Reversible stimulus-responsive polymers for the control of the surface interfacial and nanomechanical properties

Surfaces with reversible stimulus-responsive properties have great potential for a wide variety of applications, such as transport, separation, and detection of biomolecules, controlled adhesion, friction, and lubrication in microfluidic systems, and force or displacement generation in micro- and nanoscale devices. Surface bound stimulusresponsive polymers are ideal candidates for above applications due to their conformational sensitivity to many stimuli with controlled molecular weight, composition, architecture and topology. In this thesis, one particular class of stimulus-responsive polymers, pH-sensitive comb-type graft copolymers with ionizable main chain segments was investigated. Mono(end)-functional thiol-terminated poly(methacrylic acid-gethylene glycol) (HS-poly(MAA-g-EG)) with three different macromolecular architectures (number average molecular weight, Mn = 27K, PEG graft density, PEG(%) = 7.7%, backbone contour length, Lcontour= 41.1 nm; Mn= 15K, PEG(%) = 8.8%, Lcontour = 22.1 nm; Mn = 17K, PEG(%)= 1.9%, Lcontour = 39.8 nm) have been synthesized via atomic transfer radical polymerization and characterized by 'H NMR, GPC and FT-IR. Stimulus responsive surfaces were prepared via chemically end-attached "brush-brushes" formed by chemisorption of the copolymers on Au substrates. Chemically specific high resolution force spectroscopy (HRFS) was carried out with probe tips (end radius-50 nm) functionalized with HS(CH2)10COOH (a carboxy-terminated selfassembling monolayer or COOH-SAM) to measure the normal nanoscale interaction forces, F, as a function of probe-tip sample separation distance, D,in a series of aqueous buffer solutions of varied pH (=4-9) and constant ionic strength (IS=0.005M NaC1).

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

• Ye, Miao, Ph. D. Massachusetts Institute of Technology

Advisor dc:contributor.advisor

• Christine Ortiz.

• 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/1721.1/44318

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/44318