Investigation of Helicity of Water Soluble Polycarbodiimides and Preparation of Nano Particles with Amphiphilic Polycarbodiimides.

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Title: Investigation of Helicity of Water Soluble Polycarbodiimides and Preparation of Nano Particles with Amphiphilic Polycarbodiimides.
Author: Li, Haibo
Advisors: Tatyana I. Smirnova, Committee Member
Lin He, Committee Member
Alex Deiters, Committee Member
Bruce M. Novak, Committee Chair
Abstract: As a helical polymer, polycarbodiimides have been investigated for a period of time. But few water soluble polycarbodiimides had been synthesized and characterized. Since solubility of polycarbodiimides can be controlled by their side arms, achiral or chiral carbodiimides bearing hydrophilic tertiary amino group have been prepared. Single-handed sense hydrophilic polycarbodiimides were prepared from chiral monomers by achiral metal catalyst or from achiral monomers by chiral catalyst to give polycarbodiimides with predominately helical sense. The water solubility of these polycarbodiimides bearing tertiary amino groups is improved when they are methylated by methyl camphorsulfornic acid ester. Configurational and conformational predominately helical polycarbodiimides behave with different way when they are heated. For the former case, the polymers rearrange to their Thermodynamic Control Conformation (TCC) from Kinetic Control Conformation (KCC); for the later one, the polymer became racemic when annealed. The activation energies for the conformational change can be determined through Arrhenius plot analysis. Compared to the neutral polycarbodiimides bearing tertiary amino groups, the corresponding ionic polymers have higher activation energies. Helical induction of the water-soluble polycarbodiimides also has been investigated. CD spectrum was run for both the neutral and ionic polycarbodiimides and peptide mimics were found. In addition to the hydrophilic monomers, chiral or achiral hydrophobic carbodiimides were also synthesized and polymerized. Through living polymerizations, the amphiphilic polycarbodiimides were prepared from metal catalysts. Crew-cut nanoparticles have been prepared through a phase inversion method. Different conditions have been tried to achieve nano particles with different morphologies and sizes. In the nano particle preparation, water amount, acid amount and molecular weight play important roles in preparation of nano particles. TEM was used to characterize the nano particles. Amphiphilic polycarbodiimides with optical active hydrophobic blocks were synthesized and applied in the preparation of a nano-superhelix.
Date: 2006-08-04
Degree: PhD
Discipline: Chemistry
URI: http://www.lib.ncsu.edu/resolver/1840.16/5345


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