Dynamics in polymer nanocomposites containing fixed and mobile nanoparticles / Chia-Chun Lin.

Format:

Book

Manuscript

Thesis/Dissertation

Author/Creator:

Lin, Jiajun, author.

Contributor:

Composto, Russell J., degree supervisor.

Winey, Karen I., degree committee member.

Clarke, Nigel, degree committee member.

Meth, Jeffrey S., degree committee member.

University of Pennsylvania. Department of Materials Science and Engineering.

Language:

English

Subjects (All):

Penn dissertations--Materials science and engineering.

Materials science and engineering--Penn dissertations.

Local Subjects:

Penn dissertations--Materials science and engineering.

Materials science and engineering--Penn dissertations.

Physical Description:

xix, 130 leaves : illustrations (some color) ; 29 cm

Production:

[Philadelphia, Pennsylvania] : University of Pennsylvania, 2015.

Summary:

This dissertation describes experimental studies on the dynamics of polymer nanocomposites (PNC), namely, center-of-mass (COM) polymer diffusion in PNCs, and COM nanoparticle (NP) diffusion in polymer melts. Elastic recoil detection (ERD) is used for polymer diffusion studies and Rutherford backscattering (RBS) is used for NP diffusion studies. Diffusion of the tracer polymer, deuterated poly(methyl methacrylate) (dPMMA) is slowed down in a PMMA matrix filled with hydroxyl-capped spherical silica nanoparticles. A confinement parameter, ID/2Rg, where ID is interparticle distance and 2Rg is probe size is defined to account for the NP crowding effect. For highly crowded region where ID < 2Rg, D decreases by up to 80% relative to the bulk value. Surprisingly, D is reduced by 15% relative to the bulk value even when ID is eight times laRger than 2Rg in the weakly confined region. A comparison between the current PMMA and polystyrene nanocomposites indicates that attractive interactions in the PMMA system do not significantly alter the center of mass diffusion of macromolecules in polymer nanocomposites. Diffusion of deuterated polystyrene (dPS) is probed in PS matrices containing string-like chained nanoparticles (cNP) grafted with PS. This investigation connects prior diffusion studies in model spherical and cylindrical NP systems, and provides insight for technological applications, which typically involve irregularly-shaped NPs such as carbon black. We report that the presence of chained NPs in PS matrices induces a minimum in the diffusion coefficient (D) with increasing cNP concentration when the key length scale, 2Rg/L <̲ 1.5, where Rg is the gyration radius of dPS and L is the mean length of the impenetrable core of the chained NPs. The diffusion minimum is attributed to anisotropic diffusion in the vicinity of the chained NPs and requires that the long dimension of the cNP be comparable to or longer than the tracer molecule. Two normalizations are explored to account for the brush effect on polymer diffusion. These studies show that the NPs not only act as impenetrable obstacles for polymer diffusion, but that the polymer brush grafted to the cNP provides an alternative pathway to control polymer dynamics.

Notes:

Ph. D. University of Pennsylvania 2015.

Department: Materials Science and Engineering.

Supervisor: Russell J. Composto.

Includes bibliographical references.

OCLC:

945583657