Biopolymer brushes grown on PDMS contact lenses by in situ atmospheric plasma-induced polymerization

It is critical for silicone based-contact lens development by improving surface characterization to prevent protein adsorption. In this paper, the silicone (polydimethylsiloxane, PDMS) contact lenses were modified by varied molecular weights of poly(ethylene glycol) methacrylate (PEGMA, Mw 360 and 500 Da) polymer brushes by in situ atmospheric plasma-induced surface copolymerization. After PDMS contact lenses were homogenously immersed in PEGMA monomer solutions, varied gases (oxygen, nitrogen, and argon) with the atmospheric plasma were employed in the process of polymerization. The characterizations of PEGMA polymer brushes modified on the PDMS contact lenses would be evaluated by atomic force microscopy, FT-IR spectroscopy, X-ray photoelectron spectroscopy, and contact angle test. The results show that the hydrophilicity of the PEGMA polymer brush-modified surface is obviously improved. The contact angle of PEGMA-modified surface decreases about 20°–40° by varied atmospheric plasma (O₂, N₂, and Ar gases), compared to the pristine lenses. Importantly, the hydrophilicity of the PEGMA polymer brush-modified surface could be retained beyond 2 weeks. PEGMA-modified PDMS contact lenses also display superior anti-protein (fibrinogen and human serum bovine) adsorption ability. Therefore, immobilization of PEGMA polymer brushes by in situ atmospheric plasma-induced polymerization would be a great and rapid method to enhance the hydrophilicity and anti-protein adsorption ability in the PDMS contact lenses.     

PEGylation and polyPEGylation of nanodiamond

Polyethylene glycol (PEG) and poly(PEGMA) conjugated nanodiamond (ND) have been synthesized via “grafting to” and “grafting from” methods, respectively. In “grafting to” method, hydroxyl groups on ND surface were firstly oxidized to carboxyl groups, and then reacted with thionyl chloride to form acyl chloride groups. The acyl chloride functionalized ND (ND–COCl) was subsequently reacted with poly(ethylene glycol) monomethyl ether (mPEG) in the presence of triethylamine to generate mPEG conjugated ND (ND–mPEG). On the other hand, in “grafting from” method, ND–OH was modified with 2-bromoisobutyryl bromide (ND–Br), and then poly(PEG methyl ether methacrylate) (Poly(PEGMA)) chains were linked on the ND surface through surface-initiated atom transfer radical polymerization (ATRP) using ND–Br as the initiator and Cu(Br)/N,N,N′,N″,N″-pentmethyl diethylenetriamine (PMDETA) as the catalyst and ligand. The polymer conjugated ND particles were characterized using transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, thermal gravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). TGA analyses demonstrated that the polymer weight ratios through “grafting to” and “grafting from” methods were 29.8% and 34.4%, respectively. The mPEG and poly(PEGMA) conjugated ND nanoparticles exhibited enhanced dispersibility in organic media. More importantly, due to the relative high graft ratios and molecular weight, poly(PEGMA) functionalized ND was also dispersed well in water. Given the excellent physicochemical and biological properties of PEG and ND, the methods described in current work might be useful for the preparation of functional ND nanoparticles for potential biomedical applications.     

Controlled grafting of polymer brushes on poly(vinylidene fluoride) films by surface‐initiated atom transfer radical polymerization

Controlled grafting of well‐defined polymer brushes on the poly(vinylidene fluoride) (PVDF) films was carried out by the surface‐initiated atom transfer radical polymerization (ATRP). Surface‐initiators were immobilized on the PVDF films by surface hydroxylation and esterification of the hydroxyl groups covalently linked to the surface with 2‐bromoisobutyrate bromide. Homopolymer brushes of methyl methacrylate (MMA) and poly(ethylene glycol) monomethacrylate (PEGMA) were prepared by ATRP from the α‐bromoester‐functionalized PVDF surface. The chemical composition of the graft‐functionalized PVDF surfaces was characterized by X‐ray photoelectron spectroscopy (XPS) and attenuated total reflectance (ATR)–FTIR spectroscopy. Kinetics study revealed a linear increase in the graft concentration of PMMA and PEGMA with the reaction time, indicating that the chain growth from the surface was consistent with a “controlled” or “living” process. The “living” chain ends were used as the macroinitiator for the synthesis of diblock copolymer brushes. Water contact angles on PVDF films were reduced by surface grafting of PEGMA and MMA. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3704–3712, 2006     

