紫外光接枝季铵盐抗菌聚乙烯膜的制备和表征

近年来出现的高分子杀菌剂,又称表面接触消毒剂,是将杀菌基团结合在不溶性载体上．此类杀菌剂不仅可以有效的避免二次污染,而且可以重复利用．由于杀菌基团集中在载体表面且浓度高,也使得消毒时间缩短．这些优点使高分子杀菌剂成为目前研究的热点。     

Are redox probes a useful indicator of film stability? An electrochemical,AFM and XPS study of electrografted amine films on carbon

The electrochemical response of solution-based redox probes is commonly used to detect and monitor the formation and stability of films grafted to conducting substrates. In this work we examine redox probe responses at films grafted to glassy carbon (GC) and pyrolysed photoresist film (PPF) by electrooxidation of aliphatic primary amines. Cyclic voltammograms are obtained before and after soaking the modified surfaces in phosphate buffer and acetonitrile. For conditions where films exhibit large changes in electrochemical blocking properties, AFM measurements of film thickness and surface roughness, and XPS measurements of surface composition, are used to monitor the stability of the films. No changes in film structure or composition can be detected, demonstrating that electrochemical loss of blocking properties cannot be equated with large-scale loss of surface film. The origin of changes in probe response is discussed.     

Nickel (II) tetraphenylporphyrin modified surfaces via electrografting of an aryldiazonium salt

We have prepared and isolated the monodiazonium salt of nickel (II) tetraphenylporphyrin and grafted the corresponding complex to glassy carbon, pyrolysed photoresist film, gold and indium tin oxide surfaces via reduction of the diazonium moiety. Characterisations of the films by voltammetry, UV–vis spectroscopy and atomic force microscopy depth profiling confirm that the metallated porphyrin is intact in the film and is stably attached to the surface with well-behaved, but highly solvent-dependent electrochemistry. Under the grafting conditions used, the films appear to have close to monolayer thickness with the porphyrin macrocycles oriented predominantly upright on the surface.     

An electrochemical and XPS study of reduction of nitrophenyl films covalently grafted to planar carbon surfaces

Nitrophenyl (NP) films were grafted to glassy carbon and pyrolyzed photoresist films by electroreduction of the corresponding diazonium salt. The as-prepared, multilayered films were examined using electrochemistry and X-ray photoelectron spectroscopy (XPS). Electrochemical analysis confirmed the absence of electrooxidizable groups whereas XPS showed approximately 35% of N was present in a reduced form. The reduced N is assigned to azo groups, which are known to be electroinactive in the film environment. NP films were reduced electrochemically in three media and also by chemical reduction in ethanolic disodium sulfide. The concentrations of aminophenyl and hydroxylaminophenyl groups produced by each method were estimated electrochemically, and the relative amounts of unreacted NP groups were established from XPS measurements. Aminophenyl is the major product for all reduction methods, and Na2S gives the cleanest and most complete conversion to aminophenyl groups, with less than 5% residual NP. Reduced NP films were reacted with carboxylic acid and acid chloride derivatives; the highest yield of electroactive-coupled product was obtained for a film electroreduced in H2SO4 and reacted with acid chloride. The detailed electrochemical and XPS analysis reveals the limitations of electrochemistry for determining the composition of these films.     

Effect of applied potential on arylmethyl films oxidatively grafted to carbon surfaces

Arylmethyl films have been grafted to glassy carbon surfaces and to pyrolyzed photoresist films (PPFs) by electrochemical oxidation of 1-naphthylmethylcarboxylate and 4-methoxybenzylcarboxylate. Atomic force microscopy (AFM) and electrochemistry were used to characterize the as-prepared films and to monitor changes induced by post-preparation treatments. Film thickness was measured by depth profiling using an AFM tip to remove film from the PPF surface. Surface coverage of electroactive modifiers was estimated from cyclic voltammetry, and monitoring the response of a solution-based redox probe at grafted surfaces gave a qualitative indication of changes in film properties. For preparation of the films, the maximum film thickness increased with the potential applied during grafting, and all films were of multilayer thickness. The apparent rate of electron transfer for the Fe(CN)(6)3-/Fe(CN)(6)4- couple was very low at as-prepared films. After film-grafted electrodes were transferred to pure acetonitrile-electrolyte solution and subjected to negative potential excursions, the response of the Fe(CN)(6)3-/Fe(CN)(6)4- couple changed and was consistent with faster electron-transfer kinetics, the film thickness decreased and the surface roughness increased substantially. Applying a positive potential to the treated film reversed changes in film thickness, but the voltammetric response of the Fe(CN)(6)3-/Fe(CN)(6)4- couple remained kinetically fast. After as-prepared films were subjected to positive applied potentials in acetonitrile-electrolyte solution, the apparent rate of electron transfer for the Fe(CN)(6)3-/Fe(CN)(6)4- couple remained very slow and the measured film thickness was the same or greater than that before treatment at positive potentials. Mechanisms are considered to explain the observed effects of applied potential on film characteristics.     

