Polymers
Introduction
Polymers are large molecules composed of repeated subunits, known as monomers. Due to their broad range of properties, both synthetic and natural polymers play essential roles in everyday life. Polymers range from familiar synthetic plastics such as polyethylene, to natural biopolymers such as DNA and proteins that are fundamental to biological structure and function.
Structure and Bonding
Polymers are composed of very large chains of atoms, primarily carbon, hydrogen, oxygen, and nitrogen. The repeating units, the monomers, are joined together by covalent bonds to form a polymer. The structure of the polymer chain can be linear, branched or cross-linked depending on the monomers and polymerization method used.
Types of Polymers
Polymers can be divided into two categories: natural and synthetic. Natural polymers include proteins, starch, and cellulose, which are found in plants and animals. Synthetic polymers, on the other hand, are man-made and are commonly used in a variety of applications. Examples of synthetic polymers include nylon, polyethylene, polyester, Teflon, and epoxy.
Properties of Polymers
The properties of polymers are determined by the chemical structure of the monomer(s) and the arrangement of the monomer(s) in the polymer chain. These include physical properties such as density, tensile strength, and resistance to certain environments, as well as optical and electrical properties. The properties of a polymer can be modified by the addition of additives or the incorporation of other polymers.
Polymer Synthesis
Polymer synthesis is a complex process that can take place in a variety of ways. The most common methods of polymer synthesis include addition polymerization, condensation polymerization, and copolymerization. The type of polymerization used will depend on the type of monomer or monomers being used and the desired properties of the polymer.
Applications of Polymers
Polymers have a wide range of applications that far exceed those of any other class of material available to man. Current applications extend from adhesives, coatings, foams, and packaging materials, to textile and industrial fibers, composites, electronic devices, biomedical devices, optical devices, and precursors for many newly developed high-tech ceramics.
Environmental Impact and Recycling
Polymers, particularly synthetic plastics, have been the focus of much attention due to their environmental impact. Non-biodegradable polymers can take hundreds of years to decompose. On the other hand, biodegradable polymers break down faster and are therefore more environmentally friendly. Recycling of polymers is also an important aspect of the polymer industry.