Polyphthalaldehyde: Synthesis, Derivatives, and Applications

Abstract

o-Phthalaldehyde is, to this day, the only aromatic aldehyde that can be homopolymerized through chain-growth polymerization. The product, polyphthalaldehyde (PPA), is a brittle white solid, and, having a polyacetal main chain, presents the ability to depolymerize quite rapidly in the presence of an acid. This review highlights the unique polymerization chemistry of o-phthalaldehyde since its discovery over half a century ago, describing the different methods for the preparation of PPA and its derivatives, how the polymerization chemistry affects the structure and thermomechanical properties of the obtained PPA, and summarizes recent developments in PPA chemistry as a responsive material. Modern material applications such as the use of PPA as photoresists or in thermal-scanning probe lithography, as well as exploration of judiciously end-capped PPA for its use as self-immolative materials are summarized. In addition, the use of PPA blocks in copolymers is described, leading to the development of films with well-defined nanochannels or nanopores that can serve as a template for the preparation of the microorganization of nanomaterials.

Reflections on the Evolution of Smart Polymers

“…One class of SIPs is based on backbones that have low ceiling temperatures (T c ), but that can be stabilized by cyclization or endcapping. Examples include polyphthalaldehydes (PPAs), [57] polyglyoxylates (PGs), [58] poly(olefin sulfones) (POSs) [59] and poly(benzyl ether)s. [60] PPAs, PGs and POSs have been known since the 1960s to 1970s as PPAs and POSs were investigated as resists for lithography applications, [61][62] and PGs were studied as degradable detergent builders. [63] Recent advancements in their polymerization chemistry and end-capping have enabled their depolymerization to be triggered by specific stimuli such as light, acid, oxidizing and reducing species, and even combinations of these stimuli.…”

“…One class of SIPs is based on backbones that have low ceiling temperatures ( T c ), but that can be stabilized by cyclization or end‐capping. Examples include polyphthalaldehydes (PPAs), polyglyoxylates (PGs), poly(olefin sulfones) (POSs) and poly(benzyl ether)s . PPAs, PGs and POSs have been known since the 1960s to 1970s as PPAs and POSs were investigated as resists for lithography applications, and PGs were studied as degradable detergent builders .…”

Functionalized and Degradable Polyphthalaldehyde Derivatives

“…This relative lack of PPA derivatives results in part from the perception that synthesizing substituted o-phthalaldehydes is prohibitively challenging, relying on a few established, but often low-yielding, synthetic routes. 8 Furthermore, it is still unclear a priori whether a specific phthalaldehyde is polymerizable under experimentally accessible conditions due to a lack of quantitative data on the ceiling temperatures of known PPA derivatives. To address these deficiencies, we set out to synthesize a range of substituted oPA derivatives and evaluate their Lewis acid-catalyzed polymerizations.…”

“…7 Polyphthalaldehyde (PPA) is among the most thoroughly studied depolymerizable polymers. 8,9 Linear or cyclic PPA (cPPA) can be obtained via anionic or cationic polymerization (respectively) of o-phthalaldehyde (oPA) below its Tc of -36 °C. 10,11 While end-capped linear PPA and cPPA are kinetically stable at room temperature, solution-phase exposure to acid results in complete depolymerization at rates too rapid to measure using standard analytical techniques (< 1 min; Scheme 1).…”

Oligo(thioether‐ester)s Blocks in Polyurethanes for Slowly Releasing Active Payloads

“…Polyaldehydes, especially polyphtalaldehyde, are a category of polymers that can be easily degraded either by acids or by a thermal treatment due to their low ceiling temperature . Poly( o ‐phtalaldehyde) was also found to be degraded by a mechanical stimulus via a heterolytic scission mechanism .…”