Macromolecules Incorporating Transition Metals: Tackling Global Challenges: Volume 27 (Polymer Chemistry Series) - Hardcover

Alaa S Abd-El-Aziz

Hardcover

ISBN 10: 1782628991 ISBN 13: 9781782628996

Publisher: Royal Society of Chemistry, 2018

Synopsis

Strategies of incorporating transition metals into macromolecules to design functional materials for addressing global challenges.

About this title

From the Back Cover

New materials are required to solve global challenges such as the growing energy demand and reducing the threat of new and re-emerging diseases and infections. Metallopolymers is an exciting and promising area of research and this book focuses on the strategy of incorporating transition metals into macromolecules to design functional materials for addressing such problems.

The book starts with an introduction to current global challenges and the role of materials science in tackling these, it then discusses the fundamentals of metallopolymers and their synthesis. The final chapters look at specific applications of the materials from photovoltaics and light-emitting diodes for energy conservation, to biological sensors and drug delivery platforms.

Written by leading experts in the field, this book is an ideal reference for students and researchers working in polymer chemistry, organometallic chemistry and materials science interested in both the polymers and its applications in energy and health.

From the Inside Flap

New materials are required to solve global challenges such as the growing energy demand and reducing the threat of new and re-emerging diseases and infections. Metallopolymers is an exciting and promising area of research and this book focuses on the strategy of incorporating transition metals into macromolecules to design functional materials for addressing such problems.

The book starts with an introduction to current global challenges and the role of materials science in tackling these. It then discusses the fundamentals of metallopolymers and their synthesis. The final chapters look at specific applications of the materials from photovoltaics and light-emitting diodes for energy conservation, to biological sensors and drug delivery platforms.

Written by leading experts in the field, this book is an ideal reference for students and researchers working in polymer chemistry, organometallic chemistry and materials science interested in both the polymers and its applications in energy and health.

Excerpt. © Reprinted by permission. All rights reserved.

Macromolecules Incorporating Transition Metals

Tackling Global Challenges

By Alaa S. Abd-El-Aziz, Christian Agatemor, Wai-Yeung Wong

The Royal Society of Chemistry

Copyright © 2018 Alaa S. Abd-El-Aziz, Christian Agatemor and Wai-Yeung Wong
All rights reserved.

ISBN: 978-1-78262-899-6

Contents

Chapter 1 Introduction, 1, 
Chapter 2 Transition Metal Complexes as Attractive Motifs to Design Macromolecules, 12, 
Chapter 3 Synthesis of Transition-metal-containing Macromolecules, 40, 
Chapter 4 Tackling the Global Energy Crisis with Transition-metal-containing Macromolecules, 83, 
Chapter 5 Biomedical Applications of Transition-metal-containing Macromolecules, 130, 
Chapter 6 Transition-metal-containing Macromolecules as Materials for Carbon Dioxide Capture, Catalysis, and Data Storage, 192, 
Subject Index, 227, 

CHAPTER 1

Introduction

1.1 Introduction

The contemporary positive transitions in globalization, economic prosperity, and quality of life mark an epoch in human evolution, as do the aftermaths of these changes, which ironically threaten the ecosystem, the planet and human survival. Exponential growth on all fronts of human activities has, indeed, benefited our social, psychological, and biological well-being but has led to enormous pressures on the Earth's resources and the biosphere, pushing the natural system beyond sustainable limits, and challenging our achievements and survival. Climate change, food scarcity, diseases, dependence on unsustainable energy resources, and a widening gap between the rich and the poor are notable examples of these challenges (Figure 1.1). A paradigm shift in our development strategies is crucial to a sustainable future, and indeed, proactive initiatives have been taken by several stakeholders. The United Nations' Sustainable Development Goals agreed upon by the 193 member states in September 2015 exemplify initiatives that seek to address many of the challenges that face contemporary humanity. Materials scientists have also envisaged these problems for decades and have taken concrete steps to help realize a sustainable future. This monograph presents selected contributions from materials scientists, specifically the research and development that uses transition-metal-containing macromolecules to address some of these challenges. Here, the focus is on three challenges: energy, climate change and the burden of diseases, which are central and interconnected to the overall problems facing humanity. For instance, climate change affects food security and biodiversity, energy supply is a major driver of global security, and diseases are a burden to the economy and adversely affect the holistic well-being of the individual.

