Thermodynamic and kinetic considerations on the morphological stability of “hamburger-like” composite polymer particles prepared by seeded dispersion polymerization

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.

Mechanism Analysis of Selective Adsorption and Specific Recognition by Molecularly Imprinted Polymers of Ginsenoside Re

In this article, the molecularly imprinted polymers (MIPs) of ginsenoside Re (Re) were synthesized by suspension polymerization with Re as the template molecule, methacrylic acid (MAA) as the functional monomers, and ethyl glycol dimethacrylate (EGDMA) as the crosslinker. The MIPs were characterized by Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM), and surface porosity detector, and the selective adsorption and specific recognition of MIPs were analyzed using the theory of kinetics and thermodynamics. The experimental results showed that compared with non-imprinted polymers (NIPs), MIPs had a larger specific surface area and special pore structure and that different from the Langmuir model of NIPs, the static adsorption isotherm of MIPs for Re was in good agreement with the Freundlich model based on the two adsorption properties of MIPs. The curves of the adsorption dynamics and the lines of kinetic correlation indicate that there was a fast and selective adsorption equilibrium for Re because of the affinity of MIPs to the template rather than its analogue of ginsenoside Rg1 (Rg1). The study of thermodynamics indicate that the adsorption was controlled by enthalpy and that MIPs had higher enthalpy and entropy than NIPs, which contributed to the specific recognition of MIPs.

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.

Direct observation of the formation of liquid protrusions on polymer colloids and their coalescence

Monodisperse nonspherical poly (methyl methacrylate) (PMMA) particles where a central core particle had grown two extra "lobes", or protrusions, placed opposite each other were successfully synthesized by swelling and subsequent polymerization of cross-linked PMMA spheres with methyl methacrylate and the cross-linker ethylene glycol dimethacrylate. The use of large (~3 μm) seed particles allowed for real-time monitoring of the swelling and deswelling of the cross-linked particles with optical microscopy. First, a large number of small droplets of swelling monomers formed simultaneously on the surface of the seed particles, and then fused together until under certain conditions two protrusions remained on opposite sides of the seed particles. The yield of such particles could be made up to 90% with a polydispersity of 7.0%. Stirring accelerated the transfer of the swelling monomers to the seed particles. Stirring was also found to induce self-assembly of the swollen seed particles into a wide variety of n-mers, consisting of a certain number, n, of swollen seed particles. The formation of these structures is guided by the minimization of the interfacial free energy between the seed particles, liquid protrusions and aqueous phase, but stirring time and geometrical factors influence it as well. By inducing polymerization the structures could be made permanent. Some control over the topology as well as overall size of the clusters was achieved by varying the stirring time before polymerization. 3D models of possible particle structures were used to identify all projections of the structures obtained by scanning electron microscopy. These models also revealed that the seed particles inside the central coalesced body were slightly compressed after polymerization. By extending the synthesis of the monodisperse particles with n = 1 to (slightly) different monomers and/or different cores, an important class of patchy particles could be realized.