Poly(p‐phenylenevinylene) Derivatives with Defined Conjugation Segments and Post‐Polymerization Modification with Sterically Enshrouded Chromophores

Abstract

Two poly(p-phenylenevinylene) derivative alternating copolymers (P1-I and P2-I) have been prepared featuring iodo substituents and m-phenylene units to periodically disrupt conjugation. P1-I was derivatized with various chromophores to yield P1a-f. In P1a-f, the chromophores were positioned within a sterically protected pocket shielding them from interchain interactions so that intrachain interactions between polymer segments could be observed. Solution and film properties of polymers have been examined. Post-polymerization chromophore modification leads to new photophysical properties such as intramolecular charge transfer and fluorescent resonance energy transfer processes in some cases.

Conjugated polymers with regularly spacedm-phenylene units and post-polymerization modification to yield stimuli-responsive materials

“…Finally, oxidation via pyridinium chlorochromate gives 4 in a moderate yield of 67.9%. The other dialdehyde monomer 5 is commercially available, while bis(phosphonate ester) 6 is conveniently prepared as previously reported …”

“…The photophysical signatures of CPs are of particular interest when considering their application in device settings mentioned above. Photophysical properties are dramatically influenced not only by molecular weight and polydispersity, but also by the type of inter/intrachain interactions present in a film of the material, and the distribution of effective conjugation lengths of the π ‐conjugated segments of the polymer. The effective conjugation length of the π ‐conjugated segments in the backbone will have an average value, but twisting of adjacent π ‐conjugated segments from coplanarity at various points along the backbone will also give rise to some distribution of effective conjugation lengths about the average value.…”

“…The issue of variable effective conjugation lengths has also been tackled by tedious preparation of extensive series of oligomeric model compounds of increasing length in the hopes of extrapolating the property trends to predict the properties of a polymeric analogue. This approach has been only somewhat effective because properties do not scale linearly with the length of the molecule . There has also been some recent work to incorporate small segments of poly( p ‐phenylene vinylene) and poly( p ‐phenylene ethynylene) into polymers with periodic disruption of conjugation in an effort to combine the predictable photophysical/electrochemical properties of small‐molecule‐based chromophores with the processability of polymers.…”

“…The molecular weight and polydispersity influence on polymer properties can be alleviated to some extent by utilizing a single parent polymer of known molecular weight and polydispersity and altering its structure through post‐polymerization modification. This has been done with success for a wide range of organic polymers, including CPs such as hyperbranched poly( p ‐phenylene ethynylene)s and some poly( p ‐phenylene vinylene)s in which the conjugation is periodically disrupted by m ‐phenylene units. Derivatives of P1‐I (Chart ) in which the iodo substituent is replaced by small‐molecule chromophores have shown low incidence of interchain interactions while enforcing intrachain interactions between the backbone π ‐system and the small‐molecule chromophore, leading to intramolecular charge transfer and Forster resonance energy transfer (FRET) …”

“…Hybrid organic–inorganic materials such as conjugated metallopolymers resulting from metal ion binding to a ligand‐modified CP can also exhibit a synergistic combination of CP optical properties with the redox properties available to metal complexes to yield improved materials for use in thin films in organic light‐emitting diodes and solar cells . The incorporation of metal‐binding units within a sterically shielded cleft can eliminate undesirable crosslinking/network formation and thus these units are excellent candidates for soluble metal ion detection applications . In light of these findings, it was of interest to explore whether post‐polymerization modification of P1‐I and P2‐I with metal‐ligating pyridyl units could be used to yield similarly soluble conjugated metallopolymers.…”