Theoretical kinetic study of the reaction between dimethyl disulfide and OH radicals

The potential energy profile of the reaction between dimethyl disulfide and OH^? radicals is explored by utilizing ab initio and hybrid meta density functional theory methods. Having the energies and structural data of the stationary points, statistical rate theories, such as transition state theory and variable reaction coordinate-transition state theory, are employed to compute the overall rate constants, and discuss the mechanism and product channels. On the basis of the calculations, the overall rate coefficient is predicted to be 2.49?×?10^?10?cm³?molecule^?1?s^?1 at 298?K. It is found that in the most favorable pathway, the reaction proceeds via formation of the relatively unstable intermediate CH₃S^?(OH)SCH₃ decomposing rapidly to yield CH₃S^?+CH₃SOH.     

Immobilization of surface non-affinitive protein onto a metal surface by an external electric field

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Hydroxyl Group Separation Distances in Anti-Freeze Compounds and Their Effects on Ice Nucleation

Since the discovery of biological antifreeze glycoproteins (AFGPs), which can inhibit ice nucleation, there has been considerable interest in understanding their mechanisms and mimicking them in synthetic polymers. In this study, we used molecular dynamics simulations of modified polyvinyl alcohol (PVA) compounds to show that the hydroxyl (OH) group distance is a key factor in whether certain compounds promote or inhibit ice nucleation. A hydroxyl distance smaller than ~2.8 Å but greater than ~7.1 Å in modified PVA (MPVA) compounds was associated with the promotion of ice nucleation, while a hydroxyl group separation distance of approximately ~5.0 Å was correlated with a delay in ice nucleation, owing to changes in the energy of the system. Thus, these results may help explain some of the mechanisms of current known anti-freeze compounds and may have implications for designing new anti-freeze compounds in the future.     

Heterogeneous oxidation of indoor surfaces by gas‐phase hydroxyl radicals

We investigate heterogeneous oxidation kinetics of monolayer‐thick, surface‐sorbed organics, namely di‐n‐octyl phthalate (DnOP) and palmitic acid (PA), with gas‐phase OH. The pseudo‐first order rate constants for organic loss at OH concentrations of 1.6 × 10⁸ molecules/cm³ are: (2.3 ± 0.1) × 10^?4 to (4.8 ± 0.8) × 10^?4 s^?1, and (1.3 ± 0.5) × 10^?4 s^?1 for DnOP and PA, respectively. Films developed in indoor office environments over a few weeks are also oxidized using the same OH concentration. Heterogeneous decay rate constants of mass signals from these films, attributed to phthalates (MW = 390.6) and to PA, are similar to those for the single‐component films, ie, (1.9 ± 0.4) × 10^?4 to (3.4 ± 0.5) × 10^?4 s^?1, and (1.1 ± 0.4) × 10^?4 s^?1, respectively. These results suggest that the lifetimes for OH heterogeneous oxidation of monolayer‐thick indoor organic films will be on the timescale of weeks to months. To support this argument, we present the first analysis of the mass transfer processes that occur when short‐lived gas‐phase molecules, such as OH, are taken up by reactive indoor surfaces. Due to rapid chemical production, the diffusion limitation to mass transfer is less important for short‐lived molecules than for molecules with little chemical production, such as ozone.     

水性抗菌羟基丙烯酸树脂的制备及性能

以甲基丙烯酸甲酯(MMA)、丙烯酸丁酯(BA)、丙烯酸(AA)、丙烯酸羟丙酯(HPA)为单体,过氧化二苯甲酰(BPO)为引发剂,乙醇为助溶剂,采用半连续溶液聚合法合成得到了水性羟基丙烯酸树脂(hs-WA),再用三乙胺(TEA)中和,最后引入季铵盐抗菌剂3-(甲氧基硅烷基)丙基二甲基十八烷基氯化铵(TSA),合成得到了水性抗菌羟基丙烯酸树脂(hs-WAT)。利用FTIR、1HNMR、接触角、SEM、TG和DSC对样品进行了分析,并采用菌落计数法和抑菌圈法对样品进行了抗菌测试。结果表明:引入TSA反应后,树脂的表面形貌没有改变;水接触角从78.5?增大至87.5?;样品的分解温度范围为299～456℃,热稳定性提高;聚合物链柔韧性增强(Tg=8.3℃)。抗菌性能分析表明:当引入TSA的质量分数为4%(以树脂的固含量计)时,hs-WAT膜对大肠杆菌(革兰氏阴性菌)以及金黄色葡萄球菌(革兰氏阳性菌)的杀灭率达99.9%以上,TSA未发生迁移,合成的聚合物为水性非渗透性接触型抗菌材料。     