Microscale patterning of organic films on carbon surfaces using electrochemistry and soft lithography

We have demonstrated three simple strategies employing poly(dimethylsiloxane) (PDMS) molds for patterning carbon surfaces with two different modifiers in an 18 microm line pattern. The PDMS molds are patterned with microfluidic channels (approximately 22 microm wide and 49 microm deep) and form a reversible, conformal seal to the pyrolyzed photoresist film (PPF) and modified PPF surfaces. Modifiers are electrochemically grafted to the PPF surface by the reduction of aryl diazonium salts and the oxidation of primary amines. For the fill-in patterning approach, the first modifier is electrografted to the PPF surface exposed within the microchannels, and in a second grafting step after removal of the PDMS mold, the second modifier fills in the remaining surface. The selective conversion strategy involves electrografting a continuous film of the modifier to the PPF surface, sealing the PDMS mold to the modified surface and carrying out an irreversible electrochemical reaction of the modifier exposed within the microchannels. In the build-up patterning approach, the PDMS mold is sealed to the modified PPF surface, and a chemical coupling reaction is effected in the microchannels to build up the pattern. The patterns are characterized using SEM, optical microscopy, the formation of condensation figures, and SEM imaging after the assembly of Au nanoparticles.     

Multilayer nitroazobenzene films covalently attached to carbon. An AFM and electrochemical study

Nitroazobenzene films have been grafted to pyrolyzed photoresist films by electrochemical reduction of the corresponding diazonium salt in acetonitrile solution. Two component films were also prepared by electrochemically grafting methylbenzene layers to preformed NAB films. Voltammetric investigation of the films in aqueous acid medium and the measurement of film thickness using atomic force microscopy (AFM) lead to new insights into film structure. In aqueous acid solution, the azobenzene groups have no detectable electroactivity and not all nitro groups in the films can be reduced. These findings point to a compact film structure in which proton diffusion is limited. There may also be spatial inhibition of the conformational changes that accompany azobenzene reduction. For increasingly thick NAB films, the peak for reduction of the nitro groups moves to more negative potentials and the peaks become more asymmetric in shape. These changes are interpreted in terms of the dielectric properties and the rate of proton diffusion in the films. Film thickness was measured by ploughing through the film with an AFM tip. When an NAB film prepared in acetonitrile solution is reduced in aqueous acid, the film thickness decreases by more than 50%. The changes can be partially reversed by treatment in acetonitrile-electrolyte solution and hence are attributed to ion-solvent induced swelling and shrinking. Thus, the large decrease in thickness detected by AFM after treatment of the film in aqueous acid is consistent with the compact film structure revealed by electrochemistry.     

Versatility of alkyne-modified poly(glycidyl methacrylate) layers for click reactions

Functional soft interfaces are of interest for a variety of technologies. We describe three methods for preparing substrates with alkyne groups, which show versatility for "click" chemistry reactions. Two of the methods have the same root: formation of thin, covalently attached, reactive interfacial layers of poly(glycidyl methacrylate) (PGMA) via spin coating onto silicon wafers followed by reactive modification with either propargylamine or 5-hexynoic acid. The amine or the carboxylic acid moieties react with the epoxy groups of PGMA, creating interfacial polymer layers decorated with alkyne groups. The third method consists of using copolymers comprising glycidyl methacrylate and propargyl methacrylate (pGP). The pGP copolymers are spin coated and covalently attached on silicon wafers. For each method, we investigate the factors that control film thickness and content of alkyne groups using ellipsometry, and study the nanophase structure of the films using neutron reflectometry. Azide-terminated polymers of methacrylic acid and 2-vinyl-4,4-dimethylazlactone synthesized via reversible addition-fragmentation chain transfer polymerization were attached to the alkyne-modified substrates using "click" chemistry, and grafting densities in the range of 0.007-0.95 chains nm(-2) were attained. The maximum density of alkyne groups attained by functionalization of PGMA with propargylamine or 5-hexynoic acid was approximately 2 alkynes nm(-3). The alkyne content obtained by the three decorating approaches was sufficiently high that it was not the limiting factor for the click reaction of azide-capped polymers.     

