Molecular Theory for the Linear Viscoelasticity of Disordered Block Copolymers

3 Molecular Theory for the Linear Viscoelasticity of Disordered Block Copolymers 

Since the first theoretical attempts in the 1970s (Hall and DeWames 1975 Hansen and Shen 1975a, 1975b Stockmayer and Kennedy 1975 Wang and DiMarzio 1975) to describe the chain dynamics of disordered block copolymers, little progress has been made. The molecular theory for the linear viscoelasticity of disordered block copolymers is still in its infancy. In this section, we present first the currently held linear viscoelasticity theory for unentangled disordered block copolymer and then an extended version for disordered, entangled block copolymer. 

Stockmayer and Kennedy (1975) conducted a seminal smdy on the chain dynamics of Rouse chains of AB-type diblock or ABA-type triblock copolymers by modifying the bead—spring model of Rouse for linear flexible homopofymers (see Chapter 4). They calculated the spectrum of relaxation times ftp biodc) block copolymer in terms of the terminal relaxation times for the Rouse chains for the A and B blocks. Once the values of are determined, one can calculate linear dynamic viscoelastic 

Stockmayer and Kennedy (1975) constructed generalized plots showing how the block length ratio 6 and terminal relaxation times Tj and Tjg of the respective constituent components may affect the reduced zero-shear viscosity F of a block copolymer, defined by 

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