Some surface properties of plasma polymers prepared from hexamethyldisilazane and diethylaminotrimethylsilane

Plasma polymers from some silyl amines were produced by the radio frequency of 13.56 MHz, and the surface properties were investigated. The polymers were revealed to be as hydrophobic as a plasma polymer from tetramethylsilane, which does not contain nitrogen. The hydrophobicity became effective at around 50 Å thicknesses of these polymer layers deposited on micro-slide glass. These polymers have gradually become comparatively hydrophilic with the aging. The change of wettability is probably due to the oxidation of these surface layers to form oxides and peroxides, which are more hydrophilic. The hydrophobic character of silyl amine plasma polymers could be explained by the lack of amines and/or amides in these polymers, as observed with ATR-IR and ESCA spectra. These spectroscopic observations also suggest that nitrogen is a more fragile element in plasma than carbon or silicon in the silyl amines.     

Graft polymerization of vinyl monomers from initiating groups introduced onto polymethylsiloxane-coated titanium dioxide modified with alcoholic hydroxyl groups

The grafting of vinyl polymers onto the surface of polymethylsiloxane-coated titanium dioxide modified with alcoholic hydroxyl groups (Ti/Si–R–OH) were investigated. The introduction of azo and trichloroacetyl groups onto the surface of Ti/Si–R–OH was achieved by the reaction of the surface alcoholic hydroxyl groups with 4,4′-azobis(4-cyanopentanoic acid) and trichloroacetyl isocyanate, respectively. The radical polymerizations of vinyl monomers were successfully initiated by the azo groups introduced onto the surface and by the system consisting of Mo(CO)₆ and Ti/Si–R–COCCl₃. During the polymerization, the corresponding polymers were effectively grafted onto the titanium dioxide surface through propagation from surface radicals formed by the decomposition of azo groups and by the reaction of Mo(CO)₆ with trichloroacetyl groups on the surface. The percentage of grafting and grafting efficiency in the graft polymerization initiated by the system consisting of Ti/Si–R–COCCl₃ and Mo(CO)₆ were much larger than those initiated by azo groups. The polymer-grafted titanium dioxide was found to produce a stable colloidal dispersion in good solvents for the grafted polymer. The dispersibility of poly(N,N-diethylacrylamide)-grafted titanium dioxide in water was controlled by temperature. In addition, the wettability of the surface of titanium dioxide to water was readily controlled by grafting of hydrophilic or hydrophobic polymers.     

Hydrophilic surface formation on polymers by ion-assisted reaction

The wettability and adhesion of various polymers were improved using ion-assisted reaction (IAR) method, in which the polymer surfaces were irradiated by energetic ions in a reactive gas environment. The addition of new polar groups on polymer surfaces and permanent wettable polymer surfaces (water contact angle below 30° and surface free energy 60–70 mJ/m²) have been accomplished by IAR treatment. The changes in wettability and surface free energy were critically dependent on the ion dose, the ion beam energy and the flow rate of the reactive gas. Improvements in wettability and surface free energy are primarily attributed to the increase of polar components due to the formation of polar groups such as –(C=O)–, –(C=O)–O–, –(C–O)–, etc. The characteristics of the IAR treatment have been reviewed, with outstanding results regarding the wettability and adhesion of various polymers from polyolefin to fluoropolymers.     

Analysis of plasma polymerization of benzaldehyde

Plasma polymerization of benzaldehyde was investigated mainly by infrared spectroscopy. The solubility, wettability, and heat stability for the formed plasma polymer are discussed. Benzaldehyde was plasma-polymerized to yield films and/or powders. The products contained a large amount of carbonyl-containing groups, such as aromatic ketone, aliphatic ketone, α, β-olefinic ketone, and cyclic ketone. The chemical structures of formed polymer were strongly influenced by the plasma parameters and so were its solubility, surface wettability, and heat stability. The polymerization mechanism in plasma for benzaldehyde is discussed on the basis of the infrared analyses of the formed polymers at different plasma conditions.     

