Synthesis And Properties Of Polymer Composite Janus Particles With Tunable Shape

Janus materials with two different compositions distinctly compartmentalized on the same object,have gained increasing academic and industrial interests due to their unique properties.Especially,the polymer/inorganic composite Janus materials can well integrate functionality of inorganic materials and soft matter performance of polymers.It is key to develop methods to large scale produce Janus particles with tunable morphologies.This dissertation focuses on methodological development of large-scale synthesis of Janus particles with tunable morphologies by seeded swelling emulsion polymerization following by post-modifications.Some representative results are as follows:1.Against the polystyrene hollow sphere with a mean diameter of 1055 nm,a crosslinked polymer shell of poly（vinylbenzene chloride）（cPVBC）is derived by the sweeling polymerization by using the monomer mixture of vinylbenzene chloride and divinyl benzene.PEO is conjugated onto the exterior surface of the PS@cPVBC hollow sphere by a nucleophilic substitution between chloromethyl functional group from cPVBC and the amine-capped PEO（PEO-NH₂）.After removel of polystyrene by dissolution,transverse channels are generated.A thermal responsive polymer of poly（N-isopropylacrylamide）（PNIPAM）is grafted by ATRP onto the interior side of the porous shell.A Janus cage is thus achieved with a sandwiched shell of PNIPAM-cPVBC-PEO.At a high temperature over the low critical solution temperature（LCST）of PNIPAM,the PNIPAM terminate side is hydrophobic while the other PEO side remains hydrophilic.Oleophilic organic materials can be captured inside the Janus cage,which can be released at a lower temperature.This capture behavior is promising for efficient separation of both oil/water mixtures and the emulsions,which is irrelevant to continuous phase and emulsifier type.The synthetic approach toward Janus cages is general.A huge family of functional Janus cates will be derived with tunable compositions thus performances.2.Based on aforementioned approach,a new phase separation occurs to generate isolated discs of cPVBC within the PS shell when the VBC and DVB contents are synchronously increased.Similarly,PEO is grafted on the outer surface of the cPVBC disc.A Janus disc of cPVBC-PEO is achieved by dissolution of the PS shell under ultrasonication.After PNIPAM is grafted on the other side of the Janus disc of cPVBC-PEO by ATRP,a Janus disc of PNIPAM-cPVBC-PEO is derived.The Janus disc of PNIPAM-cPVBC-PEO is dually thermal responsive.At a low temperature below the LCST of PNIPAM,both sides of the Janus disc are hydrophilic.The composite disc favors formation of oil in water Pickering emulsions.On the other hand,at a higher temperature above the cloud point of PEO,both sides of the composite disc become less hydrophilic.As the result,water in oil Pickering emulsions are favored in the presence of the composite disc.Within the temperature window spanning the LCST and the cloud point,the Janus disc is amphiphilic.Stable emulsions are formed with smaller droplets,where the Janus disk adopts well defined orientation at the emulsion interface.Similarly,a series of Janus composite discs with varied compositions and performances are expected.3.A crosslinked hollow sphere of PDVB@PS is achieved by swelling polymerization against the PS hollow sphere.A snowman-like Janus particle of SiO₂@PDVB@PS is derived by an intensified phase separation when using 3-（trimethoxysilyl）propyl methacrylate as the functional monomer.The SiO₂ lobe is selectively modified with triethoxy-3-（2-imidazole-1-linyl）propylsilane to introduce imidazole functional group.Sulfonic acid group is introduced to the PDVB part after sulfonation,which can further induce a favorable growth of Fe₃O₄.Octadecyltriethoxysilane is used to cap the Fe₃O₄contained part introducing the hydrophobic moiety.The Janus particle of Im-SiO₂@PDVB-Fe₃O₄-C18 is amphiphilic.More importantly,the Im-SiO₂ can capture some desired materials by specific interactions with the hydrophilic performance well retended.This performance is promising for efficient treatment of wastewater in enhanced oil recovery,where the emulsified oil and dissolved partially hydrolyzed polyacrylamide can be synchronously captured and programmably recycled.