POLYELECTROLYTE MULTILAYERS: SIMULATIONS, EXPERIMENTS, AND APPLICATIONS IN BIOMINERALIZATION by PRITESH ARJUNBHAI PATEL Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy Department of Macromolecular Science and Engineering CASE WESTERN RESERVE UNIVERSITY January 2008 CASE WESTERN RESERVE UNIVERSITY SCHOOL OF GRADUATE STUDIES We hereby approve the dissertation of ______________________________________________________ candidate for the Ph.D. degree *. (signed)_______________________________________________ (chair of the committee) ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ ________________________________________________ (date) _______________________ *We also certify that written approval has been obtained for any proprietary material contained therein. Copyright © 2007 by Pritesh Arjunbhai Patel All rights reserved iii To my Father, Arjun R. Patel --who inspires me to achieve the impossible-- iv Table of Contents Table of Contents................................................................................. 1 List of Tables........................................................................................ 7 List of Figures ...................................................................................... 8 List of Schemes .................................................................................. 16 Acknowledgements............................................................................ 18 CHAPTER 1 ...................................................................................... 21 1 Introduction................................................................................. 21 1.1 Layer-by-Layer ‘Dipping’ Assembly (part I) ................................................... 21 1.1.1 Characterization Techniques:.................................................................... 23 1.1.2 Multilayer Structure, Properties and Growth Mechanisms....................... 24 1.1.3 Research Significance - I .......................................................................... 28 1.2 Polyelectrolyte Spin Assembly (part II) ........................................................... 29 1.2.1 Prior Studies.............................................................................................. 30 1.2.2 Scaling Model for PSA growth................................................................. 32 1.2.3 Research Significance............................................................................... 37 1.3 Biomineralization (part III)............................................................................... 38 1.3.1 Polyelectrolyte Multilayers for Biomineralization ................................... 39 1.3.2 Hydroxyapatite Formation........................................................................ 41 1 1.3.3 Silica Biomineralization............................................................................ 44 1.4 Thesis Outline................................................................................................... 53 CHAPTER 2 ...................................................................................... 62 2 Molecular Dynamics Simulations of Layer-by-Layer Assembly of Polyelectrolyte ............................................................................... 62 2.1 Synopsis ............................................................................................................ 62 2.2 Introduction....................................................................................................... 63 2.3 Model and Simulation Method ......................................................................... 63 2.4 Results............................................................................................................... 68 2.4.1 Formation of Multilayers .......................................................................... 68 2.4.2 Effect of Charge Density of Polyelectrolytes ........................................... 71 2.4.3 Effect of Chain Degree of Polymerization................................................ 75 2.4.4 Theoretical Model of Multilayer Formation............................................. 78 2.5 Discussion and Conclusion............................................................................... 80 CHAPTER 3 ...................................................................................... 96 3 Effect of Electrostatic and Short Range Interactions on the Build-Up of Polyelectrolyte Multilayers .......................................... 96 3.1 Synopsis ............................................................................................................ 96 3.2 Introduction....................................................................................................... 97 3.3 Simulation Methods and Interaction Parameters:............................................. 97 3.4 Results and Discussions.................................................................................... 99 2 3.4.1 Growth of Polymer Surface Coverage...................................................... 99 3.4.2 Distribution of Polymer Density............................................................. 100 3.4.3 Universality of the Film Growth............................................................. 104 3.4.4 Stability of the Growing Film and Chain Exchange............................... 105 3.5 Scaling Model................................................................................................. 107 3.5.1 Average Multilayer Density.................................................................... 107 3.5.2 Charge Density Oscillations ................................................................... 109 3.5.3 Multilayer Growth.................................................................................. 110 3.5.4 Chain Desorption.................................................................................... 112 3.6 Conclusions..................................................................................................... 114 CHAPTER 4 .................................................................................... 125 4 Combined Effect of Spin Speed and Ionic Strength on Polyelectrolyte Spin Assembly........................................................ 125 4.1 Synopsis .......................................................................................................... 125 4.2 Introduction..................................................................................................... 126 4.3 Experimental Procedure.................................................................................. 126 4.3.1 Preparation of Multilayers...................................................................... 126 4.3.2 Characterization ...................................................................................... 128 4.3.3 Atomic Force Microscopy (AFM).......................................................... 129 4.4 Results and Discussion................................................................................... 131 3 4.5 Conclusions..................................................................................................... 142 CHAPTER 5 .................................................................................... 155 5 Hydroxyapatite and Silica Biomineralization on Polyelectrolyte Multilayers ............................................................. 155 5.1 Synopsis .......................................................................................................... 155 5.2 Experimental Method......................................................................................157 5.2.1 Hydroxyapatite Formation...................................................................... 157 5.2.2 Experimental Methods: Silica Formation ............................................... 163 5.3 Results and Discussion: Hydroxyapatite formation........................................ 165 5.3.1 Kinetics of HA growth in Solution ......................................................... 165 5.3.2 Growth of HA on LBL Surfaces............................................................. 169 5.4 Results and Discussion: Silica Formation....................................................... 173 5.5 Conclusions..................................................................................................... 177 CHAPTER 6 .................................................................................... 187 6 Silica formation by Poly(ethylene imine)(PEI) in Solution and on Surfaces ....................................................................................... 187 6.1 Synopsis .......................................................................................................... 187 6.2 Introduction..................................................................................................... 188 6.3 Experimental Procedure.................................................................................. 188 6.4 Results and Discussion................................................................................... 191 6.4.1 Silica formation from PEI in solution..................................................... 191 4 6.4.2 Effect of PEI and TMOS Concentration on Silica Formation ................ 195 6.4.3 Morphology of Silica .............................................................................