Organo-clay formulations of pesticides: reduced leaching and photodegradation

Adsorption of organic cations on several clay minerals is reviewed with an emphasis on the effect of ionic strength and modeling. The clay exchanged with suitable organic cations forms a basis for ecologically acceptable formulations of herbicides with reduced leaching, ground water contamination and enhanced weed control efficacy. Incomplete neutralization of the clay surface charge by an organic cation may be advantageous in achieving maximal adsorption of hydrophobic herbicides. One conclusion from these studies is that optimization of clay-based herbicide formulations requires a selection of structurally compatible organic cations preadsorbed on the clay at optimal coverage. New experimental results are presented for alachlor formulations, which significantly reduce herbicide leaching under conditions of heavy irrigation. We were able to demonstrate that organo-clay formulations of alachlor and metolachlor can increase crop yields in a 1-year field experiment. The photostabilization of pesticides is reviewed and improved organo-clay formulations of the herbicides trifluralin and norflurazon are described. A pillared clay, nanocomposite micro- and/or meso porous material, was effective in reducing leaching and in conferring photostabilization, without added organic cations.     

Pesticide–clay interactions and formulations

The papers collected in this issue reveal the diversity of pesticide–clay interactions. The most important bonding mechanisms are shortly described in this introduction. These mechanisms provide the basis for attempts to design new pesticide formulations. Several examples of such formulations are reported.     

Adsorption and desorption kinetics for hydrophilic and hydrophobic vapors on activated carbon

Adsorption dynamics are of fundamental importance in applications of adsorbents in real situations. The adsorption/desorption characteristics of a series of adsorbates, with varying hydrophilic/hydrophobic and structural characteristics, for activated carbon BAX950, were investigated for temperatures in the range 288-323 K. These data provide a comprehensive kinetic study of adsorption/desorption for an activated carbon. The results are discussed in relation to the adsorbent pore structure and functional group concentration, adsorptive structure and adsorption mechanism. The study provides evidence for a compensation effect where activation energy and ln(pre-exponential factor) parameters obtained from the Arrhenius equation exhibit a linear correlation.     

内疏外亲SiO_2气凝胶的制备及表征

以正硅酸乙酯(TEOS)为硅源,无水乙醇为溶剂,硝酸为催化剂,氨水为凝胶剂,经溶胶-凝胶过程制备块状湿凝胶。再以三甲基氯硅烷(TMCS)为疏水改性剂,3-氨丙基三羟基硅烷为亲水改性剂对制备的湿凝胶进行改性处理,最后经超临界CO2干燥得到块体SiO2气凝胶。考察了亲水改性剂加入量分别为0、0.15、0.75、1.5、2.70 mL时对块体SiO2气凝胶亲水性的影响,并通过扫描电子显微镜(SEM)、接触角、吸水率、红外光谱(FT-IR)等对气凝胶进行表征。结果表明:所得气凝胶块体具有纳米多孔结构,内部疏水(最大接触角可达123°),表面亲水,试样亲水性随亲水剂用量的增加而增大;同一试样亲水性存在一定的梯度变化,亲水性由内到外逐渐增强。     

Pervaporative permeations of homologous series of alcohol aqueous mixtures through a hydrophilic membrane

The permeation behaviors of permeants were investigated in the pervaporation of a homologous series of alcohol aqueous mixtures through a hydrophilic poly(vinyl alcohol) (PVA). The PVA membrane was crosslinked with glutaraldehyde. A homologous series of alcohols used in this study were methanol, ethanol, 1‐propanol, and 1‐butanol. The pervaporation experiments were carried out with feed having 70–97 wt % of alcohol contents and at various feed temperatures. In a high alcohol content above 92 wt %, the permeation rate was increased in the order of the interaction strength between alcohol and water in the feed. However, in a low alcohol content below 90 wt %, the tendency of the permeation rate was found to be the opposite, indicating that the interactions between permeant constituents play an important role in determining the permeation and separation of the mixtures. These observations were discussed in terms of changes in the interaction between the permeant/permeant or the permeant/membrane in varying feed compositions and feed temperatures. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 703–713, 2001     

Effect of soft segment length on properties of hydrophilic/hydrophobic polyurethanes

