## 3 Supramolecular Organization of Peptide-Synthetic Polymer Hybrids  
As long as structure formation of block copolymers is solely driven by the counterbalance of thermodynamic de-mixing and chain elasticity, the size and shape of superstructures can be controlled by the relative composition of polymer chains and the number of repeating units [55]. The most commonly morphologies of block copolymers observed in solution are spherical and cylindrical micelles and vesicles, which can be originated from the non-equilibrium or the equilibrium states. Different theories have been developed in order to describe the equilibrium states of block copolymers in solution [56]. However, in case of peptide-polymer hybrids theoretical models based on rod-coil systems are the most used to explain their organization behavior. Polymer chains may exhibit a stiff conformation, \"_rod-like_\" conformation, due to extended \(\pi\)-conjugation [57, 58], aromatic groups along the polymer backbone or presence of secondary structures as in the case of peptides or other kind of biomolecules [59, 60]. Rods possess low conformational entropy which is directly related to their predisposition to form liquid crystalline alignments. The structural packing in the rod domain is the consequence of the competition between the deformation energy of coil stretching and the rod/coil interfacial energy. The prevalence of one of these parameters is based on the relation of the lengths of both domains (Scheme IX). Normally, for rod-coil block copolymers (RC-type) the interfacial energy is dominant and it results in smectic A-aggregates (the arrangement is characterized by a slippage angle greater than 67.5\({}^{\circ}\)). In contrast, for coil-rod-coil copolymers (CRC-type) the deformation energy dominates in smectic C-aggregates (denoted as smectic CI when the slippage angle varies between 67.5\({}^{\circ}\) and 60\({}^{\circ}\), and smectic CII when the angle is lower than 60\({}^{\circ}\)) [61]. **Scheme IX. ** Phase diagram, based on [61], of the structure of the rod domain for rod-coil (RC) (**a**) and coil-rod-coil (CRC) (**b**). \(I\), _S\({}_{4}\)_, and _S\({}_{C}\)_ represent the isotropic, smectic A, and smectic C arrangements of the rod domains. The corresponding morphologies are also shown. The elastic contribution from stretching of the rods is usually negligible compared to the rod/coil interfacial free energy. As a consequence, bilayers are often preferred over micelles in rod-coil systems [62]. The smectic or nematic order leads to high bilayer stiffness and high surface tensions, and makes these equilibrium vesicles very large and stable. Alternatively, \"_disk-shaped_\" micelles or \"_crew-cut_\" micelles with a planar rod-coil interface were also observed when the rod is the soluble segment. Similarly to other rod-coil block copolymers, the spontaneous formation of vesicles has been often observed in hybrids containing helical peptide segments [63; 64; 65]. Since the secondary structures of the peptide segment strongly influence the selection of the shape of the aggregate, helix to coil transitions can be used to induce dramatic shape changes such as micelle-vesicle transitions or vesicle inversions [66]. The stiffness asymmetry in rod-coil diblock copolymers results in an increase in the Flory-Huggins parameter and consequently these copolymers might self-assemble into phase-separated structures at relatively low degrees of polymerization. Thus, whereas phase separation of coil-coil diblock copolymers typically gives rise to 5-100 nm domain sizes, rod-coil diblock copolymers have the potential to render phase-separated structures of only several nanometers. Recently, a series of novel rod-rod diblock copolymers containing poly {2,5-bis[(4-methoxyphenyl)-oxycarbonyl]styrene} (PMPCS) and poly(\(\gamma\)-benzyl-L-glutamate) (PBLG) have extensively been studied. It was shown that for an \(f_{\mathrm{PBLG}}\) close to 0.5 the in bulk structure was lamellar.