Modification of polycarbonateurethane surface with poly (ethylene glycol) monoacrylate and phosphorylcholine glyceraldehyde for anti-platelet adhesion

Poly(ethylene glycol) monoacrylate (PEGMA) is grafted onto polycarbonateurethane (PCU) surface via ultraviolet initiated photopolymerization. The hydroxyl groups of poly(PEGMA) on the surface react with one NCO group of isophorone diisocyanate (IPDI) and another NCO group of IPDI is then hydrolyzed to form amino terminal group, which is further grafted with phosphorylcholine glyceraldehyde to establish a biocompatible hydrophilic structure on the surface. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy confirm the successful grafting of both PEG and phosphorylcholine functional groups on the surface. The decrease of the water contact angle for the modified film is caused by synergic effect of PEG and phosphorylcholine, which both have the high hydrophilicity. Furthermore, the number of platelets adhered is relative low on the synergetically modified PCU film compared with the PCU film modified only by poly(PEGMA). Our synergic modification method using both PEG and phosphorylcholine may be applied in surface modification of blood-contacting biomaterials and some relevant devices.     

Plasma graft polymerization of vinylimidazole onto Kapton film surface for improvement of adhesion between Kapton film and copper

Kapton film was modified by means of the plasma graft polymerization of vinylimidazole for the improvement of the adhesion with copper metal. Argon plasma exposure generated hydroperoxides at the surface of the Kapton film. Hydroperoxides generated by the argon plasma exposure could initiate the graft polymerization of vinylimidazole. The graft polymerization was restricted at the surface of the Kapton film and never occurred on the inside of the Kapton film. The graft polymer layer was 150–200 nm thick. The surface modification by the plasma graft polymerization of vinylimidazole led to the improvement of adhesion between Kapton film and copper metal. A part of the copper metal made a complex with imino groups in the vinylimidazole chains graft-polymerized onto Kapton film. The complex is considered to contribute to the improvement of the adhesion. © 1995 John Wiley & Sons, Inc.     

等离子体诱导下丙烯酸在PET表面的接枝聚合

利用等离子体对聚对苯二甲酸乙二酯（PET）薄膜进行表面处理,并诱导引发丙烯酸（AAc）在其表面接枝聚合,制备了具有结合牢固、高亲水性的聚丙烯酸（PAAc-g-PET）复合膜。通过表面衰减全反射-傅里叶红外光谱（ATR-FTIR）结构表征,证明了PAAc成功接枝到PET薄膜上。通过对AAc在PET薄膜表面接枝率的动力学影响因素的系统分析,获得了高接枝率下的PAAc-g-PET复合膜的最佳实现条件。     

Poly(vinyl alcohol) hydrogel fixation on poly(ethylene terephthalate) surface for biomedical application

A surface modification technique was developed for the covalent immobilization of poly(vinyl alcohol) (PVA) hydrogel onto poly(ethylene terephthalate) (PET) to improve the biocompatibility of the film. The PET film was first graft copolymerized with poly(ethylene glycol) monomethacrylate (PEGMA) in the presence of ethylene glycol dimethacrylate (EGDMA) as crosslinker, and then oxidized with a mixture of acetic anhydride (Ac₂O) and dimethyl sulfoxide (DMSO) to produce aldehyde groups on the PET surface. Finally, the prepared PVA solution was cast onto the film and covalently immobilized on the film through the reaction between the aldehyde groups on the PET film and the hydroxyl groups of PVA. The good attachment of the PVA layer to the PET film was confirmed by observing the cross-section of the PET-PVA film using scanning electron microscopy (SEM). Heparin was immobilized on the PVA layered PET using two different methods, physical entrapment and covalent bonding, to further improve the biocompatibility of the film. Attenuated total reflectance (ATR) FT-IR spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to characterize the chemical composition of the surface modified films. The biocompatibility of the various surface modified PET films was evaluated using plasma recalcification time (PRT) and platelet adhesion.     

