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Polymer Journal (2013) 45, 12241233 & 2013 The Society of Polymer Science, Japan (SPSJ) All rights reserved 0032-3896/13 http://www.nature.com/pj
Web End =www.nature.com/pj
Josue Addiel Venegas-Sanchez, Motohiro Tagaya and Takaomi Kobayashi
The effect of ultrasound (US) on the shear viscosity of water-soluble polymers, polyvinyl alcohol, polyethylene glycol and polyacrylic acid, was studied in aqueous solutions with US exposure of 23, 43, 96 and 141 kHz for an 8.59 W US. The US exposure signicantly decreased the shear viscosity of the solutions in this order: 434234964141 kHz.
When US exposure was stopped, the shear viscosities of the aqueous polymer solutions reverted to their original values. US stimulation during the decrease in viscosity was supported by the ultrasonic power transmitted through the aqueous polymer solution. In addition, Fourier-transform infrared spectra obtained during US exposure showed that hydrogenbonds in the aqueous polymer solution could be broken, especially at 43 kHz. We concluded that US exposure inuenced hydrogen-bond interactions between the OH groups of the polymer and water molecules in the aqueous medium.
This nding was supported by US absorption of the aqueous polymer solution in the transmittance model, which shows the US absorptivity, eUS, for each polymer system.
Polymer Journal (2013) 45, 12241233; doi:http://dx.doi.org/10.1038/pj.2013.47
Web End =10.1038/pj.2013.47; published online 15 May 2013
Keywords: hydrogen bonding; shear viscosity; ultrasound
INTRODUCTION
Ultrasound (US) has been widely applied in different elds, such as medicine, engineering and biology.1 Because of the advantages of US, it is widely used in sono-chemical processes2,3 as well as in food
engineering and separation processes.4,5 Smart materials responded when external stimuli, such as heat, light or magnetic elds, were applied.6 However, few studies of US have demonstrated the ability of external stimuli to change material properties. Recently, it was reported that US could be used as a new type of trigger in the drug delivery of polymeric composite materials. In these cases, a lowUS frequency was applied to encapsulate drugs, and the hydrophilicity and high permeability of the materials improved the penetration of water.7,8 In our previous works, copolymer microgels ofN-isopropylacrylamide and acrylic acid using methylenebisacrylamide as a cross-linker demonstrated US-responsive behavior in spherical polymer microgels.9,10 In addition, a signicant change in the shear viscosity was observed in Al2O3/polyacrylic acid (PAA)
slurry,11 and similar behavior was observed in...