Grafting of poly(ethylene oxide) to the surface of polyaniline films through a chlorosulfonation method and the biocompatibility of the modified films

Poly(ethylene oxide) (PEO) could be grafted on the surface of polyaniline (PANI) films by chlorosulfonating the films with chlorosulfonic acid followed by reacting the modified films with PEO in a pyridine solution. The modified PANI films were examined by X-ray photoelectron spectroscopy and water droplet contact angles. The surface of the PEO grafted to hydrophobic PANI films became hydrophilic and the amounts of bovine serum albumin and human blood plasma platelet adsorbed onto it were decreased by more than 80%. For comparison purposes, and because the water wetting angle can be used as a measure of biocompatibility, wetting angle experiments have been also carried out for Pluronic triblock copolymer grafted to PANI and PEO or Pluronic molecules entrapped on the surfaces of PANI films. PANI was selected as substrate because one can easily change its surface properties by PEO grafting and because being conductive can be used as a sensor.     

Protein resistant polyurethane surfaces by chemical grafting of PEO: amino-terminated PEO as grafting reagent

The objective of this work was to gain a better understanding of the mechanism of resistance to protein adsorption of surfaces grafted with poly(ethylene oxide) (PEO). A polyurethane-urea was used as a substrate to which PEO was grafted. Grafting was carried out by introducing isocyanate groups into the surface followed by reaction with amino-terminated PEO. Surfaces grafted with PEO of various chain lengths (PUU-NPEO) were prepared and characterized by water contact angle and X-ray photoelectron spectroscopy (XPS). XPS data indicated higher graft densities on the PUU-NPEO surfaces than on analogous surfaces prepared using hydroxy-PEO (PUU-OPEO) as reported previously [J.G. Archambault, J.L. Brash, Colloids Surf. B: Biointerf. 33 (2004) 111-120]. Protein adsorption experiments using radiolabeled myoglobin, concanavalin A, albumin, fibrinogen and ferritin as single proteins in buffer showed that adsorption was reduced on the PEO-grafted surfaces by up to 95% compared to the control. Adsorption decreased with increasing PEO chain length and reached a minimum at a PEO MW of 2000. Adsorption levels on surfaces with 5000 and 2000 MW grafts were similar. There was no clear effect of protein size on resistance to protein adsorption. Adsorption on the PUU-NPEO surfaces was significantly lower than on the corresponding PUU-OPEO surfaces, again suggesting higher graft densities on the former. Adsorption of fibrinogen from plasma was also greatly reduced on the grafted surfaces. From analysis (SDS-PAGE, immunoblotting) of the proteins eluted after plasma exposure, it was found that the grafted surfaces and the unmodified substrate adsorbed the same proteins in roughly the same proportions, suggesting that adsorption to the PEO surfaces occurs on patches of bare substrate. The PEO grafts did not apparently cause differential access to the substrate based on protein size.     

Functionalization of regenerated cellulose membrane via surface initiated atom transfer radical polymerization for boron removal from aqueous solution

In this study, an adsorptive membrane was prepared for efficient boron removal. Poly(glycidyl methacrylate) was grafted on the surfaces of the regenerated cellulose (RC) membrane via surface-initiated atom transfer radical polymerization, and N-methylglucamine was used to further react with epoxide rings to introduce polyhydroxyl functional groups, which served as the major binding sites for boron. The pristine and modified membranes were characterized by X-ray photoelectron spectroscopy (XPS), attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), dynamic water contact angle measurement, and scanning electron microscopy. It was shown that the designed functional groups were successfully grafted onto the RC membrane, and surface modification contributed to higher boron binding capability. The optimal pH range for boron adsorption was 4-8. Under a neutral pH condition, the maximum adsorption capacity of the modified membrane was determined to be 0.75 mmol/g, which was comparable with those of commercial resins. Studies of electrolyte influence indicated the formation of inner-sphere surface complexes on the membrane surface. The ATR-FTIR and XPS analyses showed that secondary alcohol and tertiary amine groups were mainly involved in boron adsorption, and tetrahedral boron complexes were found on the membrane surface.     

