The structure of materials

To understand the origin of the modulus, why it has the values it does, why polymers are much less stiff than metals, and what we can do about it, we have to examine the structure of materials, and the nature of the forces holding the atoms together. In the next two chapters we will examine these, and then return to the modulus, and to our bar-chart, with new understanding. 

To recapitulate, the legs of the imaginary tripod on which the structure of materials science is assembled are atoms and crystals phase equilibria microstructure. Of course, these are not wholly independent fields of study. Microstructure consists of phases geometrically disposed, phases are controlled by Gibbsian thermodynamics. 

A fresh start has been made by Samuel Allen and Edwin Thomas of MIT, with The Structure of Materials (1998), the first of a new MIT series on materials. The authors say that our text looks at one aspect of our field, the structure of materials, and attempts to define and present it in a generic, materials catholic way. They have succeeded, better than others, in integrating some crucial ideas concerning polymers into mainline materials science. 

Kevlar The Wonder Material. Microworlds Exploring the Structure of Materials, Lawrence Berkeley Laboratory, http //www.lbl.gov/MicroWorlds/Kevlar/... 

Harries rejected Pickles formula in 1911 (41), but in his subsequent work he expanded the size of his ring formula to include five and, eventually, seven isoprene units. Although incorrect in many assumptions, this work provided the background necessary for more probing thought about the structure of materials, and for the rebirth of the high molecular weight concept. 

Linus Pauling, in 1954, received the Nobel Prize for his insights into the structure of materials, mainly proteins. Pauling showed that only certain conformations are preferred because of intermolecular and intramolecular hydrogen bonding. While we know much about the structures of natural macromolecules, there is still much to be discovered. 

Read, Randy J. Overview of Macromolecular X-ray Crystallography. Available online. URL http //www-structmed.cimr.cam.ac.uk/ Course/Overview/Overview.html. Accessed May 28,2009. This Web page offers a well-illustrated description of the principles and practice of X-ray crystallography, an extremely important technique in determining the structure of materials. 

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