Copolymer architecture considerations

These results demonstrate that, in analogy to the multidomain proteins in biosili-cification, triblock copolymers can direct the assembly of silica into complex structures. Furthermore, combining complex ABC copolymer architectures with the physical, electrical, and optical properties of inorganic materials holds considerable... 

Architecture, segment length and integrity are only some of the parameters which must be controlled if block copolymers are to have the desired properties and the full potential of such systems is to be realised. Thus, considerable demands are made on the experimental technique. In terms of an ability to control the products, radical polymerizations are not as ideal as are ionic and, in particular, anionic polymerizations. 

Since the relaxation mechanisms characteristic of the constituent blocks will be associated with separate distributions of relaxation times, the simple time-temperature (or frequency-temperature) superposition applicable to most amorphous homopolymers and random copolymers cannot apply to block copolymers, even if each block separately shows thermorheologically simple behavior. Block copolymers, in contrast to the polymethacrylates studied by Ferry and co-workers, are not singlephase systems. They form, however, felicitous models for studying materials with multiple transitions because their molecular architecture can be shaped with considerable freedom. We report here on a study of time—temperature superposition in a commercially available triblock copolymer rubber determined in tensile relaxation and creep. 

Polyethylene and polystyrene are two of the most commercially important and ubiquitous polymers, primarily because of their commercial value. Since the early days of polymer research there has been considerable interest to produce copolymers from ethylene (E) and styrene (S) because of both academic and business interests. Depending on the nature and type of polymerization chemistry, a variety of different molecular architectures can be produced. In addition to the different monomer distributions (random, alternating or blocky nature), there are possibilities for chain branching and tacticity in the chain microstructure. These molecular architectures have a profound influence on the melt and solid-state morphology and hence on the processability and material properties of the copolymers. 

Except for a few notable cases there was seldom consideration in these papers about the architectures of copolymers generated and their... 

---