Surface Modification of Polyvinylidene Fluoride (PVDF) Membranes by Low-Temperature Plasma with Grafting Styrene

In order to control the surface pore sizes of polyvinylidene fluoride membranes and their distribution, low temperature plasma-induced grafting modifications of PVDF were studied to prepare hydrophobe membranes. By argon （Ar） treating and subsequent grafting reaction, a hydrophobe monomer, styrene, was introduced into the PVDF membrane. Fourier transform infrared attenuated total reflection （FTIR-ATR） was utilized to characterize the chemical and physical changes in the Ar plasma modified membrane. The surface modifications of PVDF membranes were investigated by using scanning electron microscopy （SEM）, atomic force microscopy （AFM） and differential scanning calorimeter （DSC）. The water permeability and the solute rejection were measured by PVDF membrane modified in different graft conditions. Results demonstrated that the pores in the modified membranes get smaller and the distribution of pores gets narrowed with the increase in grafting reaction duration. Longer graft time caused the water flux of PVDF membrane to decrease from 578 kg/（m^2· h） to 23 kg/（m^2· h） and the solute rejection to increase from 73% to 92%.

LAMINATION OF POLYMER FILMS BY BULK SURFACE PHOTOGRAFTING PROCESS AND PROPERTIES

A new process for lamination of polymer films by 'bulk surface photografting' has been developed. The chemical component of the invention is that the curing of reactive solution between two substrates is initiated by the surface free radicals produced by aromatic ketones and surface-hydrogen of substrates. Using the new approach, two or more polymer films are bonded together by a grafted polymer network which is grafted to adjacent substrate surfaces. The technique has been applied to film substrates of different polymers such as polyolefins, polyesters, and polyamides which have abstractable hydrogens at the surface. The photolaminated film composites containing carrier films and an intermediate functional film of low permeability give strong laminates with high barrier properties, e.g, for oxygen and air.

PHOTOINDUCED GRAFTING OF ACRYLIC AND ALLYL MONOMERS ON POLYETHYLENE SURFACE

Photoinduced grafting of acrylic and allyl monomers on polyethylene surface was generally studied by using benzophenone (BP) as a photoinitiator. The grafting process was carried out either in vapor-phase or in solution of the monomers. In the vapor-phase reaction with a filter used to cut off the short wavelength UV light, allyl amine is the most reactive of the four monomers used and acrylic amide is comparatively more reactive than acrylic acid and allyl alcohol. Acetone, as a solvent and carrier for initiator and monomers, however, shows its reactivity to participate the reaction. The solution grafting with a filter is much faster than the corresponding vapor-phase reaction, and a fully covered surface by the grafted polymer can be achieved in this way.

Surface Grafting of Phenolic Resole onto LDPE Films

Low density polyethylene film surface-grafted phenolic resole was prepared by a sequential processes. Firstly, acrylic acid was grafted to the surface of low density polyethylene by photo-grafting. Secondly, the carboxylic groups in poly（acrylic acid） chains were transferred to sulfonic groups by the reaction of carboxylic groups with sulfanilic acid. Finally, a thin layer of phenolic resole was cured onto the surface of low density polyethylene. The grafting process was characterized by FTIR-ATR and gravimetric analysis. A possible model was proposed to interpret the experimental results.

Polycaprolactone (PCL) Chains Grafting on the Surface of Cellulose Nanocrystals (CNCs) during <i>In Situ</i>Polymerization of <i>ε</i>-Caprolactone at Room Temperature

This work aimed at investigating the feasibility of surface modification of cellulose nanocrystals (CNCs) using in situ ring opening polymerization of ε-caprolactone (ε-CL) at room temperature. Residues of flax and milkweed (Asclepias syriaca) stem fibers were used as a source of cellulose to obtain and isolate CNCs. The cationic ring opening polymerization (CROP) of the monomer ε-CL was used to covalently graft polycaprolactone (PCL) chains at the CNCs surface. Silver hexafluoroantimonate (AgSbF6) was used in combination with the extracted CNCs to initiate, at room temperature, the polymerization and the grafting reactions with no other stimulus. Fourier-Transform InfraRed (FTIR), X-ray Photoelectron Spectrometry (XPS), UV/visible absorption and Gel Permeation Chromatography (GPC) analyses evidenced the presence of PCL chains covalently grafted at CNCs surface, the formation of Ag(0) particles as well as low or moderate molecular weight free PCL chains.

