Studying and controlling chromophore orientation in polyelectrolyte layer-by-layer thin films

Many properties such as electrical conductivity, liquid crystallinity, and optical properties depend on specific molecular orientation. Currently, this orientation is achieved using either inorganic crystals or rigorously processed organic materials. This thesis studied a film assembly technique that provides a mechanism for aligning polymeric materials as films are assembled. This eliminates the need for a post-processing alignment step and allows easier film construction. The fabrication technique for the polymeric thin films is layer-by-layer (LBL) electrostatic assembly. This technique takes advantage of the electrostatic attraction between oppositely charged polyelectrolytes to assembly films. For example, a polyanion and polycation are dissolved in separate aqueous solutions at a given pH and salt concentration. A charged substrate is immersed into one solution, rinsed with water, and immersed in the other solution. This cycle is repeated to assemble films. Typically, the polyelectrolytes in these films are randomly arranged; however, a few researchers have demonstrated that ordered films could be assembled with the LBL technique. We investigated the driving force of this order and how to control it by studying the processing parameters, polyelectrolytes, and surfaces used to assemble ordered LBL films. For the processing study, two side-chain chromophoric polyanions were used. One, PolyS 119, contained sulfonic acid groups while the other, PAZO, contained carboxylic acid groups. These were assembled with four polyamines. The pH of the polyanion solutions was varied to observe its effect on chromophore orientation. Chromophore orientation was measured by FTIR and UV/isible spectroscopy.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Chemical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2002

Author dc:creator

• DeWitt, David Michael, 1972-

Advisor dc:contributor.advisor

• Paula T. Hammond.

• Chemical 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/1721.1/29278

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/29278