Synthesis,characterization, and in vitro release of ibuprofen from poly(MMA‐HEMA) copolymeric core–shell hydrogel microspheres for biomedical applications

This article describes the development of a new crosslinked poly(methyl methacrylate‐2‐hydroxyethyl methacrylate) copolymeric core–shell hydrogel microsphere incorporated with ibuprofen for potential applications in bone implants. Initially poly(methyl methacrylate) (PMMA) core microspheres were prepared by free‐radical initiation technique. On these core microspheres, 2‐hydroxyethyl methacrylate (HEMA) was polymerized by swelling PMMA microspheres with the HEMA monomer by using ascorbic acid and ammonium persulfate. Crosslinking monomers such as ethylene glycol dimethacrylate (EGDMA) has also been included along with HEMA for polymerization. By this technique, it was possible to obtain core–shell‐type microspheres. The core is a hard PMMA microsphere having a hydrophilic poly(HEMA) shell coat on it. These microspheres are highly hydrophilic as compared to PMMA microspheres. The size of the hydrogel microspheres almost doubled when swollen in benzyl alcohol. These microspheres were characterized by various techniques such as optical microscopy, scanning electron microscopy, Fourier‐transformed infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. The particle size of both microspheres was analyzed by using Malvern Master Sizer/E particle size analyzer. The in vitro release of ibuprofen from both microspheres showed near zero‐order patterns. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3045–3054, 2002; DOI 10.1002/app.10310     

Time‐dependent changes of surface properties of polyether ether ketone caused by air plasma treatment

The effect of air plasma treatment on wetting and energy properties, surface composition and morphology of polyether ether ketone (PEEK) was investigated. The influence of the storage time on the surface properties of plasma‐treated polymer plate was also examined. The properties were determined by advancing and receding contact angle measurements, Fourier transform infrared spectroscopy supported by theoretical spectrum modelling, X‐ray photoelectron spectroscopy and optical profilometry. Three theoretical approaches were used in the determination of the apparent surface free energy of the untreated and plasma‐treated PEEK samples from the measured contact angles of probe liquids (water, formamide, diiodomethane): the contact angle hysteresis method, the Owens and Wendt approach and the Lifsthitz ? van der Waals acid–base approach. It was found that air plasma treatment of PEEK causes significant chemical and morphological changes of the polymer surface, which are reflected in the decrease of contact angles from 83.4° to 11.7° for water after 180 s plasma treatment. This is due to the formation of polar functional groups resulting in the increase of the surface hydrophilicity. After plasma treatment the apolar component of the surface free energy practically does not change, while the polar component increases significantly, especially for plates treated for 180 s, from 0 to 19.6 mJ m^?2. In addition, the modified PEEK surface is not stable during storage and it acquires more hydrophobic character. © 2016 Society of Chemical Industry     

Improved surface characteristics and the conductivity of polyaniline–nylon 6 fabrics by plasma treatment

The effect of plasma treatment on the surface characteristics and conductivity of polyaniline–nylon 6 composite fabrics was investigated. Plasma surface modifications with oxygen, ammonia, and argon were performed on the nylon 6 fabrics to improve the adhesion and rate of polymerization. The surface morphology of the fiber was observed with scanning electron microscopy, and functional groups introduced onto the surface of nylon 6 fibers by various plasma treatments were characterized by X‐ray photoelectron spectroscopy. With oxygen plasma treatment, the fiber surface was effectively etched; polar groups such as ? OH and ? OOH were introduced onto the surface of nylon 6 fiber, and they increased surface activity, promoted oxidation polymerization, and resulted in higher add‐on and electrical conductivity. However, the introduced amine and amide groups with ammonia treatment caused a reduction in conductivity. Argon did not significantly alter the surface characteristics of the nylon 6 fibers. In addition, to control fabric conductivity and cover as wide a range of conductivity as possible, we observed the effects of the monomer concentration and number of deposits on the fabric conductivity. The results showed that fabric conductivity increased as the monomer concentration increased up to 0.5M and then leveled off, and further increases were achieved with an increase in the number of multiple deposits. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 684–694, 2001     

Studies on the surface free energy and surface structure of PTFE film treated with low temperature plasma

The surface free energy and surface structure of poly(tetrafluoroethylene) (PTFE) film treated with low temperature plasma in O₂, Ar, He, H₂, NH₃, and CH₄ gases are studied. The contact angles of the samples were measured, and the critical surface tension γ_c (Zisman) and γ_c (max) were determined on the basis of the Zisman's plots. Furthermore, the values of nonpolar dispersion force γ^a_s, dipole force γ^b_s, and hydrogen bonding force γ^c_s to the surface tensions for the plasma-treated samples were evaluated by the extended Fowkes equation. Mainly because of the contribution of polar force, the surface free energy and surface wettability of PTFE film which was treated with H₂, He, NH₃, Ar, and CH₄ for a short time increased greatly. Electron spectroscopy for chemical analysis (ESCA) shows that the reason was the decrease of fluorine and the increase of oxygen or nitrogen polar functional group on the surface of PTFE. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1733–1739, 1997     

