Adsorption of Silica Nanoparticles onto Poly(N-vinylpyrrolidone)-Functionalized Polystyrene Latex

Preparation of Surface-Wrinkled Silica-Polystyrene Colloidal Composite Particles

In this work, we report a facile emulsion swelling route to prepare surface-wrinkled silica-polystyrene (SiO2-PS) composite particles. Submicrometer-sized, near-spherical SiO2-PS composite particles were first synthesized by dispersion polymerization of styrene in an ethanol/water mixture, and then, surface-wrinkled SiO2-PS particles were obtained by swelling the SiO2-PS particles with a toluene/water emulsion and subsequent drying. It is emphasized that no surface pretreatment on the SiO2-PS composite particles is required for the formation of the wrinkled surface, and the most striking feature is that the surface-wrinkled particle was not deformed from a single near-spherical SiO2-PS composite particle but from many ones. The influence of various swelling parameters including toluene/particle mass ratio, surfactant concentration, stirring rate, swelling temperature, swelling time, and silica size on the morphology of the composite particles was studied. This method represents a new paradigm for the preparation of concave polymer colloids.

Synthesis of dimpled polymer-silica nanocomposite particles by interfacial swelling-based seeded polymerization

Dimpled polymer-silica nanocomposite particles have the combined advantages of dimpled particles and polymer-silica nanocomposite particles. This study presents a novel approach to prepare these particles by interfacial swelling-based seeded polymerization. Polystyrene-silica (PS-SiO2) nanocomposite particles are first prepared by emulsion polymerization of styrene in the presence of glycerol-functionalized silica sols and then dimpled polymer-SiO2 particles are fabricated by interfacial swelling of butyl acrylate (BA)/toluene and subsequent seeded polymerization of BA with the PS-SiO2 particles as seeds. The effects of different parameters, such as the amount of surfactant used in the PS-SiO2/H2O dispersion, BA/toluene mass ratio, PS-SiO2/H2O mass ratio and stirring rate, on the formation of the dimpled particles are investigated. Optimization of the seeded polymerization conditions allows a relatively high percentage of dimpled particles to be achieved.

What is the role of PEO chains in the assembly of core-corona supraparticles in aqueous dispersions?

Hypothesis The assembly of core-corona supraparticles in aqueous dispersions has been regularly assisted by auxiliary monomers/oligomers which modify the individual particles with, e.g., surface grafting of polyethylene oxide (PEO) chains or other hydrophilic monomers. However, this modification complicates the preparation and purification procedures and increases potential upscaling efforts. Hybrid polymer-silica core-corona supracolloids could be more simply assembled if the PEO chains from surfactants, typically used by default as polymer stabilizers, concomitantly act as assembly promotors. The supracolloids assembly could therefore be more easily achieved without requiring particles functionalization or post-purification steps. Methods The self-assembly of supracolloidal particles prepared with PEO-surfactant stabilized (Triton X-405) and/or PEO-grafted polymer particles is compared to differentiate the roles of the PEO chains in the assembly of core-corona supraparticles. Using time-resolved dynamic light scattering (DLS) and cryogenic transmission electron microscopy(cryo-TEM), the effect of concentration of PEO chains (from surfactant) on the kinetics and dynamics of supracolloids assembly is investigated. Self-consistent field (SCF) lattice theory was used to numerically study the distribution of PEO chains at the interfaces present in the supracolloidal dispersions. Findings The PEO based surfactant can be used as assembly promoter of core-corona hybrid supracolloids due to its amphiphilic nature and via establishing hydrophobic interactions. The concentration of the PEO surfactant, and especially the PEO chains distribution over the different interfaces, crucially affect the supracolloids assembly. A simplified pathway for preparing hybrid supracolloidal particles with a well-controlled corona coverage over polymer cores is presented.

In Situ Coatings of Polymeric Films with Core Polystyrene, Core-Shell Polystyrene/SiO2, and Hollow SiO2 Micro/Nanoparticles and Potential Applications