Oxidative graft polymerization of aniline on Si(100) surface modified by plasma polymerization of glycidyl methacrylate

Modification of argon plasma-pretreated Si(100) surfaces via plasma polymerization of glycidyl methacrylate(GMA), followed by reactive coupling of the epoxide groups of the plasma deposited GMA chains with aniline, and finally by oxidative graft polymerization of aniline was carried out. An alternative approach involved the modification of the argon plasma-pretreated Si(100) surfaces via plasma polymerization of glycidyl methacrylate(GMA), followed by direct oxidative graft polymerization of aniline and thermal curing. The compositions and chemical states of the modified Si surfaces were characterized by X-ray photoelectron spectroscopy (XPS). The two methods of surface modification of the Si(100) surfaces produced similar results. The protonation-deprotonation behavior, the interconvertible intrinsic redox states, and the metal reduction behavior (the electroless plating of Pd from the Pd(II) ion solution) of the grafted polyaniline (PANI) chains on the Si(100) surface were grossly similar to those of the PANI homopolymer. The coupling of PANI to the covalently tethered GMA chains on the Si(100) surface was suggested by the cohesive failure inside the epoxy adhesive that was applied to the modified Si surface in an attempt to peel off the PANI layer from the GMA plasma-polymerized Si (GMA-pp-Si) substrate.     

Surface Modification of Nanoporous Poly(ϵ-caprolactone) Membrane with Poly(ethylene glycol) to Prevent Biofouling: Part I. Effects of Plasma Power and Treatment Time

Biofouling, a result of protein adsorption and cell adhesion on a surface, is detrimental to membrane performance. The objective of this study is to modify the polycaprolactone (PCL) membrane surface with poly(ethylene glycol) (PEG) to prevent fibroblast adhesion. To achieve this goal, oxygen plasma and PEG(400)-monoacrylate were used to graft the PEG onto the membrane surface through covalent bonding. Various plasma treatment conditions were investigated to optimize the PEG-grafting quality and to achieve minimum fibroblast adhesion. After the treatment, the water contact angle decreased significantly. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) spectra indicated that PEG was successfully grafted onto the PCL membrane with the appearance of the PEG characteristic peaks. X-ray photoelectron spectroscopy (XPS) revealed that different plasma powers and treatment times changed the surface composition of membranes. To evaluate the applicability of this new strategy for the prevention of biofouling, NIH 3T3 fibroblast was used as a model biofoulant. Cell adhesion and morphology studies indicate that either lower plasma power or shorter treatment time is able to improve resistance to the cell adhesion. This simple and efficient method can be applied to inhibit biofouling on the membrane surface.     

Improving blood compatibility of natural rubber by UV‐induced graft polymerization of hydrophilic monomers

Natural rubber (NR) latex films surface‐grafted with hydrophilic monomers, poly(ethylene glycol) methacrylate (PEGMA), N‐vinylpyrrolidone (VPy), and 2‐methacryloyloxyethyl phosphorylcholine (MPC), were prepared by UV‐induced graft polymerization using benzophenone as a photosensitizer. The grafting yield increases of vulcanized NR latex films as a function of time and monomer concentration were of lesser magnitude than those of the unvulcanized NR latex films. This can be explained as a result of the crosslinked network generated during vulcanization acting as a barrier to the permeation of the photosensitizer and the monomer. The appearance of a characteristic carbonyl stretching in the attenuated total reflectance‐Fourier transform infrared spectroscopy (ATR‐FTIR) spectra of NR latex films after the surface grafting of PEGMA and MPC indicates that the modification has proceeded at least to the sampling depth of ATR‐FTIR (∼ 1–2 μm). According to the water contact angle of the modified NR latex films, the surface grafting density became higher as the grafting time and monomer concentration increased. The complete absence of plasma protein adsorption and platelet adhesion on the surface‐modified NR latex films having grafting yield above 1 wt % is a strong indication of improved blood compatibility. Results from tensile tests suggest that graft polymerization does not cause adverse effects on the mechanical properties of vulcanized NR latex films. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Durable,hydrophilic surface modification of polypropylene films by plasma graft polymerization of glycidyl methacrylate

