Hierarchical ionic self-assembly of rod - Comb block copolypeptide - Surfactant complexes

Sirkku Hanski, Nikolay Houbenov, Janne Ruokolainen, Dimitra Chondronicola, Hermis Iatrou, Nikolaos Hadjichristidis*, Olli Ikkala

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

64 Scopus citations

Abstract

Novel hierarchical nanostructures based on ionically self-assembled complexes of diblock copolypeptides and surfactants are presented. Rod-coil diblock copolypeptide poly(γ-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 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 α-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.

Original languageEnglish (US)
Pages (from-to)3379-3384
Number of pages6
JournalBiomacromolecules
Volume7
Issue number12
DOIs
StatePublished - Dec 1 2006

ASJC Scopus subject areas

  • Bioengineering
  • Biomaterials
  • Polymers and Plastics
  • Materials Chemistry

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