Preparation Of Nonspherical Composite Particles By Phase Separation And Their Applications

Non-spherical composite particles have important applications in self-assembly,molecular recognition,chemical catalysts,superhydrophobic materials and Pikering emulsion,due to their special properties.As a widely used and simple and quick method,phase separation method is a convenient and widely adopted method to prepare composite particles with a special morphology.This study focuses on the influence of the introduction of inert solvent and the phase separation on the morphology of non-spherical composite particles during the seeded emulsion polymerization.The applications of these composite particles in superhydrophobic coatings are also demonstrated.First,the non-crosslinked PS spheres swolled by p-xylene(PX)were employed as seeds for the seeded emulsion polymerization of octafluoro-1-pentyl methacrylate(OFMA)and styrene(St).The internal PX was expelled from the particles in the form of droplets under the action of hydrophobic and oleophobic of fluorine element,leading to the formation of non-spherical composite particles with surface indentations.Golf-shaped PS/P(OFMA-S)composite particles could be obtained under low polymerization temperature and low dosage.At higher temperature or PX dosage,particles with a big indentation were achieved,and the size of the indentation increases with the increase of the temperature or PX dosage.At the polymerization temperature of 80 °C,the indentation of the largest relative size was formed.When the mass ratio of PX to PS spheres(wPX/wPS)was larger than 4/1,the increase of indentation size slowed down.When the size of PS spheres was too small or too large,the obtained particles tended to form a plurality of indentations on the surface.When the mass ratio of OFMA to St(wOFMA/wSt)was between 1/2 and 2/1,the particle with single indentation was formed.If the selected monomer was not miscible with OFMA,the obtained particles showed the morphology of raspberry shape.When w OFMA/wSt = 1/1,the particles showed good thermal and hydrophobic properties.After coating on a glass sheet and sintering at 90 °C for 10 ~ 15 min,the particle coating showed a good hydrophobic effect,and a water contact angle of 140.2°.Second,by using the non-crosslinked PS spheres swelled with PX as seeds,emulsion polymerization of 3-(trimethoxysilyl)methyl methacrylate(MPS)and St leaded to the formation of the non-spherical composites with surface wrinkles.The modification of the particles with perfluorodecyltrimethoxysilane(PFTMS)and their application in the fabrication of superhydrophobic surfaces is demonstrated.It was found that without addition of PX in the emulsion system,it just leaded to formation of PS/P(MPS-S)composite spheres.When PX was introduced to swell the seeds before polymerization,the non-spherical composite particles would be obtained.As the amount of PX was enlarged,the degree of particle deformation became larger,and the surface roughness increased and the inward indentation expanded.With the increase in the diameter of PS spheres,the formation of buckled surface was preferred to that of the local indentation,and their morphologies changed from deflated-ball shape to dried-plum shape.When the size of PS spheres was further increased,the rugby-like particles formed.When the amount of MPS was small,the surface of PS/P(MPS-S)composite particles is depressed and wrinkled.With the increase of the mass ratio of MPS to St(wMPS/wSt),only buckled surface was formed,and the thermal performance of the obtained particles increased.After modification with PFTMS,the non-spherical composite particles were used to fabricate superhydrophobic coatings.When wPX/wPS = 4/1,the particle coating showed a water contact angle of up to 160.4°.By using OFMA or GMA as a substitute for St,the resulting particles exhibited the morphologies of dried-plum.The emulsion polymerization of MPS with HEMA or MMA resulted to the formation of deflated-ball like morphology.Additionally,the snowman-shaped composite particles were prepared via two different methods solvent swelling and seeded emulsion polymerization.The first method employs PS/P(MPS-S)composite spheres as seeds and PX as swelling agent and snowman-like composite particles were prepared through swelling and deswelling.The other is that the snowman-like composite particles can be polymerized by swelling the PS/P(MPS-S)seed particles with St monomer.For the snowman-like composite particles prepared by the method of solvent swelling,the diameter of the extruded part became larger with the increase of swelling temperature,and the original part of the particles gradually formed surface folds,resulting in two kinds of surface roughness.When wPX/wseed = 4/1,almost all of the seeds were transformed into snowman-like particles with distinct morphology.As the seeds became larger,the diameter of the extruded portion gradually decreased,and the original part of the particles was less likely to form a surface fold.When the spherical PS/P(MPS-S)composite particles were used as seeds,and the surface of the snowman-shaped particles prepared by seed emulsion polymerization was formed without wrinkles.With the increase of the amount of St,the extruded compartment gradually growed up,which could be even larger than the original one.The snowman-like composite particles without surface wrinkles could also be transformed into particles with double surface roughness by solvent swelling method,and the roughness of surface wrinkles improved with the increase of swelling temperature.Also the snowman-shaped particles with double surface roughness could be prepared by seed emulsion polymerization with non-spherical PS/P(MPS-S)composite particles as seeds.With the increase of the St monomer amount or the size of seed particles,the diameter of the extruded portion gradually increases.