Chapter 1 Introduction to Polymers

1.1 Polymers History

A polymer, or macromolecule, is any material composed of many repeating subunits, building blocks, or monomers. Natural and synthetic polymers not only serve a wide range of important functions in our daily lives but are also essential for biological structure and function. They range from simple synthetic polymers like polyethylene, polypropylene, and polystyrene to naturally occurring biopolymers such as proteins, polysaccharides, and nucleic acids (DNA and RNA). Both natural and man-made polymers are formed by polymerizing small units known as monomers. They have large molecular masses and exhibit distinct physical properties such as toughness, high elasticity, and viscoelasticity, which distinguish them from small molecules.

Although most synthetic polymers were not discovered until the nineteenth and twentieth centuries, natural polymers have been used for thousands of years. For example, rubber (Figure 1.1) has been obtained from the latex of rubber trees by the indigenous peoples of Central and South America. Cellulose, another natural polymer, has been used in textiles since ancient times - Egyptians, for instance, used flax to manufacture linen (Figure 1.2). Animal-derived polymers include silk and wool. Silk is produced by silkworms (Figure 1.3), while wool is obtained from sheep (Figure 1.4). Both have been used in fabrics and textiles for millennia.

Figure 1.1: The latex of rubber trees (image credit: https://ecoterrabeds.com/blogs/eco-terras-healthy-sleep-blog/where-does-latex-come-from).

Figure 1.2: Flax and linen fibers (image credit: https://www.textilecoach.net/post/flax-or-linen-fiber).

Figure 1.3: Silkworms produce silk (image credit: Timekeep/Shutterstock. https://www.discovermagazine.com/planet-earth/silk-making-is-an-ancient-practice-that-presents-an-ethical-dilemma).

Figure 1.4: Sheep produce wool (image credit: https://www.linkedin.com/pulse/wool-where-comfort-meets-style-merchantbay/).

1.2 The Origin of Polymer Science

1.2.1 The Term "Polymer"

Jöns Jacob Berzelius, a Swedish scientist, used the term "polymer" in 1833 to characterize compounds composed of repeated structural units, now known as monomers. His hypothesis was based on his studies of organic chemicals and how basic molecules interact with larger, more complex structures. However, his notion of polymers differed from current understanding.

It wasn't until the twentieth century that scientists gained a better understanding of polymers as long-chain compounds made up of repeating units, either naturally occurring or manmade. During this time, synthetic polymers advanced rapidly, thanks in large part to the efforts of pioneers such as Leo Baekeland, who invented Bakelite, the first synthetic plastic, and Hermann Staudinger, whose 1920s research laid the framework for macromolecular chemistry.

Polymer is derived from the Greek words poly ("many") and meros ("part" or "unit"), which refer to a structure made up of several repeating components. Polymers can exist in both natural and manmade forms. Natural polymers include DNA, proteins, starch, and natural rubber, whereas synthetic polymers consist of plastics, nylon, and synthetic rubber.

1.2.2 The Discovery of Natural Rubber

The discovery of natural rubber is an important chapter in both scientific and industrial history. Indigenous peoples in South America were the first to use rubber, particularly in the Amazon Basin, where they collected the milky sap from rubber trees (Hevea brasiliensis) to create waterproof goods like footwear and clothing.

The word "rubber" is derived from its capacity to "rub out" pencil markings. Although European scientists began examining it in the seventeenth century, rubber's actual economic potential was not recognized until the nineteenth century, thanks in large part to Charles Goodyear's discovery of the vulcanization process in 1839. Vulcanization increased the durability, elasticity, and weather resistance of rubber, allowing it to be utilized in a variety of applications, such as tires and waterproof apparel.

During the nineteenth-century rubber boom, the demand for rubber surged, driving the industry's expansion. A significant turning point occurred in 1876 when British colonial officer Henry Wickham secretly transported rubber tree seeds from Brazil to Southeast Asia. This act led to the development of extensive rubber plantations in Malaysia and Indonesia. The global cultivation of rubber helped meet the growing demand, making it an essential material in various industries, including automotive and medical applications.

1.2.3 The Discovery of Cellulose Derivatives

The nineteenth century marked a breakthrough in cellulose derivatives as researchers explored the possible commercial uses of cellulose, a naturally occurring polymer found in plant cell walls. In 1838, Anselme Payen, a French scientist, was the first to identify cellulose as a distinct molecule capable of further chemical modification. In 1855, British scientist Thomas Hill successfully esterified cellulose by treating it with acetic acid to produce cellulose acetate, marking the first significant advance in cellulose derivatives. The discovery that cellulose could be chemically modified to generate a variety of useful molecules sparked the creation of cellulose derivatives.

In the years that followed, numerous additional cellulose derivatives were produced, including cellulose nitrate (discovered in 1846 by Christian Friedrich Schönbein), which led to the creation of celluloid, one of the earliest synthetic polymers. The subsequent discovery and production of other cellulose derivatives, such as methylcellulose and carboxymethylcellulose, transformed industries such as textiles, food, and pharmaceuticals, as these derivatives outperformed the original cellulose in terms of solubility, flexibility, and biodegradability. Cellulose acetate, in particular, has found extensive use in the textile industry as a precursor for synthetic fibers and in the photographic film sector. These advances paved the way for the larger area of polymer chemistry, as well as the creation of various additional synthetic polymers and materials, emphasizing cellulose as a useful raw resource for modern industrial applications.

1.2.4 The Invention of the First Synthetic Plastic

In 1869, John Wesley Hyatt developed the first synthetic polymer in response to a $10,000 award offered by a New York corporation for an alternative to ivory. The expanding popularity of billiards had greatly boosted the demand for natural ivory, which was obtained by hunting wild elephants. Hyatt discovered that by processing cellulose from cotton fibers with camphor, he could create a plastic that could be shaped into various forms and simulate materials like tortoiseshell, horn, linen, and ivory. This achievement was a turning point in manufacturing, freeing production from the constraints of naturally available resources.

1.2.5 The History of Polystyrene Synthesis

The journey of polystyrene synthesis begins in 1839, when German chemist Henri Victor Regnault created styrene, a liquid hydrocarbon derived from turpentine. Styrene turned out to be an important monomer that could polymerize into a solid substance, but its full potential wasn't recognized at the time. In 1928, German chemists Irenäus T. K. and Ludwig discovered a procedure known as radical polymerization to polymerize styrene. This was a significant step forward in synthetic polymer synthesis, demonstrating that styrene could be polymerized into a solid, crystalline form.

The German company IG Farben began commercial manufacturing of polystyrene in 1931. They developed a method for producing polystyrene by polymerizing styrene monomers in bulk, which was extremely important as it allowed for the production of polystyrene in large quantities. Dow Chemical in the United States began manufacturing polystyrene in 1937, introducing it to the mainstream market. The development of expanded polystyrene (EPS) in the 1940s marked another significant milestone. By incorporating a foaming agent into the polymerization process, a lightweight, foam variant of polystyrene was created, which became widely used for insulation and packaging materials (e.g., Styrofoam). By the 1960s, polystyrene had become one of the world's most widely produced polymers, with a broad range of applications in industries, including packaging and consumer goods. Polystyrene was further enhanced over the years, and styrene-based...