Preparation of monodisperse polystyrene spheres incorporating polyimide prepolymer by dispersion polymerization in the presence ofL-ascorbic acid

Abstract

Addition of a small amount of L-ascorbic acid (AA) unexpectedly provided uniform-sized polystyrene (PS) spheres in an ordinary dispersion polymerization process. PS spheres incorporated with polyimide prepolymer (BANI-M), designed as possible spacers for liquid crystal displays, were prepared from formulations containing a mixed solvent of isopropanol/2-methoxyethanol, 2,2 -azobisisobutyronitrile, and poly-N-vinylpyrrolidone (PVP) at 343 K. The average particle size decreased by the addition of AA; however, dramatic improvements of monodispersity were observed with various formulations. The best coefficient of variation was 1.37%, compared to 7.03% obtained without the presence of AA. Addition of AA was originally intended to scavenge a trace amount of oxygen remaining in the reactor system, promoting a rapid and short particle nucleation period, and thereby resulting in improved monodispersity. However, there was no difference in the initial reaction rate between the runs with and without AA; no noticeable induction period was observed even without AA provided that an ordinary procedure was employed to eliminate the dissolved oxygen through a nitrogen bubbling, and the nitrogen atmosphere was maintained during the reaction. It was proposed from 1 H-NMR analysis that the abstraction of hydrogen atom from the PVP chain by the oxidized form of AA promoted the formation of graft copolymer PVP-PS, which stabilizes precipitating chains in the nucleation period. Approximately 40% of BANI-M present initially was incorporated in the PS particles, which occupied 4-9% of the weight of polymer particles, well below the target value of 20%.

Self‐Assembly of Colloidal Spheres toward Fabrication of Hierarchical and Periodic Nanostructures for Technological Applications

“…Importantly, these ordered micro/nanostructure arrays are essential active components for many technological applications, ranging from data storage, solar cells, plasmonics to functional coatings, and many others . Combined with the recent advance in colloidal science, the colloidal spheres with uniform morphology and excellent disperse stability can be further realized by a number of methods, which include the suspension, dispersion polymerization, emulsion, and Stöber techniques . The diameter of colloidal spheres can also be precisely controlled in a wide range, spanning from several micrometers all the way to down to tens of nanometers.…”

Growth Kinetics of Monodisperse Polystyrene Microspheres Prepared by Dispersion Polymerization

“…As a new functional macromolecule material, monodisperse polymer microspheres have many applications in environmental conservation, biomedicine, colloid science, electronic information material, and many other areas [1][2][3] due to their superiority of good sphericity, size tunability, large specific surface area, and excellent absorbability [4][5][6]. Particularly, monodisperse micron-sized spheres are ideal materials as advanced coatings [7], fillers of chromatographic column [8,9], standard particles of electron microscope and Coulter particle size testers, and spacers in LCD [10], which has drawn increasing interest to synthesize monodisperse micron-sized spheres [11,12].…”

Synthesis and characterization of phenolic‐type beads by dispersion polymerization of 2‐phenoxyethanol with formaldehyde using gum acacia powder as stabilizer

“…Recently, polymer microspheres have been shown to be important in many fields, including electronics, biomedicine, and environmental protection, and can be exploited as the calibration standards for potential spacer in liquid crystal displays,6 immunomagnetic beads,7 viral surrogates,8–10 solid phase extractant,11, 12 filler for size exclusion chromatography,13 advanced coatings,14 and so forth. The microspheres made from cross linked phenolic resins are particularly interesting and have drawn much attention.…”