PdCl2 anchorage onto the surface of polystyrene films via oxygen and ammonia plasma treatment

The surface properties of polystyrene as a possible catalytic support for active coordinative species were investigated. To improve the surface properties, discharge treatments in the presence of oxygen and ammonia were carried out. The polymer surface was studied before and after the plasma treatments. Contact angles for the polymer surface were measured in order to determine the surface free energy. Polymer‐bound complex catalysts were prepared by anchoring PdCl₂ on the surface of the polystyrene samples. The chemical compositions were studied by X‐ray Photoelectron Spectroscopy (XPS). Plasma treatments in the presence of oxygen or ammonia caused an increase in the surface free energy of polystyrene, as a consequence of the higher concentration of oxygenated or nitrogenated functional groups, respectively, on the polymer surface. Contact angle measurements are in agreement with the corresponding values obtained by XPS. After treatment with PdCl₂, the amount of palladium anchored to the polymer surface treated with ammonia is greater than in the case of the oxygen plasma treatments; this may be explained on the basis of the higher nucleophilic character of the amine groups. No palladium was detected in the untreated polystyrene surface. © 2000 Society of Chemical Industry     

Studies on surface energetics of glass fabrics in an unsaturated polyester matrix system: Effect of sizing treatment on glass fabrics

The surfaces of glass fibers were sized by polyvinyl alcohol (PVA), polyester, and epoxy resin types in order to improve the mechanical interfacial properties of fibers in the unsaturated polyester matrix. The surface energetics of the glass fibers sized were investigated in terms of contact angle measurements using the wicking method based on the Washburn equation, with deionized water and diiodomethane as the wetting liquids. In addition, the mechanical behaviors of the composites were studied in the context of the interlaminar shear strength (ILSS), critical stress intensity factor (K_IC), and flexural measurements. Different evolutions of the London dispersive and specific (or polar) components of the surface free energy of glass fibers were observed after different sizing treatments. The experimental result of the total surface free energies calculated from the sum of their two components showed the highest value in the epoxy‐sized glass fibers. From the measurements of mechanical properties of composites, it was observed that the sizing treatment on fibers could improve the fiber–matrix interfacial adhesion, resulting in improved final mechanical behaviors, a result of the effect of the enhanced total surface free energy of glass fibers in a composite system. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1439–1445, 2001     

Effect of porosigen and hydrophobic monomer on the fast swelling–deswelling behaviors for the porous thermoreversible copolymeric hydrogels

A series of porous thermoreversible copolymeric hydrogels were prepared from N‐isopropylacrylamide (NIPAAm) and hydrophobic monomers such as 2,2,3,3,4,4,5,5‐octafluoropentyl methacrylate (OFPMA) and n‐butyl methacrylate (BMA) and CaCO₃ or poly(ethylene glycol) 8000 (PEG8000) as porosigen by emulsion polymerization. The effect of hydrophobic monomers and porosigens on the fundamental properties, such as equilibrium swelling ratio, swelling kinetics, gel strength, crosslinked densities, etc., and fast swelling–deswelling behavior for the present copolymeric hydrogels were investigated. Results showed that the deswelling rates for the gels porosigened by CaCO₃ were more rapid than those gels foamed by PEG8000. Results also showed that the swelling rates for the gel foamed by CaCO₃ were higher than those for the gel foamed by PEG8000. At the same time, results also showed that the gels with OFPMA foamed by CaCO₃ exhibit a faster swelling–deswelling behavior than those gels with BMA. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3152–3160, 2006     

氩等离子体处理聚四氟乙烯粘接性能研究

利用氩等离子体表面处理后再经丙烯酸化学接枝处理方法对聚四氟乙烯(PTFE)薄片表面进行改性,发现PTFE对水的润湿性明显改善,然后用环氧胶进行粘接,其粘接强度有较大提高。     

Conductivity of layer and matrix polyaniline–silver–copper composites by plasma

This work presents a study on the formation of polymer–metal composites by means of plasma, combining silver and copper alloys with semiconducting polymer films. The objective is to improve the electric conductivity of polyanilines by forming layer and matrix composites. In this way, it is possible to increase the superficial and/or volumetric conductivity of the polymers. Electronic variables as the electronic density and energy along the reactor and their influence on the chemical composition, deposition rate, and the morphology of plasma polymer–metal composites are taken into consideration in the course of this study, as the shower of the most energetic particles in the plasma can produce multiple bonds between the metals and the polymers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1031–1036, 2004     

