Triblock molecules

Fig. 25 Influence of the block sequence on the packing behavior of the linear ABC triblock molecules [172] phase sequences 88 ...

Figure 11. GPC traces of rod—coil triblock molecule (6) and macromolecular object. (Reprinted with permission from ref 60. Copyright 1999 American Association for the Advancement of Science).

Lee et al. also reported the assembling behavior of coil—rod—coil ABC triblock molecules where the rod block is connected as the middle block, consisting of polyethylene oxide) with different degrees of polymerization, two biphenyl unit as rod and docosyl coil (Chart 4).67 All of the coil—rod—coil ABC triblock molecules (12) exhibit three different crystalline melting transitions associated with polyethylene oxide), docosyl, and rod blocks, respectively, as determined by DSC, indicative of phase separation among blocks. 

The coil—rod—coil triblock molecule (17) based on polypropylene oxide) (PPO) coil segment was observed to show only an isotropic liquid upon melting. In contrast, the addition of greater than 0.10 mol of lithium salt/propylene oxide (PO) unit induces the formation of a liquid crystalline order (Figure 22). 

Fig. 9 Tetragonal perforated lamellar structure in an AB-BA sequence formed by tetra-branched triblock molecule...

Fig. 12 Mesophase structures of the ABA coil-rod-coil triblock molecules...

If supramolecular bundles are formed spontaneously in bulk films, by inclusion of appropriate reactive groups it should be possible to convert these into molecular objects by cross-linking, while maintaining the precise size and shape of the rod bundles. A coil-rod-coil triblock molecule 22 based on linear PPO (fcon = 0.73) with a reactive rod block self-assembles into discrete rod bundles that are encapsulated by PPO coils and subsequently organize... 

In contrast to linear coil, the triblock molecule 23, consisting of bis(penta-ethylene glycol) dendrons as coil segments at both ends of the rod with same rod building block, self-organizes into 2D columnar and 3D bicon-... 

After the discovery of well defined supramolecular units which organized into polar materials, we began integrating functionality into the molecular backbone of the triblock rodcoil motif to create novel supramolecular materials. The triblock structure posses multiple sites to design functionality into the system. Initially, a stilbene or phenylene vinylene segment was integrated into the rod portion of the triblock molecule to create luminescent supramolecular objects. For our system, phenylene vinylene represents an ideal choice because it is known to be a robust material with interesting electronic properties and the all irons conformation posses the rod-like character necessary to retain the tiiblock rodcoil structure. 

Figure 7.78 represents the heat capacities of the homopolymers polystyrene and poly(a-methyl styrene) with sharp glass transitions at 375 and 443 K, respectively [35]. On copolymerization to a triblock molecule, MS-S-MS(45), a much broader glass transition results. It stretches from the polystyrene to the poly(a-methylstyrene) glass transition and could indicate a solution, but the molar mass seems too high for solubility when compared to Fig. 7.75 in Sect. 7.3.2 (M, = 10 Da). Similarly, the figure indicates broad transition regions for the other copolymers. 

Figure 15 (a) Molecular model of the supramolecular unit composed of 100 triblock molecules of 48. (b)TheTEM micrograph representing the top view of a film, (c) Schematic representation of how mushroom nanostructures organize to form the macroscopic film. ... 

As shown schematically in Fig. 13, one can distinguish two types of configuration for the triblock molecules if the two endblocks of a molecule are incorporated in separate hard domains, the triblock will be described as a bridge. If, alternatively, both endblocks are incorporated in the same hard domain, the triblock will be described as a hairpin molecule. 

---