Multifunctional polyurethane network structures

A series of thirteen polyurethanes were synthesized using blends of monofun ctional, difunctional, and trifunctional poly(propylene oxides) reacted wit h 4,4'-diphenylmethane diisocyanate in a stoichiometric ratio. Experimental measurements were made of glass transition temperature, sol fraction, and dynamic mechanical properties. Computer simulations based on the theory of branching processes were made on the same systems. The glass transition tem perature was correlated with the number average functionality of the compon ents. Dynamic mechanical data was fitted to the Havriliak-Negami model. A c orrelation was demonstrated between the measured rubbery modulus and the co ncentration of elastically active network chains.