## 3 Supramolecular Organization of Peptide-Synthetic Polymer Hybrids
In case of modifying the amine groups with DS surfactants (e.g., sodium 1-dodecanesulfonate, SDS) a pronounced small-scale ordering of the polypeptide-surfactant complex arms, which dominated over the formation of block copolymer scale structures, was obtained. The supramolecular organization was extracted from TEM micrographs and wide angle X-ray scattering (WAXS) measurements since the lamellar periodicity fitted well with the thickness of a single PLL-DS \(\beta\)-sheet surrounded on each side by a long alkyl chain of the surfactant. Results suggest that control of the extent of frustration will be possible by tunable self-assemblies caused by the steric packing constraints, imposed by the miktoarm architecture, together with the polypeptide conformation and possible intermolecular interactions. As it has been previously described, poly(\(\gamma\)-benzyl-L-glutamate) (PBLG) or poly(Z-lysine) (PZlys) have the possibility to be hydrolyzed resulting in poly(L-glutamic acid) (PLGA) and poly(L-lysine) (PLL) displaying coil to helix transitions depending on the pH of the medium. In aqueous solution, asymmetrical block copolymers constituted by poly(L-lysine) and polystyrene displayed rod-like micelles in an energetically trapped state. However, in a recent study, changing the solvent and temperature, micelles were reorganized towards their intrinsically favored morphology as a consequence of the effects of the secondary structure of the peptide segment and/or the thermal properties of the synthetic block [76]. The results of this study underlined the complexity of the self-assembly behavior of peptide-synthetic hybrid block copolymers, which is determined not only by the tendency of the constituent blocks to phase separate, but also by effects of the secondary structure of the peptide segment and/or the thermal properties of the synthetic block. An additional work towards the effect of organic acid concentration (_i.e._, trifluoroacetic acid (TFA) in chloroform) on the conformational stability of hybrid block copolymers based on poly(\(\gamma\)-benzyl-L-glutamate) (PBLG) with polystyrene (PS) attached to the N or C terminus was recentlyperformed [77]. Although the helix-coil transformation of PBLG is a well-investigated subject, it was found that deformation of the helical structure at the \(C\)-terminal side was predominantly caused by PS attachment instead of the TFA concentration, whereas the effect of TFA addition on the helical structure was greater on the \(N\)-terminal side. Results were experimentally determined from the ratio of the helix C(\(\alpha\))H proton peaks to integral of all C(\(\alpha\))H proton peaks by \({}^{1}\)H nuclear magnetic resonance (NMR). The work allows us to assume that the interaction of free NH groups with the side-chain carbonyl groups at the N terminus of the helix was the responsible for the different sensitivities of the PBLG chain to PS attachment and TFA addition. In spite of the fact that the most part of the studies concerning supramolecular organization involved poly(\(\gamma\)-benzyl-L-glutamate) (PBLG) or poly(Z-lysine) (PZlys) as the peptidic block, other peptides with special features, derived also from natural amino acids, are currently investigated as new rod-type segments. One of these studies is related to synthesis of water soluble poly(L-proline) (PLP) to be employed to get AB or ABA block copolymers [78]. From circular dichroism (CD), infrared spectroscopy (IR) and X-ray diffraction (XRD) measurements, the two characteristic forms of poly(L-proline) were detected (_i.e._, form I with a low crystallinity and form II with a well-organized macromolecular structure). The transition between both forms was found to be cooperative and reversible on changing the solvent characteristics. From XRD powder data, in case of poly(ethylene oxide) diblock copolymers (_i.e._, PLP-PEO), the PLP peptide fully adopted the form I whereas PEO could not crystallize, implying an interfacial mixing.