How Do You Know Its a Polymer

Suppose that a polymer scientist watches a demonstration. The contents of two bottles are mixed, and a white precipitate appears. Here, I have created a new polymer for you, the demonstrator announces. The polymer scientist examines the two bottles, which are unlabeled. The demonstrator mysteriously 

In 1920 such questions were far from trivial note Appendix 5.1. Even today, questions of this nature need to be addressed. For example, the structure of ordinary (window) glass is considered polymeric by some, and not by others. It surely exhibits a glass transition (see Chapter 8) and has a high viscosity, but also apparently has a time variable structure. 

There are several types of experiments that should be performed in order to ascertain that the material is (or is not) polymeric. A key experiment is the determination of the molecular weight. If the molecular weight is above about 25,000g/mol, most scientists will consider that evidence in favor of a polymeric structure. However, it may be colloidal, as a sulfur or silver sol, and not polymeric. If the material is semicrystalline, the unit cell should be established. Hence it will become known if a chain running from cell to cell is likely to occur. 

A next series of experiments involves ordinary chemistry, as outlined in Section 2.2. Elemental analysis, characterization of degradation products, end-group analysis, and determination of the probable mer structure are all important in solving the puzzle. 

Perhaps the material can be reacted or degraded to form a soluble compound, which can then be characterized. An example is cellulose, a natural polymer that was part of the earliest discussions. Insoluble itselt it can be acetylated to form soluble cellulose acetate for molecular weight determination, by osmometry at the time. Then it was subjected to degradation to glucose and cellobiose, which were determined to be the monomer and dimer, respectively. 

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