stimuli responsive applications. Properties and characteristics PPA is a metastable polymer known for its ease of synthesis and rapid depolymerization. In addition, its properties can be easily influenced and manipulated upon either functionalizing the phthalaldehyde monomer with different groups, most efficiently, electron withdrawing groups, or employing different functional groups as end caps.3 Nevertheless, PPA on its own possesses superior attributes that will be discussed in this section and that are summarized in Figure 5. Mechanical properties PPA is known to have a rigid and brittle backbone which limits its flexibility and usage in some applications. However, it can be easily tuned by adding additives rendering it a soft material. The mechanical properties of cyclic PPA films drop cast using different solvents have recently been investigated. The study showed the polymer to possess a large elastic modulus of 2.5-3 GPa which was also previously reported in another study, in addition to tensile strength values ranging between 25 and 35 MPa and a failure strain of 1-1.5% that is highly dependent of the solvent used. Plasticizers as additives With the insurgence in the usage of PPA during the past few years for various applications, the need to ameliorate the transient properties and enhance the mechanical features of this polymer has come to surface. PPA is known to be brittle; it possesses a large storage modulus, and a glass transition temperature that is above its thermal degradation point, which renders the polymer unsuitable for a broad range of applications. One way to ameliorate its intrinsic properties is via the addition of a plasticizing agent that can disrupt the polymer’s intermolecular packing, and thus making it more flexible, decreasing its storage modulus, depressing its glass transition temperature, and increasing its shear strength. A few examples of plasticizers that have been used with PPA include dimethyl phthalate, bis(2-ethylhexyl) phthalate, diethyl adipate, and tri-isononyl trimellitate (TINTM). In a recent study, the effect of two ether-ester plasticizers on the mechanical flexibility and photo-transience speed of cyclic PPA was investigated. The authors were able to show that the addition of these additives broadened the storage modulus range and decreased it from 2300 MPa in the case of pure PPA down to 19 MPa in the PPA/plasticizer mixture, hence making the polymer more flexible and in need of less energy to be distorted. In another study published by the same research group, the effect of diethyl adipate (DEA) plasticizer