Polyurethanes (PUs) were prepared from 4,4′‐diphenylmethane diisocyanate and various molecular weights of poly(tetramethylene glycol) and polydimethylsiloxane. The physical properties of these polymers were determined using Fourier transform infrared spectroscopy and through calculation of their swelling ratios. The thermal properties were investigated through thermogravimetric analysis and dynamic mechanical analysis. The blood compatibility of each polymer was determined by calculating its relative index of platelet adhesion (RIPA). Domain separation of the resulting PUs occurred during polymerization because of the immiscibility of the hydrophilic and hydrophobic polyols. The hydrophilic/hydrophobic domain‐separated structure affected the surface tension through the formation of hydrophilic and hydrophobic domains of the PU, which reduced the adhesion of blood platelets onto the materials. The PU(PDMS/PTMO1000) = 75/25 sample, with its RIPA of 0.34, appears to be suitable for biomedical applications as a blood‐compatible material. Copyright © 2007 Society of Chemical Industry     

Dependence of morphological changes of polymer particles on hydrophobic/hydrophilic additives

Fairly uniform microspheres of poly(styrene‐co‐methyl methacrylate) were prepared by employing a microporous glass membrane [Shirasu porous glass (SPG)]. The single‐step SPG emulsification, the emulsion composed mainly of monomers, hydrophobic additives, and an oil‐soluble initiator, suspended in the aqueous phase containing a stabilizer and inhibitor, was then transferred to a reactor, and subsequent suspension polymerization followed. The droplets obtained were polymerized at 75°C under a nitrogen atmosphere for 24 h. The uniform poly(styrene‐co‐methyl methacrylate) microspheres with diameters ranging from 7 to 14 μm and a narrow particle‐size distribution with a coefficient of variation close to 10% were prepared by using SPG membrane with a pore size of 1.42 μm. The effects of the crosslinking agent and hydrophobic additives on the particle size, particle‐size distribution, and morphologies were investigated. It was found that the particle size decreased with a narrower size distribution when the additives were changed from long‐chain alkanes to long‐chain alcohols and long‐chain esters, respectively. Various microspheres with different morphologies were obtained, depending on the composition of the oil phase. The spherical poly(styrene‐co‐methyl methacrylate) particles without phase separation were obtained when using an adequate amount of the crosslinking agent and methyl palmitate as an additive. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1013–1028, 2000     

Radical/Addition polymerization silicone hydrogels with simultaneous interpenetrating hydrophilic/hydrophobic networks

Transparent silicone hydrogels with interpenetrating hydrophilic/hydrophobic networks were simultaneously synthesized on the basis of the radical polymerization of the methacrylic monomer of 3‐methacryloxypropyl tris(trimethylsiloxy) silane (TRIS)/N,N‐dimethylacrylamide (DMA) and the addition polymerization of hydroxyl‐grafted polysiloxane (HPSO)/isophorone diisocyanate. The curing temperature was set at 80°C by a differential scanning calorimetry study. The polymerization process was studied by in situ Fourier transform infrared spectroscopy. The results indicate that the curing time was about 4.5 min, and the addition polymerization had a faster rate than radical polymerization. Then, the radical polymerization rate increased rapidly, and this led to instant curing. The interpenetrating polymer network (IPN) silicone hydrogels were characterized by swelling kinetics and dynamic mechanical thermal analysis. The results show that all of the hydrogels reached swelling equilibrium at about 4 h in water, and the IPN silicone hydrogels with a hydrophobic network of HPSO indicated a slower water transport than that of the copolymerization hydrogel of DMA and TRIS. The hydrophobic network was finely dispersed in the hydrophilic network, and the increasing hydrophobic network of HPSO decreased the glass‐transition temperature of the IPN silicone hydrogels. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41399.     

Dynamic surface tension of aqueous surfactant solutions. 6. Compounds containing two hydrophilic head groups and two or three hydrophobic groups and their mixtures with other surfactants

Dynamic surface tensions (γ_t)—measured by the maximum bubble pressure method—of some surfactants containing two hydrophilic (sulfonate) groups and two or three hydrophobic groups in the molecule (“gemini surfactants”), and of their mixtures with a nonionic surfactant or an amine oxide, have been measured at 25°C in 0.1 M NaCl. Linearity of the plots of surface pressure vs. square root of the surface age indicated that the systems studied were all diffusion-controlled. For the individual surfactant systems, the apparent diffusion coefficient decreases with an increase in the number of alkyl chains and the bulkiness of the surfactant molecules. For the mixtures, when interaction between the two surfactants is weak, γ_t at short times (t<1s) is close to that of the component with the lower surface tension; at longer times, it is closer to that of the component with the lower equilibrium surface tension. When interaction is strong, γ_t at short times is greater than that of either component. The molar ratio at which maximum effect on γ_t is observed depends upon the strength of the interactions between the two surfactants.     

