Diblock copolymer network morphology

Jain S, Dyrdahl MHE, Gong X, Scriven LE, Bates FS (2008) Lyotropic phase behavior of poly(ethylene oxide)-poly(butadiene) diblock copolymers evolution of the random network morphology. Macromolecules 41 3305-3316... 

In addition to three canonical morphologies of aggregates (S, C, and L), more complex associations of block copolymer molecules could be found in certain regions of the diagram. In particular, a recent theoretical study [24] predicts the existence of branched cylinders in the vicinity of the S-C binodal line. The latter occupy a narrow corridor and coexist with cylindrical and spherical micelles. Branched structures and networks of aggregates formed by diblock copolymer with quenched PE block were also considered in [17]. 

Figure 18.2 Molecular packing models for (a) disordered state and (b) ordered state, and (c) models of five equilibrium microdomain morphologies for AB diblock copolymers. L lamellae, F Fddd network, G double-gyroid networks, C hexagonally packed cylinders, S body-centered-cubic spheres.

Hasegawa, H., Tanaka, H., Yamasaki, K., andHashimoto, T. (1987) Bicontinuous microdomain morphology of block copolymers. 1. Tetrapod-network strucmre of polystyrene-polyisoprene diblock polymers. Macromolecules, 20,1651-1662. 

Previously, we discovered an interesting band morphology formed from the nanoparticles of PLLA-PEG diblock and PLLA-PEG-PLLA triblock copolymers that were placed on a flat substrate surftice (59,60). We verified that the band morphology is directed by crystallization of the PLLA segments and that the PLLA chains take a doubly twisted structure in it with the ordinary 10/3 helical conformation preserved. Prior to this PLLA band formation, the PEG blocks are phase-separated and play an important role. The two-dimensional network formed by the PLLA-PEG-PLLA bands on the surface well simulates the structure of the three-dimensional network systems observed in melt, concentrated solution, and hydrogel. 

---