Multiscale chemomechanics of polymer deformation under contact : predicting structure-property correlations from the bulk to the interphase

The development of nanoscale polymeric materials for mechanical applications necessitates advances in small-volume experimental techniques and analyses that reflect the viscoelastoplastic behavior of such materials. In this thesis, the time-dependence and response of homogeneous engineering polymers under confined contact loading are characterized as a function of polymer physical and structural properties. The validity of the time-independent metric indentation hardness Hi is evaluated through the combination of nanoindentation and atomic force microscopy imaging. In addition, the classic, time-dependent metric creep compliance J(t) is used to establish the experimental conditions necessary for linear elastic behavior for a set of thermoplastic and thermoset materials. For large indentations (hmax > 1 um), properties are tacitly assumed to reflect the properties of bulk polymer; however, this assumption does not hold within 100 nm of a free surface or interface of amorphous polymers such as polystyrene and polycarbonate. The contact deformation mechanism near an amorphous polymer surface is found to scale with the surface area of contact, suggesting the dynamic formation of a structural interphase region. Chemical probe functionalization experiments are developed to explore the effects of probe surface charge on the probe-polymer interface and contribute to the understanding of the interphase that dominates nanocomposite material response. A technique to rapidly screen mechanical response of combinatorial polymer libraries is presented, to establish structure-property-processing relationships of such chemomechanically defined interfaces before nanoscale deformation mechanisms in confined polymers are fully understood.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Materials Science and Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2008

Author dc:creator

• Tweedie, Catherine Anne

Advisor dc:contributor.advisor

• Krystyn J. Van Vliet.

• Materials Science and Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/44684

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/44684