Glucose-sensitive Membrane with PBA-based Contraction-type Linear Polymer as Chemical Valves Prepared by Surface Grafting

Glucose-sensitive membrane has potential application in self-regulating insulin release.Phenylboronic acid(PBA)is a well-known glucose reporter.Unfortunately,most PBA-based glucose-sensitive materials are expansion-type,which are not suitable as chemical valves in membrane pores for self-regulating insulin release.According to a new glucose-sensitive mechanism,we synthesized PBA-based contraction-type glucose-sensitive liner polymer and microgels.Herein,a glucose-sensitive membrane was prepared by grafting PBA-based contraction-type glucose-sensitive linear polymer on the membrane surface.Through adjusting the chain length and chain density,the glucose-sensitivity of the membrane was optimized.The membrane can reversibly regulate insulin release at physiologically relevant glucose concentrations in simulates body fluids and fetal bovine serum.The membrane also has good stability,anti-fouling and biocom patibility.It has potential application in selfregulating insulin release.

Nitrate-group-grafting-induced assembly of rutile TiO2 nanobundles for enhanced photocatalytic hydrogen evolution

In this study,an acid-induced assembly strategy for a rutile TiO2 photocatalyst was proposed on the basis of the treatment of lamellar protonated titanate with a concentrated HNO3 solution.Nitrate groups were successfully grafted onto a TiO2 surface and induced the assembly of rutile TiO2 nanorods into uniform spindle-like nanobundles.The resulting TiO2 product achieved a photocatalytic hydrogen evolution rate of 402.4μmol h^?1,which is 3.1 times higher than that of Degussa P25-TiO2.It was demonstrated that nitrate group grafting caused the rutile TiO2 surface to become negatively charged,which is favorable for trapping positive protons and improving charge carrier separation,thereby enhancing photocatalytic hydrogen production.Additionally,surface charges were crucial to structural stability based on electrostatic repulsion.This study not only developed a facile surface modification strategy for fabricating efficient H2 production photocatalysts but also identified an influence mechanism of inorganic acids different from that reported in the literature.

GRAFTING OF HYDROPHILIC MONOMERS ONTO POLYURETHANE MEMBRANES BY SOLUTION OR PRE-ABSORBING METHODS FOR ACCELERATION OF CELL COMPATIBILITY

Two grafting methods, i.e. solution grafting and pre-adsorbing, are introduced to covalently immobilizehydrophilic polymers on segmented polyurethane (SPU) to modify its hydrophilicity and to improve its cell compatibility.Solution grafting results in higher degree of grafting and rougher surface morphology. Cell culture evaluation demonstratesthat the modified membranes thus obtained are disadvantageous to the endothelial cell (ECs) growth probably because thehydrophilic groups on the surface are over-crowded. However, pre-absorbing grafting generates lower degree of grafting,which is detected and confirmed by ATR-FTIR spectra and water conted angle. Scanning electron microscopic (SEM)measurement shows that the latter method produces a plane and smooth morphology, which is similar to the SPU controlsample controlled. When grafting with lower monomer concentration, ECs could grow on SPU-g-PHEA [poly(2-hydroxyethyl acrylate)], SPU-g-PAAm (polyacrylamide), SPU-g-PDMA [poly(2-(dimethylamino)ethyl methacrylate)] orquatemized SPU-g-PDMA surface with elongated cell shapes. Hence, the cell compatibility of SPU is improved and a usefulmethod to construct a cell compatible layer on the polymer surface has been developed.

Study on the Surface Modification of Hydrophobic Polyacrylate Intraocular Lens

In this study, the polyacrylate intraocularr lens is irradiated by argon ion which can produce free radicals. In order to obtain better hydrophilic and lower platelets adhesion, monomer vinyl pyrrolidone (NVP) is grafted onto the hydrophobic polyacrylate intraocular lens surface in a certain reaction conditions. Specific changes in intraocular lens are detected by static contact angle (CA), scanning electron microscope (SEM) and light transmittance. The results show that this surface modification can greatly improve its hydrophilic character and surface formation.

APPLICATION OF SURFACE GRAFTED POLY N-ISOPROPYL ACRYLAMIDE BY RADIATION TECHNOLOGY FOR PROTEIN SOLUTION CONCENTRATION

Poly N-isopropyl acrylamide (abbreviated as PNIPA) as a kind of thermally sensitive hydrogel is utilized to concentrate Bovin Serum Albumin (BSA) solution. In order to decrease its surface adsorption to BSA in aqueous solution, surface layer grafting of the gels by radiation technology was carried out. The results showed that hydroxyl propyl methacrylate (HPMA) grained gel exhibited a low level of BSA adsorption and still kept the original thermally sensitive properties of PNIPA hydrogels.