1.2 Key Global Challenges

1.2.1 Diseases

Science has made unprecedented advancement in disease prevention, diagnosis, and treatment, which has resulted in a significant reduction in mortality and an increase in life expectancy. These achievements notwithstanding, a significant proportion of the world's population are yet to enjoy good health and well-being as exemplified by the 14.1 million new cancer cases diagnosed each year, 387 million people living with diabetes, and 1.1 billion people having high blood pressure. Also, the progress in medicine is challenged by the substantial number of premature deaths, for instance, the over 15.8 million premature deaths from noncommunicable diseases such as cancer in 2015 (Figure 1.2). The majority of these premature deaths are preventable if a healthier lifestyle is adopted or quality health care is provided.

The scenario is bleak in developing countries where 82% of the deaths from noncommunicable diseases occur, and a projected $7 trillion USD will be lost over the next 13 years if the status quo remains. While the situation is better in developed countries whose governments implement policies that reduce risk factors and enable viable health care systems, it is still imperative that the positive epidemiological transition in these countries be sustained and copied in developing countries.

The commendable decrease in the percentage of deaths from communication diseases between 2000 and 2015 (Figure 1.2) is due to advances in medicine, including the development of antimicrobial agents. However, the evolutionary process of natural selection coupled with the selective pressure exerted on pathogens by the overuse and misuse of drugs trigger a new threat: drug-resistant pathogens (Figure 1.2). Undoubtedly, drugs such as antibiotics have greatly benefited humanity, protecting patients from fatal illnesses and mitigating the risk involved in complex medical procedures such as surgery and chemotherapy, but the emergence of resistance threatens the sustainability of these erstwhile effective medical interventions.

Globally, drug-resistant infections including malaria, HIV/AIDS, and tuberculosis kill an estimated 700 000 people yearly, and the number of deaths is projected to increase to 10 million yearly by 2050 if no pre-emptive action is taken. The burden of resistance extends beyond mortality, encompassing the economic, social and security landscapes with an estimated 100 trillion USD of the economy being at risk by 2050 if no action is taken to tackle the problem. The efforts of materials scientists on the research and development of new, affordable and accessible antimicrobial agents/drugs form part of a global action plan to mitigate the burden of antimicrobial resistance.

The therapeutic efficacy and safety of drugs directly depend on the mode of delivery, which includes the dosage form and route of administration. Indeed, drug delivery technologies affect the pharmacokinetics and pharmacodynamics of drugs as well as convenience and compliance of patients. The discovery of a new drug requires the development of a delivery technology that enables the therapeutic function and ensures patients' safety and compliance. Current research on the development of drug delivery technologies seeks to localize therapeutic function at the target cells because this approach maximizes the effect and minimizes the toxicity. The administration of a new generation of highly potent and useful drugs such as peptides, proteins, genes and polymer-based drugs remains challenging due to the inherent problems such as enzymatic degradation, renal clearance, and immune system activation associated with state-of-the-art delivery systems. Indeed, these delivery barriers limit the clinical impact of many drugs and call for next-generation drug delivery technologies that ensure drug stability, specificity, and precise control over drug release, with the ultimate effect of localizing the therapeutic effects and guaranteeing patients' safety and compliance.

1.2.2 Energy and Climate Change

The prosperity and comfort inherent in contemporary lifestyles are strongly dependent on affordable and accessible energy. With a fast-growing population and economic prosperity, especially in developing countries, energy demand is expected to increase. The United States Energy Information Administration expects a 48% increase in 28 years, from the 549 quadrillion British thermal units (Btu) of energy consumed globally in 2012 to 815 quadrillion Btu in 2040 (Figure 1.3). Most likely, an extent of the projected increase could be offset by energy-efficient technologies as governments promote awareness about sustainability but a major energy crisis will persist if we maintain the existing situation. Currently, fossil fuels provide more than 80% of the global energy demand, but the non-renewability of fossil fuel within a realistic time frame poses a sustainability issue. Though global fossil fuel resources are of a sufficient quantity to meet increasing demand in the short term, converting these resources into reserves in an economical and eco-friendly approach requires advanced innovative solutions that could hike fuel prices and eventually challenge sustainable development. Another key issue with fossil fuel technologies is the comparatively high carbon dioxide footprint, which results from the combustion process and contributes significantly to greenhouse gas (GHG) concentrations in the atmosphere. The burning of fossil fuel also releases other GHGs including methane and nitrous oxide into the atmosphere, further contributing to the total concentration of GHGs in the atmosphere, which has steadily increased to an unprecedented level over the last 800 000 years. A growing amount of empirical evidence implicates these anthropogenic GHGs, mainly carbon dioxide from fossil fuel, as unequivocal drivers of global warming, which causes climate change. The threats posed by climate change to the planet, ecosystem and human survival are wide-ranging, affecting the physical, biological, social, and economic landscapes (Figure 1.3).