Summary The plasma graft polymerization of glycidyl methacrylate (GMA) was investigated to obtain hydrophilic surface. The combination of the argon plasma and GMA vapor exposures leaded to graft polymerization of GMA at the surface of polypropylene films. This graft polymerization was initiated by the argon plasma exposure for 2 min, and was accomplished with the GMA vapor exposure for 2 min. The GMA graft polymerization made polypropyrene surface hydrophilic. The surface energy was 55.8 mJ/m². The hydrophilicity introduced by the GMA graft polymerization remained for at least 3 weeks. The graft polymerization of hydrophilic monomers was a good means of hydrophilic surface modification.     

Molecular Structure of the Interphase Formed by Plasma-Polymerized Acetylene Films and Steel Substrates

The molecular structure of the interphase between plasma-polymerized acetylene films and steel substrates was determined using in situ reflection-absorption infrared spectroscopy (RAIR) and X-ray photoelectron spectroscopy (XPS). Plasma-polymerized acetylene films were deposited onto polished steel substrates using argon as a carrier gas and inductively coupled, radio frequency (RF)-powered plasma reactors that were interfaced directly to the XPS and Fourier transform infrared (FTIR) spectrometers. RAIR showed that the plasma polymerized films contained large numbers of methyl and methylene groups but only a small number of mono substituted acetylene groups, indicating that there was substantial rearrangement of the monomer molecules during plasma polymerization. Bands were observed near 1020 and 855 cm^-1 in the RAIR spectra that were attributed to skeletal stretching vibrations in C-C-O-Fe groups, indicating that the plasma-polymerized films interacted with the substrate through formation of alkoxide bonds. Another band was observed near 1565 cm^-1 and attributed to carboxylate groups in the interphase between the films and the oxidized surface of the substrate. Results obtained from XPS showed that the surface of the iron substrate consisted mostly of a mixture of Fe₂O₃ and FeOOH and that iron was mostly present in the Fe(III) oxidation state. However, during plasma polymerization of acetylene, there was a tendency for the concentration of FeOOH groups to decrease and for the concentration of Fe(II) to increase, due to the reducing nature of argon/acetylene plasmas. Results from XPS also confirmed the formation of alkoxide and carboxylate groups in the interphase during plasma polymerization of acetylene.     

Surface grafting polymerization of vinyl monomers on poly(tetrafluoroethylene) films by plasma treatment

Poly(tetrafluoroethylene) films were surface modified by argon plasma treatment followed by graft polymerization. Peroxidе groups were introduced on the surface of poly(tetrafluoroethylene) films after plasma treatment and the consequent contact with air when the films were taken out of the reactor. Grafting polymerization initiated by the surface peroxide (hydroxide) groups was performed on the poly(tetrafluoroethylene) film surface by using acrylic acid, 4-vinylpyridine and 1-vinylimidazole as monomers. Copolymers were obtained with grafting yield from 0.436 to 0.457 mg/cm² for poly(acrylic acid), from 0.299 to 0.390 mg/cm² for poly(4-vinylpyridine) and from 0.212 to 0.256 mg/cm² for poly(1-vinylimidazole), respectively. The free surface energies of the copolymers were determined. The chemical structures and the copolymer surfaces were characterized by IR, XPS and SEM analyses. High energy resolution X-ray photoelectron spectroscopy (XPS) confirmed the grafting of acrylic acid, 4-vinylpyridine and 1-vinylimidazole. The surface hydrophilicities of modified polytetrafluoroethylene films were significantly enhanced after plasma treatment and grafting modification. It is worth emphasizing that in this work acrylic acid, 4-vinylpyridine and 1-vinylimidazole were used as the reactive monomers for grafting on the poly(tetrafluoroethylene) film by plasma treatment. We believe that this vinyl monomers may be employable as functional groups, permitting a potentially wide range of applications: as ionomers, membranes, carriers for immobilization of biomolecules, for complex formation with heavy metals as catalysts.     

