Polymers Large molecules synthetic

It is used mainly to separate large molecules, synthetic polymers, and biopolymers with molecular weights between 2,000 and 2,000,000. Figure 9.20 shows a typical separation of a surfactant in which the individual... 

We ll explore synthetic polymers, large molecules formed from low molecular weight monomer molecules. Polymers are formed most commonly via addition or condensation polymerization reactions. Their physical and chemical properties make polymers suitable for many practical uses. 

Synthetic large molecules are made by joining together thousands of small molecular units known as monomers. The process of joining the molecules is called polymerisation and the number of these units in the long molecule is known as the degree of polymerisation. The names of many polymers consist of the name of the monomer with the suffix poly-. For example, the polymers polypropylene and polystryene are produced from propylene and styrene respectively. Names, and symbols for common polymers are given in Appendix F. 

We ve seen on several occasions in previous chapters that a polymer, whether synthetic or biological, is a large molecule built up by repetitive bonding together of many smaller units, or monomers. Polyethylene, for instance, is a synthetic polymer made from ethylene (Section 7.10), nylon is a synthetic polyamide made from a diacid and a diamine (Section 21.9), and proteins are biological polyamides made from amino acids. Note that polymers are often drawn by indicating their repeating unit in parentheses. The repeat unit in polystyrene, for example, comes from the monomer styrene. 

Polymer (Sections 7.10, 21.9, Chapter 31 introduction) A large molecule made up of repeating smaller units. For example, polyethylene is a synthetic polymer made from repeating ethylene units, and DNA is a biopolymer made of repeating deoxyribonucleotide units. 

Considerable efforts have also been made toward the development of novel compounds with superior antioxidant properties. Some attempts were also made to introduce new synthetic polymeric compounds which are non-absorbable and non-toxic. These are generally hydroxyaromatic polymers with various alkyl and alkoxyl substitutions. Such compounds are usually very large molecules and their absorption from the intestinal tract is practically nil. In addition to their reportedly high antioxidant activity, they are non-volatile under deep-fat frying conditions, which result in nearly quantitative carry-through to the fried items, but they have not yet received FDA approval. 

In February 1928, Wallace H. Carothers (Figure 1.2), then an Instructor at Harvard, joined du Pont at Wilmington to set up a fundamental research group in organic chemistry. One of the first topics he chose was the nature of polymers, which he proposed to study by using synthetic methods. He intended to build up some very large molecules by simple and definite reactions in such a way that... 

In addition to the classification of liquid chromatographic enantioseparation methods by technical description, these methods could further be classified according to the chemical structure of the diverse CSPs. The chiral selector moiety varies from large molecules, based on natural or synthetic polymers in which the chirality may be based on chiral subunits (monomers) or intrinsically on the total structure (e.g., helicity or chiral cavity), to low molecular weight molecules which are irreversibly and/or covalently bound to a rigid hard matrix, most often silica gel. 

Polymers are large molecules formed by the repetitive bonding together of many smaller molecules, called monomers. As we ll see in the next chapter, biological polymers occur throughout nature. Cellulose and starch are polymers built from small sugar monomers, proteins are polymers built from amino acid monomers, and nucleic acids are polymers built from nucleotide monomers. The basic idea is the same, but synthetic polymers are much less complex than biopolymers because the starting monomer units are usually smaller and simpler. 

Polymers are large molecules (macromolecules) that consist of one or two small molecules (monomers) joined to each other in long, often highly branched, chains in a process called polymerization. Both natural and synthetic polymers exist. Some examples of natural polymers are starch, cellulose, chitin (the material of which shells are made), nucleic acids, and proteins. Synthetic polymers, the subject of this chapter, include polyethylene, polypropylene, polystyrene, polyesters, polycarbonates, and polyurethanes. In their raw, unprocessed form, synthetic polymers are sometimes referred to as resins. Polymers are formed in two general ways by addition or by condensation. 

A large fraction of the chemical industry worldwide is devoted to polymer manufacture, which is very important in the area of hazardous wastes, as a source of environmental pollutants, in toxicology, and in the manufacture of materials used to alleviate environmental and waste problems. Synthetic polymers are produced when small molecules called monomers bond together to form a much smaller number of very large molecules. Many natural products are polymers for example, cellulose in wood, paper, and many other materials is a polymer of the sugar glucose. Synthetic polymers form the basis of many industries, such as rubber, plastics, and textiles manufacture. 

A second way to change the scale of molecules is to build up a large molecule from fragments. Nature does this and obtains, for instance, chiral DNA (if stretched out, would form very thin thread about 2 m long). Chemists prepare synthetic polymers that can be chiral and be measured in meters - fabric - or in km - tethered space elevators. 

All cellular life today incorporates two processes we will refer to as self-assembly and directed assembly (Fig. 1). The latter involves the formation of covalent bonds by energy-dependent synthetic reactions and requires that a coded sequence in one type of polymer in some way direct the sequence of monomer addition in a second polymeric species. On the other hand, spontaneous self-assembly occurs when certain compounds associate through noncovalent hydrogen bonds, electrostatic forces, and nonpolar interactions that stabilize orderly arrangements of small and large molecules. Three well-known examples include the self-assembly of water molecules into ice, DNA... 

Polymers are very large molecules made up of repeating units. A majority of the compounds produced by the chemical industry are ultimately used to prepare polymers. These human-made or synthetic polymers are the plastics (polyethylene, polystyrene), the adhesives (epoxy glue), the paints (acrylics), and the fibers (polyester, nylon) that we encounter many times each day. It is difficult to picture our lives without these materials. In addition to these synthetic polymers, natural polymers such as wood, rubber, cotton, and wool are all around us. And, of course, life itself depends on polymers such as carbohydrates, proteins, and DNA. This chapter discusses synthetic polymers. Naturally occurring polymers are presented in Chapters 25, 26, and 27. 

William Schowalter I have a question related to polymer synthesis. First, an observation. In biochemistry departments, there s been tremendous interest in the structure of large natural molecules. In chemistry departments, people have run away about as fast as they can from the synthesis of large molecules, the kinds of polymers of commerce that most of us are familiar with. I would like to address the question first to Matt. He showed us results of the physical chemistry that came out of those syntheses. The work of Ned Thomas was made possible because some clever synthetic chemists made some special kinds of molecules. I am trying to figure out how that activity can be fit in. If this research is so important, how do we make a home available for the people who do the synthesis that is necessary for it to go on I don t see that happening in our educational structure, either in chemistry departments or in chemical engineering departments. 

---