Name: Rudra P. Choudhury
Diploma / M.Sc degree: Indian Institute of Science, Bangalore, India
(2004)
Title: Pulsed Field Gradient Studies of Probe Molecule Permeation Through Hollow Polymeric Capsules

Abstract of Research Project

Polyelectrolyte multilayers are novel materials of increasing interest. At present, a variety of materials such as a wide range of synthetic polyelectrolytes, biopolymers, lipids and inorganic particles have been successfully employed to fabricate multilayer films onto flat substrates. Recently this technology has been also applied for multilayer assembling on the surface of colloidal particles [1] which helps to study the structure and properties of multilayer by techniques requiring a large amount of surface such as nuclear magnetic resonance (NMR). In a new development to this field, the core colloidal particles were removed successfully and novel micro-nano sized polyelectrolyte hollow capsules are prepared [2]. The compartmentalization of materials in the small capsule volume with controlled thickness and composition of the encapsulating wall open perspectives for use of these structures as microreactors, microcarriers and sustained drug release formulation. For such application the wall permeability is a crucial parameter and it is desirable to control it by external parameters such as pH, salt concentration or temperature.

Recently, the Pulsed Field Gradient (PFG) NMR technique is introduced to study the encapsulation of the molecules which have some NMR i active nuclei [3]. The self diffusion coefficient of the molecule can give us information about the location of the probe molecules in the heterogeneous environment. So using this technique it is possible to find out whether the probe molecules are inside or outside the capsule. Using the PFG-NMR it is also possible to find out the time required for the exchange between the two sites. These informations help us to investigate the permeability of the hollow capsule wall.

The aim of my project is to study the permeability of the hollow capsule wall using the PFG-NMR technique and to investigate how the permeability depends on molecular size, pH, salt concentration, temperature and composition of the capsule wall. These information can give us some idea about the mechanism of the permeability. Again, if the time scale of the exchange of the probe molecule between the two sites of the capsule is on the order of tens of millisecond then it is possible to get quantitative information about the permeability parameters of the wall. Controlled permeability of the capsule wall by tuning different parameters of the system is also another aim of this project.

[1] Sukhorukov, G. B.; Donath, E.; Davis, S. A.; Lichtenfeld, H.; Caruso, F.; Popov, V. I.; Möhwald, H., Polym. Adv. Technol. 1998, 9, 759.
[2] Donath, E.; Sukhorukov, G. B.; Caruso, F.; Davis, S. A.; Möhwald, H., Angew. Chem., Int. Ed. Engl. 1998, 37, 2202.
[3] Adalsteinsson, T.; Dong, W.; Schönhoff, M., J. Phys. Chem. B, in press.


Publications

R. P. Choudhury, P. Galvosas, M. Schönhoff
Scaling law of poly(ethylene oxide) chain permeation through a nanoporous wall
J. Phys. Chem. B 112 (2008), 13245- 13251.

R. P. Choudhury, M. Schönhoff
Pulsed field gradient NMR study of phenol binding and exchange in dispersions of hollow polyelectrolyte capsules
J. Chem. Phys. 127 (2007), 234702.



Rudra P. Choudhury
eMail: Rudra P. Choudhury