Preparation and characterization of poly (styrene-co-Methacrylic acid) copolymer nanoparticles via precipitation polymerization

Nanoparticls of multifunctional polymers have very promising characteristics that make this type of the polymers have rapidly growing research attentions and innovations due to advantageous high surface area to volume ratio. In this study, poly (Styrene-co-Methacrylic acid) (P)St-co-MAA)) copolymer nanoparticles were synthesized using free radical polymerization method. Copolymerization takes place via a precipitation polymerization technique. Different polymerization factors such as co-monomer concentration and ratio, polymerization temperatures, polymerization time, initiator concentration and solvent composition were studied to obtain the copolymerization conditions that produce the maximum copolymerization conversion yield and the minimum particle size in nanosize range in a very narrow size distribution. The P)St-co-MAA) copolymer nanoparticles were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and Thermogravimetric analysis (TGA). When the copolymerization occurred at a monomer ratio of MAA: St (90:10) we obtained the smallest particle size of 25 nm. The maximum conversion yield reached to 99.5% within 4 h of polymerization in the case of St: MAA (1:1) comonomer ratio and 10% total monomer ratio using water:ethanol (1:1) mixture as a co-solvent system. The results clearly demonstrated that use of water as a co-solvent is indeed very effective to promote the polymerization to high conversion. The MAA content in copolymer composition was investigated by carboxylic content via titration method and also by FTIR.

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