Polymer Films by Interfacial Polycondensation: A theory of kinetics and film structure

Graduate SeminarPolymer Films by Interfacial Polycondensation:
A theory of kinetics and film structureProfessor A.K. SureshDepartment of Chemical Engineering
Indian Institute of Technology, Bombay
Powai, MumbaiAbstractInterfacial polycondensation has been used in niche polymerization applications such as the formation
of thin-film composite membranes and microencapsulation of active intermediates. The technique
offers the advantage of high rate, is less fussy about monomer purity than the melt methods, and
directly offers a polymer film as the product. On the other hand, the monomers used are highly
reactive and difficult. to handle, and the mechanisms of film formation are not well understood, so that
a prediction of film properties from preparation conditions is difficult. In the applications mentioned,
the strength of the polymer film and the permeability of solutes through it are the functional properties
of importance. In this talk, we shall present a modellng framework for interfacial polycondensation,
which accounts for the interplay between diffusion, multi-step reaction kinetics, solution
thermodynamics, and phase separation. Experiments to form polyurea microcapsules have been
carried out under various conditions, and show that the crystallinity of the polymer film formed varies
considerably depending on the synthesis conditions employed, with a loose inverse correlation being
apparent between the rate of polymerization reaction and the crystallinity of the polymer film. These
results point to opportunities for engineering film permeabilities through an understanding of the
mechanisms involved in the development of crystallinity, since the latter has a strong influence on
permeability. The modelling framework takes these experimental observations as a basis, and
accounts for polymer phase separation by nucleation and spinodal decomposition mechanisms. In
order to test the basic soundness of the postulates, we use simple models such as Flory-Huggins to
describe the solution thermodynamics. Qualitative and quantitative comparison will be presented
between certain aspects of the model predictions and experiments, and lines of further development
will be indicated.Thursday, May 10, 2007
Seminar at 1:00 p.m.
HED 116Refreshments at 12:45 p.m.The Scientific Community is Cordially Invited.

Location: Hedco Pertroleum and Chemical Engineering Building (HED) - 116

Audiences: Everyone Is Invited

Contact: Petra Pearce