Thermoresponsive Nanospheres with a Regulated Diameter
and Well-Defined Corona Layer
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Abstract
In the present work, we prepared
core–corona-type nanospheres
bearing a thermoresponsive polymer with a controlled chain length
on their surface. The corona layers were composed of poly(<i>N</i>-isopropylacrylamide) (PNIPAAm) chains (<i>M</i><sub>n</sub> = 3000–18 000) with a narrow polydispersity
index prepared by atom-transfer radical polymerization (ATRP). Nanospheres
were prepared by dispersion copolymerization of styrene with the PNIPAAm
macromonomer in a polar solvent. The obtained nanospheres were monodisperse
in diameter. The diameter of the nanospheres was regulated either
by the number or chain length of the PNIPAAm macromonomers. In fact,
the nanosphere diameter was regulated from ca. 100 to 1000 nm. When
two types of PNIPAAm macromonomers are used, the obtained nanospheres
have two different kinds of PNIPAAm on their surface. The surface
of the nanospheres was observed to be thermoresponsive nanosphere
in 0, 50, 100 mmol L<sup>–1</sup> NaCl aqueous solution. The
nanosphere diameter and the surface-grafted polymer were concurrently
adjusted for use in biomedical applications