Linyong Song

A novel approach to raspberry-like particles for superhydrophobic materials

A new strategy was developed to prepare raspberry-like particles by introducing poly(acrylic acid) (PAA)-functionalized polystyrene (PS) particles into hydrolysis reaction of tetraethoxysilane (TEOS). The monodisperse PAA-functionalized PS particles were used as cores and nanosized silica particles were then assembled on the surface of PS particles to construct raspberry-like particles during the hydrolysis process. With the increase of PAA content from 11% to 20% (wt) at the surface of latexes, the diameter of the silica particles assembled at the surface of cores decreased from 124 nm to 36 nm. The structure, morphology and constitution of the PAA-functionalized PS particles and the raspberry-like particles were characterized by Fourier transform infrared spectroscopy (FT-IR), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). In addition, the particulate films were constructed by assembling these raspberry-like particles on glass substrates. After surface modification with dodecyltrichlorosilane, superhydrophobic surfaces can be obtained and the contact angle of water on the dual-sized structured surface can be adjusted by the scale ratio of the micro/nano surface structure of raspberry-like particles.

Fabrication of hydrogel of hydroxypropyl cellulose (HPC) composited with graphene oxide and its application for methylene blue removal

Novel environmental friendly hydroxypropyl cellulose (HPC) hydrogels were fabricated upon compositing with graphene oxide (GO) in this work. In order to promote a more homogeneous dispersion of GO sheets in HPC, GO was firstly modified with HPC chains through esterification. The morphology and chemical structure of the functionalized HPC-GO were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectrometer, X-ray diffraction, and thermo-gravimetric analysis. Then scanning electronic microscope was employed to compare the morphologies of the HPC and HPC-GO/HPC hydrogels. The obtained HPC-GO/HPC hydrogels exhibited excellent adsorption performance toward methylene blue. Simulation of the practical use by preparing simple adsorption columns made from in situ formation of HPC-based hydrogels had given a visible observation of the significant adsorption effect brought by the incorporation of HPC-GO sheets. Adsorption kinetics were then imitated by Lagergren pseudo-first-order and pseudo-second-order models. Adsorption isotherms were imitated by Langmuir isotherm and Freundlich isotherm.

Synthesis and evaluation of novel dental monomer with branched carboxyl acid group

To enhance the water miscibility and increase the mechanical properties of dentin adhesives, a new glycerol-based monomer with vinyl and carboxylic acid, 4-((1,3-bis(methacryloyloxy)propan-2-yl)oxy)-2-methylene-4-oxobutanoic acid (BMPMOB), was synthesized and characterized. Dentin adhesive formulations containing 2-hydroxyethyl methacrylate (HEMA), 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy) phenyl]propane (BisGMA), and BMPMOB were characterized with regard to real-time photopolymerization behavior, water sorption, dynamic mechanical analysis, and microscale three-dimensional internal morphologies and compared with HEMA/BisGMA controls. The experimental adhesive copolymers showed higher glass transition temperature and rubbery moduli, as well as improved water miscibility compared to the controls. The enhanced properties of the adhesive copolymers indicated that BMPMOB is a promising comonomer for dental restorative materials.

CuS/MoS2 nanocomposite with high solar photocatalytic activity

Two-dimensional CuS/MoS2 heterostructure with high photocatalytic activity had been successfully obtained by a simple combination of wet chemical method and hydrothermal process. CuS nanosheets had been successfully grown on the two-dimensional MoS2 nanosheets uniformly and tightly. The obtained heterostructures were well characterized through X-ray diffraction patterns, transmission electron microscopy, Fourier transform infrared spectra, ultraviolet–visible diffuse-reflectance spectra, and Zeta potential measurement. Photocatalytic performance of the CuS/MoS2 nanocomposite was evaluated toward the decomposition of methylene blue solution under natural light. The as-prepared nanocomposite showed remarkably enhanced photocatalytic activity compared with pure CuS and MoS2. This could be attributed to the enhanced dyestuff absorption and charge transport after the conjugation between CuS and MoS2.

