Tunable transient and mechanical properties of photodegradable Poly(phthalaldehyde)

Flexible Cyclic-Poly(phthalaldehyde)/Poly(ε-caprolactone) Blend Fibers with Fast Daylight-Triggered Transience

Cyclic-poly(phthalaldehyde) (cPPHA) exhibits photo-triggerable depolymerization on-demand for applications like the photolithography of microfabricated electronics. However, cPPHA is inherently brittle and thermally sensitive; both of these properties limit its usefulness as an engineering plastic. Prior to this report, small molecule plasticizers are added to cPPHA-based films to make the polymer more flexible. But plasticizers can eventually leach out of cPPHA, then leaving it increasingly more brittle throughout product lifetime. In this research, a new approach to fabricating flexible cPPHA blends for use as spun fibers is achieved through the incorporation of poly (ε-caprolactone) (PCL) by a modified wet spinning method. Among blend compositions, the 50/50 cPPHA/PCL fiber shows fast transience (<50 s) in response to daylight while retaining the flexibility of PCL and mechanical properties of an elastomer (i.e., tensile strength of ≈8 MPa, Young's modulus of ≈118 MPa, and elongation at break of ≈190%). Embedding 2 wt% gold nanoparticles to cPPHA can further improve the transience rate of fibers comprising less than 50% cPPHA. These flexible, daylight-triggerable cPPHA/PCL fibers can be applied to an extensive range of applications, such as wearable electronics, intelligent textiles, and zero waste packaging for which modest mechanical performance and fast transience are desired.

Synthesis of Unzipping Polyester and a Study of its Photochemistry

Preparation of an unzipping polyester is reported. The monomer was prepared from benzoic acid in a four-step sequence. Step growth polymerization of the monomer provides the target polymer. Efficient depolymerization upon irradiation at 254 nm was confirmed with a quantum yield of >0.8. The photolysis mechanism was investigated, and the results of radical trapping experiments are consistent with an initial Norrish type I like homolysis followed by a radical mediated depropagation reaction driven by aromatization.