POS5-0877
Side-Chain Positional Isomerism Enhances Intrinsic Photostability in Conjugated Polymers
When and Where
Nov 30, -0001
00:00 - 00:00
Presenter(s)
Eonji Kim (Korea Research Institute of Chemical Technology)
Co-Author(s)
Abstract
Conjugated polymers offer attractive optoelectronic properties, but their conjugated backbones are susceptible to photo-oxidative degradation, limiting long-term durability. Although encapsulation can reduce environmental exposure, it does not address the intrinsic instability of the polymer itself. Here, we report a side-chain positional-isomerism strategy that improves intrinsic photostability without changing polymer composition. Para- and meta-substituted polydiphenylacetylene (PDPA) derivatives were selected as a simple, conformation-sensitive model system for isolating the geometric effects of side-chain position. Despite similar molecular weights, absorption characteristics, and thermal stability, the meta isomer (mC1) showed markedly higher photostability than the para isomer (pC1) in both solution and film. Spectroscopic and structural analyses revealed that mC1 forms a more extended and rigid chain conformation with reduced kinking and entanglement. Monomer-level comparisons ruled out simple electronic effects, indicating that polymer-chain conformation is the main origin of the stability difference. Solvent-quality titration at fixed composition further showed that chain compaction accelerates photodegradation, establishing a causal link between chain conformation and photostability. Beyond photostability, mC1 also showed greater resistance to high-energy damage, including Ga⁺ ion-beam exposure and Ar⁺ sputtering. Based on this enhanced intrinsic photostability, we developed unencapsulated, surface-exposed viscosity-sensor films that retained their fluorescence response for longer under irradiation. These results establish positional isomerism as a practical molecular design rule for intrinsically photostable conjugated polymers, especially in surface-exposed systems.
