The ring-opening polymerization (ROP) of lactones is an effective method for the preparation of biocompatible and biodegradable aliphatic polyesters, for which the development of efficient organocatalysts with high activity and good controllability is highly desirable. A series of novel pyridyl-urea catalysts has been synthesized and applied in the solvent-free ROP of lactones and trimethylene carbonate. Combined with 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD), the pyridyl-urea/MTBD systems showed a fast and living/controlled behavior in the ROP, generating polymers with narrow molecular weight distributions. The influences of catalyst structure, type of base, pyridyl-urea/base ratio, feed ratio of monomer/initiator and reaction temperature on the catalytic properties were investigated. A possible mechanism was proposed on the basis of NMR titration and dilution experiments.
The ring-opening copolymerization of ε-caprolactone and δ-valerolactone was carried out under solvent-free conditions with a pyridyl-urea ( 6C-PU )/7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene catalytic system by premixing two monomers, yielding gradient copolyesters with cyclic and linear structures in the absence or presence of an initiator, respectively. The random and block copolyesters of these two monomers were also prepared for comparison. The results of 1 H and 13 C NMR spectra determined the linear and cyclic structure of copolymers. The kinetic experiment was used to determine the consuming rates of two monomers during the polymerization. The topologies and thermal properties of all the copolymers were characterized and compared by NMR and DSC. Graphical Gradient copolymers with cyclic and linear topologies have been prepared via the ring-opening copolymerization of ε-caprolactone and δ-valerolactone in the absence or presence of BnOH catalyzed by a pyridyl-urea ( 6C-PU )/7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene system. The structure and thermal properties of copolymers with different composition or different sequential distribution were also investigated.
(Thio)urea/base systems have been widely used in the ring-opening polymerization (ROP) of lactones based on their superior performance in activity and selectivity. Herein, a pyridyl-urea ( 6C-PU )/7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene catalytic system is used to prepare the polyesters with cyclic topology via the ROP of lactones in the absence of initiator under solvent-free conditions. The catalytic system shows high activity in the ROP of δ-valerolactone (δ-VL) and cyclic polyvalerolactones (PVLs) with high molecular weights and narrow molecular weight distribution are obtained despite the existence of some linear products generated during the precipitation process. The structure of the resulting polymers is determined by proton and carbon nuclear magnetic resonance spectra, matrix assisted laser desorption/ionization time of flight mass spectrometry, and intrinsic viscosity studies. A possible mechanism is proposed on the basis of NMR analysis and characteristics of polymerization. Thermal and mechanical properties of cyclic PVLs are investigated through differential scanning calorimetry, thermogravimetric analysis, and tensile test.
It remains a challenge to design and prepare multifunctional low-cost adsorbents to dispose of diverse pollutants in wastewater. Herein, a series of bifunctional vermiculite-based adsorbents named DDPA-Vt as well as DDPU-Vt, are constructed via gemini surfactants containing pyridine-amide/pyridine-urea groups as modifiers. The morphology, physicochemistry and structure of organo-Vts are confirmed by multifarious probe methods thoroughly. The organo-Vts for the retention of anionic dye (Congo red (CR)) together with heavy metal (permanganate (MnO 4 - )) are investigated in single/mixed components in depth. More importantly, the maximum adsorption capacities are up to 504/822 mg/g for CR and 279/371 mg/g for MnO 4 - onto DDPA-Vt/DDPU-Vt, respectively. Pseudo-second-order kinetic model and Freundlich isotherm model could be depicted the adsorption processes . Competing anions have little effect on the adsorption of MnO 4 - , demonstrating that the organo-Vt could selectively removal MnO 4 - . Co-adsorption tests display that organo-Vt are still effective retention to CR and MnO 4 - , especially onto DDPU-Vt. The adsorption mechanism along with adsorptivity-structure relationship betwixt organo-Vt and pollutants are elucidated via characterization of the spent organo-Vts and DFT calculation : (i) π-π, NH-π, hydrophobic and electrostatic interactions are the mechanism for uptake of CR. (ii) Electrostatic interaction and coordination are the driving forces for retention of MnO 4 - . (iii) The diverse nitrogen-containing groups on the pyridine ring and the spacer have synergistic effects on CR and MnO 4 - retention. (iv) The greater preference of DDPU-Vt for pollutants is based on the stronger nitrogen atom-donating ability on the urea group. This work displays the potential of organo-Vt in the removal of multi-component sewage, and reclaims a prominent way for the simultaneous removal of anionic pollutants.
危险品化学品经营许可证（带存储）