Replication of laser‐textured alumina surfaces by polydimethylsiloxane: Improvement of surface hydrophobicity

Alumina tiles are textured by a laser beam to obtain improved hydrophobic characteristics at the surfaces. Since the textured surfaces are optically opaque, the resulting surfaces are copied and replicated by polydimethylsiloxane (PDMS). Some of the texture features such as whiskers‐like structures with complex shapes could not be copied by PDMS and synthesized silica particles are deposited onto PDMS copied and replicated surfaces to create a lotus effect. Analytical tools are incorporated to characterize the PDMS copied and replicated surfaces as well as synthesized silica particles deposited surfaces. Dynamic water contact angle measurements are carried out to assess hydrophobic characteristics of the resulting surfaces. It is found that PDMS copied and replicated surfaces have almost identical surface texture morphology to that of laser treated surface. Introducing synthesized silica particles improved the lotus effect on the PDMS copied and replicated surfaces; in which case, the hysteresis of droplet contact angle remains significantly low. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44015.     

Surface and wetting characteristics of textured bisphenol‐A based polycarbonate surfaces: Acetone‐induced crystallization texturing methods

Polycarbonate (PC) sheet is a promising material for facile patterning to induce hydrophobic self‐cleaning and dust repelling properties for photovoltaic panels’ protection. An investigation to texture PC sheet surfaces to develop a self‐cleaning structure using solvent induced‐crystallization is carried out using acetone. Acetone is applied in both liquid and vapor states to generate a hierarchically structured surface that would improve its contacts angle and therefore improve hydrophobicity. The surface texture is investigated and characterized using atomic force microscopy, contact angle technique (Goniometer), optical microscopy, ultraviolet‐visible spectroscopy (UV–vis) and Fourier transform infrared spectroscopy. The findings revealed that the liquid acetone‐induced crystallization of PC surface leads to a hierarchal and hydrophobic surface with an average contact angle of 135° and average transmittance <2%. However, the acetone vapor induced‐crystallization results in a slightly hydrophilic hierarchal textured surface with high transmittance; in which case, average contact angle of 89° and average transmittance of 69% are achieved. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43074.     

Synthesis and surface characterization of poly(methyl methacrylate)‐block‐polydimethylsiloxane copolymers from macroazoinitiator

Poly(methyl methyacrylate)‐block‐polydimethylsiloxane (PMMA‐b‐PDMS) copolymers with various compositions were synthesized with PDMS‐containing macroazoinitiator (MAI), which was first prepared by a facile one‐step method in our lab. Results from the characterizations of X‐ray photoelectron spectroscopy (XPS), contact angle measurements, and atomic force microscopy (AFM) showed that the copolymer films took on a gradient of composition and more PDMS segments enriched at the film surfaces, which then resulted in the low surface free energy and little microphase separation at the film surfaces. By contrast, transmission electron microscopy (TEM) analysis demonstrated that distinct microphase separation occurred in bulk. Slight crosslinking of the block copolymers led to much steady morphology and more distinct microphase separation, in particularly for copolymers with low content of PDMS. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Simultaneous graft copolymerization of 2‐hydroxyethyl methacrylate and acrylic acid onto polydimethylsiloxane surfaces using a two‐step plasma treatment

Acrylic acid (AAc) and 2‐hydroxyethyl methacrylate (HEMA) mixtures were simultaneously grafted onto the surfaces of polydimethylsiloxane (PDMS) films using a two‐step oxygen plasma treatment (TSPT). The first step of this method includes: oxygen plasma pretreatment of the PDMS films, immersion in HEMA/AAc mixtures, removal from the mixtures, and drying. The second step was carried out by plasma copolymerization of preadsorbed reactive monomers on the surfaces of dried pretreated films. The effects of pretreatment and polymerization time length, monomer concentration, and ratio on peroxide formation and graft amount were studied. The films were characterized by attenuated total reflection Furrier transformer infrared (ATR‐FTIR) spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), zeta potential, surface tension, and water contact angle measurements. The ATR‐FTIR spectrum of the modified film after alkaline treatment showed the two new characteristic bands of PHEMA and PAAc. Both increase the polar part of surface tension (γ_p) after grafting and the evaluation of surface charge at pH 1.8, 7, and 12 confirmed the presence of polar groups on the surface of grafted films with a mixture of HEMA/AAc. Morphological studies using both AFM and SEM evaluation illustrated various amounts of grafted copolymer on the surface of PDMS films. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Formation of poly(octadecyl acrylate) brushes on a silicon wafer surface

