Vanillin-Based Polymers via Ring-Opening Metathesis Polymerization

Biobased polymer synthesis is becoming an indispensable research area aimed at addressing environmental pollution and the depletion of petroleum resources. Vanillin, which can be sustainably obtained from lignin biomass, is a phenolic compound that is widely used as a food additive. We herein report our study of polymer synthesis using vanillin through ring-opening metathesis polymerization (ROMP). Our initial step involves the chemical transformation of vanillin into vanillin 5-norbornene-2-carboxylate (VN), a polymerizable monomer. This ROMP monomer has the capability to form poly(vanillin 5-norbornene-2-carboxylate) using a Grubbs catalyst. This glassy homopolymer has a molecular weight of 49,000 g/mol with a Đ of 1.23. To explore its potential in copolymers, we performed triblock copolymerization to create ABA-type thermoplastic elastomers. To achieve this, we synthesized three ROMP monomers serving as soft blocks, each containing different alkyl chains. Through a sequential addition of monomers (VN, soft block, and VN in that order), we successfully synthesized six vanillin-based triblock copolymers with molecular weights of 32,000–61,200 g/mol and Đ values of 1.24–1.40. These synthesized polymers exhibit excellent mechanical properties, including a Young’s modulus of 28 MPa, surpassing commercial thermoplastic elastomers. Atomic force microscopy (AFM) reveals microphase separation consistent with the two distinct glass transition temperatures

Highly Emissive Excimers by 2D Compression of Conjugated Polymers

Interactions between π-conjugated polymers are known to create ground-state aggregates, excimers, and exciplexes. With few exceptions, these species exhibit decreased fluorescence quantum yields relative to the isolated polymers in liquid or solid solutions. Herein, we report a method to assemble emissive conjugated polymer excimers and demonstrate their applicability in the detection of selected solvent vapors. Specifically, poly­(phenylene ethynylene)­s (PPEs) with amphiphilic side chains are organized in a Langmuir monolayer at the air–water interface. Compression of the monolayer results in the reversible conversion from a face-on organization of the π-system relative to the water to what appears to be an incline-stack conformation. The incline-stack organization creates a bright yellow emissive excimeric state with increases of 28% in relative fluorescence quantum yields to the face-on monolayer conformation. Multilayers can be transferred onto the glass substrate via a Langmuir–Blodgett method with preservation of the excimer emission. These films are metastable and the fluorescence reverts to a cyan color similar to the spectra obtained in solution and spin-cast films after exposure to selected solvent vapors. This behavior has practical utility as a fluorescence-based indicator for selected volatile organic compounds

Interfacial Pressure/Area Sensing: Dual-Fluorescence of Amphiphilic Conjugated Polymers at Water Interfaces

Exciton migration to emissive defects in π-conjugated polymers is a robust signal amplification strategy for optoelectronic sensors. Herein we report end-capped conjugated polymers that show two distinct emissions as a function of interpolymer distances at the air–water and hydrocarbon–water interfaces. Amphiphilic poly­(phenylene ethynylene)­s (PPEs) end-capped with perylene monoimides display two distinct emission colors (cyan from PPE and red from perylene), the relative intensity of which depends on the surface pressure applied on the Langmuir monolayers. This behavior produces a ratiometric interfacial pressure indicator. Relative quantum yields are maintained at the different surface pressures and hence display no sign of self-quenching of the excitons in an aggregated state. These polymers can be organized at the micelle–water interface in lytropic liquid crystals, thereby paving the way for potential applications of end-capped amphiphilic conjugated polymers in biosensors and bioimaging

Highly Emissive Excimers by 2D Compression of Conjugated Polymers

Interactions between π-conjugated polymers are known to create ground-state aggregates, excimers, and exciplexes. With few exceptions, these species exhibit decreased fluorescence quantum yields relative to the isolated polymers in liquid or solid solutions. Herein, we report a method to assemble emissive conjugated polymer excimers and demonstrate their applicability in the detection of selected solvent vapors. Specifically, poly­(phenylene ethynylene)­s (PPEs) with amphiphilic side chains are organized in a Langmuir monolayer at the air–water interface. Compression of the monolayer results in the reversible conversion from a face-on organization of the π-system relative to the water to what appears to be an incline-stack conformation. The incline-stack organization creates a bright yellow emissive excimeric state with increases of 28% in relative fluorescence quantum yields to the face-on monolayer conformation. Multilayers can be transferred onto the glass substrate via a Langmuir–Blodgett method with preservation of the excimer emission. These films are metastable and the fluorescence reverts to a cyan color similar to the spectra obtained in solution and spin-cast films after exposure to selected solvent vapors. This behavior has practical utility as a fluorescence-based indicator for selected volatile organic compounds

Highly Emissive Excimers by 2D Compression of Conjugated Polymers

Interactions between π-conjugated polymers are known to create ground-state aggregates, excimers, and exciplexes. With few exceptions, these species exhibit decreased fluorescence quantum yields relative to the isolated polymers in liquid or solid solutions. Herein, we report a method to assemble emissive conjugated polymer excimers and demonstrate their applicability in the detection of selected solvent vapors. Specifically, poly­(phenylene ethynylene)­s (PPEs) with amphiphilic side chains are organized in a Langmuir monolayer at the air–water interface. Compression of the monolayer results in the reversible conversion from a face-on organization of the π-system relative to the water to what appears to be an incline-stack conformation. The incline-stack organization creates a bright yellow emissive excimeric state with increases of 28% in relative fluorescence quantum yields to the face-on monolayer conformation. Multilayers can be transferred onto the glass substrate via a Langmuir–Blodgett method with preservation of the excimer emission. These films are metastable and the fluorescence reverts to a cyan color similar to the spectra obtained in solution and spin-cast films after exposure to selected solvent vapors. This behavior has practical utility as a fluorescence-based indicator for selected volatile organic compounds