Polymer
A polymer is a substance composed of large molecules built from many connected structural units. The smaller molecules used to construct polymer chains are called monomers. Polymers occur naturally and are also manufactured: examples include cellulose, proteins, polyethylene and nylon. The term therefore covers much more than the synthetic materials commonly called plastics.[1]
Structure and properties
The composition and arrangement of a polymer influence its behaviour. Chains may differ in length, branch from a main backbone, or be connected to one another by cross-links. Changing the monomer, chain length, branching or cross-linking can alter the properties of the resulting material. Interactions between neighbouring chains also matter; the behaviour of a bulk polymer cannot be described solely by listing its constituent atoms.[2]
Polymerisation is the process of forming polymers from monomers. A condensation reaction can join units while releasing a small molecule such as water. Other polymer-forming reactions proceed without that type of byproduct. Proteins provide a familiar natural example of long chains assembled from amino-acid units, while cellulose provides structural material in plants.[1]
Development and use
People used natural polymer materials long before their molecular structures were understood. Nineteenth-century development included the modification of cellulose to make celluloid. The preparation of Bakelite by Leo Baekeland in the early twentieth century marked a transition to wholly synthetic plastics.[3]
Polymer chemistry links molecular design to practical functions. Synthetic materials can be designed for particular combinations of flexibility, strength and other properties, while studies of natural polymers connect the subject with biochemistry. Their teaching consequently spans both molecular structure and the performance of familiar materials.[2]
References
- ↑ 1.0 1.1 American Chemical Society. Man and Materials through History. National Historic Chemical Landmarks lesson.
- ↑ 2.0 2.1 Lengthening the Chain: Polymers in General Chemistry (2017). Journal of Chemical Education.
- ↑ American Chemical Society. The Development of Bakelite.
Attribution
Adapted with reference to English Wikipedia, revision 1377817330 (contributors and history), under CC BY-SA 4.0. The prose has been rewritten and checked against the cited sources; changes have been made.