Effect of molecular weight on synthesis and surface morphology of high-density poly(ethylene glycol) grafted layers

This work describes studying the permanent grafting of carboxylic acid end-functionalized poly(ethylene glycol) methyl ether (PEG) chains of different molecular weights from the melt onto a surface employing poly(glycidyl methacrylate) ultrathin film as an anchoring layer. The grafting led to the synthesis of the complete PEG brushes possessing exceptionally high grafting density. The maximum thickness of the attached PEG films was strongly dependent on the length of the polymer chains being grafted. The maximum grafting efficiency was close to the critical entanglement molecular weight region for PEG. All grafted PEG layers were in the "brush regime", since the distance between grafting sites for the layers was lower than the end-to-end distance for the anchored macromolecules. Scanning probe microscopy revealed that the grafting process led to complete PEG layers with surface smoothness on a nanometric scale. Practically all samples were partly or fully covered with crystalline domains that disappeared when samples were scanned under water. Due to the PEG hydrophilic nature, the surface with the grafted layer exhibited a low (up to 21 degrees ) water contact angle.     

Preparation and tribological behaviors of an amide-containing stratified self-assembled monolayers on silicon surface

An amide-containing stratified self-assembled film is grafted on a silicon surface by a simple two-step method. First, N-[3-(trimethoxylsilyl)propyl]ethylenediamine (DA) molecules are self-assembled on silicon surfaces followed by deriving with stearoyl chloride (STC) through a surface coupling reaction. The films are characterized by means of contact angle measurement, ellipsometry, and attenuated total reflectance Fourier transformed infrared (ATR-FTIR) spectra. STC forms an ordered and hydrophobic film over the DA layer with a water contact angle of nearly 110 degrees. A microtribological study of the films is carried out on an atomic force microscope (AFM), and the wear-resistant property is tested on a ball-on-plate tribometer. Compared to the films in our previous study, the friction-reducing and load-affording abilities of the film are greatly improved. We contribute the improvements to the existence of two layers of hydrogen bonds, which can enhance the stability of the film by double in-plane cross-linking.     

Protein immobilization on the surface of poly-L-lactic acid films for improvement of cellular interactions

To covalently immobilize gelatin or collagen type I on poly-L-lactic acid (PLLA) film surfaces poly(hydroxyethyl methacrylate) (PHEMA) or poly(methacrylic acid) (PMAA) was grafted via photooxidization and subsequent UV-induced polymerization [Makromol. Chem. 186 (1985) 1533.1]. For films grafted with PHEMA, methyl sulfonyl chloride was used to activate the hydroxyl groups and for films grafted with PMAA 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide was used to activate the carboxyl groups. Gelatin and collagen were finally reacted with the activated hydroxyl or carboxyl groups to obtain covalently immobilized protein layers. Grafting of PHEMA, PMAA and protein on the surfaces was confirmed using ATR-IR and XPS. Surface wettability of the modified films was improved. The protein immobilized PLLA may be widely used as a biocompatible material.     

Melt-photografting polymerization of maleic anhydride onto LDPE film

Maleic anhydride (MAH) was photografted onto low density polyethylene substrates at temperatures above the melting point of MAH. The effects of some principal factors including irradiation temperature, photoinitiators, the intensity of UV radiation, and the far UV radiation on the grafting polymerization were investigated in detail. Percent conversion and grafting efficiency of the polymerizations were determined by the gravimetric method. The contact angles of the grafted film PE-g-PMAH against water and the FTIR spectrum of the grafted film were measured as characterization. The results show that the photografting polymerization of MAH can proceed smoothly at temperatures higher than the melting point of MAH; the far UV radiation and the intensity of the UV radiation affect the grafting polymerization greatly; the photoinitiators also have influence on the polymerization. According to the FTIR spectra, it is clearly confirmed that the grafted film samples contain anhydride groups. The contact angles demonstrate that the wettability of the grafted films is enhanced obviously, especially to those grafted film samples through hydrolysis.     

Solid-phase synthesis of trisubsituted guanidines

The solid-phase library synthesis of trisubstituted guanidines was accomplished. Amines were loaded onto the 4-formyl-3,5-dimethoxyphenoxymethyl linker via reductive amination. Subsequent acylation with Fmoc-4-aminomethylbenzoic acid followed by Fmoc deprotection gave solid-supported primary amines. Alternatively, sulfonylation of resin-bound secondary amines with 4-cyanobenzenesulfonyl chloride followed by borane reduction also gave solid-supported primary amines. Both resins were acylated with isocyanates to furnish solid-supported ureas. Dehydration of ureas with p-toluenesulfonyl chloride in pyridine gave solid-supported carbodiimides. Nucleophilic addition of amines to the carbodiimide bond followed by cleavage off the solid support gave trisubstituted guanidines.     