Surface modification of poly(tetrafluoroethylene) film by plasma graft polymerization of sodium vinylsulfonate

Poly(tetrafluoroethylene) (PTFE) surface was modified by the graft polymerization of sodium vinylsulfonate, and the chemical composition of the graft-polymerized PTFE surface was analyzed by X-ray photoelectron spectroscopy. Peroxides were formed on the PTFE surface by a combination procedure of argon plasma irradiation and air exposure, and the graft polymerization of sodium vinylsulfonate was initiated by the peroxide groups at 65–80°C. The peroxide concentration is 3 × 10⁺¹³ to 5 × 10⁺¹³ numbers/cm². The average degree of polymerization of the graft polymers was 3.4 × 10³. The graft polymer is distributed over the PTFE surface, but part of the PTFE surface remains uncovered. The coverage with the graft polymer is 43%. The PTFE surface graft polymerized with sodium vinylsulfonate was somewhat hydrophilic, but the hydrophilicity was lower than that of the PTFE surface modified by plasma treatment. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 77–84, 1997     

铈盐引发高吸附量氨基化PGMA高分子微球合成及去除废水中Cr(VI)(英文)

A novel polyglycidylmethacrylate(PGMA) microspheres with high adsorption capacity of Cr(VI) was prepared by cerium(IV) initiated graft polymerization of tentacle-type polymer chains with amino group on polymer microspheres with hydroxyl groups.The micron-sized PGMA microspheres were prepared by a dispersion polym-erization method and subsequently modified by ring-opening reaction to introduce functional hydroxyl groups.The polymer microspheres were characterized by scanning electron microscopy(SEM) and Fourier transform infrared spectroscopy(FTIR).The results indicated that the polymer microspheres had an average diameter of 5 μm with uniform size distribution.The free amino group content was determined to be 5.13 mmol?g?1 for g-PGMA-NH2 mi-crospheres by potentiometric and conductometric titration methods.The Cr(VI) adsorption results indicated that the graft polymerization of tentacle-type polymer chains on the polymer microspheres could produce adsorbents with high adsorption capacity(500 mg?g?1).The polymer microspheres with grafted tentacle polymer chains have poten-tial application in large-scale removal of Cr(VI) in aqueous solution.     

Electropolymerization of p‐phenylenediamine on Pt‐electrode from aqueous acidic solution: Kinetics,mechanism, electrochemical studies,and characterization of the polymer obtained

Ar plasma‐induced graft polymerization of poly(ethylene glycol) (PEG) on Ar plasma pretreated poly(methyl methacrylate) (PMMA) surfaces was carried out to improve the antistatic properties. The surface composition and microstructure of the PEG‐grafted PMMA surfaces from plasma induction were characterized by attenuated total reflectance Fourier transfer infrared (ATR‐FTIR) spectroscopy, water contact angles (CA), and atomic force microscopy (AFM) measurements. The measurements revealed that the antistatic properties can be remarkably improved with the surface resistivity of PEG‐grafted PMMA surface decreasing significantly by 3–6 orders of magnitude, with the optimum condition for polymerization grafted onto the Ar plasma pretreated PMMA surface being 40 W for RF power and 3 min for glow discharge time. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Surface modification of polyethylene by plasma pretreatment and UV‐induced graft polymerization for improvement of antithrombogenicity