High temperature water–gas shift reaction over hollow Ni–Fe–Al oxide nano-composite catalysts prepared by the solution-spray plasma technique

The effect of Fe content in Ni–Fe–Al oxide nano-composites prepared by the solution-spray plasma technique on their catalytic activity for the high temperature water–gas shift reaction was investigated. The composites showed a hollow sphere structure, with highly dispersed Fe–Ni particles supported on the outer surface of the spheres. When the water–gas shift reaction was performed over an Ni–Al oxide composite catalyst without Fe, undesired CO methanation took place predominantly compared to the water–gas shift reaction, and significant amounts of hydrogen were consumed. When appropriate amounts of Fe were added to the Ni–Al oxide composite catalyst during the plasma process, methanation was suppressed remarkably, without serious loss of activity for the water–gas shift reaction. The catalyst was characterized by STEM, XRD and H₂ chemisorption measurements.     

低温等离子体对F24表面处理的研究

本文通过失重、交联．接触角、表面能及剪切强度测定等方法研究了在不同等离子理条件下，Ｆ２４在处理前后表面结构性能的变化．结果表明，处理后的Ｆ２４润湿性和粘接性能有明显改善，较未处理时接触角下降约２０°左右，剪切强度较未处理的提高二倍多．     

Effect of oxygen and fluorine plasma surface treatment of silicon-incorporated diamond-like carbon coatings on cellular responses of mouse fibroblasts

The surface chemistry of silicon-incorporated diamond-like carbon (Si-DLC) was tailored utilizing oxygen and fluorine plasma treatments. Successful anchoring of oxygen and fluorine functional groups to the surface of Si-DLC was verified using X-ray photoelectron spectroscopy. The impact of surface modification of Si-DLC on hydrophobicity was correlated with the viability of L929 mouse fibroblasts. The confocal microscopy and viability results indicated that oxygen-treated Si-DLC showed increased cell viability compared to untreated Si-DLC and fluorine-treated Si-DLC samples 5 days after seeding. The increased cell viability was correlated with the conversion of the hydrophobic surface of Si-DLC into a hydrophilic surface by oxygen plasma treatment.     

Effect of fiber surface morphology on the hydrophilicity modification of cold plasma‐treated polypropylene nonwoven fabrics

Cold oxygen plasma was employed to give hydrophilicity modification to polypropylene (PP) nonwoven fabric (NWF). It was found that, after plasma treatment, PP NWF made from fibers with smooth surfaces can only keep its hydrophilicity for a short time and then shows a quick hydrophobic recovery at room temperature. However, this hydrophilic property can last for a long time in the case of the PP NWF made from fibers with rough surfaces. To prove the contribution of the rough surface to the long‐term hydrophilicity, this PP NWF was treated in an organic solvent to smooth the fiber surface. The hydrophilic feature of this PP NWF no longer lasts for a long time after the same plasma treatment. This observation strongly supports our opinion that the fiber surface morphology of PP NWF is a critical factor for long‐term hydrophilicity improvement after plasma treatment, which gives a positive solution to overcoming the aging effect of hydrophilicity modification often found in this technique. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Investigation of Dow Cyclotene 4026 surface amination by downstream plasma treatment

Dow Cyclotene 4026 surfaces were treated by downstream ammonia cold plasma with and without argon plasma pretreatments. The modified polymer surfaces were characterized by X‐ray photoelectron spectroscopy, Fourier transform infrared‐attenuated total reflection, and atomic force microscopy (AFM). A 2 fractional factorial design was developed to identify the optimal processing parameters. Further experimental investigation has also been conducted to optimize the operating conditions. The combined results show that the extent of surface amination of Cyclotene grows with increase of power, pressure, and temperature of ammonia plasma treatments both with and without argon plasma pretreatments. For the treatment time effect, the results indicate that N/C (nitrogen/carbon) ratios increase with time and then start to slightly decrease at the ～4‐min point, which may be tentatively explained by a competition between the modification process and the degradation process on the polymer surfaces. AFM results suggest that the upper limit of the operating condition to obtain a desirable surface topography is 175°C. Based on all the results from Design of Experiment, experimental data, and AFM analysis, the optimum processing parameters have been suggested. Finally, the aging effect of aminated surfaces is discussed; further investigation of this effect is still underway. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2418–2427, 2005     

Surface modification of polytetrafluoroethylene with tetraethoxysilane by using remote argon/dinitrogen oxide microwave plasma

