Stability of Polypeptide Multilayers As Studied by in Situ Ellipsometry : Effects of Drying and Post-Buildup Changes in Temperature and pH

• Polyelectrolyte multilayers (PEM) of poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) with an initial layer of polyethyleneimine (PEI) were built on silica and titanium surfaces using the layer-by-layer (LbL) technique. The stability of the film during drying/rewetting, temperature cycles, and pH shifts was studied in situ by means of ellipsometry. The film thickness was found to decrease significantly (approximately 70%) upon drying, but the original film thickness was regained upon rewetting, and the buildup could be continued. The thickness in the dry state was found to be extremely sensitive to ambient humidity, needing several hours to equilibrate. Changes in temperature and pH were also found to influence the multilayer thickness, leading to swelling and deswelling of as much as 8% and 10-20% respectively. The film does not necessarily regain its original thickness as the pH is shifted back, but instead shows clear signs of hysteresis.

Ämnesord

NATURVETENSKAP  -- Kemi -- Fysikalisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Physical Chemistry (hsv//eng)

Nyckelord

Drying

Ellipsometry

Hysteresis

Multilayers

Organic acids

pH effects

Polyelectrolytes

Silica

Swelling

Thermal effects

Wetting

Surface and colloid chemistry

Yt- och kolloidkemi

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)