Cell outer membrane mimetic modification of a cross-linked chitosan surface to improve its hemocompatibility

A novel strategy has been developed to improve the hemocompatibility of chitosan surface by cell outer membrane mimetic structure able to reduce protein adsorption and cell adhesion. Phosphorylcholine dichloride was synthesized and grafted onto a glutaraldehyde-cross-linked chitosan (CS-GA) film surface to prepare phosphorylcholine-coated CS-GA film (CS-GA-PC) through a heterogeneous reaction process. The spectroscopic and contact angle characterization show that a cell outer membrane mimetic structure was formed on the cross-linked chitosan surface, and the significantly improved hemocompatibility of the modified surface was shown by a suppression of 94% on platelet adhesion, a suppression of 60–70% for bovine plasma fibrinogen and bovine serum albumin adsorptions. These results demonstrated that this cell outer membrane mimetic surface modification with phosphorylcholine dichloride is a promising strategy to improve the hemocompatibility of chitosan.     

Surface modification and characterization of thermoplastic polyurethane

This work reports the modification of thermoplastic polyurethanes (TPUs) in order to enlarge their application range, for example, as biomaterials by increasing its hydrophilicity.A TPU was successfully modified by using three different strategies: ultra-violet irradiation (UV), gamma irradiation (GI) and interfacial modification (IM). The results suggested the possibility of modifying the polyurethane-based surface either with poly(ethylene glycol) (PEG) or hydroxylethyl methacrylate (HEMA) or hexamethylene diamine (HMD) or chitosan (CT) by using any of these methods. The properties of the grafted PU were evaluated by surface, structural and thermal analysis. The results suggest that, among the methods studied in this work, the modification by gamma irradiation (GI) seems to be the most promising, since this method gives high values of grafting yield and has the advantage of providing a clean modification, meaning that no initiator is needed.     

Adhesion of Cryptosporidium parvum and Giardia lamblia to solid surfaces: the role of surface charge and hydrophobicity

Adhesion of Cryptosporidium parvum and Giardia lamblia to four materials of different surface charge and hydrophobicity was investigated. Glass beads were used with and without three polymer coatings: aminosilines (A0750), fluorosilines (T2494), an amino cationic polymer. Surface charge density and hydrophobicity of the beads were characterized by measuring the zeta potential (ZP) and the contact angle, respectively. Adhesion was derived from batch experiments where negatively charged (oo)cysts were mixed with the beads and recovery was determined by counting (oo)cysts remaining in suspension using a flow cytometer. Experimental results clearly show that adhesion to solid surfaces of C. parvum is different from G. lamblia. Adhesion of C. parvum to positively charged, hydrophilic beads (82% recovery relative to control) indicated that surface charge was the more important factor for C. parvum, dominating any hydrophobic effects. Adhesion of G. lamblia cysts to negatively charged, hydrophobic beads (0% recovery relative to control) indicated that although hydrophobicity and surface charge both played a role in the adhesion of G. lamblia to solid surfaces, hydrophobicity was more important than surface charge.     

The influence of aging on surface free energy of corona treated packaging films

In packaging, plastic films are very often applied as overprinting materials. The printing properties of plastic films depend on the value of the surface free energy. Usually, during storage but before printing, the surface free energy is decreasing as a result of ageing. The aim of this study was to analyse the influence of elevated temperature and UV radiation on ageing properties and variation of the free surface energy for three commercially available plastic films: polyethylene, polypropylene and polyethylene terephthalate. The investigation was done experimentally, and the surface free energy was calculated using two approaches, Owens-Wendt and van Oss-Chaudhury-Good. The time change of polar fractions was also analysed. The calculation results were compared and it was concluded that UV radiation causes more changes in surface free energy than elevated temperature. In some cases, surface free energy values calculated with the applied methods show similar trends.     

