352 BELL SYSTEM TECHNICAL JOURNAL 



both from German sources and from their own researches to warrant taking 

 the gamble. 



As a part of the large program laid out under the auspices of the Govern- 

 ment in 1942, provision was made for a cooperative research and develop- 

 ment effort to parallel and to contribute to the constructional program 

 designed to provide the much needed rubber. A large number of company 

 laboratories as well as universities contributed to this research. The Bell 

 Telephone Laboratories because of its past contributions in this field of 

 synthetic polymers was asked to participate in this program. The present 

 discussion is intended to describe part of the Bell Laboratories investigations 

 directed toward the improvement of Buna S type rubber, particularly work 

 relating to the characterization and control of the final copolymer. 



In order to present the material in a logical and understandable form to 

 readers unfamiliar with the subject-matter, brief mention will be made of 

 the history of the synthetic rubber problem and of progress in the knowledge 

 of polymeric substances during recent years. 



The Problem of Synthetic Rubber 



The problem of synthesizing natural rubber is almost as old as man's 

 curiosity about the nature of rubber itself which began when Faraday in 

 1826 first showed it to be a hydrocarbon having the formula CioHie . Ex- 

 periments done by Williams in 1860, in which he obtained isoprene from 

 natural rubber and by Bouchardat in 1879, who showed that isoprene could 

 be polymerized to a rubber-like material, represent about as close as we 

 have come to synthesizing natural rubber in spite of many subsequent 

 efforts. In 1910 particularly, when the price of natural rubber reached $3 

 per pound, considerable pressure was exerted to bring about this synthesis. 

 Although the chemist failed in this quest his very failure, analyzed in the 

 light of more recent studies on other polymers as well as rubber, has had its 

 virtues. It has emphasized the importance of chemical structure, that is 

 the precise organization of the atoms composing the rubber molecules (in 

 addition to simply the nature of these atoms) in determining the ultimate 

 properties of a polymer. 



Although natural rubber eluded synthesis, the early organic chemical work 

 nevertheless laid the basis for our present synthetic rubber. Curiously, 

 much of this pioneering research on synthetic rubber was done in England 

 with the support of strong proponents of natural rubber. However, 

 Germany and Russia were also active contributors. The United States 

 later achieved fame by bringing forth two of the most promising rubbers yet 

 produced, Neoprene and Butyl. The early foreign synthetics were based 

 on the polymerization of hydrocarbons such as 1-methyl butadiene and 2,3 



