Synthesis of Nanostructured Organic and Inorganic Materials by Self-Assembly
Eftekharzadeh, Shirin
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https://hdl.handle.net/2142/82911
Description
Title
Synthesis of Nanostructured Organic and Inorganic Materials by Self-Assembly
Author(s)
Eftekharzadeh, Shirin
Issue Date
1998
Doctoral Committee Chair(s)
Stupp, Samuel I.
Department of Study
Materials Science and Engineering
Discipline
Materials Science and Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Materials Science
Language
eng
Abstract
This thesis investigated the nanostructure, morphology of organic and inorganic materials grown in ordered organic matrices. The matrix is a binary system of water and the nonionic surfactant of oligo(ethylene oxide) n&d1; oleyl ether. Initial studies were conducted on mineralization of a calcium phosphate mineral at the interface between ion doped hexagonal mesophases. Investigation of mesophase structure indicates that the binding of calcium and acetate ions to surfactant reduces the mesophase stability but phosphate ions, with low affinity to surfactant, do not affect the mesophase structure. SEM investigation of the mineral reveals plate-like crystals with a surface nanostructure resembling the orientational order of cylindrical assemblies in the mesophase. A similar surfactant system is considered for the organic synthesis by photopolymerization of a semi-polar monomer, carboxylated oligobutadiene, at the interfacial region of surfactant assemblies in non-lamellar mesophases. Investigation of mesophase structure in the presence of the oligomer n&d1;=6 indicates a transformation of hexagonal to lamellar structure at low oligomer contents. For a surfactant with longer hydrophile, this transformation takes place at higher oligomer concentrations. A similar phase transformation is observed with mesophases containing the oligomer ( n&d1; = 12). Photopolymerization of hexagonal mesophases of either oligomer results in elongated objects with dimensions matching the dimension of cylindrical assemblies in the hexagonal mesophase. The isotropic texture of the polymer formed by the oligomer ( n&d1; = 6) along with a larger effective diameter of the polymeric particles point to a highly interconnected structure of the elongated objects. This interconnection is reduced in the polymer formed by the oligomer ( n&d1; = 12) as observed by the shorter effective diameter and the nematic-like optical texture. The replacement of water in the hexagonal mesophase of the oligomer ( n&d1; = 12) with phosphoric acid results in a bicontinuous structure. Photopolymerization of this mesophase gives rise to nano-spherical particles with continuous hydrophilic and hydrophobic domains, which when mineralized, form a composite network of mineral and polymer with improved mechanical properties over the mineralized-nonpolymerized structure. Crosslinking seems to enhance the binding of mineral to organic matrix. This study introduces a new direction for the control of morphology via self assembly.
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