Energetics of small molecule and water complexation in hydrophobic calixarene cavities

Calixarenes grafted on silica are energetically uniform hosts that bind aromatic guests with 1:1 stoichiometry, as shown by binding energies that depend upon the calixarene upper rim composition but not on their grafted surface density (0.02-0.23 nm(-2)). These materials are unique in maintaining a hydrophilic silica surface, as probed by H2O physisorption measurements, while possessing a high density of hydrophobic binding sites that are orthogonal to the silica surface below them. The covalently enforced cone-shaped cavities and complete accessibility of these rigidly grafted calixarenes allow the first unambiguous measurements of the thermodynamics of guest interaction with the same calixarene cavities in aqueous solution and vapor phase. Similar to adsorption into nonpolar protein cavities, adsorption into these hydrophobic cavities from aqueous solution is enthalpy-driven, which is in contrast to entropy-driven adsorption into water-soluble hydrophobic hosts such as beta cyclodextrin. The adsorption thermodynamics of several substituted aromatics from vapor and liquid are compared by (i) describing guest chemical potentials relative to pure guest, which removes differences among guests because of aqueous solvation and van der Waals contacts in the pure condensed phase, and (ii) passivating residual guest binding sites on exposed silica, titrated by water during adsorption from aqueous solution, using inorganic salts before vapor adsorption. Adsorption isotherms depend only upon the saturation vapor pressure of each guest, indicating that guest binding from aqueous or vapor media is controlled by van der Waals contacts with hydrophobic calixarene cavities acting as covalently assembled condensation nuclei, without apparent contributions from CH-pi or other directional interactions. These data also provide the first direct quantification of free energies for interactions of water with the calixarene cavity interior. The calixarene-water interface is stabilized by approximately 20 kJ/mol relative to the water-vapor interface, indicating that water significantly competes with the aromatic guests for adsorption at these ostensibly hydrophobic cavities. This result is useful for understanding models of water interactions with other concave hydrophobic surfaces, including those commonly observed within proteins.     

Comparative Studies on Hydrophilic and Hydrophobic Segments Grafted Poly(vinyl chloride)

Poly(vinyl chloride) (PVC) is one of the mostly produced plastics in the world and is widely used in single-use medical devices.However,the additives that are often necessary for PVC arouse concerns of its safety,thus quests the modifications of PVC itself.In this study,poly(ethylene glycol) (PEG) and polydimethylsiloxane (PDMS) segments were grafted onto PVC backbone in similar ways,and the chemical structures of the modified PVCs were characterized by Fourier transform infrared spectra,X-ray photoelectron spectra,thermogravimetric analysis and differential scanning calorimetry.Moreover,the water contact angle,protein adsorption,platelet adhesion,cell attachment and proliferation on different material surfaces were studied and compared.It was found that both PEG and PDMS grafting yielded improvement on biocompatibility compared with bare PVC,while hydrophobic PDMS grafted PVC showed more effective on cell attachment and proliferation than that of hydrophilic PEG grafted PVC.     

表面修饰引发的ZnO纳米棒阵列膜的超疏水性

润湿性是固体表面的重要性质之一 ,它受控于固体表面自由能和表面粗糙度的大小 ,一般可用液体在固体表面接触角的大小来衡量 .由于水与超疏水表面 (水与固体表面的接触角大于 1 5 0°的表面 )的接触面积很小 ,通过水所发生的化学发应和化学键的形成受到限制 ,使这种表面具有防水、防污染和防氧化等多种功能 ,因而备受人们的关注 [1～ 6 ] .作为宽禁带半导体材料 ,Zn O以其独特的光电和催化等性质在短波激光器、气体传感器、高效催化剂、太阳能电池等方面具有广阔的应用前景 .表面润湿性的研究对于将 Zn O用于各种器件非常重要 .Pesika等 […     

Ultrathin poly(N-isopropylacrylamide) grafted layer on polystyrene surfaces for cell adhesion/detachment control

