Preface

One of the greatest challenges facing humankind is the increasingly rapid depletion of natural resources. Whether it is oil from the sea or the land, or minerals from the ground, our insatiable appetite for consumption of resources and the inexorable growth in the world population puts us on a road to disaster – unless we adopt a more sustainable approach to resource consumption. Chemistry – which dictates the ways we can make all the articles we want in modern society, starting from petroleum and crude minerals as feedstocks, is at the heart of the modern industrial society and must be at the heart of the technological revolution we surely need. Critical to this revolution will be changes to the ways we do chemical processes. We need to carry out our chemistry with a more efficient use of resources and a reduction in the amount of waste. One vastly important step change will be the introduction of low energy technologies. We continue to use conventional heating techniques in chemistry but the chemical industry is a very large consumer of energy and must follow the trends in other sectors and seek to employ more efficient and low-carbon heating techniques. Alternative techniques can also help us to make chemical processes more efficient and generate fewer by-products, for example, by avoiding uneven heating that can cause hot spots and hence partial decompositions or side-reactions.

Since their development during the mid-20th century, synthetic polymers have become extensively used in almost every application imaginable. Some applications, such as medical, clothing, electrical, transport, construction and packaging, have become increasingly dependent on the lightweight, durable, reproducible and low cost characteristics of synthetic polymers. By the beginning of this decade, the production of synthetic polymers was 280 million tonnes, which accounts for 80% of the total production of the chemical industry. The identity, feedstock and composition of future polymers is under major review, especially as we move towards more bio-based products, but for any polymer the route for production and processing should be analyzed and optimized to ensure genuine energy efficiency, minimum waste and overall sustainability.

Microwave technology has gained acceptance as a mild and controllable energy tool, allowing simple and rapid processing. Industrial-scale treatment of food and materials at temperatures below 200 °C has been established as continuous tonne-scale processes with increased process selectivity. Microwaves are also widely used as laboratory processors, where countless researchers have discovered the beneficial effects of microwaves in helping to make chemical processes cleaner, more controlled and, in particular, quicker. Numerous publications have reported how, by switching from conventional to microwave heating, reactions have been completed in minutes rather than hours. The energy efficiency of microwave processes is more controversial, but it has been shown through careful energy measurements that microwave-assisted chemical reactions can be more energy efficient, especially for reactions that normally take many hours. While most microwave chemistry has stayed at the laboratory bench scale, some has made it to a larger scale, for example, in some chemical manufacturing processes and for the treatment of biomass both to enhance its energy density and its use as a source of organic chemicals. Given the enormous importance of polymer manufacturing, it seems very important that we seek to introduce energy- and time-efficient microwave processing to the industry.

This book seeks to fill the gap between the now quite widespread use of microwave processing in small molecule chemistry and biomass processing, and that of polymer synthesis and manufacture. The book starts with a consideration of the important points about carrying out microwave processing including the different types of reactors available and the particular hazards the operator needs to be aware of. The rest of the book is dedicated to the application of microwaves to polymer synthesis and manufacture. Major types of polymer syntheses including free-radical processes and ring-opening polymerizations are considered in detail. A wide range of polymers is considered, including widely used poly(ether)s and poly(amide)s. Separate chapters on synthesis of conducting polymers and formation of hydrogels are also included. The book goes further. An important aspect of polymer chemistry is how to modify polymers, for example, through incorporation into more complex structures like composites. Microwaves can, for example, be used to promote crosslinking and accelerate curing as well as derivatization of natural polymers. Finally, one chapter is dedicated to the widely studied area of peptide synthesis.

The enormous and growing scale of the polymer industry and the vast resource consumption it represents means that it must take precedence in undergoing the resource-efficiency make-over many manufacturing processes are being subject to. Microwaves can and should play an important role in this as we strive towards a more efficient and sustainable consumer society.

Anuradha Mishra

Tanvi Vats

James H Clark