Preparation of Polyamide-6 Submicrometer-Sized Spheres by In Situ Polymerization

• Published in: Macromolecular rapid communications. 2015-11, Vol.36 (22), p.1994-1999
• Main Authors: Zhao, Xingke, Xia, Housheng, Fu, Xubing, Duan, Jianping, Yang, Guisheng
• Format: Article
• Language: English
• Subjects: Blends; Caprolactam; Caprolactam - analogs & derivatives; Caprolactam - chemical synthesis; Caprolactam - chemistry; Coalescing; Droplets; Green Chemistry Technology; Microscopy, Electron, Scanning; Microspheres; Mixtures; Nylons - chemical synthesis; Organic solvents; Particle Size; phase separation; Polyamide resins; polyamide-6; Polyamides; Polyethylene glycol; Polyethylene Glycols - chemistry; Polymer blends; Polymerization; Polymers - chemical synthesis; Propylene; Propylene glycol; Propylene Glycols - chemistry; Ring opening polymerization; ring-opening anionic polymerization; Scanning electron microscopy; Size distribution; Strategy; Surface Tension
• ISSN: 1022-1336; 1521-3927
• DOI: 10.1002/marc.201500358

Polyamide‐6 (PA6) submicron‐sized spheres are prepared by two steps: (1) anionic ring‐opening polymerization of ε‐caprolactam in the presence of poly(ethylene glycol)‐block‐poly‐(propylene glycol)‐block‐poly(ethylene glycol)(PEG‐b‐PPG‐b‐PEG) and (2) separation of PA6 spheres by dissolving PEG‐b‐PPG‐b‐PEG from the prepared blends. The PA6 microspheres obtained are regular spherical, with diameter ranging from 200 nm to 2 μm and narrow size distribution, as confirmed by scanning electron microscopy. By comparison with PA6/PS and PA6/PEG systems, it is denominated that the PEG blocks in PEG‐b‐PPG‐b‐PEG can effectively reduce the surface tension of PA6 droplets and further decrease the diameter of the PA6 microspheres. The PPG block in PEG‐b‐PPG‐b‐PEG can prevent the PA6 droplets coalescing with each other, and isolated spherical particles can be obtained finally. The phase inversion of the PA6/PEG‐b‐PPG‐b‐PEG blends occurs at very low PEG‐b‐PPG‐b‐PEG content; the PEG‐b‐PPG‐b‐PEG phase can be removed by water easily. The whole experiment can be finished in a short time (approximately in half an hour) without using any organic solvents; it is an efficient strategy for the preparation of submicron‐sized PA6 microspheres. Submicrometer‐sized polyamide‐6 micro­spheres are synthesized for the first time by reaction‐induced phase separation of PA6/PEG‐b‐PPG‐b‐PEG blends. The resulting PA6 microspheres show regular spherical shapes, with diameters ranging from 200 nm to 2 μm. The PEG block effectively reduces the surface tension of the PA6 droplets, further decreasing the microsphere diameter; the PPG block prevents the droplets coalescing, leading to the isolation of spherical PA6 microspheres.