Monosize polystyrene microbeads by dispersion polymerization

Abstract

SYNOPSISMonosize polystyrene microbeads were prepared by dispersion polymerization in different alcohol/ water media. Azobisisobutyronitrile and polyacrylic acid were utilized as initiator and steric stabilizer, respectively. The polymerizations were performed in three kinds of dispersion media having different polarities: isopropanol/water, 1-butanol/water, and 2-butanol/water. The effects of initiator and stabilizer concentrations, alcohol/water ratio, and monomer /dispersion medium ratio on the size and monodispersity of the polymeric microbeads were investigated. By dispersion polymerization, polystyrene ( PS ) microbeads were obtained in the size range of 1.0-4.0 pm with narrow size distribution or in the monosize form. The average size and size distribution of microbeads decreased with increasing polarity of the dispersion medium. The average size and size distribution increased with increasing initiator concentration in all dispersion media. The increase in the stabilizer concentration in homogeneous dispersion media resulted in a decrease in average size and size distribution of the microbeads. A clear increase was observed in the average size with increasing monomer /dispersion medium ratio. Isopropanol/water dispersion medium provided monosize microbeads with higher values of monomer/dispersion medium ratio. I NTRO DU CTlO NMany applications in the biomedical field, information industry, and microelectronics require the use of polymeric particles of controlled size and surface properties. Traditionally, micron-size particles have been prepared by suspension polymerization, where monomer droplets are broken into the micronsize range within a dispersion medium by homogenization in the presence of a stabilizer, and subsequently are polymerized by using a monomer phase soluble initiator. This technique is usually used for the production of spherical polymeric particles between about 50-1000 pm. A wide particle size distribution is usually observed because of inherent size distribution in the mechanical homogenization step and because of the coalescence problem faced in this type of polymerization.

Photon transmission method for studying film formation from polstyrene latexes with different molecular weights

“…23,24 One gram of the steric stabilizer was dissolved in the dispersion medium containing 90 mL of ethyl alcohol and 10 mL of water. The monomer phase was prepared by dissolving various amounts of AIBN (70 and 140 mg for HM and LM PS latexes, respectively) in 10 mL of styrene.…”

“…23,24 The latex from the reactor was centrifuged and the supernatant was removed. The particles were washed with fresh dispersion medium a few times, then distilled water was added and a new dispersion was stirred for 24 h at room temperature to remove any stabilizer remaining on the surface of the polymeric particles.…”

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

“…Crosslinking and adhesion between homogeneous solution, and its change during the polymerization, became recognized as one of the the panels will provide structural strength, and also prevent the movement of slightly off-sized potentially influential factors with respect to the size and monodispersity. Tuncel et al 7 correlated spacer particles. Intensive experiments revealed that the dethe average size of PS particles with the solubility parameter of the medium, and found that the sired monodispersity for the spacers, less than 4% coefficient of variation (CV), was never achieved maximum size was attained at a solubility parameter of 12.5 in mixed solvents of isopropanol, no matter how the compositions of polymerization recipe were changed on the basis of solvent-cosol-1-butanol, 2-butanol, and water.…”

Preparation of Polystyrene-Polyimide Particles by Dispersion Polymerization of Styrene Using Poly(amic acid) as a Stabilizer

“…1 To disperse particles stably, a suitable steric stabilizer was used, such as polyethylene oxide, 2 polyvinylpyrrolidone, 3 poly(2-ethyl-2-oxazoline), 4 hydroxypropyl cellulose, 5 and poly(acrylic acid). 6 Aromatic polyimides (PI) are the most useful super engineering plastics which exhibit excellent thermal, electrical, and mechanical properties, and have been used widely in aerospace, electronics, and other industries. They are generally prepared through a two-step procedure by the ring-opening polyaddition of aromatic diamines to aromatic tetracarboxylic dianhydrides giving poly(amic acid)s (PAA), followed by thermal cyclodehydration.…”