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The synthesis and stimuli-responsiveness of a diphenyl cyclopropenone (DPCP)-centered poly(methyl acrylate) (PMA) are presented. DPCP-centered PMA could release carbon monoxide (CO) upon UV light in a switched on-and-off manner. The CO-releasing process can be reported by the variations in photoluminescence spectra. In addition, DPCP moiety covalently embedded in the crosslinked polyurethane could also release CO under UV light. Of special, DPCP-centered PMA in solution was selectively dissociated at the phenol ester bond under the ultrasound, and a force-induced hydrolyzation reaction was revealed by D2O exchanging 1H NMR spectra. The kinetic study reveals that small quantity of water could enhance the chain scission rate. This work provides a DPCP-centered polymer for site-specific CO-releasing and chain dissociation.

The fast and living ring-opening polymerization (ROP) of propylene oxide (PO) by metal-free catalysis is reported. By using triethyl borane (TEB) and organic Lewis bases (LBs, e.g.: phosphazene base, amidine and guanidine) as the catalysts, various alkyl alcohols can effectively initiate the ROP of PO, yielding tailor-made poly(propylene oxide)s (PPOs) with high regioregularity, predictable molecular weights, and narrow dispersity approaching Poisson distribution. The TEB/LB catalysts present unprecedentedly high activity (turnover frequency of up to 7500 h-1 ) and a truly living character for the polymerization, as evidenced by kinetic studies that showed fast initiation and growth, unobserved chain-transfer to PO, chain extension reactions, and the synthesis of various PPO-based block copolymers with narrow dispersities (Đ

Polyester synthesis from the alternating copolymerization of epoxides with cyclic anhydrides via a metal-free route remains a key challenge. This work reports the development of a highly active organocatalytic route for the copolymerization of a spectrum of epoxides and cyclic anhydrides. Fully alternating polyesters were synthesized by a variety of organic Lewis acid–base pairs including organoboranes and quaternary onium salts. The effect of the acidity, type, and size of Lewis pairs on the catalytic activity and selectivity of the copolymerization is presented. The undesirable transesterification and etherification were effectively suppressed even in the case of complete conversion of the cyclic anhydride. This could be ascribed to the formation of a unique tetracoordinate bond-carboxylate (or alkoxide) anion. The Lewis pairs are highly active, with a turnover frequency of 102 and 303 h–1 for the copolymerization of propylene oxide with maleic anhydride and phthalic anhydride, respectively, at 80 °C. B...

White light-emitting diodes (LEDs) are very important energy-saving lighting devices. It is still a big challenge to fabricate pure white LEDs using low-cost, easy-to-process and environment-friendly phosphors. Herein, we report a pure white LED fabricated by combining rationally designed fluorescein-centered polymers with a blue LED chip. Pure white LEDs with Commission International de L’Eclairage (CIE) coordinates of (0.33, 0.33), a satisfactory color rendering index (CRI) of 82 and a correlated color temperature (CCT) of 5230 K were achieved. Covalently embedding fluorescein into the center of the polymer chain realized molecular dispersion of fluorescein. Of significance, by varying the types of the side groups of the polymer, the fluorescence properties of the embedded fluorescein unit can be regulated. The performance parameters (i.e., emission spectra, CIE coordinates, CRI and CCT) of the as-fabricated LEDs could also be tailored by varying the working voltages, and the types and amounts of fluorescein-centered polymers.

Small quantities of regio-defects in a regio-/stereoregular polymer weaken its tacticity and properties. This work clarified the origin of the regio-defect in the process of synthesizing poly(monothiocarbonate) through the copolymerization of propylene oxide (PO) and carbonyl sulfide (COS) catalyzed by a (salen)CrCl complex accompanied by bis(triphenylphosphoranylidene)ammonium chloride ([PPN]Cl). Quantitative characterization results from the MALDI-TOF-MS and 1H (13C) NMR spectroscopy suggested that the chain transfer reaction resulted in the regio-defect in the final copolymer, i.e., tail-to-tail (T–T) diad and dithiocarbonate (DTC) unit. The chain transferring to water in the reaction system led to the production of a (salen)Cr–OH intermediate, which initiated the copolymerization via either attacking PO first to result in formation of a T–T diad or first activating COS to produce mercapto (−SH) end-capped dormant chains via decarboxylation, thus generating a DTC unit in the final product through anoth...

It is a challenging topic to disconnect a linear polymer selectively at the mechanophore site by an external force in a “cold” fashion. In this work, the effect of the power output of ultrasonication on the selective cleavage at the centered urfuryl-maleimide Diels–Alder (DA) mechanophore of poly(methyl acrylate)s (DA-PMA-a and DA-PMA-b) were quantitatively investigated by comparative study on experimental and simulated chain scission kinetics as well as high-resolution 1H NMR spectroscopy (600 MHz). At low power output of the ultrasonication (2.10 W), DA-PMA-a with Mn of ca. 2Mlim (Mlim, below which no further chain scission was observed) presented a DI (degradation index)−t (sonication time) plot with a turnover point at ca. 1.0 and no clear variation of the molecular weight after the turnover, which met well with the calculated center cleavage mode. At 5.52 W, DA-PMA-a and a poly(methyl acrylate) that contained two centered ester bonds (ester-PMA) presented similar DI–t plots with turnover points less ...