Effect of environment on the degradation of starch and pro-oxidant blended polyolefins

The aim of this study was to understand the rate of degradation of commercial pro-oxidant blended and starch blended High Density Polyethylene (HDPE), pro-oxidant blended Low Density Polyethylene (LDPE), and starch blended polypropylene in three different environments, namely under direct sunlight, buried in soil and immersed in marine waters for a period of 150 days. The bio-fouling parameters were also monitored in the case of polymers deployed in sea water. Exposure to sunlight showed highest weight loss (>10%) and samples buried in soil showed the lowest (∼1%). Pro-oxidant blended HDPE showed higher weight loss when compared to starch blended (22.7 as against 11%). Scanning electron microscopy revealed surface deterioration and decrease in contact angle indicated reduction in surface hydrophobicity. Increase in the carbonyl and hydroxyl groups in the infra-red spectrum of the exposed samples suggested abiotic degradation. Starch blended PP exposed to sunlight showed the highest thermo gravimetric weight loss (63.8%) followed by the same polymer buried in soil (46.1%).     

Ultraviolet light absorber with low surface energy: synthesis and characterization

Novel fluorine-containing ultraviolet absorbers (FBPs) with low surface energy were successfully synthesized based on 2,4-dihydroxy benzophenone (BP-1), and their structures were characterized by ¹H NMR, ¹³C NMR, FTIR, and HRMS. UV absorption of FBPs was studied in 10⁻⁴ M dichloromethane (CH₂Cl₂), which demonstrated the superior UV absorption capability of FBPs (ca. ?=1.7×10⁴ to 2.2×10⁴ at λ_max) over the matrix (?=1.7×10⁴ at λ_max). Quantum chemistry calculation was performed to investigate the stable structure and UV electronic absorption bands of FBPs. The surface chemistry information of high-chlorinated polyethylene (HCPE) coating films embedded with ultraviolet absorbers (UVAs) was given by X-ray photoelectron spectroscopy (XPS) and contact angle measurement. The results show that the surface enrichment capability of FBPs is remarkably better than traditional UVAs (including BP-1, BP-3, BP-12) because of the low surface energy properties of FBPs.     

正十八烷醇在HOPG上形成自组装膜的吸附特性

研究了正十八烷醇在高定向热解石墨(HOPG)上形成自组装膜的吸附特性, 正十八烷醇在室温下从溶液中吸附至HOPG上形成整齐定向排列的单层自组装膜. 通过扫描隧道显微镜(STM)、接触角测量和X射线光电子能谱(XPS)分析了正十八烷醇单层自组装膜在HOPG上的结构. 实验结果表明, 正十八烷醇自组装膜在基底上成平铺或直立形态, 由于分子在基底上覆盖程度的不同, 会导致它在基底上排列的方式有所不同.     

Influence of surface roughness on dispersion forces

Surface roughness occurs in a wide variety of processes where it is both difficult to avoid and control. When two bodies are separated by a small distance the roughness starts to play an important role in the interaction between the bodies, their adhesion, and friction. Control of this short-distance interaction is crucial for micro and nanoelectromechanical devices, microfluidics, and for micro and nanotechnology. An important short-distance interaction is the dispersion forces, which are omnipresent due to their quantum origin. These forces between flat bodies can be described by the Lifshitz theory that takes into account the actual optical properties of interacting materials. However, this theory cannot describe rough bodies. The problem is complicated by the nonadditivity of the dispersion forces. Evaluation of the roughness effect becomes extremely difficult when roughness is comparable with the distance between bodies. In this paper we review the current state of the problem. Introduction for non-experts to physical origin of the dispersion forces is given in the paper. Critical experiments demonstrating the nonadditivity of the forces and strong influence of roughness on the interaction between bodies are reviewed. We also describe existing theoretical approaches to the problem. Recent advances in understanding the role of high asperities on the forces at distances close to contact are emphasized. Finally, some opinions about currently unsolved problems are also presented.     

