pH- and Temperature-sensitive Nanoparticles Prepared using Salt Bridge

초록

Nanoparticles could be formed by salt bridges between the amino groups of poly (N-isopropylacrylamide-co-dimethylaminoethyl methacrylate) (P(NIPAM-co-DMAEMA)) and the carboxylic groups of fatty acids (FAs, stearic acid, palmitic acid, or lauric acid). FAs constitute the cores of nanoparticles and the copolymer stabilizes them. The colloidally stable nanoparticles could be obtained in the range of pH 6.0-9.0. Under strong acidic conditions (at pH 3.0 and 4.0), however, a marked increase in the size was observed. The pH values (3.0 and 4.0) were less than pK of the carboxylic acid of FAs, so the salt bridges will significantly decrease in number, resulting in the detachment of the copolymer from the surface of nanoparticles. Thus, an agglomeration due to hydrophobic interaction would be responsible for the size increase. The nanoparticles were pH-sensitive in terms of change in their sizes, due to the pH-sensitivity of the salt bridges. In addition, the sizes were also temperature-sensitive due to the temperature-dependent hydrophilicity of P(NIPAM-co-DMAEMA).

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