Polymer Brush-Induced Hollow Colloids via Diffusion-Controlled Silication

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.

Synthetic Strategies for Polymer Particles with Surface Concavities

Over the past decade or so, there has been increasing interest in the synthesis of polymer particles with surface concavities, which mainly include golf ball-like, dimpled and surface-wrinkled polymer particles. Such syntheses generally can be classified into direct polymerization and post-treatment on preformed polymer particles. This review aims to provide an overview of the synthetic strategies of such particles. Some selected examples are given to present the formation mechanisms of the surface concavities. The applications and future development of these concave polymer particles are also briefly discussed. This article is protected by copyright. All rights reserved.

Advances in design and applications of polymer brush modified anisotropic particles

Current advancements in the creation of anisotropy in particles and their surface modification with polymer brushes have established a new class of hybrid materials termed polymer brush modified anisotropic particles (PBMAP). PBMAPs display unique property combinations, e.g., multi-functionality in multiple directions along with smart behavior, which is not easily achievable in traditional hybrid materials. Typically, anisotropic particles can be categorized based on three different factors, such as shape anisotropy (geometry driven), compositional anisotropy (functionality driven), and surface anisotropy (spatio-selective surface modification driven). In this review, we have particularly focused on the synthetic strategies to construct the various type of PBMAPs based on inorganic or organic core which may or may not be isotropic in nature, and their applications in various fields ranging from drug delivery to catalysis. In addition, superior performances and fascinating properties of PBMAPs over their isotropic analogues are also highlighted. A brief overview of their future developments and associated challenges have been discussed at the end.

Complex Polymeric Microstructures with Programmable Architecture via Pickering Emulsion-Templated In Situ Polymerization

Aside from smooth and spherical microcapsules, the concept of tailoring complex polymeric microstructures is being taken a step ahead due to their great demand in various applications and fundamental studies in the subjects of microfluidics and nanotechnology. Size, shape, and morphology are of paramount importance for their functional performance and various applications. However, simple, inexpensive, versatile, and high-throughput techniques for fabricating microcapsules with controlled morphology remain a bottleneck for discoveries in the subject of polymer colloids. In this paper, we directly fulfill this need by reporting a novel approach of Pickering emulsion-templated in situ polymerization for tailoring complex polymeric microstructures comprised of a composite shell of titanium dioxide nanoparticle (TiO₂ NP)-embedded poly(melamine-urea-formaldehyde) (polyMUF) and a core of hexadecane (HD, soft template). At first, we hydrophobize TiO₂ NPs by chemisorbing long-chain biobased myristic acid via a bidentate chelating complex and precisely tune their wettability by varying the grafting density of myristic acid to obtain highly stable oil-in-water (O/W) Pickering emulsion. Thereafter, we employ the optimized TiO₂ NPs in the intended encapsulation strategy that enables various microstructures and morphologies with the particle diameter ranging from 5 to 20 μm. Careful manipulation of reaction parameters and copolymer components leads to novel complex microstructures: smooth, raspberry-like, partially budded, hollow, filled, single-holed, and closed-cell-like microstructures. Particle properties such as morphology, size, shell thickness, and core content are governed by the TiO₂ NP content, core-to-shell ratio, copolymer component, conversion, and pH value. Based on the results of a series of control experiments, novel mechanisms for the formation of various such microstructures are proposed.

Probing polymer brushes with electrochemical impedance spectroscopy: a mini review

Polymer brushes are frequently used as surface-tethered antifouling layers in biosensors to improve sensor surface-analyte recognition in the presence of abundant non-target molecules in complex biological samples by suppressing nonspecific interactions. However, because brushes are complex systems highly responsive to changes in their surrounding environment, studying their properties remains a challenge. Electrochemical impedance spectroscopy (EIS) is an emerging method in this context. In this mini review, we aim to elucidate the potential of EIS for investigating the physicochemical properties and structural aspects of polymer brushes. The application of EIS in brush-based biosensors is also discussed. Most common principles employed in these biosensors are presented, as well as interpretation of EIS data obtained in such setups. Overall, we demonstrate that the EIS-polymer brush pairing has a considerable potential for providing new insights into brush functionalities and designing highly sensitive and specific biosensors.