CO2 Induced Formation of Polyelectrolyte Hydrogel with Tunable Mechanical Properties

The aim of this paper is to incorporate cellulose nanocrystals(CNCs) into the polyelectrolyte complex(PEC)matrix to construct polyelectrolyte hydrogels,utilizing carbon dioxide(CO_2)-induction to achieve sol-gel transition.The mechanical properties of the hydrogels were tunable with different CNC loadings.The increasing CNCs contributed to significant mechanical reinforcement of the PEC/CNC hydrogels.The study on swelling characteristics of hydrogels manifested the entanglements between CNCs and the polymer chains.The hydrogels also showed good moldability property.A cell counting kit-8(CCK-8)cytotoxicity study showed that the as-prepared composite hydrogels had good biocompatibility to confluent osteoblasts(SD rat) cells.

Toward a non-invasive cleaning of the wall painting using polyelectrolyte hydrogel

Developing advanced cleaning systems for the removal of unwanted layers from painted surfaces is still a challenging issue that needs to be addressed in the field of cultural heritage.In this work,we proposed the use of novel polyelectrolyte hydrogels prepared via free radical polymerization and freeze-thaw methods.Zwitterionic sulfobetaine methacrylate(SBMA)was crosslinked with methylacryloyloxyethyl trimethylammonium(DMC)through covalent bonding to yield zwitterionic polyelectrolyte poly(SBMA-co-DMC)(PSD).Introducing PSD into the polyvinyl alcohol/carboxymethyl chitosan(PVA/CMC)hydrogel network enhanced the intermolecular electrostatic interactions and changed the porous structure and swelling behaviors,thus leading to improved mechanical properties.The adsorption ability of the PVA/CMC/PSD polyelectrolyte hydrogels toward dyes(rhodamine B and congo red)and metal ions(Cu^(2+)and K^(+))varied with increasing amounts of PSD,which could be attributed to cationic PSD tuning the net charges in the hydrogel.The cleaning effectiveness of the PVA/CMC/PSD polyelectrolyte hydrogels was assessed on wall painting mock-ups coated with soil,red paint,and soluble salts,using microscopic and spectroscopic analyses.The results showed that the hydrogel adhered to rough surfaces and removed unwanted substances effectively without leaving determinable residues,providing a possible safe and efficient method for the cleaning of important artifacts.

Effect of Ionic Concentration on Drug Release from Polyelectrolyte Hydrogel Carriers Analyzed via Triphasic Mechanism Model

In different parts of the gastrointestinal tract, the rate of drug release from polyelectrolyte hydrogel tablets is highly affected by variance of ionic concentration. This research aims at revealing clearly how the drug release from a hydrogel matrix is affected by ionic concentration of external solution through the finite element simulation and triphasic mechanism model. The coupled relationship of the motions including the polyelectrolyte hydrogel swelling, the water flow and the ion diffusion, is illustrated in the present work. In order to simulate the drug controlled release from a swollen polyelectrolyte hydrogel carrier, the mathematical model was built on the basis of the multiphasic theory of polyelectrolyte hydrogels. Finally, the reliability of the simulation method was verified qualitatively by experimental results. The results reveal that when the initial concentration of fixed anions of polymer network is higher than the concentration of free anions in the external solution, the drug release rate increases with increasing the ionic concentration of the external solution. The research is helpful for the optimal design of oral drug release in gastrointestinal tract.

Modulation of Self-healing of Polyion Complex Hydrogel by Ion-specific Effects

We have prepared polyion complex （PIC） hydrogel consisting of poly（3-（methacryloylami no）propyl-trimethylamonium chloride） and poly（sodium p-styrenesulfonate） polyelectrolytes via a two-step polymerization procedure and have investigated specific ion effects on the self- healing of the PIC hydrogel. Our study demonstrates that the mechanical properties of the PIC hydrogel are strongly dependent on the type of the ions doped in the hydrogel. The ion-specific effects can be used to modulate the self-healing efficiency of the PIC hydrogel. As the doped anions change from kosmotrops to chaotropes, the self-healing efficiency of the PIC hydrogel increases. A more chaotropic anion has a stronger ability to break the ionic bonds formed within the hydrogel, leading to a higher efficiency during the healing.