Ph.D. at University of California at Berkeley

From August 2000 to May 2005 I was a graduate student in the Department of Chemical Engineering, at UC Berkeley and was coadvised by Clay Radke and Nitash Balsara.

Thesis Title:

Dynamics and Thermodyanmics of Diblock Copolymers at Polymer/Polymer Interfaces

Thesis as a pdf

Thesis Abstract:

The adsorption of an AB diblock copolymer to an A/B polymer/polymer interface was measured, where A is saturated polybutadiene with 90 % 1,2 addition (sPB90), and B is saturated polybutadiene with 63 % 1,2 addition. Thin trilayer films were constructed, consisting of first a layer of the homopolymer sPB90, followed by a layer of sPB63, and finally a layer of a blend of sPB90 and deuterium labeled sPB90-sPB63 diblock copolymer. The films were annealed at ambient temperature before the concentration profiles of diblock copolymer through the films were measured using dynamic secondary-ion mass spectrometry.

The adsorption isotherm of the diblock copolymer at the polymer/polymer interface was measured by constructing films with different amounts of diblock copolymer and annealing them until equilibrated. The adsorption isotherm was then determined from the various measured concentration profiles. These measurements were compared with the predictions of self-consistent field theory (SCFT). All necessary inputs for the theory were independently determined so that no adjustable parameters were required. The agreement between theory and experiment was good.

Dynamics of adsorption and desorption of the diblock copolymer to the interface were measured by annealing the films for periods of times ranging between 0.2 h and 108 h and comparing the various transient concentration profiles produced. The process was modeled as diffusion in an external field, generated from SCFT, and the diffusion coefficients were measured in independent experiments. This proposed field-theoretic diffusion model neglects the dynamics of molecular conformational change. Nevertheless agreement between theory and experiment is good. The absence of slow conformational dynamics and the absence of an energy barrier to adsorption means that adsorption and desorption are completely diffusion limited down to the length scale of the interfacial width.

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