In many industrial settings, films of polymers such as polypropylene (PP) and polyethylene terephthalate (PET) require surface treatment due to poor wettability and low surface energy. Here, a simple process is presented to prepare durable thin coatings composed of polystyrene (PS) core, PS/SiO₂ core-shell, and hollow SiO₂ micro/nanoparticles onto PP and PET films as a platform for various potential applications. Corona-treated films were coated with a monolayer of PS microparticles by in situ dispersion polymerization of styrene in ethanol/2-methoxy ethanol with polyvinylpyrrolidone as stabilizer. A similar process on untreated polymeric films did not yield a coating. PS/SiO₂ core-shell coated microparticles were produced by in situ polymerization of Si(OEt)₄ in ethanol/water onto a PS-coated film, creating a raspberry-like morphology with a hierarchical structure. Hollow porous SiO₂-coated microparticles onto a PP/PET film were formed by in situ dissolution of the PS core of the coated PS/SiO₂ particles with acetone. The coated films were characterized by E-SEM, FTIR/ATR, and AFM. These coatings may be used as a platform for various applications, e.g. magnetic coatings onto the core PS, superhydrophobic coatings onto the core-shell PS/SiO₂, and solidification of oil liquids within the hollow porous SiO₂ coating.

Physical Adsorption of Graphene Oxide onto Polymer Latexes and Characterization of the Resulting Nanocomposite Particles

Polymer/graphene oxide (GO) nanocomposite particles were prepared via heteroflocculation between 140-220 nm cationic latex nanoparticles and anionic GO nanosheets in either acidic or basic conditions. It is demonstrated that nanocomposite particles can be formed using either poly(2-vinylpyridine)-b-poly(benzyl methacrylate) (P2VP-PBzMA) block copolymer nanoparticles prepared by reversible-addition chain-transfer (RAFT)-mediated polymerization-induced self-assembly (PISA), or poly(ethylene glycol)methacrylate (PEGMA)-stabilized P2VP latexes prepared by traditional emulsion polymerization. These two latexes are different morphologically as the P2VP-PBzMA block copolymer latexes have P2VP steric stabilizer chains in their corona, whereas the PEGMA-stabilized P2VP particles have a P2VP core and a nonionic steric stabilizer. Nevertheless, both the P2VP-PBzMA and PEGMA-stabilized P2VP latexes are cationic at low pH. Thus, the addition of GO to these latexes causes flocculation to occur immediately due to the opposite charges between the anionic GO nanosheets and cationic latexes. Control heteroflocculation experiments were conducted using anionic sterically stabilized poly(potassium 3-sulfopropyl methacrylate)-b-poly(benzyl methacrylate) (PKSPMA-PBzMA) and nonionic poly(benzyl methacrylate) (PBzMA) nanoparticles to demonstrate that polymer/GO nanocomposite particles were not formed. The degree of flocculation and the strength of electrostatic interaction between the cationic polymer latexes and GO were assessed using disc centrifuge photosedimentometry (DCP), transmission electron microscopy (TEM), and UV-visible spectrophotometry. These studies suggest that the optimal conditions for the formation of polymer/GO nanocomposite particles were GO contents between 10% and 20% w/w relative to latex, with the latexes containing P2VP in their corona having a stronger electrostatic attraction to the GO sheets.

Adsorption-Reaction Processes Between Gelatin and PDMS-E Emulsion Droplets

In this work, the effects of droplet size and reaction time on the adsorption-reaction processes between gelatin and α-[3-(2,3-epoxypropoxy) propyl]-ω-butyl-polydimethylsiloxane (PDMS-E) emulsion droplets were studied. Gelatin molecules were only physically adsorbed on the surface of the PDMS-E droplet in the 0-75 min range, which was unrelated to the droplet size (100-1000 nm). For the small-size droplets (<410 nm), the physical adsorption proceeded over 75 min followed by agglomeration. For middle-size droplets (410-680 nm), the physical adsorption finished at 125 min; subsequently, the nucleophilic reaction between the primary amino group and the epoxy group began to happen, and globular-like or core-shell colloidal particles were formed. For large-size droplets (>680 nm), the nucleophilic reaction occurred at 75 min and produced core-shell or multi-layered colloidal particles. In a word, the physical absorption or nucleophilic reaction between gelatin and PDMS-E emulsion droplets could be controlled by controlling the droplet size and reaction time. Furthermore, the soft tissue paper coated with large-size droplets exhibited excellent resistance to water permeability and flame-resistant performance, which were carried out by water resistance and flammability tests.

