Hollow particles templated from Pickering emulsion with high thermal stability and solvent resistance: Young investigator perspective

Polyurethane Acrylate Oligomer (PUA) Microspheres Prepared Using the Pickering Method for Reinforcing the Mechanical and Thermal Properties of 3D Printing Resin

Some photosensitive resins have poor mechanical properties after 3D printing. To overcome these limitations, a polyurethane acrylate oligomer (PUA) microsphere was prepared using the Pickering emulsion template method and ultraviolet (UV) curing technology in this paper. The prepared PUA microspheres were added to PUA-1,6-hexanediol diacrylate (HDDA) photosensitive resin system for digital light processing (DLP) 3D printing technology. The preparation process of PUA microspheres was discussed based on micromorphology, and it was found that the oil-water ratio of the Pickering emulsion and the emulsification speed had a certain effect on the microsphere size. As the oil-water ratio and the emulsification speed increased, the microsphere particle size decreased to a certain extent. Adding a suitable proportion of PUA microspheres to the photosensitive resin can improve the mechanical properties and thermal stability. When the modified photosensitive resin microsphere content was 0.5%, the tensile strength, elongation at break, bending strength, and initial thermal decomposition temperature were increased by 79.14%, 47.26%, 26.69%, and 10.65%, respectively, compared with the unmodified photosensitive resin. This study provides a new way to improve the mechanical properties of photosensitive resin 3D printing. The resin materials studied in this work have potential application value in the fields of ceramic 3D printing and dental temporary replacement materials.

Surface microtopography construction and osteogenic properties evaluation of bulk polylactic acid implants

In this study, polylactic acid (PLA) microspheres were used as the raw material to construct bulk implants with surface microtopography through hot pressing and heat treatment, and the microtopographical structures were regulated through the sizes of the PLA microspheres. The surface microtopographies of PLA implants were successfully constructed using micron-sized bulges, which showed a wave-like structure. The ridge width of bulges ranged from 1.64 ± 0.16 µm to 82.52 ± 14.38 µm and the valley depth ranged from 0.49 ± 0.07 µm to 37.35 ± 6.78 µm according to the sizes of microspheres. The nanoindentation tests showed that the modulus and hardness of PLA implants were gradually increased with the decrease in microsphere sizes. The surface microtopography resulted in a slight increase in the hydrophobicity of the PLA implants, but no significant differences were observed. Cells cultured on the implant surface with microtopography exhibited varying morphological responses, and significantly increased osteogenic activity was observed relative to a PLA flat film. This study demonstrated that the surface microtopography derived from PLA microspheres could regulate cellular response and activate osteogenic properties of PLA implants.

Versatile Fabrication of Polymer Microcapsules with Controlled Shell Composition and Tunable Performance via Photopolymerization

In this work, a series of polymer microcapsules based on UV-curable prepolymers are prepared by combining an emulsion template and photopolymerization. The modulation of the shell structure is achieved by employing UV-curable prepolymers with different chemical structures (polyurethane acrylates, polyester acrylates, and epoxy acrylates) and functionalities (di-, tetra-, and hex-). The relationships between the shell structure and the microcapsule properties are investigated in detail. The results show that the properties of the microcapsules can be effectively regulated by adjusting the composition and cross-linking density of the shell. Epoxy acrylate-based microcapsules exhibit higher impermeability, solvent resistance, and barrier and mechanical properties than polyurethane acrylate and polyester acrylate-based microcapsules. Using UV-curable prepolymer with high functionality as a shell-forming material could effectively improve the impermeability, solvent resistance, and barrier and mechanical properties of microcapsules. In addition, the dispersion of microcapsules in the coating matrix tends to follow the "similar component, better compatibility" principle, i.e., a uniform dispersion of the microcapsule in the coating matrix is more easily achieved when the compositions of the microcapsule shell and coating are similar in structure. The convenient adjustment of the shell structure and the investigation of the "structure-property" relationship provide guidance for the further controlled design of microcapsules.

Encapsulation of hygroscopic liquids via polymer precipitation in non-aqueous emulsions

HYPOTHESIS

Encapsulation of ionic liquids (ILs) and phase change materials (PCMs) can overcome limitations associated with bulk materials, e.g., slow mass transfer rates, high viscosities, or susceptibility to external environment. Single step soft-templated encapsulation methods commonly use interfacial polymerization for shell formation, with a multifunctional monomer in the continuous phase and another in the discontinuous phase, and thus do not give pristine core material. We posit that polymer precipitation onto emulsion droplets in non-aqueous emulsions could produce a robust shell without contamination of the core, ideal for the encapsulation of water-sensitive or water-miscible materials.

EXPERIMENTS

Solutions of commodity polymers were added to the continuous phase of non-aqueous Pickering emulsions stabilized by alkylated graphene oxide (GO) nanosheets such that the change in solubility of the polymer led to formation of robust shells and the production of capsules that could be isolated.

FINDINGS

We demonstrate that a polymer precipitation approach can produce capsules with pristine core of the IL 1-ethyl-3-methylimidazolium hexafluorophosphate [Emim][PF₆] or the salt hydrate PCM magnesium nitrate hexahydrate (MNH) and shell of nanosheets and polystyrene, poly(methyl methacrylate), or polyethylene. The capsules are approximately 80 wt% [Emim][PF₆] or >90 wt% MNH, and the core can undergo multiple cycles of solidification and melting without leakage or destruction. This novel, single-step methodology provides a distinct advantage to access capsules with pristine core composition and is amenable to different core and shell, paving the way for tailoring capsule composition for desired applications.