INVESTIGATION INTO WATER-SOLUBLE PERYLENE DIIMIDES FOR THIN FILM FORMATION by COREY R. WEITZEL B.S. University of Northern Colorado, 2004 A THESIS Submitted in partial fulfillment of the requirements for the degree MASTER OF SCIENCE Department of Chemistry College of Arts and Sciences KANSAS STATE UNIVERSITY Manhattan, Kansas 2008 Approved by: Major Professor Dan A. Higgins Abstract Three water-soluble perylene diimides (PDIs) were investigated to examine differences in their thin film forming properties. The PDI thin films investigated in this thesis are formed in an electrostatic-self-assembled (ESA) layer-by-layer (LBL) process by the use of a dip coater. The 2- three PDIs employed are sodium bis (sulfonatopropyl) perylene diimide (PDISO3 ), bis (trimethylammonioethyl) perylene diimide diiodide (PDIDI2+), and N-(butoxypropyl)-N’-(2- + (N,N,N-trimethylammonio)-ethyl) perylene-3,4,9,10-tetracarboxylic diimide iodide (C7OPDI ). Thin films were made by alternately depositing the PDIs with counter polyelectrolyte (PEs). The PEs employed were poly(diallyldimethylammonium chloride) (PDDA+) and poly(acrylic acid) (PA-), depending on the charge of the PDI. PDIs were determined to be aggregated in all three PDI precursor solutions. The fraction of PDI aggregated in each was found to be 0.972, 0.903, 2- 2+ + + and 0.993, for the PDISO3 , PDIDI , and C7OPDI , respectively. The C7OPDI solution was the most aggregated only having one charge group, which makes it more hydrophobic. Thin films prepared from the solutions all displayed an absorbance spectrum similar to the aggregated form. All the composites displayed linear growth in film thickness and fiber width with bilayer 2- number. However, the three composites gave unique surface morphologies. The PDISO3 •PDDA+ composite was found to incorporate highly curled intertwined fibers compared to the PDIDI2+•PA- composite, where the fibers were not intertwined. The fiber structure was found to change after 15 bilayers. This change in morphology was attributed to the fibers grafting together and overlapping causing the loss of original fiber structure. The two symmetric 2- + composites differed in the film thickness with the PDISO3 •PDDA being thicker than the PDIDI2+•PA- composite. This was attributed to the molecular weights (MW) of the polyelectrolytes investigated during thin film deposition, with the PDDA+ having a much higher + - MW. C7OPDI •PA thin film composite had a film thickness approximately equal to the 2- + PDISO3 •PDDA composite, indicating precursor aggregation also influences deposition rate. + - The C7OPDI •PA composite incorporated wavy thin fibers that appeared aligned in the dipping direction. This alignment was visible for bulk samples in UV-vis absorption dichroism studies. The alignment was parallel to the dipping direction of the substrate. Table of Contents List of Figures ............................................................................................................................... vii List of Equations .......................................................................................................................... viii Acknowledgements ........................................................................................................................ ix CHAPTER 1 - Introduction ............................................................................................................ 1 1.2. Organic Semiconducting Polymers: ............................................................................... 2 1.3. Molecular Organic Semiconductors: .............................................................................. 3 1.3.A. P-type: ..................................................................................................................... 3 1.3.B. N-type non PDIs: .................................................................................................... 3 1.3.C. PDI: ......................................................................................................................... 4 1.4. Thin Film Formation: ...................................................................................................... 6 1.4.A. Layer by Layer Formation: ..................................................................................... 7 1.4.B. Materials Involved in Layer-by-Layer Formation: ................................................. 8 1.5. Film Structure: ................................................................................................................ 9 1.6. Present Work: ............................................................................................................... 10 References ................................................................................................................................. 12 CHAPTER 2 - Experimental Considerations ............................................................................... 17 2.1. Introduction: .................................................................................................................. 17 2.2. Synthesis of Starting Materials: .................................................................................... 17 2- 2.2.A. Synthesis of sodium bis (sulfonatopropyl) perylene diimide (PDISO3 ): ............ 17 2.2.B. Synthesis bis (trimethylammonioethyl) perylene diimide diiodide (PDIDI2+): .... 18 2.2.C. Synthesis of N-(butoxypropyl)-N’-(2-(N,N,N-trimethylammonio)ethyl) perylene- + 3,4,9,10-tetracarboxylic diimide iodide (C7OPDI ): ............................................................ 20 2.3. Preparation of PDI and Polyelectrolyte Solutions: ....................................................... 21 2.4. Instrumentation: ............................................................................................................ 22 2.4.A. Sample Preparation and Deposition: ..................................................................... 22 2.4.B. Bulk Sample Characterization: ............................................................................. 22 2.4.C. High Resolution Microscopic Sample Preparation and Imaging: ......................... 23 iv 2.5. Thin Film Deposition: ................................................................................................... 24 2.6. Analysis of Thin Films: ................................................................................................ 24 2.6.A. UV-vis Absorption Spectroscopy: ........................................................................ 24 2.6.B. Studies of Sample Morphology: ........................................................................... 27 2.6.B.1. Fiber Dimensions: ......................................................................................... 27 2.6.B.2. Determination of Film Thickness: ................................................................ 30 2.6.B.3. Fiber Alignment: ........................................................................................... 30 References ................................................................................................................................. 33 CHAPTER 3 - Towards Control of Perylene Diimide•Polyelectrolyte Composite Thin Film Growth and Morphology............................................................................................................... 34 3.1. Introduction: .................................................................................................................. 34 3.2. Experimental: ................................................................................................................ 35 3.2. A. Synthesis of Starting Film Precursors: .................................................................. 35 3.2.B. Thin Film Formation: ............................................................................................ 36 3.2.C. Solution and Thin Film Sample Analysis: ............................................................ 36 3.2.D. Analysis of Surface Features and Thickness of Samples: .................................... 36 3.3. Results: .......................................................................................................................... 38 3.3.A. Bulk Properties: .................................................................................................... 38 3.3.B. Absorbance of Thin Films: ................................................................................... 39 3.3.C: Morphology of Thin Films: ........................................................................................ 39 2- + 3.3.C.1. Morphology of PDISO3 •PDDA Thin Films: .................................................. 39 3.3.C.2. Mechanism of Fiber Growth: ............................................................................. 42 3.3.C.3. Morphology of PDIDI2+•PA-: ............................................................................ 44 + - 3.3.C.4. Morphology of C7OPDI •PA : .......................................................................... 46 3.3.D. Comparison of PDI Films: ......................................................................................... 46 3.4. Conclusion: ................................................................................................................... 50 References: ................................................................................................................................ 51 CHAPTER 4 - Nanofiber Growth and Alignment by Electrostatic Self-Assembly of Perylene Diimide•Polyelectrolyte