Synthesis and characteristics of pectiniform polyurethane‐modified polycarboxylate at room temperature

In this article, modified polyurethane prepolymer was synthesized by segmental synthesis method using isophorone diisocyanate, hydroxyl‐terminated silicone, polyether glycol dimethylolpropionic acid as raw materials. After that, pectiniform polycarboxylate, of which side chains were in roughly the same polymerization degree and main chains were in different lengths, was synthesized at room temperature in initiation system of hydrogen peroxide, ascorbic acid, and persulfate. Moreover, influence of various factors on the synthesis of polyurethane‐modified polycarboxylate at room temperature was discussed in detail and optimal synthesis process was determined. Results showed that redox initiation system, increasing initiator and monomer concentration, and extending reaction time needed to be adopted to complete the reaction. However, when the reaction time was over 4 h, water reducing of polycarboxylate declined rapidly. In addition, it could be found in Fourier transform infrared spectrum analysis that the ? C?C? double bonds in acrylic acid were opened and polymerized, macromolecular chain segments were successfully connected to polyoxyethylene chain segment, and resulting polycarboxylic acid molecule contained hydroxy, carboxyl, methyl, ester group, and other groups. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45873.     

A continuous method to prepare porous polystyrene membranes with high adsorption ability for polycyclic aromatic hydrocarbons

A convenient and continuous method to prepare porous polystyrene (PS) membranes via a microlayer coextrusion and template method is proposed. The porous PS membranes can be obtained via the acid etching of a CaCO₃ template embedded in the membranes. Scanning electron microscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy of the porous PS membranes show that most of the CaCO₃ particles can be etched away. The effects of etching time, CaCO₃ content, and membrane thickness on the porous structures are investigated, which can be used to regulate and control the porous structure. To demonstrate the adsorption performance of porous PS membranes on polycyclic aromatic hydrocarbons, pyrene is used as the model compound. Compared with that of solid PS membranes, porous PS membranes exhibit much higher adsorption performance for trace pyrene. The adsorption kinetics and isotherm of porous PS membranes can be well fit by pseudo‐second‐order kinetics and a Freundlich isotherm model. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45917.     

A comprehensive investigation of dye–chitosan blended films for green chemistry applications

In this paper, the ability of chitosan film to remove dyestuff from wastewater was evaluated for environmental applications, using three commercial direct azo dyes. Two chitosan films were adopted: the standard one prepared following a well‐known procedure to form it, and a novel one, with a weakly acidic character. Moreover, to improve the adsorption process, the hydrophobic character of the films was investigated. The pH of the dye solutions was also changed, showing an excellent ability in dye removal at pH 12. The films were characterized by means of spectroscopic and morphologic methods to better understand the nature of interactions between dyes and chitosan chains. Swelling ratio measurements were also performed. All analyses suggest that all dyes showed a strong affinity to chitosan polymer chains, with the presence of extended hydrogen bonds and Van der Waals forces perturbing the chitosan network. Interestingly, very good results were obtained in recycling experiments related to the dyeing capacities of chitosan blended films in the presence of textiles. An ecofriendly application is thus presented in this paper. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45945.     

Correlation between gas transport properties and the morphology/dynamics of crystalline fluorinated copolymer membranes

The crystalline structure, dynamics, and gas transport properties (i.e., the gas permeability, gas diffusion coefficient, and gas solubility coefficient) of poly(tetrafluoroethylene‐co‐perfluoroethylvinylether) (PFA) membranes were systematically investigated via differential scanning calorimetry, wide/small/ultra‐small‐angle X‐ray scattering, and quasielastic neutron scattering measurements. We evaluated the gas transport properties using a constant‐volume/variable‐pressure method. The gas permeability and the gas diffusion coefficient decreased with increasing crystallinity of the PFA membranes at crystallinities below 32%. However, in membranes with a crystallinity of 32% or greater, these parameters depended on the characteristics of the gas molecules, such as their kinetic diameter. The so‐called long spacing period and the thickness of the crystalline/amorphous regions increased with crystallinity according to the small/ultra‐small‐angle X‐ray scattering results. Furthermore, the quasielastic neutron scattering measurements indicated that the scattering law was well fitted to a sum of narrow and broad Lorentzian components. In particular, the narrow components, that is, the local motion of amorphous components and side chains, increased with crystallinity. These results suggest that large gas molecules could pass through the PFA membranes, assisted by the motion in the amorphous region. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45665.     

Highly effective organometallic‐mediated radical polymerization of vinyl acetate using alumina‐supported Co(acac)2 catalyst: A case study of adsorption and polymerization

An alumina support system for cobalt^(II) acetylacetonate (Co(acac)₂) catalyst was studied for the cobalt‐mediated radical polymerization (CMRP) of vinyl acetate (VAc). We report a simple but efficient technique to produce this supported catalysts through the adsorption of Co(acac)₂ on the surface of alumina particles. Moreover, kinetic and thermodynamic study of Co(acac)₂ adsorption on the alumina support were conducted and the influence of effective parameters were investigated. It was found that using alumina‐supported Co(acac)₂ for radical polymerization of VAc yields polymers with controlled molecular weight, narrow molecular weight distribution, and high purity. For the alumina‐supported CMRP, changing the polymerization mechanism and domination of termination pathway compared to degenerate transfer pathway resulted in a 2.5 times increase in polymerization rate (k_ap) and a drop in induction time while maintaining a good control of the VAc polymerization. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46057.     

