Concentration profiles at amorphous polymer-polymer interfaces
Zhang, Huanzhi
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Permalink
https://hdl.handle.net/2142/21321
Description
Title
Concentration profiles at amorphous polymer-polymer interfaces
Author(s)
Zhang, Huanzhi
Issue Date
1991
Doctoral Committee Chair(s)
Wool, Richard P.
Department of Study
Materials Science and Engineering
Discipline
Materials Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Organic
Chemistry, Polymer
Language
eng
Abstract
The concentration profiles are derived using the Rouse and reptation dynamics for the symmetric monodisperse and polydisperse interfaces, the asymmetric monodisperse interface, the symmetric blend interfaces, and the asymmetric interfaces of two different polymers. The profiles obtained are used to study the properties of corresponding interface. Specular reflectivity of neutrons (SRN) and secondary ion mass microscope (SIMS) are used to examine the profiles and the properties.
The molecular dynamics at the polymer interface is described by segmental motion and reptation. The segmental motion starts with the crankshaft motion and continues through the Rouse relaxation of segments, earlier, between entanglements and then the entire chain. Later reptation becomes the most important molecular motion. The concentration profile is thus contributed by both kinds of motion. The contribution from the segmental motion is calculated using a modified diffusion equation while that from reptation using the minor chain reptation model.
For the symmetric interface, a discontinuity at times less than the reptation time T$\sb{\rm r}$ is predicted from reptation and decreases as t$\sp{1\over2}$. This discontinuity is washed out by the segmental motion. At t $<$ T$\sb{\rm r}$, the average penetration depth goes as t$\sp{1\over4}$ and the total number of the monomers crossing the interface plane goes as t$\sp{3\over4}$ if only reptation is considered, but both become more complicated when the segmental motion is also taken into account. However, crossover in their time-dependence is expected to occur at t = T$\sb{\rm r}$.
These properties are also predicted for all other interfaces covered in this work. In addition, for the asymmetric interface, displacement of the initial interface plane goes as t$\sp{1\over2}$(a + bt$\sp{1\over4}$) for times less than T$\sb{\rm r}$ of the shorter chain with a and b being constants, and increases as t$\sp{1\over2}$ for times larger than T$\sb{\rm r}$ of the longer chain.
These properties are used to design SIMS and SRN experiments to critically test the Rouse and reptation dynamics. Both SIMS and SRN measurements are in agreements with theoretical results.
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