Synthesis of Poly(2-aminothiazole)-Coated Polystyrene Particles and Their Excellent Hg(II) Adsorption Properties

Synthesis of conjugated polymer-coated latex particles is an effective method to improve the poor processability of conjugated polyheterocycles. The key to success is to control the overlayer thickness so it is less than the size of the solvated layer of polymeric stabilizer. This paper presents a protocol to coat polymer latex particles with poly(2-aminothiazole) (PAT), which is a relatively new heterocyclic conjugated polymer. The protocol is based on chemical oxidative polymerizations of 2-aminothiazole using copper chloride as the oxidant at a fixed oxidant/monomer molar ratio of 0.5 in aqueous media in the presence of poly(N-vinyl-2-pyrrolidone)-functionalized polystyrene (PS) latex. The effects of monomer concentration, PS concentration, and polymerization temperature on the morphology of the PAT-coated PS composite particles were investigated by SEM and TEM, and the resulting composite particles characterized by FTIR and XPS. Optimization of the initial monomer concentration allowed colloidally stable PAT-coated PS composite particles to be formed at ambient temperature, and the PAT loading was easily adjusted by varying the initial PS concentration. The Hg(II) adsorption properties of selected PAT-coated PS composite particles were assessed preliminarily. The maximum adsorption capacity at 25 °C reached 440.25 mg/g, which is much higher than many other adsorbents.

Synthetic strategies for raspberry-like polymer composite particles

The strategies used for the preparation of raspberry-like polymer composite particles are summarized comprehensively.

Double in Situ Preparation of Raspberry-like Polymer Particles

Well-defined raspberry-like poly(styrene- co-4-vinylpyridine)-SiO₂ nanocomposite particles with a diameter of around 200 nm were easily prepared by a double in situ process in nanoemulsion with the water-soluble dye Eosin Y as the stabilizer. During radical polymerization of the nanodroplets comprising styrene, 4-vinylpyridine (4-VP), and tetraethoxysilane (TEOS), the silane phase is expelled from the polymer phase to the oil/water (o/w) interface. In the later polymerization stage, SiO₂ nanoparticles with a size of around 25 nm were produced via the in situ sol-gel reaction of TEOS at the o/w interface promoted by the negatively charged dye. The pyridine moieties in the copolymer fix the SiO₂ nanoparticles on the surface of the polymer particles by electrostatic interactions without any sign of free unbound silica particles as proven by transmission electron microscopy.

Preparation of Dimpled Polystyrene-Silica Colloidal Nanocomposite Particles

Preparation of polymer-silica colloidal nanocomposite particles with concave shape is challenging and seldom reported. This paper presents a novel and facile method to prepare dimpled polymer-silica nanocomposite particles with a thin silica shell through the judicious combination of alcoholic dispersion polymerization and the decane evaporation method. Submicrometer-sized polystyrene-silica (PS-SiO₂) nanocomposite particles were first prepared by dispersion polymerization of styrene in methanol in the presence of a methanolic silica sol, and then dimpled PS-SiO₂ particles were prepared by heating the near-spherical PS-SiO₂ particles dispersed in methanol/water media in the presence of decane and subsequent cooling. The effects of different heat treatment parameters, such as methanol/water ratio, stirring temperature, and stirring rate on the formation of the nanocomposite particles were investigated. Optimization of the heating conditions allowed ∼100% of dimpled particles to be achieved with one dimple on each particle. Moreover, calcination of the dimpled PS-SiO₂ nanocomposite particles led to the formation of hollow dimpled particles with a thin silica shell. This method is expected to enrich the shapes of polymer-silica nanocomposite particles.

Entrapped Styrene Butadiene Polymer Chains by Sol-Gel-Derived Silica Nanoparticles with Hierarchical Raspberry Structures

A sol-gel transformation of liquid silica precursor to solid silica particles was carried out in a one-pot synthesis way, where a solution of styrene butadiene elastomer was present. The composites, thus produced, offered remarkable improvements of mechanical and dynamic mechanical performances compared to precipitated silica. The morphological analysis reveals that the alkoxy-based silica particles resemble a raspberry structure when the synthesis of the silica was carried out in the presence of polymer molecules and represent a much more open silica-network structure. However, in the absence of the polymer, the morphology of the silica particles is found to be different. It is envisaged that the special morphology of the in situ synthesized silica particles contributes to the superior reinforcement effects, which are associated with a strong silica-rubber interaction by rubber chains trapped inside the raspberry-like silica aggregates. Therefore, the interfaces are characterized in detail by low-field solid-state ¹H NMR spectroscopy, ²⁹Si solid-state NMR spectroscopy, and energy-dispersive X-ray spectroscopy. Low-field ¹H NMR-based double-quantum experiments provide a quantitative information about the cross-link density of the silica-filled rubber composites and about the influence of silane coupling agent on the chemical cross-link density of the network and correlates well with equilibrium swelling measurements. The special microstructure of the alkoxy-based silica was found to be associated with the interaction between alkoxy-based silica and rubber chains as a consequence of particle growth in the presence of rubber chains.