高固体分、高羟值聚酯树脂的合成及性能研究

通过设计羟基聚酯树脂分子结构,选择六氢苯酐、1,6-己二醇、1,4-环己烷二甲醇、三羟甲基丙烷、三羟乙基异氰脲酸酯等原料,制备了高固体分、高羟值聚酯树脂,研究了不同原材料及合成工艺对树脂性能的影响。结果表明:采用脂环族二元酸制备的聚酯树脂综合性能优于芳香族及脂肪族二元酸制备的聚酯树脂;三羟乙基异氰脲酸酯分子中的环状结构对相邻的酯键起到了"屏蔽"作用,提高了树脂的耐水性;叔碳酸缩水甘油酯用量为固体树脂总量的15%时聚酯树脂的综合性能较好。     

Acid Hydrogen Peroxide Treatment of Norway Spruce TMP: The Effect of an Extended pH Range when Catalyzed by Free Ferrous and Free or EDG/EDTA-Chelated Ferric Ions

The influence of different types of iron salts (i.e., ferrous or ferric cations with sulphate, nitrate or chloride anions) on the reaction between coarse thermomechanical pulp and acid hydrogen peroxide (Fenton chemistry) was studied when the initial pH was 3.2 and 5.3. Also, ferric ions chelated with EDTA or EDG at different molar ratios were compared with ferrous sulphate when the initial pH was extended from about 3 to 8. Different anions of ferric ion salt gave a similar catalytic effect. At an initial pH of 7–8, the ferric-EDTA catalyzed reaction resulted in similar or higher hydrogen peroxide consumption and more detectable hydroxyl radicals than the ferrous sulphate catalyzed reaction, but less reaction with the pulp was indicated. Between pH 5–8, using Fe-EDG as a catalyst gave higher hydrogen peroxide consumption and more detectable hydroxyl radicals than if using ferrous sulphate; however, the measured effect on the pulp was similar or less.     

超声作用对短切碳纤维在水溶液中分散性的影响

利用超声波振动对短切碳纤维进行分散。研究了超声振动功率、时间及分散剂质量分数对短切碳纤维在水溶液中分散性的影响。结果表明,超声振动和羟丙基甲基纤维素(HPMC)分散剂的添加能显著改善短切碳纤维的分散性;在一定范围内,短切碳纤维分散率随着超声波振动功率和作用时间先增加后趋于饱和;HPMC在水溶液中的质量分数为0.13%时分散性较好,超声振动功率为800 W,振动7 min时短切碳纤维在水溶液中可达到较好的分散效果。     

高固体分低黏度羟基丙烯酸树脂的制备

以丙烯酸(AA)、甲基丙烯酸甲酯(MMA)、丙烯酸丁酯(BA)、叔碳酸缩水甘油酯(E-10P)、丙烯酸羟丙酯(HPA)为单体,以二叔丁基过氧化物(DTBP)为引发剂,采用溶液聚合法合成了高固体分低黏度的羟基丙烯酸树脂。通过研究引发剂用量、E-10P用量以及反应温度等反应条件对树脂固含量和黏度等性能的影响,确立了合成羟基丙烯酸树脂的最佳配方:引发剂二叔丁基过氧化物用量为2%,E-10P用量为15%,反应温度为150℃左右。在上述配方和工艺条件下制得的树脂为无色透明液体,固体分高达75%,黏度仅为1 350 mPa·s。