Monosize polymeric particles

V. BASIC FEATURES OF MONOSIZED POLYMERIC PARTICLES PREPARED BY ACTIVATED SWELLING AND POLYMERIZATION... 

D. Application of Monosized Polymeric Particles in Size Exclusion Chromatography... 

Suspension and emulsion polymerization are two classical polymerization techniques to produce spherical polymeric particles. Larger particles (usually larger than 50 tim) with an appreciable size distribution are produced by suspension polymerization. Submicron polymeric particles (usually smaller than 0.1 im) with extremely uniform in size are obtained by conventional emulsion polymerization processes. Recent techniques, such as swollen emulsion polymerization, dispersion polymerization, etc. give micron-size (usually between 1-50 im) monosize polymeric particles (23). 

Surface Modification of PS Particles. In addition to uniformity in size, surface chemistry of the polymeric particles is another main consideration for biomedical applications. Monosize polymeric particles having different surface chemical groups were also synthesized from various other monomers (29-52). 

Monosized polystyrene particles in the size range of 2-10 /am have been obtained by dispersion polymerization of styrene in polar solvents such as ethyl alcohol or mixtures of alcohol with water in the presence of a suitable steric stabilizer (59-62). Dispersion polymerization may be looked upon as a special type of precipitation polymerization and was originally meant to be an alternative to emulsion polymerization. The components of a dispersion polymerization include monomers, initiator, steric stabilizer, and the dispersion medium... 

Only particles of linear or very slightly cross-linked <0.6%) polymers may be produced by dispersion polymerization. Obviously, dispersion polymerization may be used for the production of monosized seed particles, which, after transfer to aqueous conditions, are used for the production of different cross-linked and macroporous particles by the activated swelling and polymerization method. 

This paper summarizes our recent studies related to production of nondegradable and biodegradable polymeric particles and their use in diverse biomedical applications. Nondegradable monosize polystyrene based particles were prepared in micron-size range by a phase inversion polymerization. Surfaces of these particles were then coated with styrene-acrylate copolymer layers in order to include different functional groups. These particles were radiolabelled with and succesfully used in... 

Recently, we have also produced monosize nondegradable and biodegradable polymeric particles and used these particles in diverse biomedical applications. In this paper, we reviewed our recent related studies. In each section, we briefly decribed the polymerization procedure, and then gave examples of their biomedical and related applications. 

Recently, we produced monosize polyalkylcyanoacrylate based polymeric particles in micron-size range by a dispersion polymerization method, as potential carriers for diagnosis and therapy. Details of polymerization and degradation kinetics were discussed in detail elsewhere (79). Here, the preparation procedure and degradation behaviour of the polyethylcyanoacrylate (PECA) particles are briefly presented. 

Preparation of PS Particles. We produced monosize polystyrene (PS) particles by following a "phase inversion polymerization" technique which was described in detail elsewhere (23-27). In order to obtain PS particles with different size ranges, we studied a wide variety of solvent systems with different polarities (e.g., ethanol/waler, isopropanol/ water, and ethanol/2-methoxyethanol). We also changed concentrations of the stabilizer (i.e., polyacrylic acid, PAA), the initiator (i.e., 2,2 -azobisisobutyro-nitrile), and the monomer to control the size and die monodispersity of these particles. 

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