Thermoresponsive Helical Poly(phenylacetylene)s

Poly­(phenylacetylene) (PPA) bearing dendritic oligo­(ethylene glycol) (OEG) as pendants was synthesized, and its thermoresponsiveness and helical conformation were investigated. Despite the steric hindrance of the bulky pendants in the homopolymer PPA-OEG, the chirality could be efficiently transferred from pendant alanine moieties to PPA main chain through ester linkage. In order to examine the steric effect of pendants on chiral transformation, a model PPA homopolymer PPA-Boc which carries less bulky moieties was prepared for comparison. The chiroptical properties of these thermoresponsive PPAs were further investigated by varying temperature to examine the effects of their thermoresponsiveness. In addition, PPA copolymers PPA-BDY bearing OEG dendron and fluorescent boradiazaindacene (BDY) chromophore showed excellent thermoresponsive properties and interesting fluorescence enhancement at elevated temperatures. To investigate the rigidity effects of polymer backbone on the thermally induced fluorescence enhancement, a nonchiral polymer carrying the same pendants but with polymethacrylate as the backbone (PMA-OEG) was prepared. It was found that the chiroptical and fluorescence properties of these PPAs are dependent not only on their chemical structures but also on the thermoresponsiveness

1,3,5-Triazine-Based Microporous Polymers with Tunable Porosities for CO₂ Capture and Fluorescent Sensing

The synthetic control over pore structure remains highly desirable for porous organic frameworks. Here, we present a competitive chemistry strategy, i.e., a systematical regulation on Friedel–Crafts reaction and Scholl coupling reaction through tuning the ratios of monomers. This leads to a series of spirobifluorene-based microporous polymers (Sbf-TMPs) with systematically tuned porosities and N content. Unlike the existing copolymerization strategy by which the synthesized polymers exhibit a monotonic change tendency in the porosities, our networks demonstrate an unusually different trend where the porosity increases first and then decreases with the increasing Ph/Cl ratios for the monomers. This is mainly ascribed to the completion of coexisting reaction routines and the different “internal molecular free volumes” of the repeating units. The as-made networks feature tunable capacities for CO₂ adsorption over a wide range and attractive CO₂/N₂ selectivities. Moreover, these donor–acceptor type frameworks exhibit selective and highly sensitive fluorescence-on or fluorescence-off properties toward volatile organic compounds, which implies their great potential in fluorescent sensors