Preparation And Properties Of Nanocapsules Based On SMA/CS System

In recent years, preparation of intelligent nanocapsules responded to external stimulus such as temprature, pH with the natural polymer (such as chitosan, sodium alginate etc.) materials as shell material has become a hotspot. They have potential applications in the fields of wastewater treatment, biological medicine, bio-microreactor and imaging sensors etc. because of the biocompatible and biodegradable of chitosan and environmental responsive property. In this paper, CS nanocapsules were prepared using poly(styrene-co-maleic anhydride)(SMA) as templates and natural polymer chitosan(CS) as shell material. Temperature sensitive CS-NIPAm nanocapsules were prepared by introducing the temperature sensitive monomer N-isopropylacrylamide(NIPAm). The structure and morphology of nanocapsules were characterized. The adsorption property to MB of CS nanocapsules and the temperature sensitive properties of CS-NIPAm nanocapsules were studied. The main contents of this paper are as follows:1. The characteristics, preparation methods and applications of nanocapsules were reviewed. The phase transition mechanism and applications of the temperature-sensitive polymer were introduced.2. SMA microspheres were prepared by precipitation polymerization. Then, chitosan are adsorbed on the surface of SMA microspheres by electrostatic interaction between -NH2 and -COOH, and cross-linked with glutaraldehyde. CS nanocapsules are obtained after core removal using nonsolvent/solvent-induced phase separation method. The effects of the variety of dispersion medium, solvent, reaction time on microsphers morphology were investigated. The results showed that the monodisperse SMA/CS microspheres were successfully prepared with an average diameter of 750 nm; when choosing water/n-butanol as dispersion medium with volume ratio 5 mL/5 mL, and 2 mL n-heptane,0.5 mL acetone, temperature of 50℃, the reaction time remaining 120 minutes, an expected CS nanocapsules can be obtained.3. The adsorption behavior of methylene blue (MB) from aqueous solution using the prepared CS nanocapsules as adsorbent was studied. The effects of process parameters, such as pH value, adsorption time, and initial MB concentration on the adsorption extent of MB were investigated. The results showed that CS nanocapsules have a good adsorption capacity of MB when the temperature is 25℃, the pH is 7, the initial concentration of MB is 200 mg/L, the adsorption time is 24 h, the adsorption capacity is 282mg/g. Kinetic studies showed that the kinetic data were well described by the pseudo-second-order kinetic model. The equilibrium data agrees well with the Langmuir model, it illustrated that the adsorption on the surface of CS nanocapsules was a monolayer adsorption. According to the Langmuir equation, the maximum sorption capacity for MB was 286 mg/g, is close to the experimental data. The controlled release behavior of the CS nanocapsules was investigated by adjusting the pH of the aqueous dispersions of the drug-loaded CS nanocapsules, with ibuprofen (IBU) as the model drug, it was also found that the releasing ratio of ibuprofen from the drug carriers at pH 7.4 were quicker than that of pH 2.0.4. The temperature responsive nanocapsules were prepared through the introducing of temperature sensitive monomer N-isopropylacrylamide. The PNIPAm was grafted onto the surface of SMA/CS microspheres with cerium ammonium nitrate (CAN) as a initiator via the solution radical polymerization technique, and the CS-NIPAm nanocapsules were obtained after etching the templates by dialysis. The FTIR spectroscopy results showed that the PNIPAm were successfully grafted onto the surface of chitosan. The structure and morphology of nanocapsules were investigated. The effects of dosage of NIPAm on the temperature sensitive properties of the microcapsules were studied. The results showed that uniform and monodisperse, complete morphology nanocapsules were successfully prepared, and the nanocapsules exhibit good temperature responsive property, the lower critical solution temperature (LCST) of nanocapsules is about 30℃-40℃.