Block copolymer photonic crystals

This thesis explores the photonic properties of block copolymer systems. One dimensionally periodic dielectric stacks are fabricated with symmetric, lamellar forming, copolymer systems: diblock copolymers, solvent swollen BCP materials, and homopolymer swollen BCP blends. Each system exhibits reflectivity in visible spectrum. These materials are also investigated for their phononic band properties by Brillouin scattering. A copolymer forming the three dimensional double gyroid at optically relevant length scales and its reflective properties are presented as well. Experimental results document the initial observation of photonic optical properties related to the microstructure of a block copolymer. One dimensionally periodic, lamellar polymer block copolymer systems of poly(styrene-b-isoprene) are used to fabricate multilayered optical structures with a range of lamellar dimensions. The lamellar repeat of the copolymer morphology is shown to be adjustable by blending symmetric amounts of like homopolymers of lower molecular weight with the copolymer. The composition of the blends remains symmetric and the morphology is shown to remain lamellar. An isopleth of composition is examined and photonic crystals containing up to 60 wt % homopolymer exhibit wavelength selective reflectivity from the ordered morphology. The wavelength of reflectivity is correlated with the lamellar repeat spacing and morphology. The optical properties of solvent swollen ultrahigh molecular weight block copolymers are examined. The wavelength selective reflectivity is shown to correlate with the expected behavior of the phase segregated morphology. Deformation sensitive ordered gels are fabricated by using a non-volatile, alkyl phthalate plasticizer. The optical properties are shown to respond to the material strain. A simple demonstration of the visualization of the strain field of a deforming system is presented. In addition these gels are shown to exhibit phononic band gap behavior. The system is studied by Brillouin scattering and resonant phonons arising from the morphology are predicted and observed. Three dimensionally periodic photonic crystals formed of a double gyroid styrene- isoprene diblock copolymer are also documented. The copolymer material is considered as formed and also after a series of processing steps.

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

2003

Author dc:creator

• Urbas, Augustine M. (Augustine Michael), 1974-

Advisor dc:contributor.advisor

• Edwin L. Thomas.

• 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/1721.1/29977

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/29977