Functional design of stimuli-responsive poly(phthalaldehyde)-based adhesives: depolymerization kinetics and mechanical strength management through plasticizer addition

Abstract

Through a strategic polymer engineering design, this paper shows that self-immolative poly(phthalaldehyde) (PPA) can be employed as a responsive debonding-on-demand adhesive for the detection of fluorides and acids in liquid and solid states. The engineered PPA with dimethyl phthalate plasticizer blends exhibits mechanical shear strength up to 1100 kPa when bonding smooth glass surfaces, which represents a significant enhancement compared to the o-phthalaldehyde monomer (12 kPa) and the pristine PPA polymer (up to 400 kPa). Exposure of acetyl-endcapped PPA to 8.0 eq. of trifluoroacetic acid (TFA) under ambient conditions resulted in a complete degradation of the polymer within 25 minutes via a backbone cleavage, whereas exposure of fluoride responsive silyl-ether endcapped PPA to 1.0 eq. of tetrabutylammonium fluoride (TBAF) resulted in a fast and simultaneous decomposition of the polymer within 2 minutes via end-cap cleavage. This study also illustrates the capability of PPA to undergo solid-state depolymerization, promoting on-demand release from adhesion. Overall, this study offers a unique design strategy for creating on-demand depolymerizable coatings that may find future potential applications in stimuli-responsive personal protective equipment (PPE) for the chemical detection and on-demand protection against chemical warfare agents (CWAs) in hostile environments.