Flexible polyurethane (PU) foams with different loading mass fraction (0%-2.0%) of fumed silica were synthesized by free-rising foaming method. The addition of 1.4% fumed silica makes the cells diffuse more uniform in the PU foam and the temperature of degradation occurring with a maximum weight loss rate is about 7 ℃ higher than that of pure PU foam. Most significantly, the sound absorption peaks of the filled PU foams shift to the low frequency region (from 997 Hz to 711 Hz) with increasing fumed silica content (0%-2.0%). The average sound absorption coefficients of filled PU foams increase except the content of 0.35% fumed silica. The experimental results show that flexible PU foams filled with fumed silica have excellent sound absorption characteristics in low-frequency regions.Polymeric foams show excellent characteristics, such as high strength-to-weight ratio, the resilience, the thermal, and the acoustic insulation, which makes them largely manufactured and widely used. As one kind of the largest and most versatile polymeric foams, polyurethane (PU) foams can be classified into the rigid PU foams and the flexible ones. The former are used for thermal insulation, and the latter are mainly used as acoustic or cushioning materials.Flexible polyurethane foams have been extensively applied for absorbing sound and reducing noise, whose attractive characteristics also include its excellent viscoelasticity, relative simple processing, and commercial availability. However, the sound absorption of polyurethane foams is strong in high-frequency regions but relatively weak in low-frequency regions because of the low capacity of sound energy attenuation [1] . As we know, the sound absorption ability of these materials is critical especially for the low-frequency noise (e.g., 200-1 600 Hz) where human sensitivity is high. Many researchers found various kinds of fillers to improve the acoustic performance of polyurethane foams, especially the acoustic performance in low-frequency region. Mendelsohn et al [2] studied the hollow porous microspheres of polystyrene dispersed randomly in polyurethane, and the obtained material has many properties, including high porosity, high compression strength, low acoustic reflectivity, and relative insensitivity to the changes of the frequency. Cushman et al [3][4][5] found that the mixture of high and low characteristic acoustic impedance fillers loaded in the polymer can reduce the noise generated by sound, vibration, and shock, and the obtained material has excellent sound absorption properties. Verdejo et al [6] found that low loading fraction of carbon nanotubes (CNTs) in flexible polyurethane foams have relatively high effect in sound absorption; even 0.1% CNTs can enhance the acoustic absorption dramatically, which leads the peak absorption coefficient to increase up to 90% from 70% for the pure polymer foam.Up to now, the related studies mainly focused on introducing silica into rigid PU foams to improve mechanical properties [7,8] . However, the report on the flexible PU fille...

Heterogeneous visible‐light photocatalysis represents an important route toward the development of sustainable organic synthesis. In this study visible light‐induced, heavy metal‐free atom‐transfer radical addition to unactivated terminal olefins is carried out by using the combination of heterogeneous titanium dioxide as photocatalyst and a hypervalent iodine(III) reagent as co‐initiator. The reaction can be applied to a range of substrates with good functional‐group tolerance under very mild conditions. In addition to a number of commonly used atom‐transfer reagents, the relatively challenging chloroform is also suitable.

Two new metabolites, pyrenocine J (1) and pyrenochaetic acid D (2), together with two known metabolites, pyrenocine A (3) and pyrenochaetic acid A (4), were isolated from a soil fungus, Curvularia affinis strain HS-FG-196. Their structures were established by extensive spectroscopic analysis. Compound 1 showed cytotoxic activity against the human hepatic cancer cell line HepG2 with an IC(50) value of 28.5 μg/ml.