Versatile synthesis of high performance, crosslinked polymer microcapsules with encapsulated n-hexadecane as heat storage materials by utilizing microsuspension controlled/living radical polymerization (ms CLRP) of ethylene glycol dimethacrylate with the SaPSeP method

Interfacial photocrosslinking of polymer particles possessing nucleobase photoreactive groups for hollow/capsule polymer fabrication

Herein, polystyrene-based particles possessing nucleobases in polymer side chains were prepared and nucleobase groups were applied to the interfacial photocrosslinking as photoreactive groups for the first time for fabricating hollow/capsule particles.

Synthesis of Micrometer-Sized Poly(methyl acrylate) by Temperature-Step Microsuspension Polymerization with Iodoform Based on the "Radical Exit Depression" Effect§

Previously, we have reported the successful preparation of micrometer-sized poly(methyl methacrylate) particles without submicrometer-sized byproduct particles by microsuspension iodine-transfer polymerization (ms ITP), in which the radical exit depression (RED) effect was expected, with the benzoyl peroxide initiator at 8 wt % relative to the monomer. However, it was difficult to apply it simply under a similar condition for methyl acrylate (MA), which is more hydrophilic than methyl methacrylate (MMA), because the polymerization rate in the water phase (R_p^w) arising from the oligomer radicals exiting from the monomer droplets is high, resulting in a lot of submicrometer-sized byproduct particles. In this study, the problem was overcome by utilizing a two-step temperature process in the microsuspension polymerization with iodoform (ms I) of MA, which supports the proposed mechanism in the ms ITP of MMA in the previous paper. Although the control of the molecular weight (M_n) and the molecular weight distribution (M_n/M_w) was restricted, the preparation of micrometer-sized particles without byproduct particles was realized and a high conversion was reached within a practical time that meets the demands of the industry by utilizing the ms I. The optimal conditions for MA were 70 °C for 2 h, followed by 80 °C for 4 h with a high content of initiator (8 wt % relative to a monomer).

Cross-Linker-Controlled Ostwald Ripening in Emulsion Polymerization of Hollow Copolymer Nanoparticles

We propose a synthesis method for hollow copolymer nanoparticles, in which the size is controllable by the wettability of the materials designed by relative energy difference (RED). We investigated the influence of cross-linkers in RED and the hollow polymer nanoparticle synthesis. The size of the nanoparticles was characterized by scanning electron microscopy and transmission electron microscopy images. The diameter size of the hollow copolymer (styrene-co-methyl methacrylate) changes from 400 to 141 nm and the average core-vacancy sizes changes from 330 to 71 nm as increasing the feed ratio of the cross-linker, divinyl benzene, from 0.07 to 0.43. Cross-linkers in polymerization precipitates a polymerization reaction to produce seed copolymer particles quickly. The seed copolymer is a more transferrable medium through the surfactants across emulsion droplets and inhibits emulsion growth by unstable concentration variations of seed copolymers in emulsions. Therefore, Ostwald ripening was reduced by a higher feeding ratio of the cross-linker in the copolymer, which tends to produce smaller sized hollow nanoparticles.

Size-Controllable, Single-Step, and Scalable Synthesis of Hollow Polymer Nanoparticles

Hollow polymer nanoparticles are of great importance in various industrial fields such as drug delivery vehicles in pharmaceutics, high thermal insulation materials for heat flow blocking and energy savings, and materials with unique optical properties. While the fabrication methods for hollow polymer nanoparticles have been studied and developed by numerous researchers, most synthesis methods require a rather complicated process, including a thorough core-washing step to formulate pores inside the particles. Single-step synthesis methods were developed to overcome this practical issue by utilizing the sacrificial solvent filling the pores temporarily and having it naturally evaporate without further process; however, such processes could not produce sub-200 nm diameter particles, which limit the application for high surface area applications. Herein, we have developed an innovative synthesis method that can overcome the particle size limitation by utilizing a sacrificial solvent for pore formation and a recondensation inhibitor. Pseudo-state Ostwald ripening was realized by selecting the sacrificial solvent with less affinity to the copolymer of hollow polymer particles, thus inhibiting the particle growth during polymerization. We have successfully obtained 120 nm diameter hollow PS-PMMA copolymer particles in large quantity via the single-step preparation of emulsion polymerization.

Protein-Polymer Microcapsules for PCR Technology

Protein-polymer microcapsules have attracted much attention, due to their special features and potential in biological use. How to make the most of this type of bio-abiotic hybrid material is an intriguing question. Nevertheless, several unsatisfactory technical issues significantly limited the application of these materials. For instance, introducing various biomolecules and crosslinking for the capsules remains challenging and problematic. In this report, recombinant mCherry protein was covalently linked with poly(N-isopropylacrylamide) (PNIPAAm) to form amphiphilic protein-polymer conjugates, which assembled into microcapsules. These microcapsules are thermoresistant and can be used in the polymerase chain reaction (PCR). In this setting, the reactant molecules can be readily and easily introduced into the microcapsules, and crosslinking and water-oil phase transition are not necessary. This protein-polymer microcapsule PCR system has potential in various biological applications.

The influence of microcapsules with a partially filled structure on the damping properties of an epoxy resin

Loss factor relies on the core volume fraction and the concentration of the microcapsule in the epoxy resin.