Linear and Nonlinear Optical Properties of All-cis and All-trans Poly(p-phenylenevinylene)

Poly(p-phenylenevinylene) (PPV) is a staple of the family of conjugated polymers with desirable optoelectronic properties for applications including light-emitting diodes (LEDs) and photovoltaic devices. Although the significant impact of olefin geometry on the steady-state optical properties of PPVs has been extensively studied, PPVs with precise stereochemistry have yet to be investigated using nonlinear optical spectroscopy for quantum sensing, as well as light harvesting for biological applications. Herein, we report our investigation of the influence of olefin stereochemistry on both linear and nonlinear optical properties through the synthesis of all-cis and all-trans PPV copolymers. We performed two-photon absorption (TPA) using a classical and entangled light source and compared both classical TPA and entangled two-photon absorption (ETPA) cross sections of these stereodefined PPVs. Whereas the TPA cross section of the all-trans PPV was expectedly higher than that of all-cis PPV, presumably because of the larger transition dipole moment, the opposite trend was measured via ETPA, with the all-cis PPV exhibiting the highest ETPA cross section. DFT calculations suggest that this difference might stem from the interaction of entangled photons with lower-lying electronic states in the all-cis PPV variant. Additionally, we explored the photoinduced processes for both cis and trans PPVs through time-resolved fluorescence upconversion and femtosecond transient absorption techniques. This study revealed that the sensitivity of PPVs in two-photon absorption varies with classical versus quantum light and can be modulated through the control of the geometry of the repeating alkenes, which is a key stepping stone toward their use in quantum sensing, bioimaging, and the design of polymer-based light-harvesting systems.

A sequential ROMP strategy to donor–acceptor di-, tri- and tetra arylenevinylene block copolymers

Sequential ROMP of electron rich and electron deficient paracyclophanediene monomers gives donor–acceptor di-, tri- and even tetrablock phenylenevinylene coploymers.

Stereoretentive Ring-Opening Metathesis Polymerization to Access All-cis Poly(p-phenylenevinylene)s with Living Characteristics

Poly(p-phenylenevinylene)s (PPVs), a staple of the conductive polymer family, consist of alternating alkene and phenyl groups in conjugation. The physical properties of this organic material are intimately linked to the cis/trans configuration of the alkene groups. While many synthetic methods afford PPVs with all-trans stereochemistry, very few deliver the all-cis congeners. We report herein a synthesis of all-cis PPVs with living characteristics via stereoretentive ring-opening metathesis polymerization (ROMP). Exquisite catalyst control allows for the preparation of homopolymers or diblock copolymers with perfect stereoselectivity, narrow dispersities, and predictable average molar masses. All-cis PPVs can then serve as light-responsive polymers through clean photoisomerization of the stilbenoid units.

Bidirectional ROMP of paracylophane-1,9-dienes to tri- and penta-block p-phenylenevinylene copolymers

Dialkoxy and dialkyl substituted paracyclophane-1,9-dienes undergo bidirectional ring opening metathesis polymerisation (ROMP) on addition of bifunctional Hoveyda–Grubbs initiators.

Macrocyclic poly(p-phenylenevinylene)s by ring expansion metathesis polymerisation and their characterisation by single-molecule spectroscopy

Ring expansion metathesis polymerisation (REMP) has proven to be a viable approach to prepare high purity macrocyclic phenylenevinylene polymers.

Ring expansion metathesis polymerisation (REMP) has proven to be a viable approach to prepare high purity cyclic polymers. Macrocyclic polymers with a fully conjugated defect free backbone are of particular interest as these polymers have no end groups that can act as charge traps. In this work soluble macrocyclic poly(p-phenylenevinylene)s (cPPVs) have been prepared directly via the REMP of substituted paracyclophanedienes. Single-molecule spectroscopy of the two topological forms of PPV i.e., linear (lPPV) and cyclic (cPPV) revealed that lPPV exists in an extended conformation whereas the cPPV adopts a restricted ring-like conformation. Despite such large differences in the chain conformation, the spectral properties of the two compounds are unexpectedly very similar, and are dominated by torsional deformations in relatively short conjugated segments.

Synthesis and ring opening reaction of octaoctyl substituted [2.2.2.2](2,7)-fluorenophanetetraene by photooxidation

Octaoctyl substituted fluorenophanetetraene has been synthesized and the photooxidation of the fluorenophanetetraene gives all trans linear fluorenevinylene with aldehyde end groups.

Mechanistic investigation of the ring opening metathesis polymerisation of alkoxy and alkyl substituted paracyclophanedienes

This paper discusses the living nature of the ring opening metathesis polymerisation (ROMP) of alkoxy and alkyl substituted [2.2] paracyclophane-1,9-dienes (M1 and M2), initiated with Grubbs’ second and third generation catalysts (G2 and G3).

Synthetic approaches towards structurally-defined electrochemically and (photo)redox-active polymer architectures

This review details synthetic strategies leading to structurally-defined electrochemically and (photo)redox-active polymer architectures,e.g.block, graft and end functionalized (co)polymers.

Controlled/living polymerization towards functional poly(p-phenylene vinylene) materials

Poly(p-phenylene vinylene)s (PPVs) are an important class of highly fluorescent polymeric semiconductor materials.

Alkyl substituted [2.2]paracyclophane-1,9-dienes

Highly strained alkyl-substituted [2.2]paracyclophane-1,9-dienes, suitable for ring opening metathesis polymerization to poly(phenylene vinylenes), have been prepared in excellent yields.

Alkyl substituted poly(p-phenylene vinylene)s by ring opening metathesis polymerisation

The ring opening metathesis polymerisation (ROMP) of three n-octyl substituted [2.2]paracyclophane-1,9-dienes, initiated by Grubbs ruthenium carbene complexes is reported.