Synovial fluid-inspired biomimetic lubricating microspheres:Zwitterionic polyelectrolyte brushes-grafted microgels

Synovial fluid is made up of various biomacromolecules,including hyaluronic acid,aggrecans,lubricins,and phosphatidylcholine lipid,which are assembled onto the surface of articular cartilage in a gel state.Among them,brush-like biomacromolecules or assemblies have a vital effect on human joint lubrication.Inspired by this,the combination of brush-like molecular structures and gel-like assembly may be an efficient approach for the synthesis of biomimetic lubricating matters.Learning from the lubrication system of human joints,poly(2-methacryloyloxyethyl phosphorylcholine)(PMPC)brushes grafted poly(N-isopropylacrylamide-co-acrylic acid)(poly(NIPAAm-co-AA))microgels,abbreviated as MBs-g-MGs,were synthesized as one kind of biomimetic lubricating additives.It is worth noting that this bionic strategy considered both molecular structure and assembled form,which enabled this hairy microgel to achieve low friction in aqueous medium.Meanwhile,the effective lubrication was still achieved when using MBs-g-MGs at high temperature,indicating that this microgel maintains a good lubricating effect over a wide range of temperature.In addition,this kind of microgel possessed good biocompatibility,which laid the foundation for potential biomedical applications.Looking beyond,these biomimetic microgels may provide an effective lubricating effect for water-based sliding interfaces,especially in biomedical systems.

Engineering of responsive polymer based nano-reactors for facile mass transport and enhanced catalytic degradation of 4-nitrophenol

Silver nanoparticles with average diameter of 10 ± 3 nm were synthesized within the sieves of poly（N-isopropylacrylamide-2-hydroxyethylmethacrylate-acrylic acid）（p（NIPAAm-HEMA-AAc））polymer microgels. Free radial emulsion polymerization was employed for synthesis of p（NIPAAm-HEMA-AAc） polymer microgels. Silver nanoparticles were introduced within the microgels sphere by in situ reduction method. Microgels and hybrid microgels were characterized by Fourier transform infrared spectroscopy, ultra violet-visible spectroscopy,transmission electron microscopy and dynamic light scattering measurements. Catalytic activity of Ag-p（NIPAAm-HEMA-AAc） hybrid microgels was studied using catalytic reduction of 4-nitrophenol（4-NP） as a model reaction in aqueous media. The influence of sodium borohydride（Na BH4） concentration, catalyst dose and 4-NP concentration on catalytic reduction of 4-NP was investigated. A linear relationship was found between catalyst dose and apparent rate constant（kapp）. The mechanism of catalysis by hybrid microgels was explored for further development in this area. The deep analysis of catalytic process reveals that the unique combination of NIPAAm, HEMA and AAc does not only stabilize silver nanoparticles in polymer network but it also enhances the mass transport of hydrophilic substrate like 4-NP from outside to inside the polymer network.

Preparation of CuS-P（NIPAM-co-MAA） Hybrid Microgels with Controlled Surface Structures

Copper sulfide-poly（isopropylacrylamide-co-methacrylic acid） [CuS-P（NIPAM-co-MAA）] hybrid microgels with patterned surface structures have been synthesized by means of the polymer microgel template technique. The results showed that the surface morphology of the hybrid microgels could be regulated by controlling the decomposition of thioacetamide （TAA） in an acidic medium. The rate of precipitation and the amount of metal sulfide significantly affect the surface structures of the hybrid microgels.