Synthesis Of Functional Anisotropic Particles Via Control Of Phase Separation During One-POT Dispersion Polymerization

Anisotropic particles are compartmentalized colloids with two sides of different chemistry and/or polarity. Anisotropic particles have attracted great attention recently because of their novel properties and potential applications. Recently, various strategies have been developed to synthesize anisotropic particles. It is recognized that the most promising strategy meets the following requirements:(1) The process is simple, and high yields of anisotropic particles can be achieved by it. (2) Morphology, structure, dimension and surface property of anisotropic particles are tunnable. Control of phase separation in seeded polymerzation is a comparatively ideal method. However, many limitations still remain. For instance, multiple process steps, including synthesis of seeds, additional modification to endow surface with hydrophilicity to increase interfacial tensions, cross-linking and swelling of seeds, and subsequent polymerization, are required. In this thesis, anisotropic particles with controllable morphology, structure and functional groups in surface were synthesis via control of surface hydrophilicity, swelling degree and cross-linking degree of growing particles during one-pot dispersion polymerization. The major contents are shown as follows:1. Monodisperse anisotropic particles with core-shell/hollow structures and partially rough surface were synthesized straightforward via control of phase separation during growth stage. A mixture of ethylene glycol (EG) and water (6/4, vol.) was used as medium for polymerization of styrene (St). Sodium p-styrene sulfonate (NaSS) was used as dispersant, and Azobis(isobutyronitrile) (AIBN) was used as initiator. In the presence of ammonium persulfate (APS) and vinyl acetate (VA), divinylbenzene (DVB) and styrene (St) were added at 60,180, and 360 min, respectively. Dense cross-linking was confined to exterior of swollen growing particles, resulting in phase separation and formation of anisotropic particles. The newly formed compartments were also inhomogeneously cross-linked and their phases separated, producing three and multi-compartment anisotropic particles. Asymmetrical morphologies, structures, sizes, and surface roughness of particles were continuously tuned by varying DVB amount and its start addition time. Moreover, Obtained anisotropic particles could be acted as surfactant to emulsify toluene and water.2. Monodisperse anisotropic particles were synthesized via control of phase separation during growth stage in the presence of swelling solvent. A mixture of methanol (MeOH), and water (6/4, vol.) was used as medium for polymerization of styrene (St). Sodium p-styrene sulfonate (NaSS) was used as dispersant, and Azobis(isobutyronitrile) (AIBN) was used as initiator. Swelling solvent was injected to system at 100 min,60 min after addition of DMABP/St. Two kinds of phase separation occurred. One is phase separation between growing cross-linked particles and linear polymer induced by elastic stress of the contracting particle. The other is the phase separation between n-heptane and growing particles induced by cooling the temperature during taking samples. Protrusion exhibited varying degrees of shrink due to the removal of n-heptane by centrifugation. Asymmetrical morphologies and surface roughness of particles were tuned by varying type or amount of swelling solvent.3. A mixture of methanol (MeOH), and water (6/4, vol.) was used as medium for polymerization of styrene (St). Sodium p-styrene sulfonate (NaSS) was used as dispersant, and Azobis (isobutyronitrile) (AIBN) was used as initiator. With a cross-linker of divinylbenzene (DVB), ethylene glycol dimethacrylate (EGDMA), or 4,4’-dimethacryloyloxybenzophenone (DMABP) added at 40 min, the swollen growing particles are inhomogeneously cross-linked at first. Then the growing particle phase separates and snowman-or dumbbell-like particles are generated. Morphology, surface roughness, sizes, and cross-linking degrees of each domain of final particles are tuned continuously by varying start addition time and contents of cross-linkers. Moreover, with addition of functional monomers (GMA or PMA) together with DVB or EGDMA, epoxy or alkynyl groups are asymmetrically incorporated. With the aid of these functional groups, carboxyl, amino, or thiol groups and PEG (200) are attached by thiol-ene (yne) click and photocoupling reactions.4. Monodisperse anisotropic particles were synthesized via control of phase separation during nucleation stage. A mixture of methanol (MeOH), and water (6/4, vol.) was used as medium for polymerization of styrene (St). Sodium p-styrene sulfonate (NaSS) was used as dispersant, Azobis(isobutyronitrile) (AIBN) was used as initiator, and DMABP was used as cross-linker. Morphology, structure, and surface roughness of final particles are tuned by varying the content of cross-linker. Quick reaction of 4-VP, GMA or MAA facilitated an enrichment of pyridyl, epoxy or carboxyl groups on body, while delayed consumption of monomers containing-C≡C-groups favouredan enrichment of-C=C-groups, SH-or other groups on head. Mixing MAA and a monomer containing-C≡C-groups together, enrichments of carboxyl groups on body and of -C≡C-or fluorine-containing groups on head were achieved. With the aid of these functional groups,-SH or-F were attached by thiol-yne click reaction.In this thesis, we demonstrated a facile, straightforward one-pot dispersion polymerization method for synthesis of anisotropic particles with diverse morphologies, structures and various functional groups in large scale. It is of significance to the synthesis and application of functional anisotropic particles.