To introduce an ultrahydrophobic polymeric phase onto a silicon wafer, an initiator‐modified silicon wafer was prepared with 2‐bromopropionyl bromide and then surface‐initiated atom transfer radical polymerization of octadecyl acrylate was carried out from the initiator‐grafted silicon wafer using CuBr and N,N,N′,N″‐pentamethyldiethylenetriamine as catalyst precursors. The resultant poly(octadecyl acrylate) [poly(ODA)] brushes were characterized by ellipsometry, X‐ray photoelectron spectroscopy, grazing angle Fourier transform infrared spectroscopy, atomic force microscopy, gel permeation chromatography and water contact angle measurements. Wettability of the poly(ODA) brushes was found to depend on the surface coverage (Γ) and the root mean square roughness. The most hydrophobic surface (Γ = 25.35 mg m^?2 and root mean square roughness 11.9 nm) exhibited a water contact angle of 171.1 ± 0.2°. Copyright © 2011 Society of Chemical Industry     

Physicochemical and biological evaluation of plasma‐induced graft polymerization of acrylamide onto polydimethylsiloxane

Polydimethylsiloxane (PDMS) rubbers exhibit good mechanical properties for biomedical and industrial applications, but their inherently high hydrophobicity limits biomedical applications of this material despite its favorable mechanical properties. In this work, surface modification of PDMS by radio‐frequency glow discharge and subsequently graft polymerization of acrylamide was studied. PAAm‐grafted, oxygen plasma‐treated, and control (untreated) PDMS rubbers were characterized using attenuated total reflectance Fourier transform infrared, scanning electron microscopy, dynamic mechanical thermal analyses, zeta potential, and contact angle techniques. Fibroblast (L929) cell attachment and growth onto these surfaces were examined by optical microscopy. The data from in vitro assays showed that cell attachment onto control surface was very negligible while significant cell attachment and growth was observed onto oxygen plasma‐treated and PAAm‐grafted PDMS surfaces. The method developed in this work offers a convenient way of surface modifications of biomaterials to improve attachment of cells onto substrates. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

In vitro blood compatibility of modified PDMS surfaces as superhydrophobic and superhydrophilic materials

The surface of polydimethylsiloxane rubber (PDMS) was irradiated by a CO₂‐pulsed laser. The irradiated surfaces were grafted by hydroxyethylmethacrylate phosphatidylcholine (HEMAPC) by using the preirradiation method. The laser‐treated surfaces and HEMAPC‐grafted PDMS surfaces were characterized by using a variety of techniques including ATR‐FTIR spectroscopy, scanning electron microscopy (SEM), and wettability, which was measured by a water‐drop contact angle. Different surfaces with different wettability were prepared. These surfaces, including untreated PDMS (hydrophobic), laser‐treated PDMS (superhydrophobic), and HEMAPC‐grafted surfaces (superhydrophilic), were used for a platelet adhesion study. Results from in vitro testing indicated that chemical structures, such as negative‐charge polar groups and wettability, are important factors in blood compatibility of these surfaces and the superhydrophilic (the most wettable) and the superhydrophobic (the most unwettable) of modified PDMS surfaces have excellent blood compatibility compared to the unmodified PDMS. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91:2042–2047, 2004     

Modification of polydimethylsiloxane with polyvinylpyrrolidone: Influence of reinforcing filler on physico‐mechanical properties

The present article reports an approach for the modification of hydrophobic polydimethylsiloxane (PDMS) with low molecular weight hydrophilic polyvinylpyrrolidone (PVP) via solution blending method to develop new PDMS‐based materials with improved mechanical performance and wettability which can be used in many biomedical applications. The influence of dimethyldichlorosilane treated fumed silica (FS) on physico‐mechanical properties of PDMS–PVP blends were investigated and analyzed. There was the significant improvement in mechanical, dynamic mechanical and thermal properties of PDMS–PVP blends, whereas, transparency and contact angle were slightly decreased after incorporation of FS into PDMS–PVP blends. Scanning electron microscopy revealed that the fourfold reduction in the average domain size of the dispersed PVP in the PDMS matrix in the presence of compatibilizer (PDMS‐PEO block copolymer) when compared with the uncompatibilized PDMS–PVP blend morphology. By incorporation of FS into the neat PDMS matrix, the onset of degradation (T_i), the maximum rate of degradation (T_max) and overall thermal stabilities increased significantly. On the other hand, by the addition of FS into to PDMS–PVP blends, the T_i and T_max remains unaffected, but overall thermal stabilities increased significantly. PDMS–PVP blends exhibited low contact angle (～45°) which confirmed the formation of the hydrophilic surface. POLYM. ENG. SCI., 56:491–499, 2016. © 2016 Society of Plastics Engineers     

