Effect of linear sequence length on the properties of branched aromatic etherimide copolymers

A series of AB/AB(2) etherimide copolymers with compositions ranging from 0 to 1 mole fraction AB monomer (x(AB)) were prepared and characterized. The weight-average molecular weight (M,) determined from SLLS and TriSEC experiments showed good agreement. No systematic variations were found in M, over the entire copolymer series. Rheological studies performed with concentrated solutions (10 wt % solids in NMP) showed a slight increase in viscosity with x(AB) in the composition range 0.00-0.80 AB, followed by a sharp rise in viscosity at higher x(AB) The viscosity trend was closely correlated to the calculated distance between branches (l(AB)) This observation suggests that l(AB) is an important architectural parameter that directly affects the theological properties of branched polymers. Similar behavior was observed for the intrinsic viscosities and Mark-Houwink coefficients measured from TriSEC in 0.05 M LiBr NMP solutions. We also observed a significant change in mechanical properties of copolymer films with x(AB) greater than or equal to 0.90. Films with x(AB) greater than or equal to 0.90 had the mechanical integrity to be peeled intact from a glass substrate. The glass transition temperature (T-g) showed a gradual increase with x(AB) up to x(AB) similar to 0.75, at which point a sharp rise was observed.