Plasma surface modifications for improved biocompatibility of commercial polymers

This report describes work using low pressure gas plasma techniques for the fabrication of surfaces designed for compatibility with biological tissue and fluids. The smoothness of the surfaces was investigated using scanning tunnelling microscopy (STM) and the wettability was assessed by measurement of air/water contact angles. Plasma surface treatment rendered fluorocarbon polymers wettable by polar liquids, but the wettability decreased with time during storage of the samples in air. Plasma polymerization, on the other hand, allowed the deposition of thin coatings which were more stable with time. STM of plasma polymers, which were coated with a sputtered film of platinum or gold, showed that these coatings were smooth and continuous. The attachment and growth of human umbilical artery endothelial cells was used to assess the biocompatibility of several plasma polymer surfaces. There was some correlation between the ability of a surface to grow cells and the wettability of that surface with polar liquids, but significant differences in cell growth on surfaces with very similar hydrophilicity indicated that other factors are at least as important.     

Grafting of branched polymers onto nano-sized silica surface: Postgrafting of polymers with pendant isocyanate groups of polymer chain grafted onto nano-sized silica surface

To control the surface wettability of nano-sized silica surface, the postgrafting of hydrophilic and hydrophobic polymers to grafted polymer chains on the surface was investigated. Polymers having blocked isocyanate groups were successfully grafted onto nano-sized silica surface by the graft copolymerization of methyl methacrylate (MMA) with 2-(O-[1′-methylpropylideneamino]caboxyamino)ethyl methacrylate (MOIB) initiated by azo groups previously introduced onto the surface. The blocked isocyanate groups of poly(MMA-co-MOIB)-grafted silica were stable in a desiccator, but isocyanate groups were readily regenerated by heating at 150 °C. The hydrophilic polymers, such as poly(ethylene glycol) (PEG) and poly(ethyleneimine) (PEI), were postgrafted onto the poly(MMA-co-MOIB)-grafted silica by the reaction of functional groups of PEG and PEI with pendant isocyanate groups of poly(MMA-co-MOI)-grafted silica to give branched polymer-grafted silica. The percentage of grafting increased with increasing molecular weight of PEG, but the number of postgrafted chain decreased, because of steric hindrance. The hydrophobic polymers, such as poly(dimethylsiloxane) were also postgrafted onto poly(MMA-co-MOI)-grafted silica. It was found that the grafting of hydrophobic polymer and the postgrafting of hydrophilic polymer branches readily controls the wettability of silica surface to water.     

Surface modification on nanoscale titanium dioxide by radiation: Preparation and characterization

Electron beam mutual radiation to induce graft polymerization has been carried out respectively, between nanoscale anatase‐ or rutile‐titanium dioxide particles surface and methyl methacrylate (MMA). The composition and properties of surface modified titanium dioxide were investigated by a number of surface sensitive techniques: X‐ray photoelectron spectrum (XPS), FTIR, X‐ray diffraction (XRD), and NMR. Results of the technological measurements show how surface chemistry is affected throughout the surface modification process, finally leading to a complete and homogeneous vinyl compound overlayer on top of the titanium dioxide samples. In comparison with stereochemical structures of the graft molecular chains and the PMMA induced by radiation polymerization, the surfaces of the oxides are considered to provide a template for the graft polymerization. The grafted titanium dioxide is found to produce a stable colloidal dispersion, in good solvents for the grafted polymer, and the dispersibility of grafted dioxides is influenced by temperature. In addition, the wettability of the surface of titanium dioxide to water is readily controlled by grafting of hydrophilic or hydrophobic polymers. Based on the above results, it is concluded that MMA is covalently linked to the surface of titanium dioxide by a surface modification process. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 100: 3510–3518, 2006     

Surface modification of polypropylene by a combination of photooxidation and photosubstitution reactions

An efficient photoprocess has been developed to increase polypropylene surface wettability by insertion of acid, ester, and amide functionalities. A systematic study of polypropylene surface irradiations indicates that photoxidations always precede the photosubstitution reactions that occur at the carbonyl site to form carboxyl, ester, and amide groups. Irradiations with amines to form amide groups always achieved the highest level of wettability improvement without changing bulk morphology. This process may be very beneficial in facilitating the fabrication of composite membranes with hydrophilic barriers on top of a hydrophobic polymeric support such as polypropylene. The high chemical resistance of polypropylene matrix to various solvents makes the partially hydrophilized polypropylene an ideal membrane support when hydrophilic membrane barriers made by interfacial polymerization/crosslinking are needed for a variety of separation application. © 1995 John Wiley & Sons, Inc.     

