21. June 2018.

Laboratory for Colloids, Polyelectrolytes and Interfaces

The Laboratory for Colloids, Polyelectrolytes and Interfaces was founded in fall 2012 when the CMNST, together with the other University departments, moved into our new campus building. Since then, the laboratory was in the process of equipment acquisition and teaming up, and will become fully operational through the University’s infrastructural project in 2014. At present, some basic techniques are available, while the first group members are expected in 2014.

Open PhD position – MC fellow

Research topics:

Colloids. Electrostatic charging of colloidal particles through ion binding in aqueous medium determines many of their technologically important features. Among the most important are the stability of colloidal suspensions (shelf-life), structuring in dense suspensions (turbidity, opalescence), interaction with membranes (biocompatibility) and adsorption/desorption of small molecules (drug formulation). The research is focused on the experimental determination of the surface charge of solid nanoparticles, as well as the hard core – soft shell particles that are formed by spontaneous assembly of the amphiphilic block-copolymers in aqueous medium. The main experimental technique that we explore are the potentiometric titrations at controlled ionic strength(s). The interpretation of the measured data is achieved in terms of the available models, which can become particularly challenging in the case of the composite nanoparticle-polyelectrolyte surfaces.

Polyelectrolytes. We investigate polyelectrolytes both in the dissolved and the surface-bound states. The pH-dependent charging behavior of polyelectrolytes is challenging, as it involves competition for H+ among the weakly acidic or basic groups, determined by their intrinsic acidity as well as several effects that lead to cooperative ion binding, such as the conformational rearrangements and hydration. The research is focused on the experimental determination of the proton (and other ion) binding isotherms, which are fitted in terms of models that provide physically meaningful parameters. Another topic in our focus is the change in the protonation state upon polyelectrolyte adsorption to surfaces, which substantially impacts their properties and function.

Interfaces. As partners in the Marie Curie ITN Organic bioelectronics, we will examine the ion binding and the ionic and electronic conductivities within the thin polymer films (such as for example PEDOT:PSS), which are the organic component in the organic electronic devices. Another goal is to develop protocols for producing microstructured electrode arrays functionalized with biomolecules, and to study their electrochemical responses (ion-to-electron process). The training network for PhD students is taking place among about a dozen European universities and institutes, whereby our engagement will start in May 2014.

Equipment:

High precision potentiometric titrations with ionic strength control

Visible / near infrared spectrophotometer (Metrohm-Foss)

Equipment in the process of acquisition through the University of Rijeka infrastructural project (2014):

Static/dynamic light scattering and electrophoretic mobility

Spectroscopic imageing ellipsometer

Cyclic voltammetry / Electrochemical impedance spectroscopy

 

Assistant professor, Dr. Duško Čakara (laboratory head)

tel: + 385 – (0)51 – 584555

fax: + 385 – (0)51 – 584599

email: This email address is being protected from spambots. You need JavaScript enabled to view it.”>dcakara@uniri.hr

Publications:

Salomão Pinto Zarth C., Fras Zemljič L., Čakara D, Bračič M., Pfeifer A., Stana-Kleinschek K.,Heinze T., Studies on the Hydrolytic Stability of Water-Soluble Amino Group Containing Cellulose Esthers, Macromolecular Chemistry and Physics, 213, 1669 -1676 (2012)
Borkovec M., Čakara D., Koper G.J.M, Resolution of Microscopic Protonation Enthalpies of Polyprotic Molecules by Means of Cluster Expansions, Journal of Physical Chemistry B, 116, 4300-4309 (2012)
Fras-Zemljič L., Kokolj V., Čakara D., Antimicrobial and antioxidant properties of chitosan-based viscose fibres enzymatically functionalized with flavonoids, Textile research journal, 81, 1532-1540 (2011)
Fras L., Čakara D., Michaelis N., Heinze T., Stana-Kleinschek K., Protonation behavior of 6-deoxy-6-(2-aminoethyl)amino cellulose: A potentiometric titration study, Cellulose, 18, 33-43 (2011)
Čakara D., Fras L., Bračič M., Stana-Kleinschek K., Protonation behavior of cotton fabric with irreversibly adsorbed chitosan: A potentiometric titration study, Carbohydrate polymers, 78, 36-40 (2009)
Čakara D., Kobayashi M., Skarba M., Borkovec M., Protonation of Silica Particles in the Presence of a Strong Cationic Polyelectrolyte, Colloids and Surfaces A, 339, 20–25 (2009)
Slim C., Ktari N., Čakara D., Kanoufi F., Combellas C., Polyaniline Film Based Ultramicroelectrodes Sensitive to pH, Journal of Electroanalytical Chemistry, 612, 53-62 (2008)
Čakara D., Borkovec M., Microscopic Protonation Mechanism of Branched Polyamines: Poly(amidoamine) vs. Poly(propyleneimine) Dendrimers, Croatica Chemica Acta, 80, 421-428 (2007)
Čakara D., Chassagne C., Gehin-Delval C., Borkovec M., Protonation of Carboxyl Latex Particles in the Presence of a Strong Cationic Polyelectrolyte, Colloids and Surfaces A, 294, 174-180 (2007) (impact factor: 1.988)
Kobayashi M., Skarba M., Galletto P., Čakara D., Borkovec M., Effects of Heat Treatment on the Aggregation and Charging of Stöber-type Silica, Journal of Colloid and Interface Science, 292, 148-151 (2005)
Čakara D., Kleimann J., and Borkovec M., Microscopic Protonation Equilibra of Poly(amidoamine) Dendrimers from Macroscopic Titrations, Macromolecules, 36, 4201-4207 (2003)