Wettability of model fountain solutions: The influence on topo-chemical and -physical properties of offset paper

The surface chemical and physical character of offset paper was studied before and after application of model fountain solutions based on isopropyl alcohol and an alcohol-free surfactant solution. The paper surface features were characterised with atomic force microscopy and the surface energies were determined by contact angle measurements. Changes in the surface chemical properties induced by the fountain solutions were investigated with X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectroscopy. Coated papers wetted with the surfactant solution revealed a slight increase in the root mean square roughness, but the isopropyl alcohol solution led to no observable changes. The change in sub-micro roughness is ascribed not only to substrate swelling or migration of coating constituents but also to the presence of surfactant on the surface. A change in the surface energy and particularly the polar contribution was observed after application of the surfactant solution. The X-ray photoelectron spectroscopy showed an increase in the oxygen-to-carbon ratio, which confirms the presence of surfactant on the surface. Time-of-flight secondary ion mass spectroscopy showed that the isopropyl alcohol solution did not change the elemental composition of the surface whereas the surfactant solution clearly did so. The distribution of surfactant on the surface was confirmed by mapping the characteristic fragments of the molecule.     

Wettability of proteins adsorbed on silica glasses treated with fluorosurfactants

Generally, the apolar/polar surface is probed by water-wetting, which is measured using a method such as the sessile liquid drop method. However, when one tries to measure the wetting of a surface where biological macromolecules are adsorbed, there is the problem of a change in conformation due to drying the surface; hence, using this method in situ information cannot be obtained. We have developed a new method that can be used to measure the wettability of the adsorbed protein surface without drying. This method, the dropping time method, which is based on measuring the dropping time of a film of liquid along a protein-covered surface when this surface is instantaneously vertically removed from the protein solution. The adsorption behavior of four proteins (albumin, lysozyme, β-lactoglobulin, ovalbumin) on the surface of silica glass that has been treated with various fluorosurfactants is studied using this method. At a high concentration of protein, the surfaces of adsorbed proteins of any kind are fairly hydrophilic on glass treated with all fluorosurfactants. At a lower concentration of protein, the hydrophilicity of the protein layer depends on the kind of fluorosurfactant and also on the protein adsorption process. The apolar glass surface becomes more hydrophilic with increasing dipping time in the protein solution. On the other hand, the hydrophilic glass surface shows a complex change in the hydrophilicity with elapsed time after dipping it into a solution of albumin or lysozyme, i.e., the hydrophilicity decreases in the early stage of the adsorption and then increases with proceeding adsorption. Received: 19 March 1999 Accepted in revised form: 10 June 1999     

低温等离子体处理聚酯(PET)表面润湿性与表面结构的研究

研究了O₂、N₂、He、Ar、H₂和CH₄气体低温等离子体改性聚酯(PET)的表面润湿性与表面结构的关系.用已知表面张力的液体测定接触角,作Zisman曲线,求得试样的临界表面张力γ_c;并按扩展的Fowkes式计算试样的表面张力γ_s及其三组分值γ_s^a(色散力)、γ_s^c(偶极矩力)和γ(氢键力),发现经O₂、N₂、He和Ar等离子体短时间处理的聚酯表面自由能显著增大,表面润湿性增强,主要是聚酯表面张力的氢键力成分的贡献,X射线光电子能谱分析表明,这是由于聚酯表面含氧或含氮极性基团增加所致.     

A novel technique for preparing of maleic anhydride grafted polyolefins

A novel mechanochemical method of preparation of maleic anhydride grafted polypropylene (MAPP) was developed. The preparation was performed by ball milling of polypropylene (PP) powder, maleic anhydride (MA), and peroxide initiator in balls-containing jars with a planetary ball mill for a certain time. Compared with the conventional melt-mixing method, MAPP obtained through ball-milling technique reveals higher graft degree, particularly alleviated degradation of PP, or even increased molecular mass of the resulting MAPP. Maleic anhydride grafted polyethylene (MAPE) was obtained via this technique, and the optimization of the technique is in progress. The novel technique offers new opportunities in modification of polyolefins, which has also the advantages of solventless, lower process temperature, energy efficient, low cost, and simple running process. Furthermore, it is very easy to obtain purified products.     

Status of the three-phase line tension: a review

From a thermodynamic point of view, the concept of line tension is on solid ground; it is well recognized and defined. There is a notion in the literature that there is little consensus with regards to magnitude or sign of line tension. Partly, inappropriate comparisons of line tension values may have contributed to the current uncertainty, especially some between theoretical and experimental values. A wide range of reported line tension values may not necessarily be a result of conflicting findings, but it may reflect the diversity of systems studied. However, differences among similar approaches and systems observed are sometimes caused by one or several of the following factors: difficulties in sample preparation, poor experimental techniques, non-equilibrium, or conceptual and theoretical difficulties and oversimplifications. It is important to clearly establish the magnitude and sign of line tension as it may determine its relevance to technological applications such as microfluidic systems.

