Polyesters
In the same year, Dr. Julian Hill, another member of the Carothers team, began work again on attempting to produce a polyester with a molecular weight of above 4,000. His efforts were soon met with great success when he produced a synthetic polymer with a molecular weight of about 12,000. The high molecular weight allowed the melted polymer to be stretched out into strings of fiber. Thus was created the first synthetic silk, described by the chemists as a superpolyester.
Polyesters and polyamides are examples of condensation polymers formed by step-growth polymerization. Carothers worked out the theory of step-growth polymerization and derived the Carothers equation which relates the average degree of polymerization to the fractional conversion (or yield) of monomer into polymer. This equation shows that for a high molecular weight, a very high fractional conversion is needed (for step-growth polymers only).
Hill also produced a synthetic fiber that was elastic and strong by combining glycols and diacids and heating under reduced pressure, using a molecular still to remove the last traces of water produced in the condensation reaction. Unfortunately, the fiber produced could not be commercialized because it reverted back to a sticky mass when placed in hot water. Carothers dropped his research on polymers for several years.
Read more about this topic: Wallace Carothers