Yumei Gong

A Novel Solid-Solid Phase Change Material Based on Poly(styrene-co-acrylonitrile) Grafting With Palmitic Acid Copolymers

(SAN-g-PA) as new solid-solid phase change materials (SSPCMs) were synthesized starting from poly(styrene-co- acrylonitrile) (SAN) and palmitic acid (PA). The chemical structure of the synthesized SAN-g-PA were characterized with Fourier transform infrared (FTIR), and Nuclear Magnetic Resonance (1H-NMR), their thermal energy storage properties and thermal stability were investigated with differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. Moreover, the crystalline morphology and crystal structures were also measured with polarized optical microscopy (POM) and X-Ray Diffraction (XRD). The result shows that the PA molecule was grafted onto the SAN, SAN-g-PA were obtained successfully. The crystalline morphology and crystal structures of the synthesized SAN-g-PA are different from palmitic acid and SAN. As novel SSPCMs, SAN-g-PA possess suitable phase transition temperature, the higher enthalpy value, and good heat stability.

Green preparation of hollow mesoporous silica nanosphere inside-loaded gold nanoparticles and the catalytic activity

ABSTRACT In this work, an active nano-catalyst with gold nanoparticles loaded in hollow mesoporous silica nanospheres (HMSNs/Au) was prepared by a one-pot sol-gel method, in which gold ions were loaded in hollow mesoporous silica spheres followed by sodium alginate reduction. The characterization of the HMSNs/Au were determined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), N2 adsorption–desorption isotherms (BET). The high catalytic activity of HMSNs/Au, denoted as apparent turn-over frequency (TOF), was detected by UV-Vis spectrophotometer for the catalytic reduction of 4-nitrophenol (74.5 h−1) and 2-nitrophenol (108.7 h−1) in the presence of sodium borohydride solution due to the small gold nanoparticles size and overall exposure of active sites. It is expected that this ecofriendly approach to prepare inorganic composited nanoparticles as high active catalysts based on hollow mesoporous materials was a promising platform for loading noble metal nanoparticles.

Preparation and characterization of pentaerythritol/butane tetracarboxylic acid/polyethylene glycol crosslinking copolymers as solid-solid phase change materials

ABSTRACT Pentaerythritol/butane tetracarboxylic acid/polyethylene glycol (PBPEG) crosslinking copolymers as a novel solid-solid phase change material (SSPCM) were successfully synthesized through the reaction mechanism and conditions of hydroxyl-carboxyl condensation reaction. The composition and chemical structure, crystalline properties, phase change behaviors, thermal reliability and chemical stability of PBPEG crosslinking copolymers were investigated by Fourier transform infrared spectroscopy (FT-IR), wide-angle X-ray diffraction (WAXD), polarization optical microscopy (POM), differential scanning calorimetry (DSC), and thermogravimetry (TGA), respectively. The results show that PBPEG crosslinking copolymers have typical solid-solid phase transition temperatures in the range of 10.31∼53.27°C and high latent heat enthalpy in the range of 89.6∼102.8 J/g, the synthesized SSPCMs have good thermal reliability and chemical stability after 300 thermal cycles, and PBPEG crosslinking copolymers have good thermal stability before 364°C. In summary, the synthesized PBPEG crosslinking copolymers could be potentially used for thermal energy storage.

Preparation and characterization of novel super-artificial hair fiber based on biomass materials

A novel super-artificial hair fiber basing on sodium alginate (SA) and Antarctic Krill protein (AKP) was prepared by wet spinning successfully. Such SA/AKP fiber did not only have similar crystalline structure with human hair, but also had super flame resistance and mechanical performance. It should be noted that the whole preparation process was green without any incorporation of non-toxic solution. Moreover, comparing with human hair, the SA/AKP fiber had a lot of unique groove upon the fiber surface, which contributed a lot to excellent hygroscopicity. Meanwhile, the dyeing performance could be improved notably due to incorporation of protein into the matrix. Herein, the SA/AKP fiber with superior mechanical and functional performance had practical value for application in the field of synthetic wig.

Engineering oriented hierarchical lamellar structures in SBS/PS blends via a pressure-induced flow field

Inorganic materials with a hierarchical lamellar architecture based on bio-inspired design principles found in seashell nacre and bone are expected to have high performance. Recently, great progress has been achieved in the fabrication of thin films, while incorporation of these supramolecular designs into synthetic polymer materials in the bulk still faces a great challenge. We demonstrate how a hierarchical layered micro- and nano-structure can be generated in the bulk from a variety of polymer blends such as polystyrene/poly(styrene–butadiene–styrene) (PS/SBS) as a model compound reported herein via a pressure-induced flow field technique. In this blend system, minority spherical rubbery SBS in these PS/SBS blends was biaxially deformed into lamellae having nanometer scale thickness within a rigid glassy PS phase as indicated by transmission electron microscopy and small angle X-ray scattering experimental results. Benefiting from such a hierarchical lamellar structure, the resulting strength, stiffness and toughness along the lamellar normal direction were simultaneously enhanced, while the modulus remained constant. The enhanced strength of the blend system resulted from the orientation of the macromolecules at and near the phase-separated boundaries of the lamellar domains within the PS matrix, as indicated by infrared spectroscopy results. The mechanism of this remarkably increased toughness was due to the fact that the crazes generated during impact experiments were efficiently terminated by the SBS lamellar domain. Such a biomimetic design for rubber-toughened glassy materials could also be easily transferred into other materials consisting of either blends of two immiscible polymers or semi-crystalline polymers through this efficient pressure-induced flow field technique.

