Thiết kế mạng Poly(tert-Butyl Acrylate) cho ứng dụng y sinh - Danielle R. Lewis

THE DESIGN OF POLY(tert-BUTYL ACRYLATE) NETWORKS FOR BIOMEDICAL APPLICATIONS DANIELLE R. LEWIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY IN THE GRADUATE SCHOOL OF ARTS AND SCIENCES COLUMBIA UNIVERSITY 2006 UMI Number: 3237270 INFORMATION TO USERS The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleed-through, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted.

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ProQuest Information and Learning Company 300 North Zeeb Road P. Box 1346 Ann Arbor, MI 48106-1346 © 2006 Danielle R. Lewis All Rights Reserved Abstract The Design of Poly(tert-Butyl Acrylate) Networks for Biomedical Applications Danielle R. Lewis The organization of this Dissertation is as follows.

Chapter 1 serves an an introduction to polymer networks. Different types of networks are described, as well as some rele- vant theoretical models used to characterize such networks. Chapter 2 discusses how different curing processes affect the final network structures of poly(tert-butyl acry- late) (poly(t-BA)) gels. Specifically, uncovered and covered molds are investigated in order to see how evaporation of the precursor solution effects the final network structure.

Different curing temperatures as well as different amounts and qualities of solvents are also explored. Rheological and swelling experiments are used in con- junction with equilibrium swelling theories in order to deduce poly(t-BA) network structure. Chapter 3 discusses the biocompatibility of various poly(t-BA) topogra- phies, namely brushes formed by both spin coating and supercritical carbon dioxide, and crosslinked networks. This investigation explored the possibility of using poly(t- BA) as a biomaterial, as well as answering the question of how thin we can make polymer coatings before the cells begin to respond to the underlying surface beneath the polymer layer.

Chapter 4 discusses the synthesis of end-linked networks, which are far more homogeneous in nature than networks made by free radical polymeriza- tion. One approach taken is the so-called “click chemistry” approach is discussed and results in networks that have very well-defined molecular weights between crosslinks. These end-linking procedures leads to an easy and reliable approach for making ho- mogeneous networks. Chapter 5 concludes this Dissertation with a summary and possible future outlooks.

Contents List of i;1 i11“. aaA đa List of FigUr©s. Quà gà kia Acknowledgements. HQ ng kg kia 1 Introduction 11 Polymer networks.4 Conditions for the formation of infinite networks Types ofcrosslinks.

000000 Natural and synthetic polymers .5 Factors that influence sweling.-004 12 2 Networks crosslinked in the presence of solvent 2.1 Formation of poly(t-BA) networks. ee eee ee ees 22.3 Results and Discussion.1 Evaporation of precursor solution .2 Solubility parameter of poly(t-BA) network .3 Effect of crosslinker concentration and extraction of poly(t-BA) networks.4 Solvent quantity and quality influences on poly(t-BA) network Structure. Q Q Q Q HQ HQ HQ ng Q k k k v k k xa 36 2.5 Postcure of poly(t-BA) networks .6 Aging of poly(t-BA) networks.7 Normal force effects in parallel plate rheology. 51 3 Model poly(tert-butyal acrylate) networks 57 3.

cv và kg kg va 58 3. eee ee ee ee 61 3.1 Synthesis of a,w-terminated vinyl acrylate end-linked networks 61 3.2 Synthesis of a,w-azido poly(t-BA) model networks .3 Cleavage of tert-butyl ester group on the a, w-terminated vinyl acrylate macromonomer .4 Swelling of a,w-terminated vinyl acrylate end-linked networks 63 3.5 Modulated differential scanning calorimetry of a, w-azido poly(t- BA) macromonomer.6 Swelling of a,w-azido poly(t-BA) model networks .27 Rheology of a, w-azido poly(t-BA) model networks .3 Results and Discussion.1 a,w-terminated vinyl acrylate macromonomers.2 Modulated differential scanning calorimetry of a, w-azido poly(t- BA) macromonomer. eee eee eae 66 3.3 Formation of model networks via copper(I)-catalyzed azide- alkyne cycloaddition. eee eee ee 67 3.4 Swelling of copper(I)-catalyzed azide-alkyne cycloaddition model networks.5 Gel point ofcopper(T)-catalyzed azide-alkyne cycloaddition model networks.

0 ek 70 4 Biocompatibility studies of poly(tert-butyl acrylate) architechtures 73 4.5 Cell seeding andculture .7 Cell viability test 2.9 Maintaining cells and feeding schedule .3 Results and Discussion .1 Sterilization of poly(t-BA) samples .2 Hydrolysis of tert-butyl ester «2. ee ee 85 iii 4.3 Cell response to poly(t-BA) topographies “ca ca 1 LG DU 5 Conclusion 1V List of Tables 2.1 Solubility parameters of solvents by group contributions.2 Modulus and molecular weight between crosslinks for poly(t-BA) net- works prepared in uncovered molds .3 Modulus and molecular weight between crosslinks for poly(t-BA) net- works prepared in covered molds. pee eee ns 56 3.1 Swelling ratios of a,w-terminated vinyl acrylate networks.2 Conditions for a, w-azido poly(t-BA) network synthesis .3 Swelling ratios of a,w-azido poly(t-BA) networks .1 Swelling ratios of networks before and after TFA treatment. 88 List of Figures 1.1 Schematic representation of crosslinking procedure.2 Trifunctionally branched polymer .1 Schematic of Teflon® molds .2 Schematic of stainless steel molds.3 Evaporation of precursor solution in open Teflon® molds .4 Solubility parameter of poly(¢-BA) networks .0 Modulus of poly(t-BA) networks crosslinked in uncovered molds .6 Modulus of poly(¢-BA) nelworks.7 Swelling ratios of poly(t-BA) networks prepared in uncovered molds .8 Swelling ratios of poly(t-BA) networks prepared in covered molds .9 Sol fraction of poly(t-BA) networks .10 Glass transition temperature of poly(t-BA) networks .11 Thermal postcure of poly(t-BA) networks crosslinked in uncovered molds 48 2.12 Thermal postcure of poly(t-BA) networks crosslinked in covered molds 49 2.13 Aging of poly(t-BA) networks.14 Modulus of poly(¢-BA) networks with uncontrolled normal force.1 Types of network defects.2 Copper(I) catalyzed Huisgen 1,3-dipolar cycloaddition reaction.3 Modulated DSC of a,w-azido poly(t-BA) macromonomer.5 Gel point of a,w-azido poly(t-BA) networks.1 Cell viability test for poly(t-BA) networks .2 Cleavage of tert-butyl group.3 Formation of poly(t-BA) and poly(AA) brushes.4 Cell viability response to poly(t-BA) brushes.5 Cell viability response to poly(AA) brushes.6 Cell viability response to poly(t-BA) networks.