We investigated physicochemical properties of two types of poly(N-isopropylacrylamide) (PIPAAm)-grafted tissue culture polystyrene (TCPS) surfaces, to elucidate the influential factors for thermally regulated cell adhesion and detachment to PIPAAm-grafted surfaces. The two types of PIPAAm-grafted surfaces were prepared by the electron beam polymerization method. Attenuated total reflection Fourier transform infrared spectroscopy revealed that amounts of the grafted polymers were 1.4 +/- 0.1 microg/cm2 for PIPAAm-1.4 and 2.9 +/- 0.1 microg/cm2 for PIPAAm-2.9. Both PIPAAm-grafted surfaces showed hydrophobic/hydrophilic property alterations in response to temperature. However, PIPAAm-1.4 surfaces were more hydrophobic (cos theta = 0.21 at 37 degrees C and cos theta = 0.35 at 20 degrees C) than PIPAAm-2.9 (cos theta = 0.42 at 37 degrees C and cos theta = 0.50 at 20 degrees C) both above and below the PIPAAm's transition temperature. Thicknesses of the grafted PIPAAm layers were estimated to be 15.5 +/- 7.2 nm for PIPAAm-1.4 and 29.5 +/- 8.4 nm for PIPAAm-2.9, by the use of UV excimer laser and atomic force microscope. Bovine carotid artery endothelial cells (ECs) adhere to the surfaces of PIPAAm-1.4 and proliferate to form confluent cell monolayers. The cell monolayers were harvested as single cell sheets by temperature decrease from 37 to 20 degrees C. On the contrary, ECs did not adhere to the surfaces of PIPAAm-2.9. This phenomenon was correlated with an adsorption of cell adhesion protein, fibronectin, onto surfaces ofPIPAAm-1.4 and -2.9. In the case of nano-ordered thin grafted surfaces, the surface chain mobility is strongly influenced by the thickness of PIPAAm grafted layers because dehydration of PIPAAm chains should be enhanced by the hydrophobic TCPS surfaces. PIPAAm graft amounts, that is, thickness of the PIPAAm grafted layers, play a crucial role in temperature-induced hydrophilic/hydrophobic property alterations and cell adhesion/detachment behavior.     

疏水改性MCM-41对甲草胺缓释性能的影响

采用浸渍法将甲草胺吸附到纯硅MCM-41(M41)介孔材料中, 以六甲基二硅氮烷(HMDS)为表面改性剂, 通过气-固反应对吸附了甲草胺的M41材料(Ach/M41)进行疏水改性, 得到了既具有高载药性又能有效延缓甲草胺释放的缓释体系Ach/TMS-M41. XRD、低温N₂吸附/脱附、FT-IR和TG等分析结果表明, 甲草胺在M41中的吸附量高达0.381 g·g^-1(质量分数为27.6%), 此时M41仍保持原有的孔道结构, 且甲草胺能完全分散于M41孔道中. 分别对Ach/M41和Ach/TMS-M41在水中的缓释性能进行了测试, 甲草胺释放率分别为62%和38.1%, 表明疏水改性对延缓甲草胺释放有较好的效果. 而且, 介孔材料孔壁对甲草胺具有明显的紫外屏蔽保护作用.     

Fluoroalkyl-functionalized silica particles: synthesis, characterization, and wetting characteristics

Fluoroalkyl-functionalized silica particles for use in nonwetting surfaces were prepared by treatment of silica particles with fluoroalkyl-functional chlorosilanes. Both fumed and precipitated silica were studied, as well as the efficiency of surface coverage using mono-, di-, and trifunctional chlorosilanes. The most effective surface treatment was accomplished via the surface grafting of monofunctional chlorosilanes in the presence of preadsorbed dimethylamine under anhydrous conditions at room temperature. Confirmation of covalent attachment was accomplished via Fourier transform infrared (FT-IR) spectroscopy, while elemental analysis, thermogravimetric analysis, and nitrogen adsorption isotherms were used to determine grafting densities and additional key geometric characteristics of the grafted layer. The effect of residual silanol content on the moisture uptake properties of the modified silica particles was determined by measuring the water uptake of unbound particles, while liquid wetting properties were determined by dynamic contact angle analysis of elastomeric composites. Although residual silanol content was shown to effect wetting properties, results suggest that surface geometry dominates the performance of liquid-repellent surfaces. The potential use of fluoroalkyl-functionalized silica particles for hydrophobic and oleophobic applications is discussed.     

