Preparation And Application Of Snowman-shaped Janus Particles

Janus particles show attractive prospects for application due to their unique asymmetric structure.The morphology,chemical partitioning,and microstructure of Janus particles are tunable and can be applied in different fields.In this paper,based on seeded emulsion polymerization technology,snowman-like organic/inorganic composite Janus particles with strict chemical composition partition and asymmetric shape were synthesized,which were endowed with environmental-responsive regulation of wettability and chemical reactivity through surface modification,which were applied to construct functional coatings and functional dual network gel.The main contents are as follows:1.Amphiphilic Janus particles construct superhydrophobic coatings.Snowmanshaped silica@polystyrene/polydivinylbenzene(Silica@PS/PDVB)Janus particles were prepared by a seeded emulsion polymerization-induced phase separation method.The glycidoxypropyl triethoxysilane(GPTES)modification introduces amino groups,which are capable of bonding with epoxy resin groups,to the silica side,and on the other side is the low-surface-energy polymer.The linear polystyrene on the snowman-like Janus particles was selectively etched by the solvent,which made the polydivinylbenzene side a rough nanostructure.Because of their amphiphilicity,silica@polydivinylbenzene(Silica@PDVB)Janus particles are used for coating preparation,where they can be spontaneously oriented on the surface of the substrate with the hydrophilic side facing the epoxy substrate,forming strong adhesion through bonding;the hydrophobic side facing the air,and the nano-protrusions being combined with the micro-particles to form a micronano structure in order to enhance the hydrophobic performance,and finally obtain a superhydrophobic monolayer coating.The coating can still maintain superhydrophobic properties after prolonged immersion in various aqueous and organic solvents,showing good chemical durability.The coating can also remain superhydrophobic after water rinsing and mechanical abrasion,showing good mechanical durability.2.Design and application of temperature-responsive coatings based on Janus particles.The temperature-responsive polymer PNIPAM was introduced by copolymerization on the PS/PDVB side of the snowman-shaped silica@PS/PDVB Janus particles,and the silica part was modified with 3-aminopropyltriethoxysilane(APTES)to introduce amino groups to interact with carboxyl groups and bond with the surface of the substrate.These Janus particles are temperature-responsive: when the temperature is higher than 32°C,the polymer side is hydrophobic,and the particles form micelles in water and finally precipitate;when the temperature is lower than 32°C,the polymer side is hydrophilic due to the responsiveness of PNIPAM,which can be evenly dispersed in water.The composite fabric coating can be obtained by impregnation technology on the pure cotton fabric as the base material.The composite fabric coating is also thermally responsive: hydrophobic at high temperature(side close to the skin)and hydrophilic at low temperature(side towards the air),forming a Janus wettable fabric with hydrophilic on one side and hydrophobic on the other.A reversible infiltrating response was maintained after 20 cycles.3.Janus nanoparticles for modulation of dual network hydrogels.Using linear polystyrene hollow microspheres as seeds,3-trimethoxypropyl methacrylate(MPS)and 4-chloromethylstyrene(VBC)as swellable monomers,the snowman-like silica@PS/PDVB Janus particles were synthesized by seeded-emulsion polymerization.The silica side was modified with APTES to introduce amino groups A good solvent was used to selectively etch the particles to remove linear polystyrene and obtain hemispherical silicon dioxide Janus particles,and the newly exposed side underwent quaternization treatment.The prepared hemispherical Janus nanoparticles have amino groups on the one side and quaternary ammonium salt groups on the other side.They were added to sodium alginate and chitosan double-network hydrogel(DN hydrogel)as a particle cross-linking agent.The amino side of Janus nanoparticles formed Schiff base bond with poly(ethylene glycol)dialdehyde,and quaternary ammonium salt group is connected with the carboxyl group of sodium alginate through coordination,which realize the interaction between the hydrogel double network,and the regulation of the mechanical properties of the gel.4.Construction of biphasic hydrogels based on the emulsification behavior of Janus particles.The snowman-shaped Silica@PS/PDVB Janus particles were used as particle emulsifiers to stabilize the paraffin-in-water emulsion to obtain phase-change paraffin microcapsules.Phase-change paraffin microcapsules were added to cross-linked DN hydrogels with dynamic covalent bonds and ionic interactions,and the amino groups on the hydrophilic side of Janus particles were combined with the aldehyde groups in the hydrogel through Schiff base reaction.The obtained biphasic hydrogel has the function of phase-transition temperature control and self-healing.