Preparation and properties of P(AN-co-AM)-g-MAPEG phase-change nanofibers

In this study, a new graft copolymer, P(AN-co-AM)-g-MAPEG, was synthesized by polyethylene glycol monoester of maleic acid (MAPEG), acrylonitrile (AN), and a third monomer acrylamide (AM) in water phase precipitation, in which random copolymer of P(AN-co-AM) was taken as skeleton and macromonomer MAPEG with phase transition as branched chain. The P(AN-co-AM)-g-MAPEG nanofibers were prepared by electrostatic spinning. The effects of pinhole diameter, spinning solution concentration, and spinning liquid solvent on the structure of nanofibers were investigated by scanning electron microscopy. The structure, phase-change properties, and thermal stability of the grafted copolymer were characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, and X-ray diffraction. The results show that the new solid–solid phase-change material P(AN-co-AM)-g-MAPEG was successfully prepared. The nanofiber diameter increased with the increasing pinhole diameter. The obtained phase-change nanofibers exhibit good phase transition and thermal stability.

Preparation and properties of a thin membrane based on sodium alginate grafting acrylonitrile

Sodium alginate (SA) was modified for better water resistance with potassium persulfate (as the initiator) and acrylonitrile (as the monomer) via free radical graft copolymerization, and the corresponding sodium alginate-acrylonitrile graft copolymer film (SA-g-AN) was prepared. The modified SA film was characterized by measuring contact angle and water solubility and with DSC. The copolymerization mechanism and the microstructure of the graft copolymer were studied by FT-IR, 1H NMR, TEM and SEM. The correlated properties of the SA-g-AN film materials were measured with AFM, TG, XRD and DMA. The results indicated that the pyran ring of SA was open during the reaction, the morphology of the product exhibited a solid spherical cluster, and the density of the graft copolymer decreased as the content of acrylonitrile increased. The water resistance was improved after SA was modified by acrylonitrile. Both its crystallinity and thermal stability improved by introducing the acrylonitrile unit. The storage and loss modulus were in between those of SA and PAN. The SA-g-AN materials had a better film formation property and an excellent adsorbability towards heavy metal ions. These results have proven that this is a better development prospect on the field of sewage treatment.

Validation study on the theory of composites by using three-dimensional printing technology

Abstract RoM, as a reinforcement theory of composite materials, has been widely used. With the advent of new materials and molding processes, this theory is constantly being refined and validated. In this paper, four high-tech fibers as continuous reinforcing materials and carbon nanotubes as non-continuous reinforcing materials were evaluated, and two ideal composite samples were designed using three-dimensional printing technology. The reliability of RoM was verified by tensile testing. Also, a fiber tensile fixture was designed. The fiber bundle strength was inversely proportional to the length and the number of roots of fiber. In verifying the RoM, three-dimensional printing was employed, showing the diversity and complexity of the testing samples.

Properties of cellulose/Antarctic krill protein composite fibers prepared in different coagulation baths

In this paper, cellulose/Antarctic krill protein composite fibers were obtained by wet spinning. The raw materials were recyclable cellulose (C) and Antarctic krill protein (AKP), while the solvent was an aqueous solution containing 7wt% NaOH and 12wt% urea, which is eco-friendly. The fiber was stretched in a coagulation bath containing H2SO4 and Na2SO4. The effects of coagulation at different bath concentrations on the mechanical performance, crystallinity, and morphology of the C/AKP composite fibers were studied systematically. The break strength firstly increased and then decreased with an increase in the concentration of the bath. At a coagulation bath concentration of H2SO2/Na2SO4 (12wt%/12wt%), the crystallinity was 15.16%. Scanning electron microscopy (SEM) observations revealed the presence of grooves on the fiber surface. The type and percentage of hydrogen bonds in the C/AKP composite fibers were analyzed by Fourier transform infrared spectroscopy (FT-IR). On the basis of the obtained results, we finally optimized the coagulation bath composition and concentration.

Starch-graft-polyacrylonitrile nanofibers by electrospinning

Graft copolymer starch-graft-polyacrylonitrile (St-g-PAN) was synthesized by homo-grafting acrylonitrile (AN) from water soluble starch as Ce(IV) was used as an initiator. St-g-PAN nanofibers were prepared via electrospinning St-g-PAN solution in dimethyl sulfoxide (DMSO). The effects of the spinning parameters such as flow rate, spinning voltage, and collector distance on the St-g-PAN nanofiber diameter were investigated. Fourier transform infrared spectra (FT-IR), solid-state nuclear magnetic resonance (13C NMR) and scanning electron microscope (SEM) were used to characterize the structure and surface morphology of the nanofibers. The results showed that the nanofiber diameter depended strongly on the processing parameters. Moreover, the nanofiber had good water resistance, biocompatibility, and tensile intensity. As the cyano groups on St-g-PAN nanofibers were transformed to amidoxime groups, the obtained St-g-PAO nanofiber displayed an excellent adsorption ability, with the adsorption of Cr 533.4 mg·g-1 at pH = 2.0 as K2Cr2O7 solution 500 mg·L-1 in water was used as the adsorption target. Therefore, these St-g-PAN nanofibers may find potential applications in a wide variety of fields such as tissue engineering, pharmaceutics, energy, and environmental science and engineering.