Evaluation of the etching and chrome plating on the ABS,PVC, and PVC/ABS blends surface

As replacement for acrylonitrile‐butadiene‐styrene (ABS), which is commonly used in the manufacture of chrome parts, polyvinyl chloride (PVC) and PVC/ABS blend parts were produced by injection process, etched in sulfochromic solution in different concentrations, immersion time, and temperature, and they were subsequently chrome‐plated by conventional method. After etching, the sample surfaces were analyzed by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), roughness, and contact angle, and compared with the ABS surface. The metal deposition was assessed by visual inspection and adhesion test. The roughness influenced the adhesion of the metal layer directly. The chemical etching increased the surface wettability. To achieve a good metal layer adhesion, higher temperatures, immersion time, and etching solution concentration were necessary. A concentration of 350 g/L chromic acid and 400 g/L sulfuric acid, a 70 °C temperature and a 15 min immersion time resulted in good adhesion in PVC and PVC/ABS blends. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44571.     

Preparation and characterization of superhydrophobic surface based on polydimethylsiloxane (PDMS)

Biomimetic superhydrophobic surfaces exhibit excellent self-cleaning properties due to their special micro/nano-scale binary structures. In order to prepare the superhydrophobic surface of the polydimethylsiloxane (PDMS), a facile fabrication method for replicating micro/nano-scale binary aluminium structures into PDMS is presented. The microscopic morphology, composition, surface roughness (Ra) and wettability of the sample surface were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy, roughness measurement equipment and contact angle meter respectively. Based on the measurements of the contact angles of deionized water (DI water) and ethanediol, surface free energies of the coatings were estimated according to the Owens two-liquid method. The superhydrophobic PDMS exhibited lower surface free energy than flat PDMS with a DI water contact angle (WCA) of 165°. The surface roughness (Ra) increased with the increasing of etching time in the range 0–80?min, and then decreased with the change of etching time, similar to the variation of contact angle with etching time. Moreover, the prepared surface had different micro-morphologies and its wettability was changed by regulating the chemical etching time. In addition, the superhydrophobic PDMS also showed good self-cleaning properties and the bouncing effect of the water droplets.     

Microscopic surface and bulk morphology of semicrystalline poly(dimethylsiloxane)–polyester copolymers

In this study, two series of semicrystalline poly(dimethylsiloxane) (PDMS)–polyester segmented copolymers with various PDMS contents were synthesized. One series was based on polybutylene adipate (PBA) as the polyester segment and the other was based on a polybutylene cyclohexanedicarboxylate ester (PBCH) segment. The copolymers were characterized using ¹H‐nuclear magnetic resonance, size exclusion chromatography, dynamic mechanical analyses, differential scanning calorimetry (DSC), and wide‐angle X‐ray diffraction (WAXD). The microscopic surface morphology and the microscopic bulk morphology were investigated using atomic force microscopy (AFM) and transmission electron microscopy, respectively. The effects of the polyester type and the PDMS content on the crystallinity degree as well as the copolymer surface and bulk morphology at room temperature were investigated for each series. DSC and WAXD results showed the ability of the copolymers to crystallize, to various degrees, depending on the polyester type and the PDMS content. The results showed that the PDMS content had a greater influence on the crystallinity degree in the PDMS‐s‐PBCH (cycloaliphatic) copolymer series than in the PDMS‐s‐PBA (aliphatic) copolymer series. In the copolymers with a low PDMS content, the AFM images showed spherulitic crystal morphology and evidence of PDMS nanodomains in between the crystal lamellae of the ester phase on the copolymer surface. A heterogeneous distribution of the PDMS domains was also observed for these copolymers in the bulk morphology as a result of this segregation between the polyester lamellae. All the copolymers, in both series, showed microphase separation as a result of the incompatibility between the PDMS segment and the polyester segment. Three types of surfaces and bulk morphologies were observed: spherical microdomains of PDMS in a matrix of polyester, bicontinuous double‐diamond type morphology, and spherical microdomains of polyester in a matrix of PDMS as the PDMS content increases. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Surface modification of polydimethylsiloxane microfluidic chips by polyamidoamine dendrimers for amino acid separation

In order to improve the hydrophilicity of polydimethylsiloxane (PDMS) microfluidic chips, a series of polyamidoamine (PAMAM) dendrimers were grafted onto the PDMS pretreated by oxygen plasma and silanized with γ‐glycidoxypropyltrimethoxysilane (γ‐GPS). Fourier transformed infrared absorption by total attenuated reflection (ATR‐FTIR) and scanning electronic microscopy (SEM) showed that PAMAM dendrimers had been grafted on the PDMS surface and a dense and uniform coating was generated. The contact angle decreased from 108.1° to 31.8° compared with the unmodified PDMS, which indicated that the hydrophilicity of PDMS improved markedly. In the modified PDMS microfluidic chips, the EOF reduced obviously and the nonspecific adsorption between the amino acids and the microchannel surface was prevented effectively. The separation efficiency of arginine and phenylalanine were as high as 7.34 × 10⁴ plates/m and 8.61 × 10⁴ plates/m, respectively, and the resolution (R_S) was 4.41. Furthermore, the reproducibility of modified chips was also very excellent, which suggested they had good stability and long service life. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43580.     