Surface grafting of polymers onto glass plate: Polymerization of vinyl monomers initiated by initiating groups introduced onto the surface

The surface grafting of polymers onto a glass plate surface was achieved by the polymerization of vinyl monomers initiated by initiating groups introduced onto the surface. Azo groups were introduced onto the glass plate surface by the reaction of 4,4′-azobis(4-cyanopentanoic acid) with isocyanate groups, which were introduced by the treatment with tolylene-2,4-diisocyanate. The radical polymerization of various vinyl monomers was initiated by azo groups introduced onto the glass plate surface and the corresponding polymers were grafted from the surface: The surface grafting of polymers was confirmed by IR spectra, and the contact angle of surface, with water. The contact angle of the glass plate increased by the grafting of hydrophobic polymers, but decreased by the grafting of hydrophilic polymers. The radical postpolymerization was successfully initiated by the pendant peroxycarbonate groups of grafted polymer on the surface to give branched polymer-grafted glass plate. The cationic polymerization of vinyl monomers was also successfully initiated by benzylium perchlorate groups introduced onto the glass plate surface and the corresponding polymers were grafted onto the surface. The contact angle of the glass plate surface obtained from the cationic polymerization of styrene was larger than that obtained from the radical polymerization. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2165–2172, 1997     

Bioinspired steel surfaces with extreme wettability contrast

The exterior structures of natural organisms have continuously evolved by controlling wettability, such as the Namib Desert beetle, whose back has hydrophilic/hydrophobic contrast for water harvesting by mist condensation in dry desert environments, and some plant leaves that have hierarchical micro/nanostructures to collect or repel liquid water. In this work, we have provided a method for wettability contrast on alloy steels by both nano-flake or needle patterns and tuning of the surface energy. Steels were provided with hierarchical micro/nanostructures of Fe oxides by fluorination and by a subsequent catalytic reaction of fluorine ions on the steel surfaces in water. A hydrophobic material was deposited on the structured surfaces, rendering superhydrophobicity. Plasma oxidization induces the formation of superhydrophilic surfaces on selective regions surrounded by superhydrophobic surfaces. We show that wettability contrast surfaces align liquid water within patterned hydrophilic regions during the condensation process. Furthermore, this method could have a greater potential to align other liquids or living cells.     

Modifying and managing the surface properties of polymers

An ongoing challenge in polymer science is the preparation of materials with bespoke surface properties which differ from that of the bulk, for example hydrophobicity, wettability, chemical resistance, adhesion or biocompatibility. We highlight here recent efforts in the design, development and application of (multi)end‐functionalized polymers as additives for the efficient modification of polymer surface properties. Aryl‐ether moieties bearing up to eight functional groups have been used as initiators for the controlled polymerization of both styrene and methyl methacrylate by atom transfer radical polymerization (ATRP) and of lactide by ring opening polymerization (ROP). The resulting polymers have been used as additives to modify the surfaces of the corresponding bulk polymers. Fluorinated polymer surfaces are particularly appealing in terms of their liquid repellence, chemical inertness and low coefficient of friction. When an additive consisting of a low molecular weight polystyrene chain, end‐capped with four C₈F₁₇ groups, is present in a matrix of polystyrene at levels as low as 0.1%, near polytetrafluoroethylene‐like surface properties result. Copyright © 2007 Society of Chemical Industry     

Water wettability/non-wettability of polymer materials by molecular orbital studies

The water wettability and non-wettability onto various kinds of polymers, which have so far been macroscopically described by the water contact angle, were investigated using the molecular orbital theory. An atomistic model consisting of an H₂O molecule and a selected polymer crystal surface was analyzed in the isolated and the physisorbed states. The degree of interaction between the water molecule and the polymer surface was evaluated by considering the change of Mulliken charge at the oxygen site in the water molecule, and also the work of adhesion during the physisorption process. Such energetic quantities for several polymers were compared with the macroscopic water wettability/non-wettability. We found fairly good agreement between these approaches for the highly non-wettability polymers.     

