Simple and convenient synthetic methods are highly in demand for the preparation and application of patchy particles (PPs) with diverse morphologies, functionalities and behaviors. Very recently, step-growth heterogeneous click polymerizations have been developed to fabricate monodisperse, spherical, soft and clickable particles. However, so far, this technique has seldom involved forming structures (core–shell, or pores, etc.), anisotropic shapes and compositions of particles. Herein, we prepare PPs with a hard body and soft, clickable dimple- or bulge-patches by incorporating step-growth thiol–ene polymerizations into the chain-growth polymerization of styrene (St) in a dispersion system. The phase separation between thiol–ene polymers and PSt in growing particles occurs due to their differences in the glass transition temperature (Tg) and hydrophilicity, forming core–shell and dimple- or bulge-patched particles. SEM and TEM images of the degraded particles confirm that the patches are primarily composed of click polymers. Varying the addition time, amounts, feed ratio and type of thiol/ene monomer, degree of phase separation, shape, number and size of patches, and contents of thiol/ene segments in/on patches are tuned flexibly. FI-IR analyses reveal that off-stoichiometric thiol and ene segments are incorporated, owing to off-stoichiometric thiol–ene reactions concurrent with the polymerization of St, even when stoichiometric thiol and ene are added. Moreover, Fe3O4 or Ag nanoparticles are attached on the PSt body with –SO3− groups or on click polymer patches with –SH groups. Post-modifications of PPs are carried out through reactions of excess –SH or –CC– groups on patches with –CC– or –SH group-containing monomers. Superhydrophobic or hydrophilic particulate films, or fluorescent tagged PPs are prepared.

Previously, it was a challenge to develop a direct and convenient synthetic means for production of anisotropic particles, formation of structures (core–shell, cavity, hollow, etc.) and functionalization of domains all at once. Herein, we present a simple one-step dispersion polymerization (Dis.P) approach to synthesize particles with a combination of anisotropies in morphology, surface roughness, structure and composition. This approach needs no delayed addition of agents, and is of comparable simplicity to the preparation of conventional spherical particles. A cross-linker of dimethacryloyloxybenzophenone (DMABP) is added at the beginning of Dis.P of styrene (St). Evolution of monomer conversion, particle gel content and morphology during Dis.P indicates that DMABP is consumed early and rapidly, creating a high cross-linking of a growing particle at a low conversion, thus inducing phase separation and producing snowman- or dumbbell-like particles which contain a firstly cross-linked, coarse growing particle domain (G domain) and an uncross-linked or subsequently cross-linked, smooth, new domain (N domain). The size, surface roughness, structure and composition of the domains are tuned by initially adding various amounts of DMABP and a low amount of functional monomers. Due to the quick reaction of hydrophilic 4-vinylpyridine (4-VP), glycidyl methacrylate (GMA) or methacrylic acid (MAA), the G domain is enriched with pyridyl, epoxy or carboxyl groups, as detected by XPS and EDS. Through the delayed reaction of monomers containing alkynyl groups (–CC–), the N domain is enriched with –CC– groups, and the core–shell (cross-linked) structure is formed. With aids of thiols added during Dis.P, SH– or fluorine-containing groups are primarily incorporated on the N domain, and the porous, cavity or hollow structure of the N domain is generated due to phase separation between polystyrene (PSt) and the polymer produced by the click reaction. On adding two functional monomers (MAA and monomer containing –CC– groups), various functional groups enrich G and N domains, respectively, owing to the sequential reactions of monomers.

Preparation of anisotropic particles based on phase separation of prefabricated seeds in polymerizations generally involves multiple process steps. In conventional one-pot dispersion polymerization, only spherical particles are produced. Herein, anisotropic particles with asymmetrical core-shell structure, multiple compartments, and continuously tunable surface roughness and sizes were synthesized by a modified one-pot dispersion polymerization. A mixture of polar solvents, ethylene glycol (EG), and water (6/4, vol.) was used as medium for polymerization of styrene (St). In the presence of ammonium persulfate (APS) and vinyl acetate (VA), divinylbenzene (DVB, 16.1–66.4 %) and (St, 50.3–0 %) 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 snowman-like particles with coarse, core-shell structured body, and smooth, no or partially cross-linked head. The newly formed compartments were also inhomogeneously cross-linked and their phases separated, producing three and four compartment anisotropic particles with an aspect ratio up to 2.3. Gel content of final particles was less than 75 %. Due to a sequential cross-linking from growing particle to newly formed compartments, reaction stability and particle monodispersity were maintained even when high amounts of DVB were added. Asymmetrical morphologies, structures, sizes, and surface roughness of particles were continuously tuned by varying DVB amount and its start addition time. This one-pot method provides a simple, efficient route for synthesis of anisotropic particles.

