Jinbao Xu

One-step synthesis of hyperbranched biodegradable polymer

Hyperbranched poly(e-caprolactone) (h-PCL) is synthesized via hybrid copolymerization of e-caprolactone (CL) with glycidyl methacrylate (GMA) as the branching agent and (1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)phophoranylidenamino]-2Λ5,Λ5-catenadi(phosphazene) (t-BuP4) as the catalyst in one step. Proton nuclear magnetic resonance (1H NMR) and Fourier transform infrared (FTIR) spectroscopy show that the polymerization regarding the double bonds and ring-opening take place simultaneously. Size exclusion chromatography measurements with light scattering and viscosity detection indicate that the resultant polymer has a hyperbranched structure.

Metal-free controlled ring-opening polymerization of ε-caprolactone in bulk using tris(pentafluorophenyl)borane as a catalyst

Narrowly distributed poly(e-caprolactone) (PCL) was synthesized by the ring-opening polymerization (ROP) of e-caprolactone (CL) using tris(pentafluorophenyl)borane (B(C6F5)3) as an acidic catalyst and benzyl alcohol (BnOH) as the initiator in bulk at 80 °C. The use of functional initiators such as 2-hydroxyethyl methacrylate (HEMA), propargyl alcohol (PGA), 6-azido-1-hexanol (AHA) and methoxy poly(ethylene glycol) (mPEG) leads to end-functionalized PCLs. 1H NMR, SEC and MALDI-TOF MS measurements clearly indicate the presence of an initiator residue at the chain end of the obtained PCL homopolymers. The study on polymerization kinetics confirms the controlled/living nature of the B(C6F5)3-catalyzed ROP of CL. Accordingly, the block copolymerization of CL with δ-valerolactone (VL) and trimethylene carbonate (TMC) successfully proceeded to give PCL-b-PVL and PCL-b-PTMC copolymers. Macrocyclic PCL was also prepared by the intramolecular click reaction of the heterotelechelic α-azido,ω-ethynyl-PCL.

Hybrid copolymerization of cyclic and vinyl monomers

In this work, we report the hybrid copolymerization of various cyclic monomers and vinyl monomers. Our studies demonstrate that 1-tert-butyl-4,4,4-tris-(dimethylamino)-2,2-bis[tris(dimethylamino) phophoranyliden-amino]-2Λ5,Λ5-catenadi(phosphazene) (t-BuP4) can catalyze the hybrid copolymerization of caprolactone (CL), lactide (LA) or cyclic carbonate ester with acrylate or methyl acrylate. However, the polymerization of cyclosiloxane with vinyl monomers yields two corresponding homopolymers, and the polymerization of lactone with acrylonitrile (AN) produces only polyacrylonitrile. Clearly, the extent of matching of activity between a monomer and an active center determines whether or not there is hybrid copolymerization.

Ethylene ethyl phosphate as a multifunctional electrolyte additive for lithium-ion batteries

The effects of ethylene ethyl phosphate (EEP) as a multifunctional electrolyte additive on safety characteristics and electrochemical performance of lithium-ion batteries are investigated. Based on the flammability test, the self-extinguishing time of the electrolyte with 10% EEP is only less than half of the baseline electrolyte, which indicates that EEP is a highly efficient flame retardant for the electrolyte. During overcharging the LiNi1/3Co1/3Mn1/3O2/Li cells, incorporation of EEP into the electrolyte can postpone the sharp voltage rise. Therefore, EEP is an improver of safety characteristics of lithium-ion batteries, both in terms of flame resistance and overcharge protection. Furthermore, the EEP-containing electrolyte in the half-cells and full-cells both exhibit higher initial coulombic efficiency and cycling stability than the baseline electrolyte. It is concluded that EEP is a good film-formation additive not only for the graphite anode, but also for the LiNi1/3Co1/3Mn1/3O2 cathode. Therefore, EEP is proposed as a promising multifunctional electrolyte additive for lithium-ion batteries.

One-pot synthesis of poly(L-lactide)-b-poly(methyl methacrylate) block copolymers

By using 1,8-diazabicyclo-[5.4.0]undec-7-ene (DBU) as both the atom transfer radical polymerization (ATRP) ligand and ring-opening polymerization (ROP) catalyst, we have combined copper-catalyzed ATRP and organo-catalyzed ROP in one-pot, and successfully synthesized poly(L-lactide)-b-poly(methyl methacrylate) (PLA-b-PMMA) diblock copolymers. The structure of the block copolymers is confirmed by nuclear magnetic resonance (NMR), size exclusion chromatography (SEC) and differential scanning calorimetry (DSC).