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Polymers

 Accidental discovery of Teflon Accidental discovery of Teflon Teflon is a thermoplastic polymer of tetrafluroethylene (PTFE) widely used to coat non–stick frying pans as it is hydrophobic and possesses fairly high heat resistance. A group of scientists in DuPont company researching for new synthetic refrigerants, the freons chlorofluorocarbons, CFCs. One of the scientists named Roy Plunkett accidentally discovered the so called Teflon. Plunkett hypothesized that a new refrigerant could be made by combining tetrafluoroethylene, or TFE, with hydrochloric acid. But he found white colored flakes instead of a CFC gas. Plunkett wrote in his lab book that, "a white solid material was obtained, which was supposed to be a polymerized product."

Learning Objectives

After completing the topic, the student will be able to:

  • Define the terms – monomer, polymer and polymerization.
  • Appreciate their importance of polymers and identify the monomer unit in a given polymer.
  • Classify polymers in different ways based on origin, type of monomer, structure and mode of synthesis.
  • Describe different ways of polymerization.
  • Describe the preparation of some important synthetic polymers.
  • Discuss the general properties of commercially important polymers.
  • Give effects of synthetic polymers on environment.
  • Appreciate the synthesis and use of biodegradable polymers.
Silk Silk is a natural polymer that humans have used for centuries to fabricate articles of clothing. By chemical composition, the polymer represents a fibrous protein. It is composed of smaller units called amino acids. In living organisms like silkworm, about 20 amino acids are added in a second. Hence, protein synthesis is said to be fast when compared with that of other macromolecules.
Macromolecules

Simple organic molecules are produced from the elements such as carbon, oxygen, hydrogen, nitrogen that are present in Earth’s atmosphere under the influence of ultraviolet radiations of the Sun and other energy sources. When these small organic molecules are joined by biological medium, a "giant" molecule known as macromolecule is produced.

Macromolecules are polymers(in the Greek, polys means-many and meris-part). For example: A large molecule of protein consists of many small "units" linked together by covalent bonds. The repeated units of a polymer are called monomers. These serve as the building blocks.

Silk is a fibrous protein and has the α–helix formation over most of its length. In an α–helix, the peptide chain coils and their turns are held together by hydrogen bonds. In contrast to this, another type, β structure is possible in which the protein chains are stretched out as a folded sheet. The secondary structure arises due to the regular folding of the backbone of the polypeptide chain due to intramolecular hydrogen bonding between the carboxyl and amino groups.

Synthesis of protein is one fundamental biological processes by which individual cells build their specific proteins. The process takes place in multiple ribosomes simultaneously and all throughout the cell cytoplasm. A living cell can synthesize hundreds of different proteins every single second.

DNA is a polymer of nucleotides DNA is a polymer of nucleotides DNA is a polymer. The monomer units of DNA are nucleotides, and the polymer is known as a "polynucleotide."
Synthesis of macromolecules

Cells make and alter many small organic molecules by a series of different chemical reactions. In contrast, cells can obtain macromolecules only by making them. Their synthesis entails linking together a specific set of small molecules (monomers) to form polymers through repetition of a single type of chemical–linkage reaction.

Some small molecules function as precursors for synthesis of macromolecules, and the cell is careful to provide the appropriate mix of small molecules needed. Small molecules also store and distribute the energy for all cellular processes; they are broken down to extract this chemical energy, as when sugar is degraded to carbon dioxide and water with the release of the energy bound up in the molecule.

Other small molecules (e.g. hormones and growth factors) act as signals that direct the activities of cells and nerve cells communicate with one another by releasing and sensing certain small signaling molecules. The powerful effect on our body of a frightening event comes from the instantaneous flooding of the body with a small‐molecule hormone that mobilizes the “fight or flight” response.

Macromolecules are the most interesting and characteristic molecules of living systems, in a true sense. The evolution of life, as we know it is the evolution of macromolecular structures. Proteins, the workhorses of the cell are the most abundant and functionally versatile of the cellular macromolecules.

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