Degradation of biomedical polydimethylsiloxanes during exposure to in vivo biofilm environment monitored by FE‐SEM,ATR‐FTIR,and MALDI‐TOF MS

Polymers used for biomedical purposes in medical devices are usually requested to be inert to degradation. This article describes that slow irreversible changes were observed in silicone surfaces exposed to in vivo biofilms even if silicone, in general, is supposed to have excellent long‐term properties. Tracheostomy tubes made of silicone rubber were exposed to in vivo biofilm environments in clinical tests for periods of 1, 3, and 6 months. The chemical degradation was monitored by MALDI‐TOF MS, ATR‐FTIR, and FE‐SEM. In addition, the physical changes were monitored by contact angle and hardness measurements. Cyclic polydimethylsiloxane (PDMS) was detected on the surfaces of new (unaged) silicones. On the surfaces of the in vivo samples new compounds, presumably linear methyl‐hydroxyl‐terminated PDMS, were detected in addition to cyclic PDMS. These compounds may be formed as a result of the hydrolysis of linear dimethyl terminated PDMS, which is also present in the silicone rubber. ATR‐FTIR spectroscopy confirmed that hydrolysis had indeed occurred during the in vivo exposure, since Si? OH groups were detected. Furthermore, significant changes in the topography were detected by FE‐SEM, indicating the initiation of degradation. No significant changes in the contact angle of the in vivo used samples were observed, but this information may be shielded by the fact that biofilm may remain on the surface, despite the thorough cleaning before the analysis. It is also possible that the surface hydrophobicity was recovered by the diffusion of linear low‐molecular‐weight compounds from the bulk. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation of superhydrophobic surfaces by cauliflower‐like polyaniline

Cauliflower‐like polyaniline (PANI) was successfully prepared using an interfacial polymerization method. By modification with polydimethylsiloxane (PDMS) using chemical vapor deposition method, the surface wettability of cauliflower‐like PANI can be tailored to be superhydrophobic with a water contact angle of 160.4°. The deposition of the low‐surface‐energy silicon coating originated from PDMS pyrolysis on the cauliflower‐like PANI was confirmed by X‐ray photoelectron spectroscopy and Fourier Transform Infrared Spectroscopy. The changes in thermal stability and conductivity of the as‐prepared PANI before and after PDMS treatment were also investigated by thermogravimetric analysis and using a four‐probe method. Compared with nanofiber‐shaped PANI by electrodepositing polymerization, the PDMS‐treated cauliflower‐like PANI has superior surface wettability. Our study may open a new way for fabrication of superhydrophobic surfaces by developing novel nanostructured PANI. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39767.     

Fabrication of superhydrophobic unplasticized poly(vinyl chloride)/nanosilica sheets using Taguchi design methodology

This study introduces a relatively simple technique for the manufacture of superhydrophobic coatings on polymeric surfaces. Plastics such as unplasticized poly(vinyl chloride) (UPVC ) do not have a strong hydrophobic nature that is characterized by their low contact angles. Techniques of both increasing surface roughness and lowering surface energy are required to change their hydrophilicity to superhydrophobicity. In the present study, a coating of a low‐surface‐energy thermoplastic polyurethane (TPU ) was spin‐coated with chemically treated nanosilica to reduce the surface energy of UPVC . Nanosilica particles were embedded on the surface using a hot‐press. Taguchi design was used to optimize multiple processing parameters. Samples spin‐coated with 10 g L^?1 nanosilica suspension in ethanol at a rate of 400 rpm for 5 s and then hot‐pressed at 155 °C under 2 atm (203 kPa ) for 4 min had a contact angle of ca 157° and sliding angle of ca 6°, which are characteristic of superhydrophobic surfaces. Atomic force microscopy (AFM) and scanning electron microscopy (SEM ) imaging showed that these superhydrophobic surfaces were highly rough with nanoscale features. Peel test and SEM analysis showed that silica nanoparticles embedded in the TPU coating were more stable than particles immobilized on UPVC sheet without TPU coating, proving that a layer of more flexible coating can improve the longevity of superhydrophobic surfaces manufactured using this facile method. © 2016 Society of Chemical Industry     

