## 3 Supramolecular Organization of Peptide-Synthetic Polymer Hybrids
Specifically, PMPCS was arranged in a columnar nematic phase whereas PBLG gave rise to a hexagonally packed-cylinder structure. In this system, a stacked bilayer structure in a hexagon in lamella morphology was proposed (Scheme Xb,c). On the contrary, on increasing \(f_{\mathrm{PBLG}}\) to nearly 0.7 a micro-separated hexagon in cylinder morphology was found. Basically, PMPCS domains constituted the core of the cylinders which were surrounded by the PBLG matrix where helices were arranged in a hexagonal structure. Both PMPCS and PBLG rods were packed in an interdigitated way in their own domains (Scheme X, d and e). These results obtained from TEM observation and 2D WAXD patterns [67] are significant since indicate that the development of the liquid crystal phases did not destroy the self-assembling structures from microphase separation. Thus, both mesogen-jacketed liquid crystalline polymers and polypeptides obtained from controlled polymerization methods are excellent rod-like building blocks to form rod-rod block copolymers with nanoscale hierarchical structures. The most part of the works focused on the supramolecular organization of peptide-synthetic polymer hybrids have selected poly(\(\gamma\)-benzyl-L-glutamate) (PBLG) or poly(Z-lysine) (PZlys) as the peptide block. These blocks have a capability to easily adopt \(\alpha\)-helices or \(\beta\)-sheets by just adjusting the distribution of D/L units in their sequences. Moreover, both peptides have the possibility to be hydrolyzed resulting in poly(L-glutamic acid) (PLGA) and poly(L-lysine) (PLL), which show pH-responsive behavior displaying coil to helix transitions depending on the pH of the medium. Specifically, PLGA adopts \(\alpha\)-helical conformations at low pHs (_i.e._, pH \(\leq\) 6.3), while PLL becomes \(\alpha\)-helical at high pHs (_i.e._, pH \(\geq\) 8.4) [17]. **Scheme X. ** Schematic representation of the proposed model for the self-assembly of the rod-rod diblock copolymer in poorly ordered packing (**a**), hexagonal in lamella (**b**), and cylinder (**d**) structures, respectively. Schematic drawings of the shearing geometry with the X-axis being the shear direction are shown in (**c**) and (**e**) for lamellar and cylinder structures, respectively. Reprinted with permission from [67]. Copyright (2010) American Chemical Society. [PERSON] _et al._[68], have recently studied the influence on the secondary structure of different predefined D/L stereosequences by considering three block copolymers with the same composition and constituted by poly(ethylene oxide) and monodisperse peptide segments of 18 (\(N^{\mathrm{c}}\)-benzyloxycarbonyl)lysine (ZLys) units. Secondary structures (_i.e._, random coil, \(\beta\)-sheet or \(\alpha\)-helix) of these bioconjugate samples were determined by \({}^{1}\)H NMR, FTIR and CD spectroscopies and evaluated according to their ability to gelate tetrahydrofuran at room temperature (using viscosimetry and scanning force microscopy). The tendency for organogelation was gradually increased when the secondary structure of the peptide block changed from random coil (peptide with a close to random distribution of 8 and 10 D and L units, respectively), \(\alpha\)-helix (peptide sequence constituted by only L units) to \(\beta\)-sheet (peptide sequence constituted by two blocks having 7 L units each one and a middle block with 4 D units), which was the one exhibiting the highest tendency to form a gel. Microscopy images showed the formation of fibrils (1 nm in height and 10-14 nm in width) constituted by \(\beta\)-sheet assemblies of congener peptide-PEO conjugates. This fibrillation phenomenon seemed to occur via antiparallel \(\beta\)-sheet formation since the width of the fibrils obtained were in agreement with the estimated value found in the literature (_i.e._, 11.1 nm). On the other hand, the hybrid conjugate possessing a peptide block with \(\alpha\)-helix secondary structure presented fibrils with a lower width (_i.e._, close to 6-10 nm), which was explained by a structure of interdigitated \(\alpha\)-helices.