Tris(hydroxymethyl)aminomethane polyamide thin‐film‐composite antifouling reverse osmosis membrane

For the applications of reverse osmosis (RO) process, membrane fouling caused by organic molecule adsorption is still a serious problem which significantly decreases membrane lifespan and increases operation costs. In this present article, we report the thin film composite (TFC) RO membrane functionalized with tris(hydroxymethyl)aminomethane (THAM) using one‐step method for improved antifouling property. The results of surface characterization indicated that THAM was successfully grafted onto the active layer of membrane by covalent linkage. Mult‐hydroxyl‐layer was generated and remained steadily on TFC membrane surface after modification. The contact angle decreased from 75.9 ± 3.0° to 46.9 ± 2.3°, which showed a distinct improvement of membrane surface hydrophilicity after modification. The grafted THAM improved water flux by 28.3%, while salt rejection was almost unchanged in membrane property tests. The modified membranes presented preferable antifouling property to foulants of bovine serum albumin, sodium alginate, and dodecyl trimethyl ammonium bromide than that of pristine membranes during dynamic fouling experiments. The method in this study provided an effective way to improve antifouling property of the polyamide thin‐film‐composite RO membrane. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45891.     

Fabrication of ceramic nanofibers using polydimethylsiloxane and polyacrylonitrile polymer blends

Nanofibers with several hundred of nanometers were successfully fabricated using electrospinning process and a mixture of two types of polymers which are: polydimethylsiloxane and polyacrylonitrile as precursors. After stabilization and carbonization at 1000 °C, three phases which are: silicon carbide (SiC), carbon, and oxy‐SiC were presented. Spectroscopic and microscopic techniques had confirmed the presence of nanocrystalline SiC and turbostratic carbons. These phases formed an intertwined network at the nanometric scale. In addition, the resulted fibers showed a core‐skin effect with skin richer in carbon and a core mainly dominated by silicon‐based phases in the form SiC or Si? O? C ceramics. A significant improvement was observed in both tensile strength and elastic modulus in these hybrid fibers. In term of crystallography, these nanofibers seem to exhibit similar microstructure that was observed in Nicalon fiber. However, it was difficult to determine the ratio of these phases and their influence on the physical properties of these hybrid fibers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45967.     

Effects of aging on poly(1‐trimethylsilyl‐1‐propyne) membranes irradiated with vacuum ultraviolet radiation for gas separation

In this study, we investigated the effects of physical aging on the surface and gas‐transport properties of highly gas permeable poly(1‐trimethylsilyl‐1‐propyne) membranes irradiated with vacuum ultraviolet (VUV) radiation. VUV excimer lamp irradiation was performed on one side of the membrane for 6 or 60 min. The gas permeabilities for carbon dioxide (CO₂) and nitrogen (N₂) were determined through a volumetric measurement method at 23 °C. The gas permeabilities for CO₂ and N₂ increased temporarily at 7 days after 6 and 60 min of VUV irradiation of the membranes. The change in the gas permeability for N₂ was more remarkable than that for CO₂. These changes were related to the C?O or SiO_x ratio. The C?O ratio was related to the gas permeability of the membranes VUV‐irradiated for 6 min, whereas the SiO_x ratio was related to the gas permeability of the membranes VUV‐irradiated for 60 min. These changes affected the gas selectivities of the membranes. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45973.     

Preparation,analysis, and isothermal crystallization behavior of poly[1,3‐bis(aminomethyl)cyclohexamethylene oxamide]

Poly[1,3‐bis(aminomethyl)cyclohexaneoxamide] (PBAC2) was synthesized using 1,3‐bis(aminomethyl)cyclohexane (BAC) and dibutyl oxalate (DO) via spray/solid‐state polycondensation (SSP). The structure of the synthesized polyoxamide was confirmed by ¹H‐nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy. The weight average molecular weight (M_w) of the polyoxamides prepared was 1.35 × 10⁵. The polyoxamides showed excellent thermal properties with glass transition temperature (T_g) of 150 °C, melting temperature (T_m) of 318 °C, crystallization temperature(T_c) of 253 °C, and initial degradation temperature (T_d) of 417 °C suggesting higher thermal stability than commercial polyamide 6 (T_d = 378 °C). Kinetic studies of PBAC2 predicted a two‐dimensional crystal growth. X‐ray diffraction powder diffraction suggested that the polymer has high crystallinity. A saturated water absorption of 2.8 wt % was recorded for the new polyoxamide, giving it a competitive edge for applications in civil aviation, reinforced plastics, and electronics industry where precise dimensional stability and high thermal resistance properties are a priority. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46345.     

Removal of cadmium(II) cations from an aqueous solution with aminothiourea chitosan strengthened magnetic biochar

An aminothiourea chitosan modified magnetic biochar composite (TMBC) was prepared for the efficient removal of Cd(II) from wastewater. The synthesized materials were characterized, and the detailed adsorption mechanisms and thermodynamics were studied. The adsorption experiments revealed that TMBC had a higher affinity for Cd(II) than the magnetic biochar composite, raw biochar, and other carbon‐based adsorbents did. The Cd(II) adsorption process fit the pseudo‐second‐order kinetic model, and the maximum adsorption capacities on the basis of the Langmuir model were 93.72, 121.9, and 137.3 mg/g at 298, 308, and 318 K, respectively. The practical efficacy of the adsorbent was also tested with a real mine water. The metal‐ion‐loaded TMBC could be conveniently collected by a magnet and could be easily regenerated with adsorption efficiencies up to 84% after five adsorption–desorption cycles. The as‐prepared TMBC might be a promising adsorbent for the treatment of heavy‐metal‐ion‐contaminated water or highly mineralized mine water. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46239.