화학공학소재연구정보센터
Biomacromolecules, Vol.7, No.12, 3379-3384, 2006
Hierarchical ionic self-assembly of rod-comb block copolypeptide-surfactant complexes
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 (M-n = 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 rodcomb 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 R-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 rodlike liquid crystallinity can open new routes to design functional materials.