No abstract

A linear polyester was synthesized from furfural-based monomer through solvent-free polymerization using sunlight and the polymer structure was confirmed by a single crystal X-ray structure of a partially polymerized intermediate.

Two stereoregular 2D polyesters were synthesized by using topochemical polymerization of symmetric four-armed monomers. The monomers contain reactive carbon–carbon double bond(s) on each arm. The critical assemblies with multiple preorganized reactive centers were characterized by powder and single crystal X-ray diffraction. The solvent-free polymerization could be carried out with sunlight or UV irradiation. The locally confined photopolymerization process dimerized all of the olefins within the 2D bricklayer packing, which led to the formation of 2D polymers in the solid state. The process was monitored by FT-IR, and the products were confirmed by solid state NMR. After hydrolysis of the 2D polyester, the newly formed carbon–carbon single bonds during the [2 + 2] photocyclization were directly revealed by the single crystal structure of the hydrolysis product. Ultrathin sheets of the 2D polymer were observed under SEM and TEM after exfoliation.

Irreversible adsorption at polymer/substrate interfaces has been reported to influence glassy properties in thin films. However, consideration has yet to be extended to the nanocomposite geometry, wherein a large interfacial area and high processing temperatures afford especially favorable conditions for irreversible adsorption at the polymer/nanoparticle interface. Here, we present an approach for directly measuring the site-specific glassy properties at the polystyrene (PS)-adsorbed layer interface in PS−silica nanocomposites. We achieved this using a stepwise assembly approach to localize fluorescent dyes within the nanocomposite adsorbed layer, subsequently measuring the glass transition temperature (T g ) via fluorescence. We found that PS adsorption within nanocomposites strongly influenced the local T g . By measuring the thickness of the PSadsorbed layers atop nanoparticles via transmission electron microscopy, we found a correlation between adsorbed layer T g and thickness. Our results provide compelling evidence that adsorbed layer formation within polymer nanocomposites can have a profound impact on local interfacial properties.

While ultraviolet light is hailed for its renewability, nontoxicity, and lack of resulting waste products, photochemistry is relatively out of reach for many researchers and industries because conventional ultraviolet radiation sources are not always accessible. For example, the availability of sunlight varies with weather conditions, geographical location, and daylight duration. The use of commercial incandescent light as an alternative to conventional ultraviolet radiation was explored in this article. The classic [2 + 2] photocycloaddition of trans-cinnamic acid was tested under controlled conditions in the solid state, and it was found that 150 W light bulbs provided satisfactory results and 1.5 cm away from the light source was a viable distance for the photoreaction. A [2 + 2] cycloaddition of 10 mg trans-cinnamic acid finished in as few as 4 h. Gram-scale synthesis was also achieved in 40 h by using a 500 W floodlight bulb. The incandescent floodlight also effectively facilitated a cutting-edge photopolymerization in 24 h to produce a two-dimensional (2D) polymer. The use of reliable, inexpensive, and nonhazardous incandescent light in place of sunlight or even ultraviolet lamps for certain photoreactions will allow for the wider study and development of photochemistry.