Molecular theory for gelation of polymer and colloidal systems / Annemarie Ott Weist.

Format:

Book

Manuscript

Microformat

Thesis/Dissertation

Author/Creator:

Weist, Annemarie Ott.

Contributor:

Glandt, Eduardo D., advisor.

University of Pennsylvania.

Language:

English

Subjects (All):

Penn dissertations--Chemical engineering.

Chemical engineering--Penn dissertations.

Local Subjects:

Penn dissertations--Chemical engineering.

Chemical engineering--Penn dissertations.

Physical Description:

xvii, 238 leaves : illustrations ; 29 cm

Production:

1992.

Summary:

Gelation can be viewed as a transition from local clustering of molecules to an extended cluster that spans a macroscopic system which is accompanied by singularities in the transport properties. Two liquid theory techniques: Monte Carlo simulations and integral-equation theory are used in this thesis to study the gelation of polymer and colloidal systems.

The effect of particle shape and orientation on the percolation threshold was studied by determining the threshold concentration for a model system of concentric-shell ellipsoids. It was found that percolation in the direction of the major axes occurs at lower densities and both prolate and oblate isotropic systems show re-entrant behavior similar to that of the extended sphere model.

The main result of this work consists of an extension of Wertheim's multi-density formalism for chain forming particles to the study of connectivity and gelation of these systems. Expressions are derived for the weight-average molecular weight, the end-to-end distance and the radius of gyration of the chains. These results are used to study the effect of interparticle attractions, covalent bonding and particle shape on the gel point. The effect of particle shape is studied by solving the Percus-Yevick equations analytically for two types of model dumbbell fluids: penetrable and adhesive dumbbells. Both studies reveal that there is a critical bond-length below which dimer formation increases the percolation threshold and above which dimer formation facilitates percolation and lowers the threshold.

Both physical and chemical gelation are studied in systems of chain forming particles. It was found that systems of polymerizing penetrable spheres display re-entrant behavior. The results for chemical gelation support Flory's idea that gelation occurs when a critical number of intermolecular linkages has been exceeded.

Notes:

Supervisor: Eduardo D. Glandt.

Thesis (Ph.D. in Chemical Engineering) -- Graduate School of Arts and Sciences, University of Pennsylvania, 1992.

Includes bibliography.

Local Notes:

University Microfilms order no.: 92-27783.

OCLC:

80749387