93 Vil Acknowledgements It would not be fitting to submit this work without acknowledging the many people who have each had a tremendous impact on me along this journey. First and foremost, I would like to thank my thesis advisor, Jeffrey Koberstein for allowing me to work in his research group. His intellectual curiosity keeps his students inspired and yearning to learn more. Under his guidance, I feel prepared to conquer challenging science questions in the future.

I would like to express my graditude to my committee members for their continued support during my Ph. in my time. Thanks to Nina Shapley, who was always there when I needed an expert opinion on rheology. I am indebted to Helen Lu, whose collaboration on the biocompatibility studies allowed me to not only use her laboratory space and equipment for my research, but also taught me how to approach and conduct biological experiments.

And to Charles Maldarelli, your willingness to help was even more impressive since it came from our neighbor to the north, City College. I would also like to thank Sanat Kumar for his enthusiastic participation despite being at Columbia for only a few short months. Thanks to my fellow group members who have been there with me every step of the way. Special thanks to Dr.

Lucy Vojtova, who was the first one to take me under her wing whenI first joined this research group. Her enthusiasm was contagious, and she gave me the confidence to succeed at independent research. Derek Wong, I will forever be grateful for the wisdom and knowledge you were so free to share with me about science, research ideas, and life. And thanks to Kristen Moffat, who taught me invaluable biological research skills that I would not have learned otherwise.

While at Columbia Universtiy, I have had the priveledge of pursuing my Ph. alongside some of the most wonderful researchers. To Nicholas Hudak, Mona Utne Vili Larsen, Tracey Moraczewski, Joshua Gallaway, Doris Glykys, and Dr. Patrick John- son, you were not only my friends, you were also fellow collegues and I have learned a great deal from each and every one of you.

You all made my years here rich in knowl- edge, laughter, and fun. I will never forget the support you showed me throughout my years organizing the student seminars, nor the many happy hour beers we consumed after a hard day of work. I would also like to recognize my parents, Rick and Susan Lewis. Their constant love and encouragement gave me the strength to conquer this endeavor.

I know that no matter where life leads me they will be behind me all the way. And finally, I would like to say that this work would not be possible without the unwaivering love and support of Barry Rand. Barry, it was your steadfast belief in me that kept me sustained. And although I am closing this chapter of my life, I am excited about the new one I am about to begin with you.

ix For my parents, Rick and Susan, and for Barry Chapter 1 Introduction Abstract Research in polymer networks has seen constant interest for many decades. Although polymer networks come in many different forms, there is a strict criteria that must be met in order to technically qualify a material as a network. Classic theories of rubber and swelling have been used throughout the decades in order to attempt to describe such networks in a quantitative approach, with progress to both theories documented as certain phenomena were discovered. These topics will be reviewed in this chapter.1 Polymer networks A polymer network is an infinite molecular weight molecule composed of long polymer chains connected by junctions called crosslinks.

A more common word for a polymer Figure 1.1: Schematic representation of crosslinking procedure. The black dots represent crosslinks. network is a gel. It is these crosslinks that prevent the network from dissolving in solvent.

Instead, the network expands and swells to an equilibrium value. This concept will be described in detail later. Hydrogels are a specific type of network in that they swell in the presence of water. A physical characteristic of gelation is the occurrence of a sharp gel point.

The gel point is a well-defined stage in the polymerization at which the viscous liquid suddenly transforms to an elastic solid. Prior to the gel point, the polymer is soluble in suitable solvent. However, after the gel point, it is no longer entirely soluble in solvent [1]. The changes in polymer structure that occurs during the crosslinking of polymer chains is depicted in Fig.1 shows, the crosslinking procedure is a random one, with the only requirement of a crosslink being formed is that the pair of units be in suitable proximity at the instant of the formation of the linkage [1].

Because this random crosslinking process leads to inhomogeneities within the network, efforts have been made to design polymers with pre-determined sites for crosslinking. Many polymers have been synthesized in this manner and, as a result, more ordered final networks have been attained. This concept will be discussed in more detail in a later section.1 Applications Because of their ability to absorb many times their weight of water, hydrogels are ideal candidates for certain biomaterials. In 1960, Wichterle and Lim [2] were the first to report on using poly(2-hydroxyethyl methacrylate) (poly(HEMA)) as a biomaterial for the application of contact lenses.

Since then, the literature on the synthesis of new polymer materials has exploded. Hydrogels have seen great use in the drug delivery area. Researchers are able to control the swelling properties and bioadhesive characteristics of the hydrogels in the presence of a biological fluid. Thus, hydrogels can be useful devices for releasing drugs in a controlled manner at desired sites in the body.

One relatively recent application of certain hydrogels is their use as polymer scaf- folds in tissue engineering.