Conducting polymers are not just conducting: a perspective for emerging technology

Conducting polymers, such as polyaniline and polypyrrole, are organic semiconductors with mixed electronic and ionic conductivity. In addition to electrical properties, their electrochemical activity opens research opportunities in corrosion protection or energy‐storage devices. Conducting polymers are active in catalysis, the photocatalytic decomposition of dyes or electrocatalysts in fuel cells being examples. In contrast to classical polymers, conducting polymers respond to various stimuli by changes in conductivity, colour or other physicochemical parameters; this is used in sensors. Conducting polymers are good adsorbents of organic pollutants in wastewater treatment and are likely to be applicable for environmental issues. The perspectives of these polymers are briefly outlined. © 2019 Society of Chemical Industry     

A novel fluorinated polymeric product for photoreversibly switchable hydrophobic surface

A new chemical product, that is, photoreversibly switchable hydrophobic surface coating, was synthesized by atom transfer radical polymerization and graft‐from method based on molecular design. Focusing on the strategy of new product development from the chemical product engineering perspective, the product characterization, switching mechanism analysis, performance evaluation, and model interpretation were carried out to confirm the new product manufacture and to ensure the product application with a following aging test. The results show that the product enables surfaces to have reversibly switchable wettability and excellent stability after a month‐long test with eight irradiation cycles. Additionally, the wetting behavior of silicon surface can be tuned between hydrophilicity and hydrophobicity based on blank sample using the surface engineering technique (decorated with functional film and surface roughening). The product presented here can be utilized for constructing a hydrophobic surface with photo‐induced controllable wettability in moisture‐resistance, and it also offers a new technique for the manipulation of liquids in microfluidic devices. © 2014 American Institute of Chemical Engineers AIChE J 60: 4211–4221, 2014     

Sorption of aromatic compounds in water using insoluble cyclodextrin polymers

Insoluble β-cyclodextrin (β-CD) polymers have been used for the recovery of various organic pollutants from aqueous solutions. These resins have been prepared by polymerization using epichlorohydrin (Epi) as a crosslinking agent. Several crosslinked polymers with various degrees of β-CD were used. Several studies (time, concentration, kinetics, and pH) are presented here. The results show that these sorbents exhibit high sorption capacities toward substituted benzene derivatives. The mechanism of sorption is both physical adsorption in the polymer network and/or the formation of an inclusion complex and/or the formation of hydrophobic guest–guest interactions. © 1998 John Wiley & Sons, Inc. J Appl Polm Sci 68: 1973–1978, 1998     

Synthesis of nano polyaniline and poly-<Emphasis Type="Italic">o</Emphasis>-anisidine and applications in alkyd paint formulation to enhance the corrosion resistivity of mild steel

Protection of oxidizable metals against corrosion has now being intensively investigated, by applying or developing different methods such as coatings and conversion films; however, all reported methods involve environmentally hazardous materials. Conducting polymers have now been used as corrosion inhibitor coatings that are either chemically or electrochemically deposited on the metal substrate. The application of nanotechnology in the corrosion protection of metals has recently gained momentum. Environmental impact can also be improved by utilizing nanostructure particulates in coatings and eliminating the requirement of toxic solvents. We report here the synthesis of nanoparticles of polyaniline (PANI) and poly-o-anisidine (POA) using emulsion polymerization method in micellar solution of SDS and their anticorrosive property has been experimentally checked. The prepared nanoparticles have been characterized by FTIR and TEM. The nanoparticles of the synthesized polymers were dispersed in alkyd paint formulation for coatings on the metal surface (mild steel). The water absorption in the prepared coatings was also studied. The corrosion rate of polymeric film was determined by weight loss measurement and the surface morphology was examined by SEM. The nano PANI/Alkyd coatings showed considerable protection against corrosion than the POA/alkyd coatings.     

