In this study, a series of crosslinked waterborne polyurethane/acrylate copolymer latexes with different compositions were fabricated via emulsion polymerization using oil-soluble initiator (AIBN) ...based on a solvent-/emulsifiers-free method. Using the blend of styrene (St), butyl acrylate (BA) and crosslinkers (pentaerythritol triacrylate (PET3A) and pentaerythritol tetraacrylate (PET4A)) instead of acetone as a diluent and modifier, polyurethane prepolymers terminated with hydroxyethyl acrylate composite emulsions were prepared using polypropylene glycol (PPG), toluene diisocyanate (TDI), 2,2-dihydroxymethylpropionic acid (DMPA) and diethylene glycol (DEG) without other solvents. It was found that for all the emulsion polymerization of waterborne polyurethane and acrylates initiated by AIBN, the monomer conversions exceeded 96% when the concentration of AIBN was in the range of 0.5% to 0.9% (w/w) and the optimal reaction temperature was 75 °C. The introduction of St, BA and crosslinkers would form the polymer network, improving the tensile strength, water absorption of the copolymer latex films. Dynamic light scattering analyses showed that the copolymer latexes exhibited a unimodal distribution and showed no precipitates and unstable aggregates. The average particle size distribution was in the range of 131-154 nm. Transmission electron microscopy studies have confirmed the similar results and the latex particles possessed the core-shell morphology structure.
In order to prepare polyurethane–polysiloxane block copolymers, α,ω-hydroxyalkyl polysiloxanes with methacrylate side chain and α,ω-bis(2-methyl-3-hydroxypropyl)polymethyl(2-methyl-methylpropanoate) ...siloxanes, were synthesized and characterized in this study. The syntheses process included hydroxyl protection, hydrosilylation, deprotection, and ring-opening equilibrium reactions. The intermediates and target products were characterized by Fourier transform infrared spectroscopy and
H nuclear magnetic resonance methods. The characterization results showed that each step was successfully carried out in all the cases. Then the waterborne polyurethane–polysiloxane block copolymers were prepared via step-growth polymerization. The properties of the block copolymer films were characterized by thermal gravimetric analysis, differential scanning calorimetry, and dynamic thermomechanical analysis methods in detail. The experimental results showed that the block introduction of hydroxyalkyl polysiloxane could reduce the water absorption of waterborne polyurethane from 62 to 11%, and significantly improve the water resistance of polyurethane. With the introduction of polysiloxane, the tensile strength decreased and the elongation at break increased. At the same time, with the increase of the polysiloxane content, the glass transition temperature of the soft segment decreased to −56.4°C and the thermal decomposition temperature increased to 300°C. The results revealed that the introduction of polysiloxane could effectively improve the comprehensive performance of polyurethane–polysiloxane block copolymer films.
In this paper, by optimizing synthesis process of α,ω-hydroxyalkyl telechelic polydimethylsiloxane, α,ω-bis(3-(1-methoxy-2-hydroxypropoxy)propyl)polydimethyl siloxane (PMTS), the yield of ...hydrosilylation product, 1,3-bis(glycidoxypropyl) tetramethyldisiloxane exceed 86.5%. By tracing the change of methanol (gravimetry) and measuring the change of molecular weights of polydimethylsiloxanes at different reaction time (titration), the optimum reaction time of methoxylation reaction and ring-opening polymerization was determined as 8 and 12 h. Using α,ω-bis(3-(1-methoxy-2-hydroxypropoxy)propyl)polydimethyl siloxane with different molecular weights, waterborne polyurethane-polydimethylsiloxane block copolymer were prepared. The influences of molecular weights and content of α,ω-hydroxyalkyl telechelic polydimethylsiloxane on the waterborne polyurethane-polydimethylsiloxane block copolymers were investigated in detail. The addition of α,ω-hydroxyalkyl telechelic polydimethylsiloxane could improve the water-resistance property obviously and increase the elongation at break. However, the mechanical property was reduced with increase of content and molecular weight of α,ω-hydroxyalkyl telechelic polydimethylsiloxane.
An efficient Ni(ClO4)2·6H2O-promoted amidoalkylation reaction for the synthesis of 3-substituted isoindolinones involving various γ-hydroxy lactams and nucleophiles has been successfully developed. ...The transformation proceeds with both carbon (ketones and arenes) and heteroatom (alcohols, thiols, and amines) nucleophiles and in both intermolecular and intramolecular manners. The prominent features of the present strategy are wide substrate scope, excellent group tolerability, and moderate to good yields (up to 96% yield). The present strategy is also characterized by remarkable superiority over the current synthetic methods. Furthermore, the reaction could be scaled up to the multigram scale.
•Substantial adsorption capacity of phosphorus is obtained.•adsorption equilibrium can be reached rapidly in less than 30 min.•Excellent adsorption capacity for phosphorus at low content.•High ...phosphorus adsorption capacity in weakly acidic solution.
Water deterioration and eutrophication caused by phosphorus (P) contamination necessitates P removal from polluted water, and has been a research focus since the second half of last century. In this study, novel mesoporous micropheres based on silicon and calcium (Ca) was prepared as an adsorbent by direct pyrolysis to enrich and remove P. The maximum adsorption capacities of the prepared adsorbents were 356.34 and 496.73 mg g−1 P−PO43− for potassium phosphate (K3PO4) and potassium dihydrogen phosphate (KH2PO4) solutions, respectively, and adsorption equilibrium was attained rapidly in less than 30 min. The Langmuir isotherm and pseudo-second-order kinetic model adequately fit the adsorption process for K3PO4 solution, while the Langmuir isotherm and pseudo-first-order kinetic appropriately fit the KH2PO4 solution. The adsorption of P was due to the reaction between Ca2+ and PO43−, forming different phosphates. Addition of interfering ions had no significant effect on the adsorption ability of the prepared adsorbents. The proposed adsorbent was successfully applied to remove P from real wastewater. Notably, this new Ca-modified mesoporous silicon micropheres is an excellent adsorbent for treating wastewater containing low P content, providing an effective approach for facile preparation of P adsorbents and exhibiting promising P removal from wastewater.
Display omitted
We synthesized polydimethylsiloxane–polyurethane dispersions modified with graft copolymerization (PDMS-
G
-PUDs) and polydimethylsiloxane–polyurethane dispersions modified with block ...copolymerization (PDMS-
B
-PUDs). We systematically investigated the effects of PDMS’s structure, content, and molecular weight on properties of copolymer including viscosity, particle size, and stability of dispersions as well as the properties of the film formed by dispersions including gloss, contact angle, water resistance, oil resistance, and mechanical properties. The results demonstrated that the viscosity, particle size, water resistance increased but gloss decreased with the increase of PDMS content and molecular weight. In addition, we compared the properties of PDMS-
B
-PUD films and PDMS-
G
-PUD films with the same amount of PDMS and similar molecular weight. PDMS-
G
-PUD films showed higher water and oil resistance, but lower gloss and poorer mechanical properties. Scanning electron microscopy–energy dispersive spectroscopy analysis (SEM–EDS) indicated that the films of PDMS-
G
-PUD had better microphase separation and PDMS surface enrichment.
PDF
