CHAIN STIFFNESS OF COPOLYCARBONATES CONTAINING A SPIRO LINKAGE

Physical properties relating to chain stiffness are determined for a s eries of copolycarbonates of Bisphenol A and 1,1'-spiro[bis(3,3'-dimet hyl-6-hydroxyindan)] (SBI) of varying composition. The entanglement mo lecular weight, M(e), is derived from the rubbery plateau modulus. The recoverable compliance, J(e)(0), is determined from the dynamic modul i as well as from steady shear creep and recovery experiments. It is f ound that all properties change in a nonlinear fashion with SBI conten t. For small SBI content the entanglement density is hardly affected, whereas T-g and J(e)(0) increase strongly. With further increase in SB I content the effect on T-g is less pronounced. M(e), however, starts increasing progressively to about 10 times that of pure Bisphenol A po lycarbonate. The functional dependence of M(e) on composition is not p redicted correctly from group contributions.