Triblock terpolymer frustrated

Figure 18.3 Microdomain morphology models for linear ABC triblock terpolymers based on lamellar morphology (A gray, B black, C white) (a) //, (b) cil, (c) sil, (d) lil, (e) col, (f) sol. (d), (e) and (f) are frustrated systems with A/C interfaces, which do not have any junctions.

Figure 18.6 Molecular packing and microdomain interfaces in linear ABC triblock terpolymers for (a) nonfrustrated system, and (b) frustrated system.

The morphology in linear ABC was reported independently by two research groups in 1999. Shefelbine et al reported a mesostructure in PI-PS-PDMS frustrated system. With only SAXS and TEM investigations they could not confirm the structure. But by supplementing their experimental analysis with SCFT calculations they could conclude that the PI-PS-PDMS triblock terpolymer had formed a pentacontinuous morphology with two discrete domains... 

An interesting layered structure, the so-called knitting pattern, was found in BCP SA [8]. The structure has been observed in frustrated ABC triblock terpolymers both experimentally and theoretically, where repulsive interactions between the two terminal blocks are weaker than those between middle block and terminal blocks. The morphology is regarded as a metastable state because the structure formation is driven by the relatively poor solvent miscibility of the middle block [8]. The middle block constitutes cylinders bridging wavy lamellae generated via agglomeration in a poor solvent. 

Most of the noncubic structures are not continuous in all three directions. However, one of the 070 structures Fddd, 070 space group) is bicontinuous, as shown in Fig. 2. Its structural characteristics are quite similar to the gyroid morphologies [29], where triple nodes are connected in all three directions. Non-frustrated ABC triblock terpolymers, where interactions between terminal blocks are most repulsive, generate the bicontinuous structure [29, 30]. Later, it was shown that the structure exists in di-BCP phase space both theoretically and experimentally [5, 31]. Interestingly, it appears in a very narrow regime of di-BCP phase space but occupies quite a wide phase space in non-frustrated triblock terpolymer SA [5, 30]. 

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