1.3 Meeting the Global Challenges with Materials Science

Since humans have walked the planet, the fundamental knowledge of materials (ceramics, metals, and polymers) has contributed immensely to their survival. Evolutionists connect the emergence of the genus Homo with the development of sharp-edged stone tools among other factors such as climate change. Archaeological evidence suggests that the dexterous exploitation of the macroscopic properties of materials by hominins predates the emergence of Homo sapiens, our species. Exemplarily, fossil artifacts revealed the use of mussel shells for tool making and engraving by Homo erectus about 0.43 ± 0.05 million years ago, and the use of stones as anvils, hammers, and cutters by hominins assumed to be Kenyanthropus platyops or Australopithecus afarensis 3.3 million years ago (Figure 1.4). The use of materials as technological solutions to routine chores and extraordinary challenges is, probably, as old as the evolution of hominins, and has shaped our evolution and enabled the conquest of the harsh environment.

Materials science as a scientific discipline is comparatively new and has evolved beyond mere serendipitous discoveries within our environment to encompass, as a central feature, the deliberate manipulation of the microstructure of matter to create custom-made or new-to-the-world materials for task-specific applications (Figure 1.4). Modern materials science is an interdisciplinary field that explores the fundamentals of physics, chemistry, and engineering to design, synthesize and fabricate ceramics, metals, and polymers as well as composites materials with wide-ranging implications for diverse facets of life including medicine, energy, and the environment. The ability to manipulate the microstructure of matter to create new materials enables innovative solutions to the global challenges of diseases, energy, and climate change. On energy, the United States Department of Energy's Basic Energy Sciences Advisory Committee asserted in a 2003 report that "Many of the current technological barriers related to energy hinge on improved materials. Thus, materials research is an area in which scientific advances could have a key impact on future energy security." To keep the energy crisis in perspective, scientists must recognize that the goal is not just fossil fuel alternatives, rather affordable, accessible and clean energy that improves the quality of life of the 7.5 billion people on earth and sustain the earth's natural system for future generations. Towards this goal, materials scientists are exploiting the redox-active, photophysical, and magnetic properties of transition metals (Chapter 2) and integrating these metals into polymers/macromolecules (Chapter 3) to design advanced materials. The inherent properties of the metals in these materials enable the realization of energy-efficient and storage materials (Chapter 4). Also, these materials can efficiently harness renewable energy resources such as the sun and biomass (Chapter 4). While these materials provide energy solutions that reduce the emission of GHGs, and therefore, climate change, they do not mitigate the effect of previously emitted GHGs. Thus, materials scientists are exploring the coordination chemistry of transition metals (Chapter 2) to design materials with carbon dioxide capture capabilities that can sequester carbon dioxide from the atmosphere or industrial flue gases (Chapter 6). Also, in Chapter 6, we examine the development of transition metal-containing macromolecules with catalytic properties. Indeed, catalysts lower the activation energy of reactions, eventually reducing the energy required to achieve chemical and biochemical transformations. Catalysts, therefore, are an essential component of the sustainable development action plan since the chemical and biochemical industry are pivotal to economic prosperity.

