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Systematically studying slippery surfaces

Researchers explore the structure-property relationship of polymer brushes

August 21, 2017
Kyushu University, I2CNER
Polymer brushes are polymers grown on surfaces, and are attractive for use in lubrication and anti-fouling applications. Researchers varied the length of the chain separating negatively and positively charged functional groups in polymer brushes to investigate how chain length affected the interaction of the polymer brushes with water. They found that the chain length influenced the ionic strength sensitivity for the hydration of the polymer brushes in water but not their water uptake or hydration structure.

Betaines are materials with both a positively charged functional group and a negatively charged functional group linked by an alkyl chain spacer. This combination of functional groups causes betaines to strongly attract water, which makes them useful for water retention. Betaines are important in numerous organisms, where they help to prevent cell dehydration and also play roles in some reactions. Commercially, betaines are used in DNA amplification and chemical synthesis. Betaine groups can be included in polymer brushes, which are polymers that are tethered to a surface. The resulting polymer brushes are attractive for use in lubrication and anti-fouling applications because the hydrated betaine groups help to prevent adhesion of other materials. However, the hydration states of polymer brushes are still poorly understood.

It is known that the length of the alkyl chain spacer between the charged functional groups in a betaine affects its hydration state. A Japanese collaboration led by Kyushu University recently investigated the effects of the charged group spacer length of betaines in polymer brushes on their hydration state to provide a clearer picture of the relationship between the structure and properties of these materials.

The researchers first synthesized a series of polymer brushes containing alkyl chain spacers of different lengths on silicon wafers. The polymer brushes were then characterized by a range of techniques. In particular, neutron reflectivity was used to probe the hydration states of the polymer brushes. The results of polymer brush characterization revealed that only some parameters depended on the length of the alkyl chain spacer. Water uptake by the polymer brushes exposed to water or humid air did not depend on chain spacer length.

"We found that the polymer brushes swelled in humid air and water because the hydration of the charged betaine groups led to the decrease of the interfacial free energy between water and the brushes," says Yuji Higaki, an assistant professor at Kyushu University's Institute for Materials Chemistry and Engineering (IMCE) / International Institute for Carbon-Neutral Energy Research (WPI-I2CNER).

"Our findings reveal how the charged group spacer length of betaines modulates the interaction of polymer brushes with water," states team leader Atsushi Takahara, a professor at IMCE and WPI-I2CNER.

The team's results should aid the development of lubricating and anti-fouling surfaces for use in marine environments or under physiological conditions.

Story Source:

Materials provided by Kyushu University, I2CNER. Note: Content may be edited for style and length.

Journal Reference:

  1. Yuji Higaki, Yoshihiro Inutsuka, Tatsunori Sakamaki, Yuki Terayama, Ai Takenaka, Keiko Higaki, Norifumi L. Yamada, Taro Moriwaki, Yuka Ikemoto, Atsushi Takahara. Effect of Charged Group Spacer Length on Hydration State in Zwitterionic Poly(sulfobetaine) Brushes. Langmuir, 2017; DOI: 10.1021/acs.langmuir.7b01935

Cite This Page:

Kyushu University, I2CNER. "Systematically studying slippery surfaces." ScienceDaily. ScienceDaily, 21 August 2017. <>.
Kyushu University, I2CNER. (2017, August 21). Systematically studying slippery surfaces. ScienceDaily. Retrieved June 21, 2024 from
Kyushu University, I2CNER. "Systematically studying slippery surfaces." ScienceDaily. (accessed June 21, 2024).

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