The adsorption of lysozymes: A model system

Hen egg white lysozyme was adsorbed onto clean borosilicate glass and n-pentyl silane-treated glass surfaces. Both modified (reductively methylated) and native lysozyme were studied. Variable angle X-ray photoelectron spectroscopy (VA-XPS) suggested differences in the nature of the adsorbed layer depending on substrate properties, as well as on degree of methylation of the protein. Adsorbed film thickness (as measured in the dehydrated state by XPS) ranged from 14 Å on hydrophilic glass to 25 Å on the hydrophobic surface. Degree of surface coverage ranged from 45% on the hydrophobic to 69% on the hydrophilic surface. The results suggest that lysozyme unfolds to a greater extent and covers more surface on the hydrophilic glass, possibly due to strong electrostatic interactions at the pH 7.4 conditions used in the study. An analysis of the surface structure of native hen lysozyme by molecular graphics has also been performed, suggesting that adsorption on hydrophobic surfaces should occur via the hydrophobic patch opposite the enzyme active site cleft. A comparison with human lysozyme has also been made using total internal reflection fluorescence (TIRF) spectroscopy to measure protein adsorption on model surfaces. The two proteins have significantly different interfacial properties.     

氨基硅烷偶联剂改性凹凸棒土的制备及其吸附性能

采用双氨基硅烷偶联剂KH-792对盐酸改性凹凸棒土(HATT)进行改性,使用FTIR、TGA、DSC、XRD和BET等对目标产物(KHATT)进行了表征。 研究了KHATT对模拟水样中Cr(Ⅵ)的吸附性能,系统考察了模拟水样中Cr(Ⅵ)的初始浓度、pH值、吸附时间及KHATT用量等因素对Cr(Ⅳ)去除率的影响。 结果表明,在KHATT用量为3 g/L、吸附时间为40 min、pH值为5.5的条件下,KHATT对Cr(Ⅵ)的去除率最高,达85.15%;且KHATT经再生后第4次的吸附量仍可达到第1次吸附量的90%以上。 对吸附的过程和机理进行了初步探讨。     

Effect of Charge and Hydrophobicity on Adsorption of Modified Starches on Polyester

Polyester fabric (poly(ethylene terephthalate)) is a hydrophobic polymer. Its hydrophobic nature can be a disadvantage for certain applications like dyeing, finishing, detergency, etc. Physical or chemical modification of the polyester to make it more hydrophilic is therefore desirable for certain performance characteristics. Surface modification of polyester to make it hydrophilic can be achieved by adsorbing polymers on the polyester surface. Starch is a commonly available, hydrophilic polymer used in many textile applications that can be used to modify polyester. However, it needs to be chemically modified so that it can adsorb on the polyester fabric and physically modify the fabric characteristics. The polymers used in this study are two different modified starches—cationic and anionic starches and mixtures of the two. The adsorption kinetics on a polyester substrate was studied. The effect of charge and hydrophobicity on adsorption was investigated. Cationic starches were shown to readily adsorb on polyester and this was attributed to electrostatic interactions. Hydrophobic substituents on the cationic moiety resulted in increased adsorption. This was attributed to the weak hydrophobic interaction between the polymer chains which could result in a more coiled polymer conformation. It is hypothesized that more starch molecules are required for surface coverage of the polyester, resulting in an increase in adsorption. Anionic starch was adsorbed on the substrate but at a slower rate than the cationic starches. It is likely that there is a H bonding between acid groups on the starch and the ester groups of the polyester. However, the anionic starch is desorbed when the polyester is placed in an aqueous medium. When a blend of cationic starch and anionic starch was used, a low concentration of anionic starch was seen to increase adsorption, indicating that the polyelectrolyte complex itself may be adsorbing on the substrate. Further increases cause a decrease in adsorption as no sites may be available on the complex for adsorption. When hydrophobic substituents are present, addition of the anionic starch causes a decrease in adsorption at all concentrations. This was attributed to the “crosslinking” between the hydrophobically modified starch and the anionic polymer.     