This review has examined a wide range of recent and past studies on the subject of line tension. The review classifies line tension studies into theoretical and experimental; it further groups the studies into liquid–liquid–vapor and solid–liquid–vapor systems for each category. The review provides a comparison between similar studies in an attempt to clarify the current status of line tension research. The majority of theoretical line tension studies (excluding the near wetting studies) have estimates for line tension of about 10⁻¹⁰ N; however, for special cases, values as high as 10⁻⁶ N are also reported. There is less consensus regarding the sign for the line tension as theoreticians often assert that line tension can have either a positive or a negative sign. In experimental studies of liquid–liquid–vapor systems the majority of studies reported positive values for line tension; for film studies, the magnitude of line tension reported was between 10⁻⁹ and 10⁻⁷ N, whereas for studies of liquid lens values as high as 10⁻⁶ N were also reported. The clear majority of studies for solid–liquid–vapor systems reported a positive sign for line tension. In studies involving particles, line tension values ranged from 10⁻⁹ to 10⁻⁶ N. Studies using drop size dependence of contact angles reported values mostly in the span of 10⁻⁹–10⁻⁶ N; however, a clear majority of the reported values fell in the higher end of the above range. The special topic of line tension near wetting was also studied. While the interface displacement model appears to have brought about consensus with respect to certain aspects of line tension behavior near wetting, this model maybe still too phenomenological to be satisfactory from a more fundamental standing. Experimentalists have just begun studying line tension for systems near wetting, this is encouraging, but more comprehensive studies are needed.     

Immobilization of antioxidants via ADMET polymerization for enhanced long-term stabilization of polyolefins

Novel macromolecular antioxidants with multiple hindered phenolic antioxidant moieties along a linear, unsaturated olefinic backbone are prepared and their antioxidative ability in polypropylene (PP) blends is investigated. Firstly, α,ω-diene monomers bearing one alcohol functionality are prepared from 10-undecenoic acid, sourced from the renewable resource castor oil, and are subsequently coupled to hindered phenolic antioxidants to prepare antioxidant bearing α,ω-diene monomers. The preparation of macromolecular antioxidants is then described, via ADMET polymerization of the hindered phenol bearing monomers. Upon blending with polypropylene, the resultant blends show excellent antioxidative stabilization in comparison to commercially available antioxidants and thus represent promising additives for the long-term stabilization of polyolefins in extreme environments, for example in the construction of solar water heating systems.     

Aging behavior and mechanism of ethylene-propylene-diene monomer (EPDM) rubber in fluorescent UV/condensation weathering environment

Ethylene-propylene-diene monomer (EPDM) rubber was exposed to an artificial weathering environment produced by fluorescent UV/condensation weathering device for different time periods. The surface chemical changes were detected by X-ray Photoelectron Spectroscopy (XPS) and Raman spectroscopy. The plausible aging mechanism of EPDM was proposed. The surface energy was calculated through contact angles of water and formamide measured by optical contact angle measuring device. The thermal stability was evaluated by thermo-gravimetric analysis (TGA).The results showed that oxygenated species such as C-O-C, CO and O-CO groups were formed in fluorescent UV/condensation weathering environment. EPDM aging occurred from EPDM surface and propagated to EPDM inner body. The surface energy of EPDM increased to a maximum at 36 days of aging and then decreased slowly. Fluorescent UV/condensation weathering environment does not affect the thermal stability of EPDM predominantly.     

Polypropylene ionic thermoplastic elastomers: Synthesis and properties

Polypropylene ionic thermoplastic elastomers have been prepared by melt radical grafting of maleic anhydride onto polypropylene in the presence of N-bromosuccinimide followed by neutralization of the resulting elastomeric grafted polypropylene using sodium salts. Sodium hydroxide and sodium acetate were compared in aqueous solution, as anhydrous or hydrated powders. The neutralization reaction was followed by Fourier transform infrared spectroscopy, allowing the development of a method to determine the effective neutralization degree. Important physical changes were recorded upon neutralization. Especially thermal stability, shear storage modulus and complex viscosity in the flow region were largely increased as a function of the neutralization degree.     

