Graduate Defense: Kyle Nogales

Dissertation Information

Title: Poly(alkyl aldehyde)s: New Class of Closed-Loop Recyclable Plastics

Program: Doctor of Philosophy in Materials Science and Engineering

Advisor: Dr. Scott Phillips, Materials Science and Engineering

Committee Members: Dr. Clare Fitzpatrick, Mechanical and Biomedical Engineering; Dr. Eric Jankowski, Materials Science and Engineering; and Dr. Nishad Dhopatkar, Materials Science and Engineering

Abstract

This dissertation will describe a new class of closed-loop recyclable, self-immolative polymers that undergo selective, complete, and rapid depolymerization in the solid state when triggered. Self-immolative poly(alkyl aldehyde)s are synthesized efficiently in approximately 60% yield using anionic polymerization, which provides access to polymers in accessible lengths ranging from short (Mn value of 2 kDa) to long polymers (Mn value of 5,000 kDa). The physical and thermal properties of the polymers can be tuned rationally by appropriate choice of the aldehyde monomer, with some of the polymers displaying mechanical properties that are similar to traditional plastics. The polymers depolymerize within minutes when the end-cap (i.e., detection unit) is cleaved from the polymer in response to a specific applied signal, where the signals can be selected from base (with a hydrogen end-cap) or fluoride (silyl ether end-cap). Poly(alkyl aldehyde)s also depolymerize readily in the solid state when heated above the degradation temperature, which enables direct, low-energy, closed-loop recycling of polymeric materials by converting plastics to monomers without dissolving the plastics. These favorable properties, coupled with the low cost and wide availability of aldehyde monomers, makes poly(alkyl aldehyde)s promising candidates for replacing certain types of traditional plastics that are difficult to recycle.