Self-assembled polymer nanostructures controlled by molecular architecture and polypeptide conformation

Susanna Junnila

Research output: ThesisDoctoral ThesisCollection of Articles

Abstract

Supramolecular chemistry, block copolymer self-assembly and biopolymer conformations are powerful tools for controlling structure formation in the nanoscale. In this thesis, we have studied how self-assembly of polypeptide-based materials can be controlled in the bulk solid state by molecular architecture of surfactants, lipids and block copolymers and by polypeptide conformation. The effect of surfactant architecture on the conformation and self-assembly of homopolypeptide-surfactant complexes has been studied in Publications I and II. The branching of the surfactant influences the polypeptide conformation, self-assembly of the supramolecular comb-shaped complexes, crystallization of the alkyl tails and periodicity of organization in the material after precipitation from aqueous solution. Externally triggered conformational and structural transformations are accessible in the solid state. In addition, the brittle complexes can be plasticized by adding excess surfactants in organic solvent. The effect of lipid architecture on the self-assembly of homopolypeptide-lipid complexes has been studied in Publication III. The PEGylated triple-tail lipids include two alkyl tails and one polyethylene glycol tail. Saturated lipid alkyl tails are able to crystallize at room temperature, and polypeptide alpha-helices are arranged in an oblique lattice. Unsaturated tails remain amorphous, and a hexagonal cylindrical morphology is observed. This morphology is also achieved by melting of the crystalline alkyl tails, proving that crystallization of the alkyl side chains plays a significant role in determining the packing symmetry of alpha-helical complexes. The temperature-controlled order-order transition is full and reversible. In Publications IV and V, miktoarm star copolymers with ABC, A2B and A2B2 architectures have been studied. The rod-like packing of alpha-helical polypeptide arms leads to lamellar block copolymer morphologies in all of the architectures and, in addition, to a hierarchical smectic packing in the ABC miktoarm architecture. The number of arms influences the degree of organization and packing of the rigid alpha-helices. Polypeptide side chain modification, on the other hand, influences the polypeptide conformation which has a major effect on the packing of the molecules.
Translated title of the contributionPolymeerien nanorakenteiden itsejärjestymisen ohjaaminen molekyyliarkkitehtuurilla ja polypeptidien konformaatioilla
Original languageEnglish
QualificationDoctor's degree
Awarding Institution
  • Aalto University
Supervisors/Advisors
  • Ikkala, Olli, Supervising Professor
  • Ikkala, Olli, Thesis Advisor
Publisher
Print ISBNs978-952-60-4763-8
Electronic ISBNs978-952-60-4764-5
Publication statusPublished - 2012
MoE publication typeG5 Doctoral dissertation (article)

Keywords

  • self-assembly
  • polypeptide
  • block copolymer
  • surfactant
  • lipid
  • conformation
  • supramolecule

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