Postfunctionalization of Self-Immolative Poly(dithiothreitol) Using Steglich Esterification

Self-immolative polymers (SIPs) are a class of degradable polymers that upon exposure to specific stimuli will degrade into small monomer-like products. The polymer poly(dithiothreitol) (pDTT) has been shown to behave as a SIP, but expanding its practical use in various applications requires adjustment of its chemical functionalities and physiochemical properties. To address this, we report the use of Steglich esterification as a versatile synthetic method for the postpolymerization modification of pDTT. In this manner, we were able to introduce various side groups to the self-immolative backbone with a wide variety of pendant groups, including saturated, unsaturated, and halogenated alkyl groups, let alone aromatic and heteroaromatic groups. In general, Steglich esterification proceeds with both high yields and full conversions of hydroxyl groups in the polymer. The chemical modification changes significantly both the physiochemical behavior and processability of the SIPs. In addition, depolymerization of pDTT containing the pendant anthraquinone group can be electrochemically triggered.