title: Hierarchical ionic self-assembly of rod-comb block copolypeptide-surfactant complexes.
abstract: Novel hierarchical nanostructures based on ionically self-assembled complexes of diblock copolypeptides and surfactants are presented. Rod-coil diblock copolypeptide poly(gamma-benzyl-L-glutamate)-block-poly(L-lysine), PBLG-b-PLL (Mn = 25,000 and 8000 for PBLG and PLL, respectively, polydispersity index 1.08), was complexed with anionic surfactants dodecanesulfonic acid (DSA) or dodecyl benzenesulfonic acid (DBSA), denoted as PBLG-b-PLL(DSA)1.0 and PBLG-b-PLL(DBSA)1.0, respectively. The complexation leading to supramolecular rod-comb architectures was studied by transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), Fourier transform infrared spectroscopy (FTIR), and polarized optical microscopy (POM). PBLG-b-PLL, PBLG-b-PLL(DBSA)1.0, and PBLG-b-PLL(DSA)1.0 self-assemble with alternating PBLG lamellae and PLL-containing lamellae with a periodicity of 27-33 nm. Within the PBLG lamellae, the rod-like PBLG helices pack with a periodicity of ca. 1.3 nm. The internal structure of the PLL-containing lamellae depends on the complexation. For pure PBLG-b-PLL, the PLL chains adopt a random coil conformation and the PLL domains are disordered. For PBLG-b-PLL(DSA)1.0, lamellar self-assembly of periodicity of 3.7 nm within the PLL(DSA)1.0 domains is observed due to crystalline packing of the linear n-dodecyl tails. For PBLG-b-PLL(DBSA)1.0 with branched dodecyl tails, a distinct SAXS reflection is observed, suggesting self-assembly within the PLL(DBSA)1.0 domains with a periodicity of 2.9 nm. However, due to the absence of higher order reflections, the internal structure cannot be conclusively assigned. The efficient plasticization which leads to fluid-like liquid crystallinity in PBLG-b-PLL(DBSA)1.0 and an alpha-helical conformation according to FTIR allows us to suggest that the PLL(DBSA)1.0 domains have a hexagonal internal structure. The interplay of self-assembly at different length scales combined with rod-like liquid crystallinity can open new routes to design functional materials.
authors.affiliation: Department of Engineering Physics and Mathematics and Center for New Materials, Helsinki University of Technology, P.O. Box 2200, FIN-02015 HUT, Espoo, Finland.
authors.forename: Sirkku
authors.initials: S
authors.lastname: Hanski
authors.forename: Nikolay
authors.initials: N
authors.lastname: Houbenov
authors.forename: Janne
authors.initials: J
authors.lastname: Ruokolainen
authors.forename: Dimitra
authors.initials: D
authors.lastname: Chondronicola
authors.forename: Hermis
authors.initials: H
authors.lastname: Iatrou
authors.forename: Nikos
authors.initials: N
authors.lastname: Hadjichristidis
authors.forename: Olli
authors.initials: O
authors.lastname: Ikkala
mesh_terms: D001557:Benzenesulfonates / Q000737:chemistry; D008854:Microscopy, Electron; D049329:Nanostructures / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry; D011099:Polyglutamic Acid / Q000031:analogs & derivatives; D011107:Polylysine / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D001557:Benzenesulfonates; D010455:Peptides; D013501:Surface-Active Agents; C104155:poly(gamma-benzylglutamate)poly(ethylene oxide); D011107:Polylysine; D011099:Polyglutamic Acid; D011092:Polyethylene Glycols; C032365:benzenesulfonic acid