Kinetics of Self-Immolative Degradation in a Linear Polymeric System: Demonstrating the Effect of Chain Length

Abstract

We describe here a study demonstrating that the degradation time of self-immolative linear polymers is dependent on chain length. These materials are unique relative to most degradable polymers, in that they undergo end-to-end depolymerization in response to the cleavage of an end-cap. Although one of their cited attributes is a dependence of their degradation time on chain length, no conclusive study has been conducted to demonstrate and study this effect. In this work, using a linear self-immolative polymer backbone derived from alternating 4-hydroxybenzyl alcohol and N, N ′-dimethylethylenediamine based spacers, we show that there is a proportional relationship between chain length and depolymerization time. This is first accomplished using a series of oligomers synthesized using a convergent, iterative route and then applied to the polydisperse case on a set of polymers displaying varying molecular weights. We also report the first development and validation of a self-immolative degradation model relating monomer kinetics to polymer degradation and show its application in explaining oligomeric and polymeric degradation profiles.