Ultrahydrophobic Surfaces : Effects of Topography on Wettability
Total Page：16
File Type：pdf, Size：1020Kb
University of Massachusetts Amherst ScholarWorks@UMass Amherst Doctoral Dissertations 1896 - February 2014 1-1-2001 Ultrahydrophobic surfaces : effects of topography on wettability. Didem, Oner University of Massachusetts Amherst Follow this and additional works at: https://scholarworks.umass.edu/dissertations_1 Recommended Citation Oner, Didem,, "Ultrahydrophobic surfaces : effects of topography on wettability." (2001). Doctoral Dissertations 1896 - February 2014. 1022. https://scholarworks.umass.edu/dissertations_1/1022 This Open Access Dissertation is brought to you for free and open access by ScholarWorks@UMass Amherst. It has been accepted for inclusion in Doctoral Dissertations 1896 - February 2014 by an authorized administrator of ScholarWorks@UMass Amherst. For more information, please contact [email protected]. ULTRAHYDROPHOBIC SURFACES- EFFECTS OF TOPOGRAPHY ON WETTABILITY A Dissertation Presented by DIDEM ONER Submitted to the Graduate School of the University of Massachusetts Amherst in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY September 2001 Polymer Science and Engineering © Copyright by Didem Oner 2001 All Rights Reserved ULTRAHYDROPHOBIC SURFACES- EFFECTS OF TOPOGRAPHY ON WETTABILITY A Dissertation Presented by DIDEM ONER Approved as to style and content by: Thomas J. McCarthy, Chair Mark T. Tuominen, Member Thomas J. McCarthy, Department Head Polymer Science and Engineering To Nesli§ah, Liitfi and Kerem Oner, and Sinan Deliormanli with all my heart ACKNOWLEDGMENTS I would like to acknowledge advisor, my Dr. Tom McCarthy, for all his enthusiasm, advice and understanding during the last 4 years while we worked on this exciting Ph.D. thesis. Thank you Tom, for making this so special. Also, I want to thank Dr. Tuominen and Dr. Strey for their time and input. It would not have been possible if the McCarthy group were not there. Especially, I want to thank: Jack for helping me out with many things in the lab; Chris for his help, input and his friendship; Jeff for our interesting conversations (from nutrition to ultrahydrophobicity); Xinqiao (a great office mate); Margarita for the wonderful memories we shared in such a short period of time; Misha for his sincere help; Chuntao; Terry for our discussions in teaching me how to become an 'engineer'; Kevin; Ebru; like and Wei (was always so supportive). Special thanks to the PS&E faculty and staff for all the things they have done- from teaching in class to the kind support they provided to make me feel like home. I sincerely thank Ho-Cheol, Robin, Firat, Elif, Sabri and Serkan for making this journey so enjoyable. Also, I will never forget the support from the very special people in my life, Mutlu, Kutay, Iskender and Emel Yilgor. I want to thank my brother, Kerem, for our unforgettable memories and for his patience during our 'Amherst years' together. Also, I am always grateful to Sinan's family for their sincere support and love. And to Sinan Deliormanli, my other half. It was him who always believed in me, filled me with his endless love and care. Thank you, hayatku§um. Most of all, I feel so blessed to have the everlasting love of the most wonderful parents in the universe, Nesli§ah and Liitfi Oner. Thanking them will never be enough. V ABSTRACT ULTRAHYDROPHOBIC SURFACES- EFFECTS OF TOPOGRAPHY ON WETTABILITY SEPTEMBER 2001 DIDEM ONER, B.S., KOC UNIVERSITY M.S., UNIVERSITY OF MASSACHUSETTS AMHERST Ph.D., UNIVERSITY OF MASSACHUSETTS AMHERST Directed by: Professor Thomas J. McCarthy The overall objective of this Ph.D. thesis is to control the wetting behavior of surfaces by exploring the effects of topography on wettability, and ultimately make ultrahydrophobic surfaces. Tliree different approaches were taken in preparing rough surfaces with controlled wettability. The first approach involved the use of photolithography that resulted in a series of silicon surfaces with different post size, shape and separation (Chapter 2). The second approach was the surface modification of low density polyethylene (Chapter 3). The last one was to adsorb polystyrene colloids with different diameters onto polyelectrolyte multilayers (Chapter 4). The wettability of the patterned silicon surfaces prepared by photohthography and hydrophobized using reactive silane chemistry was explored. Surfaces containing square posts with X-Y dimensions of 2 )iim-32 )im exhibited ultrahydrophobic behavior with high advancing and receding contact angles. The contact angles were independent of the post height and surface chemistry. Surfaces with larger posts were not ultrahydrophobic- vi water droplets pinned on these surfaces, hicreasmg the separation between the posts caused increases in receding contact angles up to the point that water intruded between the posts. Changing the shape of the posts also increased the receding contact angles due to the more contorted contact lines. The oxidative etching of low density polyethylene films followed by uniaxial or biaxial tension resulted in the formation of micron size fragments. 