Date of Award
The primary goal of solid phase polymer synthesis is to create monomers that will serve as base units for polymers. The monomers must be designed so that certain features of the polymer, such as its length, sequencing, and end group functionality, can be controlled. One way to link these building blocks is to use click chemistry. The term “click chemistry” refers to reactions that conform to a very specific set of criteria. These reactions must be carried out under simple conditions in a safe solvent, be stereospecific, and supply a high yield of product with little or no byproduct.
One type of click reaction is copper-catalyzed azide-alkyne cycloaddition (CuAAC), in which an azide reacts with a terminal acetylene to produce a cyclic triazole. This study involves using this reaction to build polymer chains on nanoparticles. It is simple to add one layer of polymers to a nanoparticle decorated with terminal alkynes via CuAAC, but extending the polymer chain is more difficult. Simply using a polymer with an azide on one end and an alkyne on the other will not work because the two ends of such a polymer would react with each other and the polymer would cyclize. Furthermore, there must be a way to remove the polymer from the nanoparticle once synthesis is complete.
The solution to these problems is to use alkyne protecting groups and degradable linkers. Protecting groups prevent the alkyne on the polymer from reacting. Once the polymer is safely attached to the nanoparticle, the alkyne can then be deprotected to undergo further CuAAC reaction. Moreover, the first unit to attach to the nanoparticle is not a polymer but a degradable linker. Once attached, it is deprotected to allow a polymer chain to grow. When the desired polymer chain length is achieved, the linker is degraded, freeing the polymer from the nanoparticle.
Bali, Sheeba, "Determining the Stability of Alkyne Protecting Groups and Degradable Linkers Used in the Solid Phase Synthesis of Block Copolymers" (2013). Senior Theses. 741.