The purpose of this study was to enhance blood compatibility of polyethylene (PE) films. Glycidyl methacrylate (GMA) was grafted onto the surface of PE by Ar plasma pretreatment and UV‐induced graft polymerization without photo‐initiator, then heparin was immobilized onto the poly (glycidyl methacrylate) segments. The surface compositions and microstructure of GMA graft polymerized PE films were studied by X‐ray photoelectron spectroscopy (XPS) and Attenuated Total Reflectance Fourier Transfer Infrared (ATR‐FTIR) spectroscopy. It was confirmed that heparin was successfully immobilized onto the surface of PE films by XPS analysis. The antithrombogenicity of the samples was determined by the activated partial thromboplastin time (APTT), prothrombin time (PT), thrombin time (TT), and plasma recalcification time (PRT) tests and platelet adhesion experiment. Results indicated that the antithrombogenicity of modified PE was improved remarkably. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2014–2018, 2004     

Graft polymerization of acrylamide onto UV-irradiated films

Graft polymerization of acrylamide was attempted onto the surface of films preirradiated with UV radiation. The films employed are nylon 6, polypropylene, and ethylene–vinyl acetate copolymers. Following UV irradiation in air on films without photosensitizer, they were placed in monomer solution, degassed, and then heated to 50°C to effect the graft polymerization. After rigorous removal of homopolymers, polyacrylamide chains were found to be grafted in the surface region of the films to amounts up to several hundred micrograms per square centimeter of films. An ESCA study revealed the UV-irradiated but not yet grafted surfaces to be oxidized, and formation of peroxides was strongly suggested by the reaction of irradiated films with 1,1-diphenyl-2-picrylhydrazyl. It is likely that the initiator responsible for the graft polymerization is peroxides generated at and near the film surfaces upon UV irradiation. The grafted films became very slippery when contacted with water, in contrast with the films UV-irradiated but not yet grafted.     

Characterization of surface‐modified polyalkanoate films for biomedical applications

Poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBHV) films prepared by solvent casting were treated with oxygen, argon, and nitrogen radiofrequency‐generated plasmas. The analysis by attenuated total reflectance infrared spectroscopy and X‐ray absorption near edge spectroscopy of modified surfaces showed an increase of hydroxyl and unsaturated groups, compared with unmodified surfaces. Water contact angles decreased after a short time of exposure (<30 s) for all types of plasma. At long exposure times (>30 s), the water contact angles appeared to be independent of treatment time for nitrogen and argon plasmas, whereas they continuously decreased for films treated with oxygen. HaCaT cultures on nontreated and treated PHBHV films showed that short plasma exposures of 10–20 s improve cell attachment to a greater extent than long exposure times habitually used in polymer surface plasma treatment. The film surface topology did not influence cell attachment. These results illustrate the importance of a detailed characterization of the surface physicochemistry in plasma‐modified substrates designed as part of a strategy to optimize specific cell–biomaterial interactions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Chemical grafting of metallocene‐catalyzed functional polypropylene copolymer on glass substrates through surface modification

This work deals with surface modification of soda‐lime glass slides which, by itself, does not have hydroxyl groups at the surface. So, a glass surface pretreatment is needed, to create hydroxyl groups onto it, before carrying out the polypropylene (PP) grafting reaction. Different acid/base pretreatments were performed to develop an adequate concentration of superficial hydroxyl groups. Subsequently, a metallocenic polymerization (propylene‐α olefin graft reaction, catalyzed by EtInd₂ZrCl₂/methylaluminoxane), was carried out to provide graft‐PP chains chemically linked to the glass surface. The surface so modified can be further functionalized and tailored for different applications, including polymer composites. The pretreatment conditions that best preserved homogeneity and caused less damage to the glass surface resulted from a step of contact with dilute HF/NH₄F buffer, a washing step with distilled water, and a final exposure to KOH. After the propylene copolymerization was performed, part of the graft copolymer formed remained chemically bonded to the glass slide surface. The presence of grafted PP at the surface was confirmed by SEM, FTIR, and EDAX characterization, even after the physically adsorbed polymer was excluded by a severe solvent extraction treatment. From these results, the copolymerization of a hydroxy α‐olefin, grafted on a MAO‐pretreated glass slide, is foreseen as a possible way to graft polymers onto inorganic solids. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008