Surface energy of hydrophobic adsorbents

The adsorption of water vapor and the heat of wetting of hydrophilic hydromica and hydrophobized samples of kaolinite and Silochrom were studied. The contact angles for the wetting of the investigated materials with water were obtained. The thermodynamic characteristics of the surface of the sorbents and the interfacial region at their boundary with water were calculated from the obtained data. It was shown that the boundary water layers close to the hydrophilic surface of the hydromica are more ordered while those close to the hydrophobic surfaces of the modified samples of kaolinite, Silochrom, and the reference sample (extremely hydrophobic Teflon) are less ordered than liquid water. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 2, pp. 87–91, March–April, 2006.     

Adsorption and wetting characterization of hydrophobic SBA-15 silicas

This work describes adsorption and wetting characterization of hydrophobic ordered mesoporous silicas (OMSs) with the SBA-15 motif. Three synthetic approaches to prepare hydrophobic SBA-15 silicas were explored: grafting with (1) covalently-attached monolayers (CAMs) of C(n)H(2)(n+1)Si(CH(3))(2)N(CH(3))(2), (2) self-assembled monolayers (SAMs) of C(n)H(2)(n+1)Si(OEt)(3), and (3) direct ("one-pot") co-condensation of TEOS with C(n)H(2)(n+1)Si(OEt)(3) in presence of P123 (n=1-18). The materials prepared were characterized by nitrogen adsorption, TEM, and chemical analysis. The surface properties of the materials were assessed by water contact angles (CAs) and by BET C constants. The results showed that, while loadings of the alkyl groups (%C) were comparable, the surface properties and pore ordering of the materials prepared through different methods were quite different. The best quality hydrophobic surfaces were prepared for SBA-15 grafted with CAMs of alkylsilanes. For these materials, the water CAs were above ～120°/100° (adv/rec) and BET C constants were in the range of ～15-25, indicating uniform low-energy surfaces of closely packed alkyl groups on external and internal surfaces of the pores respectively. Moreover, surfaces grafted with the long-chained (C(12)-C(18)) silanes showed super-hydrophobic behavior (CAs～150-180°) and extremely low adhesion for water. The pore uniformity of parental SBA-15 was largely preserved and the pore volume and pore diameter were consistent with the formation of a single layer of alkylsilyl groups inside the pores. Post-synthesis grafting of SBA-15 with SAMs worked not as well as CAMs: the surfaces prepared demonstrated lower water CAs and higher BET C constants, thereby indicating a small amount of accessible polar groups (Si-OH) related to packing constrains for SAMs supported on highly curved surfaces of mesopores. The co-condensation method produced substantially more disordered materials and less hydrophobic surfaces than any of the grafting methods. The surfaces of these materials showed low water CAs and high BET C constants (～100-200) thereby demonstrating a non-uniform surface coverage and presence of unmodified silica. It is concluded that CAMs chemistry is the most efficient approach in preparation of the functionalized OMS materials with uniform surfaces and pores.     

具有双亲特性的水相哑铃型SiO2纳米粒子的制备

以纳米SiO2水溶胶为原料,3?氨丙基三乙氧基硅烷(APTES)和3?氯丙基三乙氧基硅烷(CPTES)为改性剂,在水基环境下分别对SiO2纳米粒子进行改性,得到了具有亲水特性的APTES改性SiO2粒子和具有亲油特性的CPTES改性SiO2粒子水溶胶。2种粒子按不同比例混合,利用接枝在SiO2粒子表面氨基和氯丙基的取代反应,使得2种具有亲水/亲油特性的改性SiO2纳米粒子偶联,制备了粒径为40~50 nm的哑铃型SiO2纳米粒子。并通过透射电镜(TEM)、傅里叶变换红外光谱(FT?IR)、X射线光电子能谱(XPS)以及动态光散射(DLS)等方法对其进行了系统表征。结果表明,2种粒子成功偶联形成了具有哑铃型结构的水相SiO2纳米粒子,该粒子两面具有不同的亲水性,粒径近似等于APTES改性SiO2粒子和CPTES改性SiO2粒子的粒径之和。     

Characterisation of hydrophilic ceramic membranes modified by fluoroalkylsilanes into hydrophobic membranes

In order to avoid high hydrophilic behaviour of ceramic membranes prepared with metal oxides, different zirconia membranes were grafted by different fluoroalkylsilanes. Hydrophobicity was characterised by contact angle and water permeability measurements. Results show high hydrophobic behaviour of surfaces with high values of contact angle. An outlet pressure, characteristic of each grafted membranes, was obtained. Different characterisation methods were used on grafted zirconia powders and membranes as XPS, ¹H-RMN, TGA, IR. Although SiOmetal boundings were not clearly detected, a reaction instead of a simple adsorption of molecules on substrates was identified.     

