The synthesis of dendrimer-like polystyrene (PS) of second and third generations by combination of atom transfer radical polymerization (ATRP) and chain end modifications is reported. Calixarene-based cores were used as initiators for ATRP of styrene yielding star polymers containing precisely 4, 6, or 8 arms. The latter were modified in two steps so as to generate PS stars carrying 8, 12, or 16 terminal bromoisobutyrate groups, respectively. These precursors served as multifunctional macroinitiators for the formation of the second generation of dendrimer-like PS. Reiteration of the aforementioned sequence of reactions allowed to derive dendrimer-like polystyrene of third generation that were constituted of 16, 24, or 32 outer arms, respectively. The chain end modification was monitored by 1H NMR spectroscopy. The dendrimer-like PS were also characterized by size exclusion chromatography equipped with a multiangle laser light scattering detector (SEC/MALLS). The actual polymer architecture and the functionality of the stars were confirmed by analysis of the individual arms obtained upon hydrolysis of the ester links present at the core of the stars and at the branching points. The intrinsic viscosities of these dendrimer-like polystyrenes are similar to those reported for regular dendrimers.

Two oligo(p-phenylenevinylene)-peptide hybrid amphiphiles have been synthesized using solid- and liquid-phase strategies. The amphiliphiles are composed of a pi-conjugated oligo(p-phenylenevinylene) trimer (OPV) which is coupled at either a glycinyl-alanyl-glycinyl-alanyl-glycine (GAGAG) silk-inspired beta-sheet or a glycinyl-alanyl-asparagyl-prolyl-asparagy-alanyl-alanyl-glycine (GANPNAAG) beta-turn forming oligopeptide sequence. The solid-phase strategy enables one to use longer peptides if strong acidic conditions are avoided, whereas the solution-phase coupling gives better yields. The study of the two-dimensional (2D) self-assembly of OPV-GAGAG by scanning tunneling microscopy (STM) at the submolecular level demonstrated the formation of bilayers in which the molecules are lying antiparallel in a beta-sheet conformation. In the case of OPV-GANPNAAG self-assembled monolayers could not be observed. Absorption, fluorescence, and circular dichroism studies showed that OPV-GAGAG and OPV-GANPNAAG are aggregated in a variety of organic solvents. In water cryogenic temperature transmission electron microscopy (cryo-TEM), atomic force microscopy (AFM), light scattering, and optical studies reveal that self-assembled nanofibers are formed in which the helical organization of the OPV segments is dictated by the peptide sequence.