Review: Polymers,Surface-Modified Polymers,and Self Assembled Monolayers as Surface-Modifying Agents for Biomaterials

Biocompatibility and nontoxicity of biomaterials are of utmost importance when foreign bodies come in contact with a biological system. Irrespective of the nature of material, nonspecific protein adsorption is the first process observed at surface–biological system interfaces followed by cellular processes. Nonspecific protein adsorption leads to deleterious cellular processes such as biofouling and finally immunological host response. Hence, surface modification becomes mandatory for preventing undesirable implant failure and inflammatory responses. Various polymers, surface-modified polymers and surfaces withself assembled monolayers, have been tested to tune surface properties for a given application. Surface functional groups and surface structures of polymers and copolymers regulate surface hydrophobicity, nonspecific protein adsorption, biomaterial stability, and antifouling property, etc. Self assembled monolayers are formed by covalent linkage with more controlled surface structure and smoothness. Mixed and hybrid self assembled monolayers containing both hydrophilic and hydrophobic groups result in moderate wettability. Further, we have discussed different methods of surface modification using polymers, modified polymers, and self assembled monolayers for improved surface biocompatibility and nonfouling properties.     

Conductive polymer‐coated mesh films with tunable surface wettability for separation of oils and organics from water

Here, we reported the preparation of hydrophobic mesh films by coating conductive polymers including polyaniline and polypyrrole (PPy) onto stainless steel grid through a simple electrodepositing process by combination with modification of hydrophobic materials. The hydrophobic mesh films can be used for continual separation of oils and organics from water with high selectivity. Furthermore, mesh film with reversible switching wettability from hydrophobicity to hydrophilicity can be obtained by electrodepositing of PPy in the presence of perfluorooctanesulfonate dopants at different electric potential, which makes it possible to prepare functional mesh materials with remotely controllable surface wettability for selective absorption and purification. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40759.     

Dry coating of talc particles with fumed silica: Influence of the silica concentration on the wettability and dispersibility of the composite particles

Even though dispersion operations have been the object of several investigations, the importance of the various parameters and especially the physicochemical and surface properties are rarely treated. Dry particle coating can be used to create new-generation materials by combining different powders exhibiting different physical and/or chemical properties. In such processes relatively large particles (host particles) are mechanically coated with fine particles (guest particles), without using solvents and subsequent drying, to create new functionalities or to improve initial characteristics. The purpose of this study is to modify the surface of Talc particles by dry coating with different concentrations of hydrophobic Silica (Aerosil R972®), to examine the effect of the coating on the wettability of the coated Talc particles and to study the effects on the dispersibility of these same composite particles. Dry coating is found to modify the surface of Talc particles and to control their wettability and dispersibility in aqueous solutions.     

十四酸铜超疏水表面的溶剂热法制备及其润湿性

超疏水表面是防止低温条件下风机叶片表面结冰、保证机组安全运行的重要材料之一。本文以十四酸乙醇溶液和铜片为前体,基于溶剂热法将十四酸铜原位生长于铜片表面,通过调控前体浓度和反应时间获得了不同润湿性的疏水表面,实现了疏水表面润湿性的有效调控。此外,采用扫描电子显微镜（SEM）观察了十四酸铜团簇的微结构及分布状态;借助X射线衍射仪（XRD）验证团簇粉末的晶格成分;通过接触角测量仪量化不同条件下样品的表面润湿性。结果表明,随着铜片表面十四酸铜团簇密集程度的增加,液滴与铜片的接触角增大,铜片润湿性降低;十四酸乙醇溶液浓度及反应时间可以显著改变十四酸铜分布状态,进而改变表面润湿性。疏水表面润湿性的变化是由于Ostwald熟化促进晶体生长,使表面的“禾苗”状聚合物逐渐生长成十四酸铜微米花。