Pollen-like Particles can be Prepared by Exposure of Polymer Microparticles to an Electron Beam

Abstract

Plant pollen shows a wide variety of surface structures that develop during pollen sporogenesis. Some of the structures are similar to wrinkle structures that are formed when a layered material with different Young's moduli is compressed. Here we report on the formation of wrinkled surface structures in polymer particles that is caused by electron beam irradiation of poly(methyl methacrylate) microparticles.

Synthetic Strategies for Polymer Particles with Surface Concavities

“…According to the detailed process, the surface treatment-based method might be further categorized into three different strategies: surface treatment-swellingdeswelling, [198][199][200][201][202][203] swelling-coating-deswelling, [204,205] and other surface treatment-based processes. [206][207][208][209][210][211][212] Surface Treatment-Swelling-Deswelling: In this surface treatment-swelling-deswelling strategy, various surface treatment techniques have been reported to create a skin layer, including UV irradiation, [198][199][200] UV-ozone treatment, [201] oxygen plasma [202] and ion sputtering. [203] In 2011, Godinho and co-workers described the fabrication of micrometer-to millimeter-sized labyrinth-wrinkled Janus particles.…”

“…Surface‐wrinkled (or crumpled) particles that have significantly enlarged surface areas widely exist in the nature (e.g., pollens, plant seeds, microorganisms, etc.). [ 177–180 ] Inspired by them, surface‐wrinkled polymer particles have been investigated both theoretically [ 181,182 ] and experimentally [ 56,57,139,183–226 ] in recent years. The synthesis of surface‐wrinkled polymer particles can also be conducted by polymerization or post‐treatment methods, as discussed below.…”

“…According to the detailed process, the surface treatment‐based method might be further categorized into three different strategies: surface treatment‐swelling–deswelling, [ 198–203 ] swelling–coating–deswelling, [ 204,205 ] and other surface treatment‐based processes. [ 206–212 ]…”

“…The wrinkling stems from the unique strain loading on the Au layers during the particle recovery. Coating‐Electron Beam Irradiation Karthaus and co‐workers reported the preparation of pollen‐like particles by coating of PMMA microparticles with a thin metal layer through ion sputtering (Pd/Pt target), followed by exposure to a 12 kV electron beam. [ 211 ] It works because the PMMA particles decompose and shrink by electron beam irradiation due to main chain scission of PMMA molecules. Coating‐Desolvation Very recently, Wang and co‐workers reported a unique strategy to synthesize wrinkled PGMA‐SiO 2 core–shell particles by utilizing a diffusion‐controlled silication reaction on the surface of a solvated PGMA particles (see Figure 13D). [ 212 ] Specifically, the epoxide groups of the PGMA particles are hydrolyzed under a basic condition to form soluble hydroxyl groups, leading to a well‐solvated polymer brush on the particle surface.…”

“…To date, several post-treatment methods have been proposed for the fabrication of surface-wrinkled polymer particles, which involve surface treatment-based methods, [198][199][200][201][202][203][204][205][206][207][208][209][210][211][212] microfluidic emulsification/emulsion-solvent evaporation, [213][214][215][216][217] electrospraying/solvent evaporation, [218,219] templating methods [220][221][222][223][224] and some other methods. [225][226][227]…”