Effect of a poly(dimethylsiloxane) modified polyolefin additive on the processing and surface properties of LLDPE

A polydimethylsiloxane (PDMS) modified polyolefin (obtained by reacting an ethylene‐ethyl acrylate‐maleic anhydride (EEAMA) copolymer with an amine terminated PDMS in the melt phase) was used as a processing aid to facilitate the extrusion of linear low density polyethylene (LLDPE). In blends of LLDPE and PDMS modified polyolefin (PMPO), apparent viscosity and shear stress at the die wall are reduced in comparison to pure LLDPE, and extrusion instabilities are delayed as evidenced by the fact that extrudate surface roughness only occurs at higher shear rates when the additive is present. A higher PDMS content in the PMPO leads to a more pronounced delay of extrusion instabilities. Single‐screw extrusion of LLDPE compounds with a PMPO results in nearly doubled throughput per unit input energy. The reduction of viscosity and improvements in extrudate quality are attributed to the decreasing surface free energy of the PMPO with an increasing PDMS content, as determined by contact angle measurements. Chemical composition analysis of the extrudate surface and cross‐section reveals silicon enrichment at the surface. The friction coefficients of pure PMPO and PMPO/LLDPE blends are measured and found to decrease as a result of the presence of PDMS. POLYM. ENG. SCI., 47:1309–1316, 2007. © 2007 Society of Plastics Engineers     

铜表面超疏水界面的构建与调控(英文)

Super hydrophobic copper wafer was prepared by means of solution immersion and surface self-assembly methods. Different immersion conditions were explored for the best hydrophobic surface. Scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS) and water contact angle measurements were used to investigate the morphologies, microstructures, chemical compositions and hydrophobicity of the produced films on copper substrates, respectively. Results show that the super hydrophobic surface is composed of micro structure of Cu 7 S 4 . The films present a high water contact angle larger than 150°, a low sliding angle less than 3°, good abrasion resistance and storage stability. The molecular dynamics simulation confirms that N-dodecyl mercaptan molecules link up with Cu 7 S 4 admirably, compared with Cu, which contributes to the stable super hydrophobic surface.     

Surface photochemical graft polymerization of acrylic acid onto polyamide thin film composite membranes

Surface modification is an effective approach to enhance the properties of polymeric membranes. In this work, the UV‐photo‐induced graft polymerization of acrylic acid (AA) onto the surfaces of polyamide thin film composite (TFC‐PA) membranes was carried out using an immersion method performed under ambient conditions. The experimental results indicate that the membrane surface becomes more hydrophilic because of the appearance of new carboxylic groups on the surface after the modification. This reduces the water contact angle and increases the water permeability compared with the unmodified membrane. The membrane surface is relatively compact and smooth due to the formation of the polymeric AA‐grafted layer. The separation performance of the modified membrane is improved with enhancements of the permeate flux and the retention of humic acid from aqueous feed solutions compared with those of the unmodified membrane. The fouling resistance of the membrane is also improved because of the higher maintained flux ratios and the lower irreversible fouling factors for the removal of various organic compounds from feed solutions. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44418.     

Fabrication of Super Hydrophobic Surfaces on Copper by Solution-immersion

Super hydrophobic copper wafer was prepared by means of solution immersion and surface self-assembly methods. Different immersion conditions were explored for the best hydrophobic surface. Scanning ele...     

Surface Molecular Mobility for Copolymers Having Both Hydrophobic and Hydrophilic Side Chains Via Dynamic Contact Angle Measurement

The reorganization of a surface structure in response to a change in environmental media was investigated for copolymers having both hydrophobic polydimethylsiloxane (PDMS) and hydrophilic methoxypoly-ethyleneglycol (MPEG) side chains via dynamic contact angle (DCA). These copolymers showed a large contact angle hysteresis and a dependency of the advancing and receding contact angle on dipping velocity (DV). Composition dependency of DCA for these copolymers is also discussed. In addition to this, adhesion tension relaxation, F(t), for MMA/MPEGMA/PDMSMA was determined. F(t) in the advancing process increased with elapsed time and decreased in the receding process. These phenomena were explained by the adsorption and reorientation of hydrophilic segments to the water/copolymer interface in water. In XPS analysis, more oxygen atoms were detected on the surfaces of MMA/MPEGMA after immersion in water than before. For MMA/MPEGMA/PDMSMA, the atomic ratio of Si to C increased with an increase in PDMSMA content.