Carbonaceous sorbents for high‐temperature interactive liquid chromatography of polyolefins

The elution behavior of polyethylene (PE) and the three stereoisomers of polypropylene (PP) was studied on porous graphite along with three other carbon‐based sorbents, carbon‐clad zirconia particles, activated carbon, and exfoliated graphite in a systematic way in this work. Decahydronaphthalene, 1,2,3,4‐tetrahydronaphthalene, 1,3,5‐trimethylbenzene, tetrachloroethylene, xylene and p‐xylene were used as mobile phases. While PE is adsorbed to various extents on all the tested carbonaceous sorbents from the majority of the solvents, PP is fully adsorbed only in selected cases. Testing alcohols (C7–C9) as mobile phase with Hypercarb? indicates that all stereoisomers of PP are selectively adsorbed and desorbed when a solvent gradient alcohol→1,2,4‐trichlorobenzene is used at 160°C. The retention of all stereoisomers of PP increases with the polarity of the alcohol. Linear PE is retained on Hypercarb? even from 1,2‐dichloro‐ and 1,2,4‐trichlorobenzene, when a temperature below 120°C is applied, while it is not retained from these solvents at higher temperatures. All stereoisomeric forms of PP are not adsorbed under the same conditions. Some of the tested new sorbent/solvent systems have potential to be applied in routine analysis of industrially synthesised polyolefins.     

SURFACE MODIFICATION OF POLYPROPYLENE MICROFIBRE BY PLASMA-INDUCED VAPOR GRAFTING WITH ACRYLIC ACID

The hydrophilicity, dyeing and antistatic ability of polypropylene microfibre (PPMF) wereimproved by plasma-induced vapor grafting with acrylic acid. The effects of plasma discharge time, power,liquid phase acrylic acid temperature and environmental temperatore on grafting yield were investigated. Theexistence of grafted polyacrylic acid (PAA) was verified by ESCA and ATR FT-IR. The morphology ofgrafted PAA was directly observed by SEM. The wicking test shows that the hydrophilicity of modifiedPPMF is greatly enhanced. The dyeability test of modified PPMF was carried out using Dispersion Yellow. Itwas found that the dye uptake ratio is linear to the weight percent of grafting. The antistatic ability wasindicated by specific resistance. The specific resistance of modified PPMF was reduced to 10~6～10~7Ω·cm,thus the antistatic ability was considerably improved.     

Regularity modes in Raman spectra of polyolefins: Part I. Propylene/olefin copolymers

Behavior of the regularity modes of isotactic polypropylene is analyzed in Raman spectra of a number of random propylene/olefin copolymers. The regularity modes at 809, 841, 973, 998, and 1220 cm⁻¹ decrease in intensity with growth of the content of the incorporated monomer. For the lines at 809, 973, and 1220 cm⁻¹ the rate of intensity damping varies depending on the structure of the incorporated monomer. The type of the incorporated monomer has inconsiderable effect on the evolution of intensity of the regularity bands at 841 and 998 cm⁻¹. Anomalous behavior of the mode at 1220 cm⁻¹ was observed for the propylene/1-butene copolymers.     

Ageing of polylactide and polylactide nanocomposite filaments

An experimental study was carried out in order to check the influence of various parameters on the ageing of PLA filaments performed in a climatic room. Initially, two grades of PLA with different d-isomer contents were analysed. Even after several weeks of ageing, properties of PLA filaments with less than 0.5% d-isomer content did not vary extensively. On the other hand, the mechanical and thermal properties of PLA filaments with 4% d-isomer content underwent strong modifications. Subsequently, a selected organomodified bentonite (Bentone^®104 - noted as B104) was blended with PLA and then melt-spun to study the influence of a nanofiller on the ageing of PLA filaments. Faster degradation of PLA nanocomposite filaments was then observed.