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Recent Publications

Neutron Reflectivity and Computer Simulation Studies of Self-Assembled Brushes Formed by Centrally Adsorbed Star Polymers


Ioannis Hiotelis, Alexandros G. Koutsioubas, Nikolaos Spiliopoulos, Dimitris L. Anastassopoulos, Alexandros A. Vradis, Chris Toprakcioglu, Alain Menelle, George Sakellariou, and Nikos Hadjichristidis

Macromolecules 2008 ASAP(Article)

DOI: 10.1021/ma702749z



 

Abstract:

The equilibrium properties of polymer brushes formed by starlike polymers with varying number of arms attached to a surface by their center were studied experimentally with neutron reflectrometry (NR). Polystyrene (PS) stars in a good solvent (toluene) were centrally adsorbed onto a quartz substrate via a zwitterionic anchor group. Increasing the number of arms resulted in significantly lower equilibrium adsorbance, while replacement experiments of a 3-armed star brush by linear chains revealed interesting equilibrium and kinetic features related to the special architecture of star polymers. These results are compared with scaling theoretical calculations and Monte Carlo simulations of centrally adsorbed star polymers that were performed under the bond fluctuation simulation scheme. Several features of the experimental results are reproduced in our simulation study.

Shear-Induced Desorption in Polymer Brushes


D. L. Anastassopoulos, . Spiliopoulos, A. A. Vradis, C. Toprakcioglu, S. M. Baker, and A. enelle


Macromolecules; 2006; 39(26) pp 8901 - 8904; (Communication to the Editor)

DOI: 10.1021/ma061532o


 

 

 

 

 

 

Nanoporous alumina enhanced surface plasmon resonance sensors

 

Alexandros G. Koutsioubas, Nikolaos Spiliopoulos, Dimitris Anastassopoulos, Alexandros A. Vradis, and George D. Priftis

J. Appl. Phys. 103, 094521 (2008) (Article)


http://link.aip.org/link/?JAPIAU/103/094521/1

 

Abstract: The signal enhancement of an easy to fabricate, nanoporous alumina assisted surface plasmon resonance (SPR) sensor is investigated. It is theoretically shown that the presence of a thin (under 200  nm) porous alumina layer on top of an aluminum film supporting the surface plasmons, may significantly increase (over one order of magnitude) the sensitivity of the SPR method in the case where the adsorption of relatively small molecules is probed. The comparative experimental investigation of self-assembled monolayer formation on planar metal films and porous alumina layers verifies the theoretical predictions. Based on these results, we discuss the extended applicability of this setup in biosensor and other related applications.

 

 

Adsorption behavior of PS-PEO diblock copolymers on silver and alumina surfaces: A surface plasmon resonance study
 

Alexandros G. Koutsioubas, Nikolaos Spiliopoulos, Dimitrios L. Anastassopoulos, Alexandros A. Vradis, Chris Toprakcioglu, George D. Priftis

Journal of Polymer Science Part B: Polymer Physics (2006) 44, 1580

DOI: doi.wiley.com/10.1002/polb.20806

Abstract: In this work, the adsorption behavior at the silver/toluene and alumina/toluene interface of polystyrene-polyethylene oxide (PS-PEO) diblock copolymers of various molecular weights was investigated by implementation of the surface plasmon resonance (SPR) technique. This was accomplished under a careful choice of

 experimental setup and the use of a suitable physical model for the interpretation of the experimental data. Comparison between polystyrene homopolymer and PS-PEO diblock copolymer adsorption measurements indicate that PS-PEO is anchored on the alumina surface via the PEO block, while on silver the copolymer is attached by various chain segments. The measured final adsorption amounts on alumina are typical of end-attached polymeric brush formation while the dynamics of the adsorption process present two clearly different evolution regimes. This work provides insight into the many advantages of the use of the SPR technique as a valuable tool for similar surface studies.





 

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