Investigation of Changes in the Microscopic Structure of Anionic Poly(N-isopropylacrylamide-co-Acrylic acid) Microgels in the Presence of Cationic Organic Dyes toward Precisely Controlled Uptake/Release of Low-Molecular-Weight Chemical Compound.
Changes in a microscopic structure of an anionic poly(N-isopropylacrylamide-co-acrylic acid) microgel were investigated using small- and wide-angle X-ray scattering (SWAXS). The scattering profiles of the microgels were analyzed in a wide scattering vector (q) range of 0.07 ≤ q/nm(-1) ≤ 20. In particular, the microscopic structure of the microgel in the presence of a cationic dye rhodamine 6G (R6G) was characterized in terms of its correlation length (ξ), which represents the length scale of the spatial correlation of the network density fluctuations, and characteristic distance (d*), which originated from the local packing of isopropyl groups of two neighboring chains. In the presence of cationic R6G, ξ exhibited a divergent-like behavior, which was not seen in the absence of R6G, and d* was decreased with decreasing the volume of the microgel upon increasing temperature. At the same time, the amount of R6G adsorbed per unit mass of the microgel increased upon heating. These results suggested that a coil-to-globule transition of the poly(N-isopropylacrylamide) chains in the present anionic microgel occurred because of efficiently screened, thus, short ranged electrostatic repulsion between the charged groups, and hydrophobic interaction between the isopropyl groups in the presence of cationic R6G. The combination of hydrophobic and electrostatic interaction between the cationic dye and the microgel affected the separation and volume transition behavior of the microgel.
Graduate School of Textile Science & Technology, Shinshu University , 3-15-1 Tokida Ueda, Nagano 386-8567 Japan.
Takuma
T
Kureha
Graduate School of Textile Science & Technology, Shinshu University , 3-15-1 Tokida Ueda, Nagano 386-8567 Japan.
Takahisa
T
Shibamoto
Graduate School of Textile Science & Technology, Shinshu University , 3-15-1 Tokida Ueda, Nagano 386-8567 Japan.
Shusuke
S
Matsui
Graduate School of Textile Science & Technology, Shinshu University , 3-15-1 Tokida Ueda, Nagano 386-8567 Japan.
Takaaki
T
Sato
Graduate School of Textile Science & Technology, Shinshu University , 3-15-1 Tokida Ueda, Nagano 386-8567 Japan.|Division of Smart Textiles, Institute for Fiber Engineering, Interdisciplinary Cluster for Cutting Edge Research, Shinshu University , 3-15-1 Tokida, Ueda, Nagano 386-8567, Japan.
Daisuke
D
Suzuki