Micron-sized, monodisperse, snowman/confetti-shaped polymer particles by seeded dispersion polymerization

Janus Composite Particles and Interfacial Catalysis Thereby

Janus composite particles (JPs) with distinct compartmentalization of varied components thus performances and anisotropic shape display a variety of properties and have demonstrated great potentials in diversify practical applications. Especially, the catalytic JPs are advantageous for multi-phase catalysis with much easier separation of products and recycling the catalysts. In the first section of this review, typical methods to synthesize the JPs with varied morphologies are briefly surveyed in the category of polymeric, inorganic and polymer/inorganic composite. In the main section, recent progresses of the JPs in emulsion interfacial catalysis are summarized covering organic synthesis, hydrogenation, dye degradation, and environmental chemistry. The review will end by calling more efforts toward precision synthesis of catalytic JPs at large scale to meet the stringent requirements in practical applications such as catalytic diagnosis and therapy by the functional JPs.

Synthesis of dimpled polymer particles and polymer particles with protrusions - Past, present, and future

Since the development of emulsion polymerization techniques, polymer particles have become the epitome of standard colloids due to the exceptional control over size, size distribution, and composition the synthesis methods allow reaching. The exploration of different variations of the synthesis methods has led to the discovery of more advanced techniques, enabling control over their composition and shape. Many early investigations focused on forming particles with protrusions (with one protrusion, called dumbbell particles) and particles with concavities, also called dimpled particles. This paper reviews the literature covering the synthesis, functionalization, and applications of both types of particles. The focus has been on the rationalization of the various approaches used to prepare such particles and on the discussion of the mechanisms of formation not just from the experimental viewpoint but also from the standpoint of thermodynamics. The primary motivation to combine in a single review the preparation of both types of particles has been the observation of similarities among some of the methods developed to prepare dimpled particles, which sometimes include the formation of particles with protrusions and vice versa. The most common applications of these particles have been discussed as well. By looking at the different approaches developed in the literature under one general perspective, we hope to stimulate a more ample use of these particles and promote the development of even more effective synthetic protocols.

Nanosphere Lithography: A Versatile Approach to Develop Transparent Conductive Films for Optoelectronic Applications

Transparent conductive films (TCFs) are irreplaceable components in most optoelectronic applications such as solar cells, organic light-emitting diodes, sensors, smart windows, and bioelectronics. The shortcomings of existing traditional transparent conductors demand the development of new material systems that are both transparent and electrically conductive, with variable functionality to meet the requirements of new generation optoelectronic devices. In this respect, TCFs with periodic or irregular nanomesh structures have recently emerged as promising candidates, which possess superior mechanical properties in comparison with conventional metal oxide TCFs. Among the methods for nanomesh TCFs fabrication, nanosphere lithography (NSL) has proven to be a versatile platform, with which a wide range of morphologically distinct nanomesh TCFs have been demonstrated. These materials are not only functionally diverse, but also have advantages in terms of device compatibility. This review provides a comprehensive description of the NSL process and its most relevant derivatives to fabricate nanomesh TCFs. The structure-property relationships of these materials are elaborated and an overview of their application in different technologies across disciplines related to optoelectronics is given. It is concluded with a perspective on current shortcomings and future directions to further advance the field.

Janus particles: A review of their applications in food and medicine

In contrast to conventional particles that have isotropic surfaces, Janus ("two-faced") particles have anisotropic surfaces, which leads to novel physicochemical properties and functional attributes. Janus particles with differing compositions, structures, and functional attributes have been prepared using a variety of fabrication methods. Depending on their composition, Janus particles have been classified as inorganic, polymeric, or polymeric/inorganic types. Recently, there has been growing interest in preparing Janus particles from biological macromolecules to meet the demand for a more sustainable and environmentally friendly food and pharmaceutical supply. At interfaces, Janus particles exhibit the characteristics of both surfactants and Pickering stabilizers, and so their behavior can be described using adsorption theories developed to describe these surface-active substances. Research has highlighted several potential applications of Janus particles in food and medicine, including emulsion formation and stabilization, toxin detection, antimicrobial activity, drug delivery, and medical imaging. Nevertheless, further research is needed to design and fabricate Janus particles that are suitable as functional ingredients in the food and biomedicine industries.