Effects of hydrophilic/hydrophobic surfaces on polymer‐complexation kinetics

To establish hydrophilic/hydrophobic effects on polymer‐complexation kinetics, chitosan resins were prepared by radical copolymerization of methacryloyl‐modified chitosans with 2‐hydroxyethyl methacrylate and/or styrene monomers. The primary particles of the gelled copolymers in the suspensions were nicely solidified by basic coagulation bath to form globular beads. Degree of the hydrophilic/hydrophobic properties was controlled by the copolymerization ratio, and each ion‐adsorption kinetics was evaluated by batch method. The initial rate of adsorption in hydrophilic chitosans was higher than that in hydrophobic chitosans, which was attributed to less thickness of the boundary film. We quantitatively evaluated the rate‐determining steps by the initial‐rate analysis, in which the viscosity of the suspension contributes to the film‐diffusion kinetic resistance. The role of hydrophilic/hydrophobic properties of the resins is reasonably rationalized to the length of the boundary films by considering long‐range interactions between the ion and surface. Our results are robust evidence for the ion‐surface interactions. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46493.     

Separation and purification of isobutanol from dilute aqueous solutions by a hybrid hydrophobic/hydrophilic pervaporation process

In this study, a hybrid hydrophobic/hydrophilic pervaporation process was employed to separate and purify isobutanol from its dilute aqueous solutions. For this purpose, composite polydimethylsiloxane membranes were initially used for the recovery of isobutanol by hydrophobic pervaporation. Then the hydrophilic pervaporation with a composite polyvinyl alcohol membrane was utilized to separate water from the organic phase of the permeate stream of the hydrophobic pervaporation. The effect of feed flow rate on the performance of pervaporation was investigated. The resistance in series model was also applied to calculate the transport resistances through the composite membranes. It was observed that an enhancement in the feed flow rate led to higher permeation flux and selectivity of the more permeable component, while the flux of the less permeable component was almost constant. Also, the ratio of liquid boundary layer resistance to membrane layer resistance decreased by an increase in the feed flow rate. The isobutanol with a purity of higher than 99 wt.% was produced by the hybrid hydrophobic/hydrophilic pervaporation technique from a 2 wt.% aqueous isobutanol solution.     

环境对改性塑料表面亲/疏水转变的作用机制

塑料制品因其质量轻、性质稳定等优点而得到广泛使用,但大部分废旧塑料未被合理回收而成为污染物,对环境造成了危害。因此,废旧塑料回收、再加工成为保护环境和资源利用的有效途径。而分离是废旧塑料能进行再加工的重要环节,目前已经发展了丰富的分离方法,其中塑料浮选法因具有工艺简单、污染少的特点而受到人们的青睐。但在塑料浮选中,其表面亲疏水性受环境的影响,该过程进一步恶化分离效果。为了避免分离过程的波动性,急需探究环境因素对亲疏水性的作用。基于此,本文选取了ABS、PC、PS三种废旧塑料,探究环境对浮选分离及表面亲疏水性基团重构的影响。结果表明：氧化改性后的ABS、PC、PS处于极性环境时,塑料可浮性基本未发生改变,接触角发生轻微浮动,表面仍保持亲水性。处于乙醇环境中,塑料可浮性上升,其接触角上升至75°左右,表面疏水性恢复速度大于极性环境。而在非极性环境中,塑料可浮性上升速度较快,表面完全恢复为未改性前的疏水性。在极性环境中,亲水基团更容易停留在表面,随着极性的减小,亲水基团逐渐迁移至本体,塑料表面恢复为疏水。因此,极性环境更有利于塑料表面保持亲水性。     

Method for the preparation of hydrophilic/hydrophobic patterned surfaces with photoinitiated hydrosilylation

Recently, there has been considerable interest in hydrophilic/hydrophobic patterned surfaces because they serve as important templates for the selective deposition of various materials. We report a novel and simple method for the creation of hydrophilic/hydrophobic patterned surfaces using soft UV irradiation (365‐nm wavelength). The method employs a photoinitiated hydrosilylation reaction of vinyl‐terminated polydimethylsiloxane with H? Si groups catalyzed by platinum(II) acetylacetonate. In UV‐irradiated regions, the photohydrosilylation reaction occurs, forming hydrophobic regions. In unirradiated regions, the remaining H? Si groups are converted into HO? Si groups in the presence of aqueous sodium hydroxide to form hydrophilic regions. The photoinitiated hydrosilylation reaction is completed within a little over 1 min, and this has been confirmed by reflection–absorption spectroscopy. The value of the water contact angle for the hydrophilic regions is about 10°, and that for the hydrophobic regions is about 103°. The success of pattern formation at the micrometer scale has been confirmed by scanning electron microscopy. The difference in the chemical structure at the surface has been confirmed by the decoration of the hydrophilic regions by a fluorescent dye and characterization with a fluorescence analyzer. Atomic force microscopy has shown that the height of the hydrophobic regions is about 20 nm. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Switchable surfaces from highly hydrophobic to highly hydrophilic using covalent imine bonds

