- Ryan Bennett
- Doctoral Candidate, Chemical Engineering
- Thesis: tbd
- B.S. Chemical Engineering, University of Florida 2002
- Email: firstname.lastname@example.org
- Phone: (617) 253-6478
- Office: 66-357
In my research I plan to use the ability of di-block copolymers to self-assemble as a route to sequester metal nanoclusters in lateral hexagonal arrays within a polymer thin film. These films could then be used as catalysts to synthesize vertically aligned carbon nanotube forests. The di-block copolymer that I have initially used is polystyrene-block-polyacrylic acid (PS-b-PAA). When this polymer is added to a toluene solution above its critical micelle concentration, micelles are formed with hydrophobic PS shells and hydrophilic PAA coronas. By spin-coating this solution onto a substrate, thin polymer films with a thickness on the order of 20 nm can be formed. These films consist of spherical domains of PAA with diameters on the order of 10-15 nm that are “quasi”-hexagonally packed within a matrix of PS. By submerging these films in an aqueous metal salt solution, the electrostatic interactions between the carboxylic acid groups in the PAA domains and the metal ions in solution cause the metal ions to be selectively loaded into the PAA domains.
In carbon nanotube (CNT) synthesis, metal nanoparticles are used as catalysts for the CNTs to grow in a chemical vapor deposition (CVD) process. Each metal nanoparticle produced will catalyze the growth of one CNT. The difficulty that arises is controlling the size distribution and the spacing of the metal nanoparticles. By using the block copolymer self-assembly route, the metal nanoparticles produced are nearly monodisperse in size and are arranged in a “quasi”-hexagonal array with near uniform spacing. The method proposed above would increase the density of vertically aligned CNTs on the order of one hundred times the density currently produced in the literature. These vertically aligned CNT forests could have possible applications in surface coatings, measurements of CNT’s mechanical properties, and also as electron emitters for flat-screen televisions.