5 minutes oxidized films had smaller islands than the 1 5 minutes oxidized ones. The fragments became smaller and more distant from each other with increase in strain that affected the wettability of the surfaces. At 400%, the films exhibited ultrahydrophobic behavior. At a higher strain, the islands were very small and apart from each other, the receding contact angle dropped significantly. Submicron and micron scale rough surfaces were prepared by adsorbing polystyrene colloids onto polyelectrolyte muUilayers. The negatively charged colloids were efficiently adsorbed onto the outermost cationic polyelectrolyte surface, showing no aggregation. The advancing water contact angle increased and the receding contact angle decreased as the surface coverage increased, resulting in a remarkable hysteresis of -122°. Thus, hydrophobic surfaces could not be achieved by making rough surfaces by colloidal adsorption. vii TABLE OF CONTENTS Page ACKNOWLEDGMENTS V ABSTRACT VI LIST OF TABLES XI LIST OF FIGURES ••• Xlll CHAPTER 1 . INTRODUCTION 1 Overview I Wetting Behavior of Surfaces 3 Contact Angle Hysteresis 8 Topography of Roughness 10 Three-Phase Contact Line...: 12 Surface Characterization Techniques 14 Dynamic Contact Angle 14 Atomic Force Microscopy 15 X-Ray Photoelectron Spectroscopy 17 Notes and References 20 2. MODEL LITHOGRAPHIC SURFACES TO EXPLORE ULTRAHYDROPHOBICITY 22 Introduction 22 Photolithography 23 Dry Etching 25 Reactive Silane Chemistry 29 Experimental 31 Materials 31 Preparation of Silicon Substrates 32 Reaction of Silicon Substrates with Organosilanes 33 Results and Discussions 34 viii Reaction of Silicon Substrates with Organosilanes 34 Critical Size Scale of Roughness for Hydrophobicity 35 Structure of 3-Phase Contact Line '""^ 4j Laplace Pressure Critical Tilt Angle Conclusions Notes and References SURFACE MODIFICATION OF LOW DENSITY POLYETHYLENE 55 Motivation Surface Treatments of Low Density Polyethylene 56 Deformation of Thin Film Coatings Upon Uniaxial and Biaxial Tension 59 Experimental Materials 64 General Methods 64 Preparation of Polyethylene Substrates 65 Oxidation of Polyethylene Substrates 65 Uniaxial Streching of LDPE 65 Biaxial Streching of LDPE 66 Self-Assembled Monolayers of 1-dodecanethiol 66 Results and Discussions 67 Oxidation of Polyethylene Substrates (o-LDPE) 67 Uniaxial Deformation 69 Change in Surface Roughness of o-LDPE with Strain 72 Biaxial Deformation of o-LDPE 76 Deformation of Gold Coating Bonded to LDPE 78 Conclusions 80 Notes and References 82 4. ADSORPTION OF POLYSTYRENE COLLOIDS ONTO POLYELECTROLYTE MULTILAYER ASSEMBLIES AND WETTING BEHAVIOR OF THESE ROUGH SURFACES 86 Introduction 86 Polyelectrolyte Multilayer Assemblies 87 Adsorption of Colloids onto Polyelectrolytes 89 Self-Assembled Monolayers of Alkanethiols on Gold 91 Experimental ^5 ix Preparation of Silicon Substrates c)y Pretreatment of Silicon Substrates 9-7 Reaction of Silicon Substrates with (4-aminobutyl)dimethylmethoxysilane 97 Layer-by-Layer Deposition of Polyelectrolytes '95 Adsorption of Polystyrene Colloids onto Polyelectrolyte Multilayers 98 Kinetic Study of the Adsorption Behavior of Colloids 99 Solution Casting Polystyrene Colloids onto Polyelectrolyte Multilayers 99 Gold Coating and Self-Assembled Monolayers (SAMs) of 1-dodecanethiol jqq Results and Discussions 1 qq Pretreatment of Silicon Substrates 1 00 Adsorption of Polystyrene Colloids onto Polyelectrolyte Multilayers.... 102 Kinetic Study of the Adsorption Behavior of Colloids 104 Summary of the Rough Surfaces Prepared 114 Solution Casting Polystyrene Colloids onto Polyelectrolyte Multilayers 118 Conclusions 120 Notes and References 122 BIBLIOGRAPHY 126 1 LIST OF TABLES Table Page 2. Atomic concentration (XPS) 1 of silicon/silicon oxide surfaces reacted with DMDCS, ODMCS and FDDCS at 15° 75° and takeoff angles 35 2.2 Water contact angle data for silane-modified hexagonally arrayed 40 - high square post surfaces described in figures 2.7 and 2.8 38 2.3 Water contact angle data for ODMCS-modified surfaces containing 1 6 x 16 ^im, x 32 32 |im, 64 |im x 64 |im, 128 x 128 ^im square posts of different height 4q 2.4 Water contact angle data for silane-modified surfaces containing different shaped posts and 8 |im x 8 |nm square posts spaced at various distances (described in figures 2.10 and 2.12) 45 2.5 Laplace pressure calculated using equation 4.1 48 2.6 Tilt angle and hysteresis exhibited by the DMDCS-modified silicon surfaces 50 3.1 Tensile failure modes for thin