Visible-Light Initiated Free-Radical/Cationic Ring-Opening Hybrid Photopolymerization of Methacrylate/Epoxy: Polymerization Kinetics, Crosslinking Structure, and Dynamic Mechanical Properties

The effects of polymerization kinetics and chemical miscibility on the crosslinking structure and mechanical properties of polymers cured by visible-light initiated free-radical/cationic ring-opening hybrid photopolymerization are determined. A three-component initiator system is used and the monomer system contains methacrylates and epoxides. The photopolymerization kinetics is monitored in situ by Fourier transform infrared-attenuated total reflectance. The crosslinking structure is studied by modulated differential scanning calorimetry and dynamic mechanical analysis. X-ray microcomputed tomography is used to evaluate microphase separation. The mechanical properties of polymers formed by hybrid formed by free-radical polymerization. These investigations mark the first time that the benefits of the chain transfer reaction between epoxy and hydroxyl groups of methacrylate, on the crosslinking network and microphase separation during hybrid visible-light initiated photopolymerization, have been determined.

Synthesis and evaluation of novel siloxane-methacrylate monomers used as dentin adhesives.

OBJECTIVES The objectives of this study were to synthesize two new siloxane-methacrylate (SM) monomers for application in dentin adhesives and to investigate the influence of different functionality of the siloxane-containing monomers on the adhesive photopolymerization, water sorption, and mechanical properties. METHODS Two siloxane-methacrylate monomers (SM1 and SM2) with four and eight methacrylate groups were synthesized. Dentin adhesives containing BisGMA, HEMA and the siloxane-methacrylate monomers were photo-polymerized. The experimental adhesives were compared with the control adhesive (HEMA/BisGMA, 45/55, w/w) and characterized with regard to degree of conversion (DC), water miscibility of the liquid resin, water sorption and dynamic mechanical analysis (DMA). RESULTS The experimental adhesives exhibited improved water miscibility as compared to the control. When cured in the presence of 12 wt% water to simulate the wet environment of the mouth, the SM-containing adhesives showed DC comparable to the control. The experimental adhesives showed higher rubbery modulus than the control under dry conditions. Under wet conditions, the mechanical properties of the formulations containing SM monomer with increased functionality were comparable with the control, even with more water sorption. SIGNIFICANCE The concentration and functionality of the newly synthesized siloxane-methacrylate monomers affected the water miscibility, water sorption and mechanical properties of the adhesives. The experimental adhesives show improved water compatibility compared with the control. The mechanical properties were enhanced with an increase of the functionality of the siloxane-containing monomers. The results provide critical structure/property relationships and important information for future development of durable, versatile siloxane-containing dentin adhesives.

Weak acid–base interaction induced assembly for the formation of rambutan-like poly(styrene-alt-maleic anhydride)/silica composite microspheres

To investigate the effect of surface functionality on the morphology of polymer/silica composite, poly(styrene-alt-maleic anhydride) (SMA) spheres prepared via precipitation polymerization method was employed. In water/ethanol solution, diethanolamine (DEA) was used to catalyze the hydrolysis reaction of tetraethoxysilane (TEOS), and rambutan-like poly(styrene-alt-maleic anhydride)/silica (SMA/SiO2) microspheres were synthesized through in situ sol–gel process. The obtained structure and morphology were characterized by FTIR, NMR, TEM, SEM, and TGA. The results showed that the hydrolyzed SMA chains on the surface was crucial to the nucleation and growth of silica, and the morphologies of SMA/SiO2 composite microspheres can be controlled by the amount of DEA and the ratio of SMA/TEOS. In addition, the SMA/SiO2 microspheres were used to prepare hierarchical structure of SMA/SiO2/Ag particles, which were utilized for the construction of surface-enhanced Raman scattering substrate (SERS).

Tris(trimethylsilyl)silane as a co-initiator for dental adhesive: Photo-polymerization kinetics and dynamic mechanical property

OBJECTIVES The purpose of this study was to evaluate the polymerization behavior of a model dentin adhesive with tris(trimethylsilyl)silane (TTMSS) as a co-initiator, and to investigate the polymerization kinetics and mechanical properties of copolymers in dry and wet conditions. METHODS A co-monomer mixture based on HEMA/BisGMA (45/55, w/w) was used as a model dentin adhesive. The photoinitiator system included camphorquinone (CQ) as the photosensitizer and the co-initiator was ethyl-4-(dimethylamino) benzoate (EDMAB) or TTMSS. Iodonium salt, diphenyliodonium hexafluorophosphate (DPIHP) serving as a catalyst, was selectively added into the adhesive formulations. The control and the experimental formulations were characterized with regard to the degree of conversion (DC) and dynamic mechanical properties under dry and wet conditions. RESULTS In two-component photoinitiator system (CQ/TTMSS), with an increase of TTMSS concentration, the polymerization rate and DC of CC double bond increased, and showed a dependence on the irradiation time and curing light intensity. The copolymers that contained the three-component photoinitiator system (CQ/TTMSS/DPIHP) showed similar dynamic mechanical properties, under both dry and wet conditions, to the EDMAB-containing system. SIGNIFICANCE The DC of formulations using TTMSS as co-initiator showed a strong dependence on irradiation time. With the addition of TTMSS, the maximum polymerization rate can be adjusted and the network structure became more homogenous. The results indicated that the TTMSS could be used as a substitute for amine-type co-initiator in visible-light induced free radical polymerization of methacrylate-based dentin adhesives.

