Order in side-chain liquid crystalline diblock copolymers

The architecture of side-chain liquid crystalline diblock copolymers (SCLCBC's) involves order on two different but interdependent length scales. Through molecular-scale interactions, liquid crystalline moieties self-assemble into a variety of mesophases, and on a larger length scale, chemical differences between the two blocks can result in phase-segregated block copolymer microstructures. This combination of organizational tendencies offers experimentally and theoretically challenging problems that precede a wide array of applications. Using sequential anionic polymerization we synthesized a large number of well-defined SCLCBC's. These materials consist of an amorphous, polystyrene (PS) block and a methacrylate-based, LC block with side-chain mesogens that exhibit the Sc* mesophase. The samples' block copolymer morphology was evaluated using a combination of small angle X-ray scattering (SAXS) and electron microscopy, and thermal transitions were identified using polarized microscopy, calorimetry, and elevated temperature-SAXS. We found the formation of micron-sized domains and focal-conic superstructures to depend on the length of the PS block and the overall molecular weight. A morphological phase diagram was constructed based on LC volume fraction for molecular weights up to 40,000 Daltons. A broad lamellar regime was identified that extends to unusually low LC compositions. At intermediate LC fractions, just over 50 %-wt. LC, where one would expect lamellar morphologies for analogous coil-b-coil diblocks, morphologies are predominately lamellar, but exhibit perforated defects that connect the lamellar LC microdomains.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Chemical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2001

Author dc:creator

• Anthamatten, Mitchell

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/1721.1/8206

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/8206