Properties of New Synthetic Rubbers and Plastics

Relationship between Molecular Structure and Physical Properties

“…Head-to-tail, head-to-head, etc., sequence of unsymmetrical monomer units Alternation of comonomer units Diolefin (1,4), (3,4), and (1,2) addition cis-trans structure at double bonds Chain branching For purposes of illustration, these structural features may be represented as follows:…”

“…Information as to the proportion of (1,4), (1,2), and (3,4) addition in polymers is available from methods of ozonolysis, perbenzoic acid titration, and infrared absorption. Roughly about 20% of 1,2 units occur in emulsion polybutadiene and polybutadiene copolymers.…”

“…Natural rubber has long been regarded, from many lines of evidence, as consisting of long-chain unbranched molecules of isoprene units in regular (1,4), head-to-tail, cis configurations (14)• These firm ideas about the molecular structure of natural rubber, although still regarded as essentially correct, are now being questioned. Small proportions of vinyl groups, doublebond shifts, and trans structure are suspected from the most re- cent infrared studies (47,68).…”

Elastomers

“…A study has been made of many copolymers of butadiene and substituted vinyl and isopropenyl derivatives of benzene, including fluoro derivatives of styrene (vinylbenzene), furan, thiophene, pyridine, and quinoline (14)• Some of the products are superior to GR-S in the properties tested, some are brittle or plastic solids. A new method of determining the refractive index of transparent solids was developed, and a new property of plastics-the sticking point-is defined and a method proposed for measuring it conveniently.…”