Preparation of Polypropylene-Composite Particles by Dispersion Polymerization

Polypropylene (PP)/poly(benzyl methacrylate) (PBzMA) composite particles were prepared by dispersion polymerization of benzyl methacrylate (BzMA) in the presence of PP particles without a conventional dispersant. The polymerization process yielded a stable emulsion of composite particles with a "currant bun"-like morphology consisting of a PBzMA core and PP bumps, indicating that the PP particles operate as colloidal stabilizers. Conversely, when BzMA was replaced with styrene as the monomer, dispersion polymerization yielded a large amount of aggregates. Finally, a stable emulsion was formed by copolymerizing a small amount of methyl methacrylate (MMA) with styrene. This result suggested that PP must interact with a second polymer to prepare stable composite particles. The surfaces of the PP particles, which are highly hydrophilic due to their carboxyl groups, were involved in the attachment and stabilization of the polymer precipitated in the medium. A film prepared from the obtained PP/PBzMA composite particles was highly hydrophobic and strongly adhesive to a PP sheet.

Monodisperse Liquid Crystalline Polymer Shells with Programmable Alignment and Shape Prepared by Seeded Dispersion Polymerization

Monodisperse, micrometer-sized liquid crystalline (LC) shells are prepared by seeded dispersion polymerization. After polymerizing LC monomer mixtures in the presence of non-crosslinked polymer seeds, hollow LC polymer shells with programmable alignment and shape are prepared by removing the seeds. The LC alignment in the LC polymer shells can be easily manipulated by the polymer seeds, as a radial alignment is observed with amorphous poly(phenyl methacrylate) seeds and a bipolar alignment is observed with bipolar LC polymer seeds. After removal of the seeds, the radially aligned samples give radially aligned shells with small dimples. The resulting bipolar LC polymer shells collapse into a biconcave shape. Polarized optical microscopy and transmission electron microscopy indicate that the collapse occurs at the defect points in the shell. In the case of a lower crosslink density, LC polymer hollow shells with larger dimples are obtained, resulting in cup-shaped polymer particles. Biconcave LC polymer shells based on other LC mixtures have also been prepared, showing the versatility of the seeded dispersion polymerization method.

Morphology control of silicone/poly(methyl methacrylate) (elastic/glassy) composite particles

Composite particles consisting of elastic silicone and glassy poly(methyl methacrylate) were prepared. The morphology of the particles could be alternated between sea-island and core–shell structures by controlling the annealing temperature.

Current status and future developments in preparation and application of nonspherical polymer particles

Nonspherical polymer particles (NPPs) are nano/micro-particulates of macromolecules that are anisotropic in shape, and can be designed anisotropic in chemistry. Due to shape and surface anisotropies, NPPs bear many unique structures and fascinating properties which are distinctly different from those of spherical polymer particles (SPPs). In recent years, the research on NPPs has surprisingly blossomed in recent years, and many practical materials based on NPPs with potential applications in photonic device, material science and biomedical engineering have been generated. In this review, we give a systematic, balanced and comprehensive summary of the main aspects of NPPs related to their preparation and application, and propose perspectives for the future developments of NPPs.

A general strategy to synthesize chemically and topologically anisotropic Janus particles

Emulsion polymerization is the most widely used synthetic technique for fabricating polymeric particles. The interfacial tension generated with this technique limits the ability to tune the topology and chemistry of the resultant particles. We demonstrate a general emulsion interfacial polymerization approach that involves introduction of additional anchoring molecules surrounding the microdroplets to synthesize a large variety of Janus particles with controllable topological and chemical anisotropy. This strategy is based on interfacial polymerization mediated by an anchoring effect at the interface of microdroplets. Along the interface of the microdroplets, the diverse topology and surface chemistry features of the Janus particles can be precisely tuned by regulating the monomer type and concentration as well as polymerization time. This method is applicable to a wide variety of monomers, including positively charged, neutrally charged, and negatively charged monomers, thereby enriching the community of Janus particles.

Preparation of “hard-soft” Janus polymeric particles via seeded dispersion polymerization in the presence of n-paraffin droplets

A newly emerged class of Janus polymer particles, so-called “hard-soft” ones, were produced using seeded dispersion polymerization (SDP) of 2-ethylhexyl methacrylate (EHMA) with polystyrene (PS) particles in the presence of n-paraffin droplets.