The use of remote microwave plasma for the polymerization and deposition of tetraethoxysilane on the surface of polytetrafluoroethylene was investigated using a mixture of Argon and dinitrogen oxide as carrier gas. Layers with thicknesses of 0.5–3 μm were obtained, differing in chemical composition, surface energy, and flexibility/brittleness, depending on the plasma power and both the treatment and aging times. In general, milder treatments and shorter aging times resulted in higher contents of organic structural elements in the layers and greater flexibility and surface energy. Anchoring between the layers and the bulk polytetrafluoroethylene was at least partially caused by fibrils interconnecting the two components. These results were obtained by X‐ray photoelectron spectroscopy, Fourier transform infrared spectroscopy in the attenuated total reflection mode, contact angle measurements, and scanning electron microscopy combined with energy dispersive X‐ray analysis. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1207–1216, 2000     

Surface modification of polypropylene membrane by low‐temperature plasma treatment

Microporous polypropylene membranes were low temperature plasma treated with acrylic acid and allylamine. Parameters of plasma treatment were examined and optimized for the enhancement of membrane performance properties. Excess power damaged the membrane surface and excess monomer flow rate increased the reactor pressure to interfere with the glow discharge. Longer plasma treatment time resulted in even more plasma coating and micropore blocking. The contact angle with water decreased and wettabilities increased with the increase of plasma treatment time. Deposition of the plasma polymer on the membrane surface was confirmed by FTIR/ATR spectra of the treated surface. In determining the flux, the hydrophilicity of the surface played a role as important as that of the micropore size. Adequate plasma treatment could enhance both water flux and solute removal efficiency. Results from the BSA (bovine serum albumin) solution test confirmed that fouling was greatly reduced after the plasma treatment. The BSA solution flux through the plasma‐treated membranes depended on pH, whereas pH variation had no serious effects on the untreated membrane. Modification of the surface charge by the plasma treatment should exert a substantial influence on the adsorption and removal of BSA. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1555–1566, 2001     

Plasma‐induced surface modification and adhesion enhancement of polypropylene surface

Unoriented (UPP) and biaxially oriented (BOPP) polypropylene films were treated under radio frequency plasma of air, nitrogen, oxygen, and ammonia. Surface modification of polypropylene films was investigated by using surface energy measurement and attenuated total reflection (ATR)‐FTIR spectroscopy. Surface energy of air and nitrogen plasma‐treated polypropylene film increased for shorter treatment time and then decreased and attained an equilibrium value. Such changes in surface energy were not observed for oxygen and ammonia plasma‐treated polypropylene film, which increased to an equilibrium value. ATR‐FTIR studies revealed characteristic differences in the absorption spectra for short‐duration and long‐duration treatments. From the relative intensity change in the C—H stretching vibration, the mechanism of surface chemical reaction could be inferred. Studies regarding the durability of surface modification due to plasma treatment were evaluated by investigating surface energy of samples aged for 2 months. Treated films subjected to peel strength measurement showed improvement in bondability for UPP and BOPP film by hydrophilic surface modification accompanied by surface crosslinking. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 925–936, 2002     

Plasma treatment effect on the surface energy of carbon and carbon fibers

The surface energy dispersive (γ^D_S) and polar (γ^P_S) components of carbon model surfaces (bal planes, prismatic surfaces, vitreous carbon) and of carbon fibers (high strength and high modulus, respectively) were determined systematically before and after plasma treatment. The method used is essentially based on the wetting contact angle measurements within two liquids. In all cases (γ^P_S) is markedly increased by the plasma treatment. For carbon fibers, with increasing plasma treatment duration (γ^P_S) is increasing toward a limiting value (-30 mJ/m²) while (γ^D_S) is depressed toward low values (-10 mJ/m²). The parallel evolution of surface topography is followed by SEM observations. The changes in surface energy of carbon model surfaces is also discussed.     

Solid‐state hydrolysis of postconsumer polyethylene terephthalate after plasma treatment

Plasma treatments were applied on the surface of postconsumer polyethylene terephthalate (PET) bottles to increase their wettability and hasten the subsequent hydrolysis process. Sixty‐four treatments were tested by varying plasma composition (oxygen and air), power (25–130 W), pressure (50–200 mTorr), and time (1 and 5 min). The best treatment was the one applied in air plasma at 130 W and 50 mTorr for 5 min, as it provided the lowest contact angle, 9.4°. Samples of PET before and after the optimized plasma condition were subjected to hydrolysis at 205°C. Although the treatment changed only a thin surface layer, its influence was evident up to relatively high conversion rates, as the treated samples presented more than 40% higher conversion rates than the untreated ones after 2 h of reaction. Infrared spectroscopy showed that the terephthalic acid obtained from 99% of depolymerization was similar to the commercial product used in PET synthesis. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013