Materials scientists are among the pioneers of innovative solutions to health care problems. By exploiting the redox-active, photophysical, and magnetic properties of transition metals, materials scientists are creating new materials with intelligent behavior, bioactivity, and sensing capability (Chapter 5). Materials with redox-active metals are rationally programmed to feature redox-responsive behavior that is integrated into drug delivery systems to realize precise control over drug release and to target specific diseased sites. The redox activity is strongly connected with bioactivity and is exploited to tackle drug-resistant pathogens and to treat cancer via redox-induced generation of reactive oxygen species. The photophysical and magnetic properties of transition metals are integrated into macromolecular frameworks to realize bioimaging technologies that enable deep tissue as well as 3D profiling of diseased tissues. Materials scientists are also at the frontline designing biosensors by incorporating redox-active and photoactive transition metals into macromolecular frameworks. Indeed, transition-metal-containing macromolecules enable the design of therapeutic and diagnostic technologies to combat challenging health care problems.

1.4 Conclusion

To summarize, humanity's achievements in the last decades are historically unprecedented, as are their side effects. Accelerated human activity, such as burning of fossil fuel to power industries, has afforded prosperity and comfort but has increased the level of GHGs to induce climate change with its mostly deleterious effects. Diseases are becoming increasingly difficult to treat due to misuse of antimicrobial agents, and the results are increased health care costs and premature deaths. Materials scientists are interested in solving these problems, and this monograph highlights their contributions towards a sustainable future.

CHAPTER 2

Transition Metal Complexes as Attractive Motifs to Design Macromolecules

2.1 Introduction

Transition metal complexes, which include organometallic and coordination compounds, constitute a major class of compounds in chemistry and occupy a prominent niche in academic and industry research. Their significance is understandable given that transition metals represent more than half of the elements in the periodic table (Figure 2.1). Empirical data, as well as theoretical calculations, validate the unique redox activity, photoactivity, magnetic properties and coordination chemistry of these complexes. Undoubtedly, these properties inform the extensive exploration of these complexes as functional and structural motifs to design and construct macromolecules. Information about these properties is abundant in the literature, but in this chapter, we focus on empirical data and fundamental concepts that lead chemists to explore these complexes as building blocks in macromolecules.

Whereas the use of molecular transition metal complexes is ideal in certain applications, the installation of these complexes into macromolecules extends the applications into the realms of materials science and engineering. As an example, redox-active transition metal complexes are incorporated into polymers to realize antimicrobial polymers, which can be fabricated into bioactive medical devices and implants to combat microbial infections. A macromolecular scaffold provides a platform to amplify the functionality as several of the transition metal complexes can be grafted into a single scaffold. Also, the scaffold ensures chemical stability and prevents leaching, thereby guaranteeing longer lifetimes of activity, and better environmental compatibility compared with the use of small molecules. The ability to design various macromolecular architectures and install the transition metal complex at different locations offers the opportunity to modify the functionality of the complex (Figure 2.2). The incorporation of these metals into macromolecules, therefore, offers many advantages and the subsequent discussion focuses on the attractive properties of molecular transition metal complexes that are transferable into macromolecules.

2.2 Attractive Properties of Transition Metal Complexes

2.2.1 Chemistry of Transition Metals

The chemistry of transition metals primarily drives their continuous exploration as motifs to design macromolecules. Several inorganic chemistry textbooks thoroughly cover the fundamentals of this chemistry, which is not the focus of this monograph; nonetheless, we outline some basic concepts and empirical evidence that inspire their use in the design of functional macromolecules. In principle, transition metals, typically, "have partially filled d sub-shell, or yield cations with incomplete d sub-shell", but in practice, scientists include the f-block elements, lanthanides and actinides, regarding them as the inner transition metals (Figure 2.1). The chemistry of these elements depends on the number and electronic configuration of the d- or f-electrons, which also influence their redox-activity, photoactivity, and magnetism. Of importance is the selective interaction of these metals with ligands to form cationic, anionic, or neutral complexes that retain the intrinsic functionalities of the ligand and the metal center as well as exhibit new properties.

(Continues...)

Excerpted from Macromolecules Incorporating Transition Metals by Alaa S. Abd-El-Aziz, Christian Agatemor, Wai-Yeung Wong. Copyright © 2018 Alaa S. Abd-El-Aziz, Christian Agatemor and Wai-Yeung Wong. Excerpted by permission of The Royal Society of Chemistry.
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Edition details

• Publisher: Royal Society of Chemistry
• Publication date: 2018
• Language: English
• ISBN 10: 1782628991
• ISBN 13: 9781782628996
• Binding: Hardcover
• Number of pages: 248