Biodegradable Ultrafine Nanoparticles of Poly(Methyl Methacrylate-co- Methacrylic Acid) Prepared via Semicontinuous Heterophase Polymerization

IntroductionThe biodegradable copolymer methyl methacrylate (MMA)-co-methacrylic acid (MAA) 2/1 (mol/mol), under the commercial name of Eudragit S-100 (ES-100), is used for the elaboration of drug-loaded pills because its... [ view full abstract ]

Introduction

The biodegradable copolymer methyl methacrylate (MMA)-co-methacrylic acid (MAA) 2/1 (mol/mol), under the commercial name of Eudragit S-100 (ES-100), is used for the elaboration of drug-loaded pills because its solubility at pH > 7.¹ Nanoparticles of this material were prepared by semicontinuous heterophase polymerization at monomer starved conditions. As far as we know this is the first report on the preparation of ultrafine nanoparticles of this copolymer.

Experimental Part

For polymerization at 70°C, a micellar solution containing the initiator was prepared in a 150 mL glass reactor. Then the monomers mixture was dosed on this solution. Conversions and surface tension of samples taken along the polymerization were determined. Additionally, these samples were analyzed by QLS, STEM, DSC and GPC.

Results and Discussion

Kinetics corresponds to that typical of a polymerization at monomer starved conditions.² Surface tension measurements indicate the absence of micelles in the final latex. Mean particle diameter decreases as polymerization evolves (Fig. 1) as a result of the diminution in the polymerization rate within the particles, attaining a value ≈ 10 nm. Glass transition temperature indicates that a copolymer with a composition similar to that of the feed one was obtained. In accordance with the average molecular weighs obtained, bimolecular reaction is probably the dominant mode of chain growing termination. The slight increase in molecular weights with X was probably due to a decrease in termination rate, resulting from a decrease in the radicals to nanoparticles ratio.

Conclusions A latex containing P(MMA-co-MAA) nanoparticles with ≈ 10 nm in mean diameter and ≈ 10 % in solid content was prepared. Furthermore, the copolymer composition was similar to that of the feed one.