes from water to methanol using a quartz crystal microbalance with dissipation (QCM-D). A solvation to desolvation transition of the grafted chains accompanied by swelling to the collapse transition of the brushes is observed for Na(+). In the case of Cs(+), the brushes undergo solvation to desolvation to resolvation accompanied by swelling to collapse to reswelling transitions.

Insight into the amplification by methylated urea of the anion specificity of macromolecules.

Methylated urea and sugar are chaotropic and kosmotropic osmolytes, respectively. In the present work, we have investigated the specific anion effect on the lower critical solution temperature (LCST) behavior of poly(N-isopropylacrylamide) (PNIPAM) in the presence of methylated urea or sugars. Differential scanning calorimetry studies revealed that tetramethylurea can adsorb onto the PNIPAM surface, but glucose is excluded from the PNIPAM surface.

Specific anion effect in water-nonaqueous solvent mixtures: interplay of the interactions between anion, solvent, and polymer.

Ethanol (EtOH) and dimethylsulfoxide (DMSO) are polar protic and aprotic organic solvents, respectively. In the present work, we have investigated the anion-specific lower critical solution temperature (LCST) and upper critical solution temperature (UCST) behaviors of poly(N-isopropylacrylamide) (PNIPAM) in the H2O-EtOH and H2O-DMSO mixtures. The turbidity and differential scanning calorimetry studies show that the LCST for the anions follows the Hofmeister series at the molar fraction of EtOH (xE) or DMSO (xD) of 6%.

Ion specificity at a low salt concentration in water-methanol mixtures exemplified by a growth of polyelectrolyte multilayer.

By use of a quartz crystal microbalance with dissipation (QCM-D), we have investigated the specific ion effect on the growth of poly(sodium 2-acrylamido-2-methylpropanesulfonate)/poly(diallyldimethylammonium chloride) multilayer at a salt concentration as low as 2.0 mM in water-methanol mixtures. QCM-D results demonstrate that specific ion effect can be observed in methanol and water-methanol mixtures though it is negligible in water.

Mechanistic insights into amplification of specific ion effect in water-nonaqueous solvent mixtures.

Ethylene glycol (EG) and hydrogen peroxide (H2O2) can act as both hydrogen-bond donors and acceptors in the formation of solvent complexes with water molecules. In the present work, we have systematically investigated the ion-specific lower critical solution temperature (LCST) behavior of poly(N-isopropylacrylamide) (PNIPAM) in H2O–EG and H2O–H2O2 mixtures. The results obtained from turbidity measurements show that the specific anion effect is amplified with the increasing molar fraction of EG (x(EG)) but is independent of the molar fraction of H2O2 (x(H2O2)).