An Approach to the Flame Retardancy of EVA Copolymer by Plasma Treatmentc2

An attempt was made in the paper aiming at imparting flame retardancy to polymers by plasma grafting technique Based on EVA copolymers with different VA contents the author tried to use the Ar plasma followed by grafting with/without subsequent saponification and metal ion exchange expediting the charring of polymers upon heationg Characterization of the flammability of the plasma treated EVA copolymers grafted with acrylic monomers(MAA,AA and AAm)indicates that this approach turns out to be a promising way and worthy doing whatever in research and/or applications

Preparation and shape memory properties of TiO_2/PLCL biodegradable polymer nanocomposites

The preparation of TiO2/poly（L-lactide-co-ε-caprolactone）（PLCL） nanocomposites and their properties were reported.TiO2nanoparticles were surface modified by ring-opening polymerization of ε-caprolactone（ε-CL）.The resulting poly（ε-caprolactone）-grafted TiO2（g-TiO2） was characterized by Fourier transform infrared spectroscopy（FTIR）,thermogravimetric analysis（TGA） and transmission electron microscopy（TEM）.The g-TiO2can be uniformly dispersed in chloroform and the g-TiO2/PLCL nanocomposites were successfully fabricated through solvent-casting method.The effects of the content of g-TiO2nanoparticles on tensile properties and shape memory properties were investigated.A significant improvement in the tensile properties of the 5% g-TiO2/PLCL mass fraction nanocomposite is obtained：an increase of 113% in the tensile strength and an increase of 11% in the elongation at break over pure PLCL polymer.The g-TiO2/PLCL nanocomposites with a certain amount of g-TiO2content have better shape memory properties than pure PLCL polymer.The g-TiO2nanoparticles play an additional physical crosslinks which are contributed to improvement of the shape memory properties.

PLASMA MODIFICATION OF POLYPROPYLENE SURFACES AND GRAFTING COPOLYMERIZATION OF STYRENE ONTO POLYPROPYLENE

The surface of polypropylene （iPP） is modified with glow discharge plasma of Ar, so that the modified surfaces of iPP films are obtained. The studies of scanning electron microscopy （SEM） show the surface etching pattern of iPP films. The chemical structures of iPP films are confirmed by X-ray photoelectron spectroscopy （XPS） and Fourier transform infrared （FTIR） spectroscopy. The wetting properties of modified surfaces of iPP films are characterized by contact angle, and the free energy of surfaces is calculated. The free radical of modification surfaces of iPP is measured by chemical method. The surfaces of iPP are achieved with Ar plasma treatment followed by grafting copolymerization with styrene （St） in St. The grafting polymer of St onto iPP is characterized by FTIR. The grafting rate is dependent on plasma exposure time and discharge voltage. The studies show that homopolymerization of St is undergone at the sane time during the graftingcopolymerization of St onto/PP.

Preparation of new hybrid organic/inorganic polymeric chiral stationary phases for ligand-exchange chromatography

Three new hybrid organic/inorganic polymeric ligand-exchange chiral stationary phases were developed by radical chain transfer reaction and surface grafting on silica gel, and successfully used for the enantioseparations of DL-amino acids and DL-hydroxyl adds. The resolutions were achieved by using water containing 2.0 × 10^-4 mol/L of CuAc2 as a mobile phase, column temperature of 40 ℃, flow rate of 1.0 mL/min and detection at UV 254 nm. The elution order of D-isomer before L-isomer was observed for all DL-amino acids resolved except DL-Pro.

Thermal and mechanical properties and micro-mechanism of SiO_(2)/epoxy nanodielectrics

In addition to electrical insulation properties,the thermal properties of nanodielectrics,such as glass transition temperature,thermal expansion coefficients,thermal conductivity,and mechanical properties,including Young's modulus,bulk modulus,and shear modulus,are also very important.This paper describes the molecular dynamics simulations of epoxy resin doped with SiO_(2)nanoparticles and with SiO_(2)nanoparticles that have been surface grafted with hexamethyldisilazane(HMDS)at 10%and 20%grafting rates.The results show that surface grafting can improve certain thermal and mechanical properties of the system.Our analysis indicates that the improved thermal performance occurs because the formation of thermal chains becomes easier after the surface grafting treatment.The improved mechanical properties originate from two causes.First,doping with SiO_(2)nanoparticles inhibits the degree of movement of molecular chains in the system.Second,the surface grafting treatment weakens the molecular repulsion between SiO_(2)and epoxy resin,and the van der Waals excluded region becomes thinner.Thus,the compatibility between SiO_(2)nanoparticles and polymers is improved by the grafting treatment.The analysis method and conclusions in this paper provide guidance and reference for the future studies of the thermal and mechanical properties of nanodielectrics.

Grafting of PEG400 onto the surface of LLDPE/SMA film

Linear low-density polyethylene(LLDPE)was melt and blended with styrene-maleic anhydride copolymer(SMA).The blending films were then immersed in poly(ethylene glycol)400(PEG400)at room temperature.The surface composition of the blend films was determined by Fourier transform infra-red spectroscopy coupled with a variable incidence angle attenuated total reflection accessory(ATR-FTIR).Results show that PEG400 can be grafted onto the surface of the films via esterification with SMA.The immersion of PEG promotes the enrichment of SMA onto the surface of the films.The water contact angle data show that grafting of PEG400 onto PE can greatly improve the hydro-philicity of the PE surface.These experiments show that sur-face functionalization of polyethylene films by blending SMA and then surface grafting of PEG is feasible,which suggest an effective and simple route for PE surface modification via blending and grafting.

