Versatile Postmodification of Conjugated Microporous Polymers Using Thiol-yne Chemistry

Radical thiol-yne chemistry is used for the modification of microporous networks with aliphatic alcohols. The degree of functionalization can be tuned by varying the reacted amount of thiol. Porosity analysis indicates that the microporosity can be preserved within a certain range, however, a decrease in pore size is observed

Phenolic Naphthoxazines as Curing Promoters for Benzoxazines

The effect of phenolic hydroxyl bearing naphthoxazines as catalysts for the ring-opening polymerization (ROP) of simple 1,3-benzoxazines was investigated. The latent catalytic role of napthoxazines in the curing process of the mixtures was demonstrated by DSC and FT-IR investigations. It was found that phenolic naphthoxazines cause clear reduction in ROP temperature, particularly when electron-withdrawing groups are attached and an onset ROP temperature as low as 169 °C is attained. Thermal properties of the final polymers were also analyzed, and no significant effect of naphthoxazines on the thermal stability of the cured polybenzoxazines was observed

Benzoxazine-Based Thermosets with Autonomous Self-Healing Ability

A self-healing strategy for poly­(propylene oxide)­s bearing benzoxazine units (PPO-Benz) through supramolecular attractions is described. Poly­(propylene oxide) bisamine (PPO) with a molecular wieght of 2000 Da was reacted with formaldehyde and bisphenol A to yield desired PPO-Benz with 12 360 Da. The cross-linked polymer films were then prepared by solvent casting of suitable compositions of PPO-Benz and carboxlic acid containing benzoxazine monomer (Carb-Benz) in chloroform followed by thermal ring-opening reaction of benzoxazine groups at 200 °C. Thermal curing and thermal stability of the film and final products were investigated. It was demonstrated that the self-healing capacity of the films was improved by employing Carb-Benz in the formulation

Hydroxyl Functional Polybenzoxazine Precursor as a Versatile Platform for Post-Polymer Modifications

A new postmodification approach for the benzoxazine based thermosets is described. The approach involves attachment of hydroxyl functional groups to the main-chain polybenzoxazine precursors through monomer synthesis method. Hydroxyl functional polybenzoxazine precursor was successfully synthesized by using appropriate combinations of hexamethylene diamine with hydroxy functional diamine, namely 1,3-diaminopropan-2-ol in conjunction with bisphenol A and paraformaldehyde, and characterized. Modification reactions were performed by simple esterification reactions of hydroxyl groups with 2-bromopropanoyl chloride and methacryloyl chloride to yield ATRP macroinitiator and methacrylate containing polybenzoxazine precursors, respectively. ATRP macroinitiator was used to obtain polystyrene grafted polybenzoxazine precursors and photopolymerization of methacrylate groups was carried out successfully. The benzoxazine groups present in the all structures were shown to readily undergo thermally activated ring-opening polymerization in the absence of an added catalyst forming cross-linked networks. The thermal stability of the cured polymers was investigated and compared to that of a classical polybenzoxazine precursor

Teaching New Tricks to an Old Indicator: pH-Switchable, Photoactive Microporous Polymer Networks from Phenolphthalein with Tunable CO₂ Adsorption Power

Switchable, organic microporous networks were synthesized by Sonogashira coupling of tetrabromophenolphthalein with 1,4-diethynylenebenzene using optimized reaction conditions. The resulting networks are microporous and have specific surface areas exceeding 800 m² g^–1. The microporosity and the pore polarity are sensitive to the pH value as evidenced by nitrogen and carbon dioxide physisorption experiments. The switching between the open and closed form of the lactone ring is reversible, but some porosity is lost throughout the process. The colored, alkaline salts of these networks are photochemically active, as shown by the effective heterogeneous photosensitization of the photopolymerization of methyl methacrylate with visible light

Post-Modification of Polybutadienes by Photoinduced Hydrogen Abstraction from Benzoxazines and Their Thermally Activated Curing

Side-chain benzoxazine functional polybutadienes was synthesized by photoinduced hydrogen abstraction process. First, photoactive benzoxazines having both chromophoric carbonyl and hydrogen donating sites were synthesized using vanillin or 4-hydroxybenzophenone by conventional benzoxazine synthesis methodology. Irradiation of neat polybutadiene (PB) in the presence of the corresponding benzoxazines, namely benzophenone benzoxazine (BPh-ptol) and vanillin benzoxazine (Van-a) under 300–350 nm light, gave PBs with approximately 4–5 benzoxazine units per chain. Successful modification was confirmed by the spectral and thermal investigations. It is demonstrated that PBs attached with benzoxazines undergo thermally activated curing without any catalyst to form polybutadiene thermoset with high char yield

Combining Elemental Sulfur with Polybenzoxazines via Inverse Vulcanization

A novel strategy to obtain sulfur-rich polybenzoxazine copolymers by reacting allyl functional benzoxazine (BA-ala) and elemental sulfur was described. Simultaneous inverse vulcanization and ring-opening reactions of benzoxazine generated soluble copolymers in specific feed ratios. Parameters such as monomer structure and feed ratios on the polymerization were studied. The thermal stability of the copolymers was investigated and compared to that of polybenzoxazines derived from neat BA-ala by using thermogravimetric analysis and differential scanning calorimetry. The surface properties of the materials as examined by scanning electron microscopy confirmed that elemental sulfur and benzoxazine copolymers can be produced without a phase separation at the micrometer level. Moreover, a sponge-like insoluble macroporous polybenzoxazine networks was obtained at the 20 wt % feed ratio of sulfur

Preparation of microporous organic polymer through Schiff base chemistry and its potential application

<div><p>The uniform microporous organic polymer (MOP) was obtained in one-pot and one-step polymerization process through Schiff base chemistry under thermal conditions. The obtained anthraquinone–melamine based MOP (AM-MOP) displays high surface area (215 m²/g). AM-MOP was manually filled into a column with high pressure and used as packing material in the high-performance liquid chromatographic applications. The analysis of compounds such as polycyclic aromatic hydrocarbons, pesticides, flavonoids, and phenolic acids was performed to display a possible application by using AM-MOP packed column. Compared to the commercial columns, AM-MOP exhibits better selectivity factor and column efficiency arising from its strong <i>π</i>–<i>π</i> interaction activity. Furthermore, it has similar solvent uptake in both polar and nonpolar media, which explains good compatibility of the material with all mobile phases, from acetonitrile to methanol and water.</p></div

Mesoporous Graphitic Carbon Nitride as a Heterogeneous Visible Light Photoinitiator for Radical Polymerization

The use mesoporous graphitic carbon nitride (mpg-C₃N₄) in conjunction with tertiary amines as initiators in visible-light-induced free radical polymerization is described. The initiation mechanism involves photoinduced free radical generation by scavenging holes with amines and subsequent hydrogen abstraction. The efficiency of the photoinitiation is controlled by the nature of the amines and specific surface area of the carbon nitride powder. Apparently, amines with higher basicity and available hydrogens provide more favorable conditions for the photoinitiation process. Due to its heterogeneous nature, the photoinitiator preserves its photoinitiation activity after the polymerization and can easily be separated and used for further polymerizations