The formation of materials with switchable wettability is extremely important for various applications such as in separation membranes or liquid transportation. Here, we report for the first time the use of imine bonds in order to prepare switchable hydrophobic/hydrophilic surfaces. Based on a poly(3,4‐ethylenedioxythiophene) surface bearing amino groups, imination reaction allows for reversible functionalization of surfaces with various carbonyl groups. Here, surfaces functionalization induces high hydrophobic properties while the surface structures are preserved. This reaction can be a choice method to prepare switchable surfaces for a large range of applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43130.     

基于亲水/憎水复合膜的全热交换器换热换湿性能

膜全热交换器由于可以同时回收空调排风中的潜热和显热而受到重视。研究了基于PVAL/PVDF复合透湿膜的全热交换器的透热透湿性能,实验测定了新风与排风之间的显热交换能力和水蒸气交换能力,并建立了基于亲水/憎水复合膜的逆流膜全热交换器传热传质计算模型,实验与理论结果吻合较好。结果表明,该复合膜全热交换器的总传热系数为20～35 W·m-2·℃-1,总传质系数为（1.5～3.5）×10-3 m·s-1。     

亲疏水交替碳纸的制备及其在气体扩散层中的应用

气体扩散层（GDL）作为控制质子交换膜燃料电池（PEMFC）水气传输的核心部件，对PEMFC的性能具有重要影响。将碳纤维纸（CP）浸渍聚四氟乙烯（?PTFE）乳液后，通过模具夹持进行干燥，得到了亲疏水交替的CP，并通过微孔层（MPL）涂敷工艺制备了基底层亲疏水交替的GDL，以期提高PEMFC性能。通过SEM、EDS、接触角、垂直平面（TP）电阻率、垂直平面（TP）透气率和电化学性能等测试对基底层亲疏水交替GDL的结构与性能进行了分析。结果表明：浸渍PTFE乳液的CP经模具夹持干燥后，形成条纹状亲水区和疏水区。将基底层亲疏水交替的GDL组装成单电池，在2 A/cm2电流密度（简称电密）下的电压为0.47 V，功率密度为948 mW/cm2；相同条件下，采用基底层无差别疏水处理的GDL组装成单电池，其电压为0.44 V，功率密度为884 mW/cm2，与基底层无差别疏水处理的GDL相比，电压及功率密度分别提高了6.82%和7.24%。     

Preparation of nanoparticles by the self-organization of polymers consisting of hydrophobic and hydrophilic segments: Potential applications

This review describes the preparation of core-corona type polymeric nanoparticles and their applications in various technological and biomedical fields. Over the past two decades, we have studied the synthesis and clinical applications of core-corona polymeric nanoparticles composed of hydrophobic polystyrene and hydrophilic macromonomers. These nanoparticles were utilized as catalyst carriers, carriers for oral peptide delivery, virus capture agents, and vaccine carriers, and so on. Moreover, based on this research, we attempted to develop novel biodegradable nanoparticles composed of hydrophobic poly(γ-glutamic acid) (γ-PGA) derivatives (γ-hPGA). Various model proteins were efficiently entrapped on/into the nanoparticles under different conditions: encapsulation, covalent immobilization, and physical adsorption. The encapsulation method showed the most promising results for protein loading. It is expected that biodegradable γ-hPGA nanoparticles can encapsulate and immobilize various biomacromolecules. Nanoparticles consisting of hydrophobic and hydrophilic segments have great potential as multifunctional carriers for pharmaceutical and biomedical applications, such as drug, protein, peptide or DNA delivery systems.     

Plasma-induced polymerisation of hydrophilic coatings onto macroporous hydrophobic scaffolds

Macroporous poly(methyl methacrylate) scaffolds with a well-interconnected pore architecture were coated with poly(2-hydroxyethyl acrylate) following a particular protocol of plasma-induced polymerisation. Plasma-polymerised PHEA (plPHEA) was grafted onto two macroporous poly(methyl methacrylate) scaffolds with varying cross-linking density showing significant differences in the interpenetration of the coating and the PMMA substrate. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) proved that the surface of the pore structure in the whole volume of the sample was coated. The stability of the plPHEA coating was studied by extraction with distilled water at different temperatures. After the extraction, these samples were observed by SEM and analysed by differential scanning calorimetry (DSC) and FTIR showing that only in very drastic conditions plPHEA suffers hydrolytic degradation.