纳米银修饰的超疏水界面用于农药的超灵敏检测

采用化学还原法,在具有不同微观结构的规整的不锈钢网和聚纤维素酯薄膜表面合成了银纳米颗粒.利用氟化试剂对复合界面进行处理,形成超疏水性能的界面,能有效地浓缩目标分子.以罗丹明6G(R 6G)为分析物,纳米银修饰聚纤维素酯薄膜为基底,采用表面增强拉曼散射(SERS)分析了氟化处理前后基底对目标分子的检测能力.实验结果表明,具有超疏水性能的复合基底对R 6G分子的检出限为1 ×10-16 mol/L.以纳米银修饰的不锈钢网和聚纤维素酯两种复合材料为基底,对常用杀虫剂敌百虫的检出限分别为1×10-15 mol/L和1×10-16 mol/L.     

Efficient removal of partially hydrolysed polyacrylamide in polymer-flooding produced water using photocatalytic graphitic carbon nitride nanofibres

In this work, graphitic carbon nitride (GCN) photocatalyst-incorporated polyacrylonitrile (PAN) nanofibres (GCN/PAN nanofibres) were successfully prepared using electrospinning technique. The physicochemical properties of the fabricated GCN/PAN nanofibres were analysed using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), elemental analyser, X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and UV–vis–NIR spectroscopy. The photocatalytic degradation by GCN/PAN nanofibres exhibited 90.2% photodegradation of partially hydrolysed polyacrylonitrile (HPAM) after 180 min under UV light irradiation in a suspension photocatalytic reactor. The results suggest that the photodegradation of HPAM contaminant by GCN/PAN nanofibres was due to the synergetic effects of HPAM adsorption by the PAN nanofibres and HPAM photodegradation by the GCN. This study provides an insight into the removal of HPAM from polymer-flooding produced water (PFPW) through photocatalytic degradation of liquid-permeable self-supporting nanofibre mats as a potentially promising material to be used in industrial applications.     

The surface energy of hydrophilic and hydrophobic adsorbents

Water vapor adsorption and heats of water wetting are studied for hydrophilic quartz, hydrophobic-hydrophilic talc, and hydrophobized Silochrom samples. Water contact angles on the materials under examination are found. The surface thermodynamic parameters of the sorbents are calculated from the data obtained. It is shown that boundary water layers on hydrophilic quartz surface are ordered to a higher extent, while those on hydrophobic basal surfaces of talc particles and hydrophobic surfaces of modified Silochrom samples are ordered to a lower extent relative to liquid water. An empirical equation relating the surface pressure of water films adsorbed on hydrophilic high-energy surfaces with the surface free energy of the latter is proposed. The values of surface free energy are estimated from this equation for a number of important hydrophilic adsorbents.     

Fouling and protein adsorption effect of low-temperature plasma treatment of membrane surfaces

Adsorption of proteins and the effect of the chemical nature of membrane surfaces on protein adsorption were investigated using¹⁴C-tagged albumin and several microporous membranes (polyvinilydene fluoride, PVDF; nylon; polypropylene, PP; and polycarbonate, PC). The membrane surfaces were modified by exposing them to low-temperature plasma of several different monomers (n-butane, oxygen, nitrogen alone or as mixtures) in a radiofrequency plasma reactor. Transients in the permeability of albumin solutions through the membranes and changes in flux of distilled water through the membranes before and after adsorption of albumin were used to investigate the role of protein adsorption on membrane fouling. The results show that the extent of adsorption of albumin on hydrophobic membranes was considerably more than that on hydrophilic membranes. The hydrophilic membranes were susceptible to electrostatic interactions and less prone to fouling. A pore-blocking model was successfully used to correlate the loss of water flux through pores of defined geometry