Polymerization-Induced Nanostructural Transitions in Diblock Copolymer Monomer Blends

Open Access
Author:
Zofchak, Everett
Area of Honors:
Chemical Engineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Robert John Hickey, III, Thesis Supervisor
  • Scott Thomas Milner, Honors Advisor
  • Manish Kumar, Faculty Reader
Keywords:
  • self-assembly
  • diblock copolymers
  • polymers
  • SAXS
  • nanotechnology
Abstract:
Nanostructured polymeric materials have attracted the interest of researchers in recent years for their use in a vast array of technologically relevant applications. One common method of creating nanostructured polymer materials is through diblock copolymer self-assembly, which occurs due to the microphase separation of two chemically distinct polymers covalently attached at a single point. The phase behavior of linear diblock copolymers has been exhaustively researched, yet less well understood is how selective polymer grafting from one block of a diblock copolymer effects the mesoscale ordering of the system. The work presented in this thesis illustrates how polymerization-induced nanostructural transitions can be achieved via in situ polymer grafting from the diblock copolymer poly(styrene)-block-poly(butadiene) (PS-PBD). Emphasis will be placed on the determination of the resultant static morphology after removal of residual monomer and annealing, the dominant grafting mechanism at play, and the in situ characterization of these nanostructural transitions. Through this in situ grafting process lamellar, hexagonally packed cylinders, and disorder spheres structures have been achieved as the final static dried and annealed morphology, as determined by small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). In addition to the static phase behavior, the phase behavior of blends of diblock copolymer and monomer was monitored via in situ SAXS and rheology experiments during polymerization. The in situ measurements revealed an interesting and unexpected phase trajectory for the 60% PS-PBD and 40% styrene monomer by volume blend. This thesis outlines our current knowledge regarding the phase behavior of these nanostructured polymeric materials made via in situ polymer grafting, as well as the limitations of this method and future work in this arena of research