Recent developments in functional organic polymer coatings for biomedical applications in implanted devices

Organic polymer coatings have been commonly used in biomedical field,which play an important role in achieving biological antifouling,drug delivery,and bacteriostasis.With the continuous development of polymer science,organic polymer coatings can be designed with complex and advanced functions,which is conducive to the construction of biomedical materials with different performances.According to different physical and chemical properties of materials,biomedical organic polymer coating materials are classified into zwitterionic polymers,non-ionic polymers,and biomacromolecules.The strategies of combining coatings with substrates include physical adsorption,chemical grafting,and self-adhesion.Though the coating materials and construction methods are different,many biomedical polymer coatings have been developed to achieve excellent performances,i.e.,enhanced lubrication,anti-inflammation,antifouling,antibacterial,drug release,anti-encrustation,anti-thrombosis,etc.Consequently,a large number of biomedical polymer coatings have been used in artificial lungs,ureteral stent,vascular flow diverter,and artificial joints.In this review,we summarize different types,properties,construction methods,biological functions,and clinical applications of biomedical organic polymer coatings,and prospect future direction for development of organic polymer coatings in biomedical field.It is anticipated that this review can be useful for the design and synthesis of functional organic polymer coatings with various biomedical purposes.

Smart biomaterials: Surfaces functionalized with proteolytically stable osteoblast-adhesive peptides

Engineered scaffolds for bone tissue regeneration are designed to promote cell adhesion,growth,proliferation and differentiation.Recently,covalent and selective functionalization of glass and titanium surfaces with an adhesive peptide(HVP)mapped on[351e359]sequence of human Vitronectin allowed to selectively increase osteoblast attachment and adhesion strength in in vitro assays,and to promote osseointegration in in vivo studies.For the first time to our knowledge,in this study we investigated the resistance of adhesion sequences to proteolytic digestion:HVP was completely cleaved after 5 h.In order to overcome the enzymatic degradation of the native peptide under physiological conditions we synthetized three analogues of HVP sequence.A retro-inverted peptide D-2HVP,composed of D amino acids,was completely stable in serum-containing medium.In addition,glass surfaces functionalized with D-2HVP increased human osteoblast adhesion as compared to the native peptide and maintained deposition of calcium.Interestingly,D-2HVP increased expression of IBSP,VTN and SPP1 genes as compared to HVP functionalized surfaces.Total internal reflection fluorescence microscope analysis showed cells with numerous filopodia spread on D-2HVP-functionalized surfaces.Therefore,the D-2HVP sequence is proposed as new osteoblast adhesive peptide with increased bioactivity and high proteolytic resistance.

Preparation of a PTE simulacrum based on surface molecular imprinting

Firstly,we synthesized N-methacryloyl-histidine monomer and N-methacryloyl-histidine-Cu^2＋ complex（MAH-Cu^2＋）.Then the molecular imprinting polymers（MIP） has been prepared by surface grafting on uniform polystyrene（PS） core using reversible addition-fragmentation transfer polymerization（RAFT） with MAH-Cu^2＋ as the functional monomer,methyl paraoxon as the template to simulate phosphodiesterase（PTE）.Finally,we have investigated the catalytic hydrolytic activities of MIP and non-imprinting polymers（NIP） to the template methyl paraoxon and the template analogue ethyl paraoxon respectively by UV spectrophotometry.The results showed that the catalytic hydrolytic activity of MIP to the template methyl paraoxon was highest and the value of k is 8.67×10^-5 mmol L^-1 min^-1,3.89-fold higher than MIP to the template analogue ethyl paraoxon,2.79-fold higher than NIP to the template methyl paraoxon.The KM,rm of MSP are also determined,and KM = 3.95×10^-4）mol/L,rm = 2.12μmol/ min.The MIP can be reused with only lose 7%of catalytic activity for four cycles.

Liquid crystal of nanocellulose whiskers' grafted with acrylamide

12%acrylamide（AM） was grafted onto the surface of nanocellulose whiskers（NCW）,which was self-assembled to be the chiral nematic suspension at 3%content.The acrylamide grafted NCW（AM-g-NCW） was characterized with Fourier Transform Infrared Spectroscopy（FTIR）.The grafting ratio was measured by elemental analysis.The degrees of crystallinity of the AM-g-NCW were measured by X-ray diffraction（XRD）.The liquid crystalline properties of the AM-g-NCW were investigated by the polarizing optical microscopy（POM）.The AM-g-NCW was found to self-assembly to be a lyotropic state.