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Title:Click chemistry for colloidal assembly
Author(s):Waqar, Asfand
Advisor(s):Braun, Paul V.
Department / Program:Materials Science & Engineerng
Discipline:Materials Science & Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Click Chemistry
Cu(I)-catalyzed azide alkyne cycloaddition (CuAAC)
Colloidal Crystals
Colloidal Assembly
Abstract:Abstract Click chemistry has gained significant importance over the period of last decade as an efficient tool for synthetic chemistry. These set of highly efficient, high yielding and extremely resilient reactions use an approach similar to the one employed by nature, with very few by products and almost no side reactions, they work perfectly fine in a multitude of reaction conditions. This new synthetic arsenal of reactions has been successfully used in the diverse fields of drug discovery, pharmacological synthesis, polymer synthesis, surface science and materials science for achieving a myriad of goals. In this study we have used one of the best reactions from the arsenal of click chemistry, called Cu(I)-catalyzed azide alkyne cycloaddition (CuAAC) to develop an approach for directed colloidal assembly. Colloidal crystals are used here as an ideal model system for studying directed self assembly. This study develops a modular approach towards colloidal assembly in which click chemistry is employed as an assisting agent via a layer by layer process in an attempt to devise a route for creating colloidal crystals which are not readily synthesizable using conventional approaches like simple vertical deposition or spin coating. For achieving this goal several surface functionalizations were studied, for the glass and silica substrates, as well as for colloidal particles of polystyrene (PS) and silica. A couple of surface functionalization approaches are utilized for achieving alkyne surface functionalization of glass substrates, and colloidal PS-PEG-azide and silica- azide particles were made. These azide particles were then used in two distinct studies of colloidal assembly. The first system used sedimentation to study the viability of 1 surface click chemistry for colloidal systems, and it was found that click chemistry can be efficiently used as a chemical tool to anchor PS-PEG-azide particles on the glass- alkyne surfaces. Patterned colloidal arrays are also fabricated, and a number of control experiments are done to provide sufficient proof that click chemistry can be used to anchor colloidal particles to the substrate. Once it was established that functionalized colloids and appropriately functionalized surfaces can be used to anchor these colloids on the surface the second system was studied. The second system was based on a technique called vertical deposition which can be used to create opals and colloidal crystals of various types of microspheres. Vertical deposition of Silica-azide particles as well as PS-PEG-azide was done on alkyne functionalized glass substrates. Multilayered colloidal crystals were successfully created, and then upper layers were washed away to obtain a colloidal monolayer. The idea under study here was to find out if click chemistry can be used to create a colloidal crystal using a layer by layer approach. This layer by layer approach, will utilize particles of two different alternating functionalities. Monolayers of each type of particle will be formed step by step on a functionalized substrate, where in each step it is locked in the structure while still providing chemical functionality for the next layer above it to be anchored on it. The first monolayer of Silica-azide was successfully fabricated in this study, thought its quality can be greatly improved. Several experiments are discussed here which attempt to improve the quality of the first monolayer and important recommendations are given.
Issue Date:2011-05-25
Rights Information:Copyright 2011 Asfand Waqar
Date Available in IDEALS:2011-05-25
Date Deposited:2011-05

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