One-pot facile synthesis of half-cauliflower amphiphilic Janus particles with pH-switchable emulsifiabilities

A facile synthesis strategy for generating two types of highly uniform amphiphilic polymer Janus particles, spherical seeds and half-cauliflower particles, is first presented.

Synthesis of "hard-soft" janus particles by seeded dispersion polymerization

The majority of studies on Janus particles focus on those that show amphiphilicity, with distinct hydrophilic and hydrophobic domains. Here, we demonstrate the synthesis of a different class of Janus particles: "hard-soft" biphasic dumbbell- or peanut-shaped particles with distinct lobes of "soft" poly(n-butyl acrylate) and "hard" poly(styrene). The particles are made by seeded dispersion polymerization of butyl acrylate in the presence of poly(styrene) seed particles. Surface nucleation by capture of the oligoradicals onto the surface of the seed particles thereby forming a distinct new polymer phase is found to be the formation mechanism of these particles. The total available poly(styrene) seed surface area plays a significant role in the size and number of poly(butyl acrylate) lobes grown off a single particle. At particularly low values of the surface area, we observe the formation of multilobe particles. We further demonstrate that our synthesis method is versatile and can be extended to the submicrometer domains by using seed particles of 200 nm in diameter.

Facile preparation of raspberry-like superhydrophobic polystyrene particles via seeded dispersion polymerization

A simple and facile approach was developed to fabricate raspberry-like or snowman-like particles via seeded dispersion polymerization by just changing the ratio of second monomer styrene (St) to seeds in which poly(styrene-co-hydrolyzed-methacryloxypropyltrimethoxysilane) [P(St-co-MPS)] latex was used as seeds with hydrolyzed-MPS as a cross-linking agent. The morphologies of final products were confirmed by field-emission scanning electron microscopy and transmission electron microscopy. Interestingly, the seed part of snowman-like particles showed raspberry-like with adsorbing quantities of PS particles while the other part smooth. The formation mechanism of the raspberry-like particles was also discussed. The superhydrophobic surface with both the static contact angle of 158° and high adhesion to water could be achieved by the hydrophobization of the particulate film with octadecyltrimethoxysilane that was formed from the raspberry-like particles decorated by a thin layer of silica nanoparticles. Further, through encapsulating Ag nanoparticles within the surface, the obtained raspberry-like PS/Ag/SiO2 nanocomposite particles exhibited excellent antibacterial property simultaneously.

Facile preparation route toward speckled colloids via seeded polymerization

A facile method to prepare monodisperse speckled colloids has been developed via one-step seeded polymerization from noncross-linked latex particles. It was found that both cross-linking agents in the added monomer mixture and charged initiation species are essential for the formation of speckles on composite latex particle surface in seeded polymerization. The size and number density of speckles on the surface are tunable by adjusting the concentration of surfactant. A possible mechanism for the formation of such speckled colloids has been proposed based on a series of control experiments. Speckled colloidal particles were used as substrates for the adsorption of tobacco mosaic virus, and a much stronger adsorption was observed compared to smooth particles, implying a potential application of these speckled particles in virus collection and more.

Conducting Material-incorporated Electrorheological Fluids: Core-shell Structured Spheres

Conducting material-based electro-responsive particles have become important as the smart soft matter in electrorheological (ER) fluids. These materials include conducting polymers, such as polyaniline, polypyrrole and poly(3,4-ethylenedioxythiophene), and carbon materials, such as carbon nanotubes and graphene oxide. Core-shell structured ER particles containing these materials as either core or shell species have attracted increasing interest owing to their outstanding advantages of an enhanced ER effect or diverse ER mechanism, lighter particulate density and lower cost. This paper summarizes the recent advances in synthesis methods as well as the critical characteristics of the core-shell structured particles, such as shear stress, yield stress and dielectric properties.

Sonochemical synthesis of magnetic Janus nanoparticles

The sonochemical synthesis of nanosized surface-dissymmetrical (Janus) particles is described. The Janus particles were composed of silica and polystyrene, with the polystyrene portion loaded with nanosized magnetite particles. It is shown that the Janus particles can be used to form kinetically stable oil-in-water emulsions that can be spontaneously broken on application of an external magnetic field. The one-pot synthetic process used to prepare the Janus particles has several advantages over other conventional methods of producing such particles.