Previously, synthesis of anisotropic particles by seeded polymerizations has involved multiple process steps. In conventional one-pot dispersion polymerization (Dis.P) with a cross-linker added, only spherical particles are produced due to rapid and high cross-linking. In this Article, a straightforward one-pot preparation of monodisperse anisotropic particles with tunable morphology, dimensions, surface roughness, and asymmetrically distributed functional groups is described. With a cross-linker of divinylbenzene (DVB, 8%), ethylene glycol dimethacrylate (EGDMA, 6%), or dimethacryloyloxybenzophenone (DMABP, 5%) added at 40 min, shortly after the end of nucleation stage in Dis.P of styrene (St) in methanol and water (6/4, vol), the swollen growing particles are inhomogeneously cross-linked at first. Then, at low gel contents of 59%, 49%, and 69%, corresponding to the cases using DVB, EGDMA, and DMABP, respectively, the growing particle phase separates and snowman- or dumbbell-like particles are generated. Thermodynamic and kinetic analyses reveal that moderate cross-linking and sufficient swelling of growing particles determine the formation and growth of anisotropic particles during polymerization. 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. The snowman-like particles fabricated with DVB have a gradient cross-linking and asymmetrical distribution of pendant vinyl groups from their body to head. The dumbbell-like particles prepared using DMABP have only one domain cross-linked; i.e., only one domain contains photosensitive benzophenone (BP) groups. With addition of glycidyl methacrylate (GMA) or propargyl methacrylate (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.

In order to achieve monodisperse particles with high content of antibacterial groups covalently bonded on surface, a bicationic viologen, N-hexyl-N′-(4-vinylbenzyl)-4,4′-bipyridinium bromide chloride (HVV) was devised as a surfmer in dispersion polymerization of styrene (St) using a mixture of methanol (or ethylene glycol) and water as media. Effects of content of HVV, its addition profile and composition of reaction media on particles size and incorporation of HVV moieties were mainly investigated. The attachment of silver and gold nanoparticles on particle surface under UV irradiation ascertained the surface-bonded HVV segments. SEM, TEM observations and XPS, zata potential measurements indicated that increase of initial HVV contents and addition of HVV (when polymerization had been performed for 3 h) led to grown particles and enhanced immobilization of HVV moieties. Using a mixture of ethylene glycol and water as reaction media, small particles (5202-142 nm) with highly attached HVV moieties were prepared. Furthermore, antibacterial efficacy of the resultant particles against S. aureus was assayed, and particles with more HVV moieties anchored on surface demonstrated greater efficiency of antibacterial activity.

By exploringly introducing a bicationic viologen, N-hexyl-N'-(4-vinylbenzyl)-4,4′-bipyridinium bromide chloride (HVV) to dispersion polymerization of styrene (St) in a mixture of methanol and water, we achieved the following results: (1) monodisperse, core-shell microspheres with antibacterial surface were prepared by a simple one-step procedure, (2) diameter, core radii and shell thickness of resultant particles could be controlled by concentrations of HVV, monomer and initiator, and composition of media, (3) HVV could act not only as a monomer as that in previous modifications, but also as an efficient, novel stabilizer, and its copolymerization with St at interfacial layer and coagglutination of (co-)oligomers on core surface due to its moderate reactivity and hydrophilicity were conceived to be main reasons for formation of core-shell structures. Effects of HVV on polymerization behavior of St, evolution of core-shell structure, and morphology, size of particles were investigated. Moreover, antibacterial activity of resulted microspheres against Staphylococcus aureus was assayed.