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 exper iments showed good agreement. No systematic variations were found in M, ove r the entire copolymer series. Rheological studies performed with concentra ted 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 t he theological properties of branched polymers. Similar behavior was observ ed for the intrinsic viscosities and Mark-Houwink coefficients measured fro m TriSEC in 0.05 M LiBr NMP solutions. We also observed a significant chang e in mechanical properties of copolymer films with x(AB) greater than or eq ual to 0.90. Films with x(AB) greater than or equal to 0.90 had the mechani cal integrity to be peeled intact from a glass substrate. The glass transit ion temperature (T-g) showed a gradual increase with x(AB) up to x(AB) simi lar to 0.75, at which point a sharp rise was observed.