Huagao Fang

Constructing pendent imidazolium-based poly(phenylene oxide)s for anion exchange membranes using a click reaction

A series of poly(phenylene oxide)s (PPOs) bearing a flexible pendent imidazolium cation were prepared by an azide–alkyne cycloaddition between azidomethylated PPO and a novel alkyne-containing imidazolium, and their structures were confirmed by 1H NMR, 13C NMR, and FT-IR. The corresponding anion exchange membranes (AEMs) showed distinct hydrophobic/hydrophilic phase-separated morphology at higher imidazolium content, as evidenced by AFM and SAXS techniques, which favors for the construction of interconnected hydroxide transport channels. As a result, the as-prepared AEMs exhibited higher conductivity (95 mS cm−1, 80 °C, 100% RH) than conventional imidazolium benzylic-type AEM (55 mS cm−1, 80 °C, 100% RH) with even lower IEC. Furthermore, the introduction of a 1,2,3-triazole moiety into the polymer side chain does not compromise its thermal and alkaline stability. This investigation demonstrated that the “click chemistry” strategy will benefit further tailoring of high performance AEMs with “side-chain-type” architectures.

A well-defined biodegradable 1,2,3-triazolium-functionalized PEG- b -PCL block copolymer: facile synthesis and its compatibilization for PLA/PCL blends

A novel biodegradable 1,2,3-triazolium-functionalized PEG-b-PCL copolymer (TAPEC) was synthesized by the “click” coupling of methoxypolyethylene glycol azide and α-propargyl-ω-hydroxyl-poly(ε-caprolactone), followed by the quaternization of the 1,2,3-triazole moiety with iodomethane. All the intermediates and TAPEC were characterized by 1H NMR, FT-IR, and gel permeation chromatography (GPC). Taking advantage of the characteristics of ionic liquid and block copolymer, this ion-containing diblock copolymer is expected to be used as a novel compatibilizer in mixed biopolyester for regulating the interface and crystallization behaviors. Hence, the TAPEC was evaluated as a compatibilizer and an interface emulsifier in the blends of polylactic acid (PLA) and poly(ε-caprolactone) (PCL). Non-isothermal crystallization experimental results showed that the TAPEC with the higher amount of ε-caprolactone units induces a plasticization and nucleate effect that increased the crystallization ability of the PLA phase; meanwhile, in the PCL phase, the agminated ionic cluster acting as a nucleating agent significantly increased the crystalline of PCL.

Waterborne epoxy-modified polyurethane-acrylate dispersions with nano-sized core-shell structure particles: synthesis, characterization, and their coating film properties

Abstract Waterborne epoxy-modified polyurethane-acrylate (EPUA) dispersions with nano-sized core-shell structure particles, with polyacrylate (PA) as core and epoxy-modified polyurethane (EPU) as shell, were successfully prepared via a two-step procedure. The waterborne EPU dispersions were first synthesized to serve as seeds, and then the butyl acrylate (BA) and methyl methacrylate (MMA) monomers were introduced into EPU particles to form polymeric core by radical polymerization under the assistance of ultrasonic treatment. Fourier transform infrared (FT-IR) spectroscopy revealed that the epoxy and PA components were successfully incorporated onto the chain of the PU and EPU to form EPU and EPUA, respectively. The transmission electron microscopy (TEM) photograph demonstrated that the EPUA particles have the core-shell structure. The as-prepared EPUA coating films exhibited good thermo-stability and mechanical properties, as revealed by thermogravimetric analysis (TGA) and tensile testing, respectively. The results of potentiodynamic polarization curves and immersion corrosion testing in 5 wt% NaCl aqueous solution both demonstrated that the anticorrosive properties of EPUA mainly depended on the mass content of PA, with the optimized value of 30 wt%.

Tailoring elastomeric properties of waterborne polyurethane by incorporation of polymethyl methacrylate with nanostructural heterogeneity

Although modification of waterborne polyurethane (WPU) using acrylic polymer (PA) is a widespread approach to prepare PU materials with high performance, not much attention has been paid to the variation of elastomeric property of the obtained WPUA hybrid materials with the presence of PA component. In this work, a series of aliphatic polycarbonate (PCDL) based waterborne polyurethane and polymethyl methacrylate (PMMA) hybrid dispersions (WPUA) were fabricated via a two-step procedure. The heterogeneous structure of hybrid dispersions was investigated, showing that the dispersed particles possess a nano-sized core–shell morphology. The hydrogen-bond interactions in hard domains are weakened by incorporation of PMMA component. The nanostructural heterogeneity in the dried films was determined by using MDSC, AFM, SAXS, DMA and linear rheology techniques. The tensile strength and strain-hardening modulus increase and the elongation at break decreases with increasing PMMA content. Plastic deformation of PMMA domains in WPUA only results in a loss in recoverable elasticity at low strains. With an optimized content of PMMA, the WPUA2 sample shows sharp yielding behavior while maintaining high extensibility and good recoverable elasticity at large strains. The improvement in elastomeric properties and other physical properties by incorporating PMMA component can expand the applications of waterborne PUs as environment-friendly thermoplastic elastomers.

Thermal stability and crystallization behavior of cellulose nanocrystals and their poly(l-lactide) nanocomposites: effects of surface ionic group and poly(d-lactide) grafting

Construction of stereocomplexation on the interface of cellulose nanocrystal (CNC) and poly(l-lactide) (PLLA) has been proven to be an efficient way to strengthen interfacial interaction of the nanocomposite. However, the surface structure variation of CNC with different types of ionic group after grafting of poly(d-lactide) (PDLA) and its influence on the properties of their PLLA nanocomposites are still unrevealed. In this current work, the sulfonated CNC (SCNC) and phosphorylated CNC (PCNC) are prepared and grafted with PDLA by surface-initiated ring-opening polymerization. The removal of ionic groups is observed on the surface of SCNC and PCNC after modification, but it has an opposite effect on the thermal stability of the grafted CNC particles. The thermal stability of SCNC-g increases compared with SCNC while PCNC-g decreases compared with PCNC. Consequently, the large difference in thermal stability of the pristine CNCs disappears after grafting and PCNC-g only shows slightly higher thermal stability than SCNC-g. Although the average PDLA grafting content is similar, the number and length of grafted chains are different on SCNC-g and PCNC-g. The grafted chain length on SCNC-g is 4 times as large as that on PCNC-g, which facilitates the formation of interfacial stereocomplex (SC) crystallites in the SCNC-g/PLLA nanocomposites. The SC crystallites improve the thermal stability of the nanocomposites and accelerate the matrix crystallization kinetics. PCNC-g/PLLA samples contrarily show earlier decomposition and lower crystallinity due to the absence of SC crystallites. This study could provide some insights into the effects of ionic groups in the surface grafting process of CNC and the influences on interfacial structure and property of the PLLA nanocomposite.Graphical abstract