Molecular Dynamics Simulation of Antipolyelectrolyte Effect and Solubility of Polyzwitterions

In this work, by using coarse-grained molecular dynamics simulations, we found that poly（2-metha-cryloyloxyethyl phosphorylcholine）（PMPC） showed a strong solubility and a so-called antipolyelectrolyte effect（APE）in water. In contrast, obvious aggregations but no APE were found in n-butyl-substituted choline phosphatepolymers（PMBP） solutions. The underlying mechanisms for different solution behaviors of PMPC and PMBP wereinvestigated in detail. Our results indicate that the presence of butyl groups in PMBP enhances both the electrostaticinteractions and the hydrophobicity of PMBP molecules in the system. Both factors were found to contribute to theformations of aggregates in the PMBP system. Further researches revealed that hydrophobicity arising from the butylgroup plays a more important role than electrostatic interactions in inducing the PMBP aggregation. In addition, thestrong hydrophobicity in PMBP was found to be responsible for the absence of APE. These results are expected tocontribute to a better understanding and a better design of the solution properties of polyzwitterions.

A saturated saltwater drilling fluid based on salt-responsive polyampholytes

Based on special antipolyelectrolyte effect of zwitterion polymer with same quantity of anionic and cationic charges, we developed two types of salt-responsive polyampholytes, one with high molecular weight and low charge density(HvL) and the other with low molecular weight and high charge density(LvH), by inverse emulsion polymerization. Molecular structure and salt-responsiveness of them were characterized by 1 H-NMR and rheology measurement, respectively. HvL and LvH were evaluated in saturated-salt bentonite suspension and influences of their ratio on apparent viscosity and fluid loss were investigated as well. The results indicate that HvL is better at decreasing fluid loss while LvH is better at maintaining low viscosity. A saturated saltwater drilling fluid centering on HvL and Lv H with simple formula was designed and applied. It is indicated that salt-responsive polyampholytes are fundamentally better than AM-AMPS anionic copolymer and AM-AMPS-DMDAAC amphoteric copolymer. The saturated saltwater drilling fluid has excellent thermal stability, tolerance to bentonite and shale cuttings, and certain resistance to CaCl_2. Salt-responsive polyampholytes can be used in KCl-saturated drilling fluid, with universal adaptability.

Anti‑polyelectrolyte Zwitterionic Block Copolymers as Adaptable Uranium Harvester in High‑Salinity Environments:Catalyst‑Free Light‑Driven Polymerization and Conformational Dynamics Study

Developing polymeric adsorbents for uranium harvesting from high-salinity environments remains a daunting challenge due to the‘polyelectrolyte effect’-induced conformational collapse compromising the ligand availability.A catalyst-free,visible light-controlled radical polymerization has been presented here for the tailor-made synthesis of zwitterionic block copolymers(BCPs)bearing uranophilic ligands.The novel anti-polyelectrolyte uranium harvesters exhibited significant salinity resistance.The facile and robust photosynthetic strategy offers a significantly high monomer conversion(α>95%)that facilitates“one-pot”chain extension to develop the BCPs.Metal catalyst residues,as found in conventional controlled radical polymerizations,are avoided and promoted to synthesize fascinating polymeric materials.We also highlight the first study,by integrating computational modeling with QCM-D analysis,on the interplay between polymer conformational dynamics and chemical adsorption behaviors.With zwitterionic polymer segments as conformational regulators,the BCPs exhibit remarkable‘anti-polyelectrolyte effect’by maintaining stretched conformations in saline solutions.Improved ligand accessibility and promotion of diffusional mass transfer are achieved,enabling a high adsorption capacity toward uranium with remarkably fast kinetics in spiked natural seawater and salt lake brines.