Polymer collapse due to pH or electric potential change monitored with MP-SPR

Application Note #136


"Polymer  layer  conformational  changes  in  different  pH and electric potential was seen"

Conductive polymers (CP) are utilized in drug delivery systems, microelectronics, photonics and also for material in biomedical engineering. CP polymer poly (3,4-ethylenedioxythiophene) (PEDOT) was deposited on a sensor slide and above that Poly (acrylic acid) (PAA) brush which is a promising biointerface material.

Multi-Parametric Surface Plasmon resonance (MP-SPR) was utilized to follow PAA polymer brushes swelling and collapse caused by pH or electric potential change. MP-SPR with electrochemical cell was utilized to form potential change to the conductive sensor surface. Multi wavelength MP-SPR measures whole SPR curve with two different wavelength and this can be utilized to calculate deposited layer thickness (for more details see AN#128).

On a sensor slide had 18 nm thick PBrEDOT layer and 15 nm thick PAA layer on top of that. BrEDOT-g-PAA revealed to be pH sensitive as expected. In acidic environment (pH4) PAA polymer brushes collapsed resulting a decrease in thickness of the layer and an increase in refractive index of brushes. Electric potential change seemed to cause PAA brushes conformational collapse also in basic environment due to conductive polymer oxidation.

Recommended instrument for this application:

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Further reading

  • If you are interested in reading more about polymers, you can see also AN#149 -  Polymer characterization using MP-SPR - Adsorption studies and layer thickness, and AN#159 about vapour induced polymer swelling.

  • Do you want to see how MP-SPR instruments work? Click here.

  • Do you want to see comparison of MP-SPR instruments? Click here.

  • Here are a few publications you can have a look at.


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