Synthesis, characterization and drug release properties of thermosensitive poly(N-isopropylacrylamide) microgels
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This study was aimed at optimizing the structure and properties of poly(N-isopropylacrylamide) (PNIPAAm) microgels prepared by inverse suspension polymerization. The influence of the oil-to-water phase ratio, the concentration of emulsifier, and the monomer-to-crosslinker molar ratio on selected properties of the PNIPAAm microgels was examined. Regularity of the microgels shape was estimated by optical microscopy. Laser diffraction technique was used to determine the microgels mean size and size distribution. Equilibrium swelling ratio was studied gravimetrically. Morphology of microgels was followed by SEM. Volume phase transition temperature of PNIPAAm microgels was determined by differential scanning calorimetry. The results obtained imply that the mean diameter of microgels and their equilibrium swelling ratio highly depend on the concentration of emulsifier in oil phase and the crosslinking degree of PNIPAAm. The crosslinking degree of PNIPAAm has no substantial effect on the volume phase transition temperature that is demonstrated to be around 33 °C even after complete heating-cooling-heating cycle. In addition, it was confirmed that the swollen microgels have a porous, honeycomb-like structure. Release profiles of procaine hydrochloride from the PNIPAAm microgels confirmed their potential to be considered as efficient matrices in drug release applications.
KeywordsPoly(N-isopropylacrylamide) Thermosensitive microgels Inverse suspension polymerization Volume phase transition Controlled drug release
The financial support for this research work has been provided by the project ARCUS 2006 – Nord-Pas-de-Calais/Bulgarie – Roumanie – Serbie, granted by the French Ministry of Foreign Affairs and the Region Nord-Pas-De-Calais. The research is also supported in part by the project number III46010, granted by the Ministry of Education and Science of Republic of Serbia. The authors would like to thank Dr. Smilja Markovic from the Institute of Technical Sciences of the Serbian Academy of Sciences and Arts from Belgrade for her valuable help in laser diffraction analysis.
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