Polystyrene(PS)is rich in plastic materials,but it produces a large amount of waste every year,causing a huge burden on the environment.Although PS plastic is the source of a common"white pollution"in daily life,it still has a high utilization value.At the same time,the flammability of PS material determines that it cannot be applicated in places where fire accidents occur frequently.As a result,its application has been greatly limited.In order to realize the efficient utilization of waste PS and broaden its scope of application,PS was modified by hyper-crosslinking in order to improve its fire-retardant performance.In this method,the PS solution with high purity was obtained by dissolving waste PS foam with 1,2-dichloroethane(DCE),and then the hyper-crosslinked polymer with high specific surface area was prepared by adding cross-linking agent formaldehyde dimethyl acetal(FDA)and a Lewis-acid catalyst ferric chloride(FeCl_(3)).Further studies showed that the effects of the amount of cross-linking agent FDA,catalyst FeCl_(3) and PS on the reaction products were different.In addition,compared the as-prepared fire-retardant materials with PS foam from the aspects of flame retardancy and thermal insulation,it can be concluded that the fire-retardant performance of the materials prepared by this method has been significantly enhanced.And it is proved that this method is feasible towards the preparation of a large number of fire-retardant composite materials by using a scale-up experiment.
Understanding the processes of protein adsorption/desorption on nanopartieles＇ surfaces is important for the development of new nanotechnology involving biomaterials; however, an atomistic resolution picture for these processes and for the simultaneous protein conformational change is missing. Here, we report the adsorption of protein GB 1 on a polystyrene nanoparticle surface using atomistic molecular dynamic simulations. Enabled by metadynamics, we explored the relevant phase space and identified three protein states, each involving both the adsorbed and desorbed modes. We also studied the change of the secondary and tertiary structures of GB 1 during adsorption and the dominant interactions between the protein and surface in different adsorption stages. The results we obtained from simulation were found to be more adequate and complete than the previous one. We believe the model presented in this paper, in comparison with the previous ones, is a better theoretical model to understand and explain the experimental results.
Spherical polystyrene‐supported ammonium salts containing different linking chains between the support and ammonium groups were prepared as efficient and easily reusable heterogeneous catalysts for the cycloadditions of CO2and epoxides.The effects of the length of the linking chains and a hydroxyl group pendent on the linking chain on the catalytic performance of ionic liquid immobilized catalysts and their mechanisms were studied through experiments and density functional theory calculations.It was found that,compared with a short linking chain,a long chain can make the halogen anion more negative and provide a larger contact area of the catalysts with the reactants,thus enhancing the reaction kinetics.The hydroxyl group can stretch the C-O bonds of the epoxides,promoting the reaction thermodynamics.As a result,for the cycloaddition of propylene oxide,the yield of propylene carbonate is much higher for the catalyst with a long linking chain(yield:91.4%)compared with the yield for that with a short chain(yield:70.9%),and is further increased in the presence of pendent hydroxyl groups(yield:98.5%).The catalyst also shows a high catalytic activity even at mild temperature and good reusability(yield:≥96%for10cycles),and the selectivity is always above99%.
Xiaoming YanXuan DingYu PanXiaowei XuCe HaoWenji ZhengGaohong He