Probing the dual function of a novel tertiary amine compound in dentin adhesive formulations

OBJECTIVES A novel tertiary amine compound containing three methacrylate-urethane groups was synthesized for application in dentin adhesives. The synthesis, photopolymerization kinetics, and leaching were examined in an earlier study using this novel compound as the co-initiator (0.5 and 1.75wt% based on the total resin mass). The objective of this work was to investigate the potential of TUMA (8-(2-(((2-(methacryloyloxy)ethyl)carbamoyl)oxy)propyl)-6,10-dimethyl-4,12-dioxo-5,11-dioxa-3,8,13-triazapentadecane-1,15-diyl bis(2-methylacrylate)) to serve simultaneously as a co-initiator and co-monomer (15-45wt% based on the total resin mass) in dentin adhesive formulations. The polymerization kinetics, water sorption and dynamic mechanical properties of these novel formulations were determined. MATERIALS AND METHOD The monomer system contained Bisphenol A glycerolate dimethacrylate (BisGMA), 2-hydroxyethylmethacrylate (HEMA) and TUMA (synthesized in our lab) at the mass ratio of 45/(55-x)/x. Two photoinitiator (PI) systems were compared. One initiator system contains three components: camphorquinone (CQ), diphenyliodonium hexafluorophosphate (DPIHP) and ethyl-4-(dimethylamino) benzoate (EDMAB) and the second initiator system contains CQ and DPIHP. The control adhesive formulations are: C0-3: HEMA/BisGMA 45/55 (w/w) and 3-component PI and C0-2: HEMA/BisGMA 45/55 (w/w) and 2-component PI. These controls were used as a comparison to the experimental adhesive resins (Ex-3 or Ex-2), in which x represents the weight percentage of synthesized co-monomer (TUMA) to replace part of BisGMA. The control and experimental adhesive formulations were photo-polymerized and compared with regard to the degree of conversion (DC), polymerization rate (Rp), water sorption and dynamic mechanical analysis (DMA) under both dry and wet conditions. RESULTS C0-3 and Ex-3 formulations had similar DC, while the DC of Ex-2 formulation was higher than C0-2. The DC was similar when comparing the two- component with the three-component photoinitiator system when TUMA was used at the same concentration. DMA under dry conditions shows higher rubbery storage modulus for all experimental formulations, while storage modulus at rubbery region under wet conditions was decreased as compared with control (C0-3). There was no statistically significant difference for the DMA results under both dry and wet conditions when comparing two- and three-component initiator systems with the same TUMA concentration. SIGNIFICANCE The newly synthesized TUMA could serve simultaneously as a co-monomer and co-initiator in the absence of commercial co-initiator. This study provides information for the future development of new co-monomer/co-initiator for dentin adhesives and dental composites.

Incorporation of disodium alkyl polyoxyethylene ether sulfosuccinate inside styrene droplets: mechanism and its application for preparation of multihollow polymer spheres.

Emulsion polymerization of styrene was carried out using two kinds of alkyl polyoxyethylene ether sulfosuccinates as surfactant: disodium cetyl polyoxyethylene (25) ether sulfosuccinate (CPS) and octyl-phenol polyoxyethylene (10) ether sulfosuccinate (OPS). In experiments, the incorporation of CPS or OPS inside styrene droplets and polystyrene particles was clearly observed. Based on this phenomenon, multihollow polymer spheres are prepared in a one-step reaction and this strongly supports the proposed incorporation mechanism. CPS is more effective than OPS during the preparation of multiporous spheres. This difference between the two surfactants mainly contributes to the difference of the length of the EO (polyoxyethylene) group, which can determine the affinity among surfactant, styrene, and water molecules.