Dielectric and Mechanical Investigations on the Hydrophilicity and Hydrophobicity of Polyethylene Oxide Modified on a Silicon Surface.
Polyethylene oxide (PEO) has been widely used in biomedical fields. The antibiofouling property of the PEO-modified surface has been extensively investigated but is far from being fully understood. A series of PEOs with narrowly distributed molecular weight (Mw), synthesized with the technique of high vacuum anionic polymerization, have been successfully grafted onto the surface of silicon wafers. The power-law relationship between the thickness of the monolayer versus the Mwof the grafted PEO shows a scaling of 0.3, indicating compact condensing of the chains. The static contact angles show higher hydrophobicity for the layer of PEO with higher Mw, which can be attributed to the closely packed conformation of the chains with high density. The frequency shift of the contact resonance indicates that the Young's modulus decreases and the loss factor increases with the increase in the Mwof PEO and the thickness of the PEO layers. Dielectric spectroscopy of bare or PEO-grafted wafers in the aqueous solutions reveals an interfacial polarization, which results from compositional and structural changes in the interface layer and depends on temperatures and salt concentrations. At a given grafting density, the PEO chains are swollen in pure water, demonstrating hydrophilic behavior, whereas they collapse in salt solutions, showing hydrophobic characteristics.
Jiangsu Key Laboratory of Bio-functional Materials, School of Chemistry and Materials Science, Nanjing Normal University , Nanjing 210023, China.
Jing
J
Shang
Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831-6494, United States.
Kunlun
K
Hong
Department of Chemical Physics, Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China , Hefei 230026, P. R. China.
Tao
T
Wang
Jiangsu Key Laboratory of Bio-functional Materials, School of Chemistry and Materials Science, Nanjing Normal University , Nanjing 210023, China.
Dan
D
Zhu
Jiangsu Key Laboratory of Bio-functional Materials, School of Chemistry and Materials Science, Nanjing Normal University , Nanjing 210023, China.
Jian
J
Shen