Preparation of a nanocomposite film from poly(diallydimethyl ammonium chloride) and gold nanoparticles by in-situ electrochemical reduction, and its application to SERS spectroscopy and sensing of ascorbic acid

A nanocomposite film is described that is composed of alternating layers of poly(diallydimethyl ammonium chloride) and gold nanoparticles that interact through electrostatic forces. The films of varying thickness were prepared by the layer-by-layer technique, and Au-NPs were generated by electrochemical reduction of hexachloroauric acid. The composite films were characterized by UV?Cvis spectroscopy, X-ray photoelectron spectroscopy, and cyclic voltammetry. Most nanocomposite films exhibit linear, uniform, and regular layer-by-layer growth during the process of formation. The films exhibit unique performance in terms of surface enhanced Raman scattering and electrocatalytic activitiy towards the oxidation of ascorbic acid.

Radiation-induced grafting of diallyldimethylammonium chloride onto acrylic acid grafted polyethylene

Diallyldimethylammonium chloride (DADMAC) was grafted onto polyethylene (PE) films by a double grafting procedure. The PE film was initially modified by grafting acrylic acid (AA), through a mutual irradiation method. AA-g-PE film, thus obtained was subjected to subsequent radiation grafting reaction of DADMAC, to give a DADMAC-g-AA-g-PE film having a comb-type structure. The influence of different conditions, such as the extent of AA grafting, DADMAC concentration, absorbed dose and dose rate, on the grafting yield of DADMAC was investigated. A maximum DADMAC grafting of 30% was achieved. The equilibrium degree of swelling (EDS) of the grafted films were gravimetrically determined. TGA and FT-IR techniques were employed to characterize the grafted PE films.     

Enhanced interlayer interaction in cellulose single nanofibre and poly(l-lactic acid) layered films by plasma-initiated surface grafting of poly(acrylic acid) onto poly(l-lactic acid) films

The surface of a poly(l-lactic acid) (PLLA) film was modified with poly(acrylic acid) (PAA) by plasma-initiated polymerization to increase the interaction between PLLA and cellulose single nanofibres (CSNF). The surface wettability of the PAA grafted PLLA film (PLLA-PAA film) was investigated by contact angle measurements. Modification of the PLLA film with PAA decreased the contact angle from 61° to 50°. The surface morphologies of the PLLA film, PLLA-PAA film and CSNF-coated PLLA-PAA film were studied by atomic force microscopy. The interaction between the CSNF and PLLA layers was strengthened by incorporation of a PAA layer onto the PLLA films and it is higher than 2N as proved by a peeling test. This is probably because the carboxyl groups of PAA form hydrogen bonds with the hydroxyl groups of CSNF.     

Surface modification of polymers. V. Biomaterial applications

Polyethylene films were surface grafted with glycidyl methacrylate (GMA) by UV irradiating the film for 5 min together with benzophenone. Poly(ethylene glycol) (PEG) was attached to the grafted surface through reaction with the epoxy groups. This yielded a surface which consisted of 95% PEG as measured with ESCA. The adsorption of human transferrin onto this film was significantly reduced as compared with a pure polyethylene film. Heparin was also reacted with a GMA grafted PE surface. ESCA showed that heparin was grafted to the surface, and in vitro blood clotting tests on the heparinized PE surface showed a reduced thrombus formation. GMA grafted polystyrene wells were reacted with carbohydrazide, to the formed carbohydrazide surface a rabbit antibody raised against mouse urinary protein (RaMUP) was covalently coupled. The RaMUP coupled surfaces was used in the detection of mouse urinary protein (MUP) at low concentrations (ca. 1 ng/mL) with an ELISA technique.     

Graft polymerization of styrene initiated by covalently bonded peroxide groups on silica

The graft polymerization of styrene initiated by immobilized peroxide groups was investigated. Three different types of modification reactions were used to introduce peroxide groups which are directly attached onto the surface of two different silica supports. Silanol groups were chlorinated using thionyl chloride or tetrachlorosilane. In another reaction pathway 1,3,5-benzenetricarbonyl chloride enabled the introduction of free acid chloride residues bonded onto the surface of silica. tert-Butyl hydroperoxide (TBHP) was used to transform the chlorosilyl and the acid chloride groups into peroxide residues. In a further reaction step the covalently bonded peroxides initiated the polymerization of styrene to form grafted polystyrene directly attached onto the silica support. Solid-state 13C CP/MAS NMR spectroscopy, and thermogravimetric and scanning electron microscope measurements enabled a clear structure and property elucidation of the different bonded phases. The highest amount of grafted polystyrene was achieved employing the acid chloride synthesis pathway with silica-gel, whereas modification of spherical silica only led to minor amounts of grafted polymer. The results contribute to the evolving need to understand particle surface modifications and may have positive impact on development of new HPLC stationary phases for improved elutant resolution.     

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 chemicalcomponent of the invention is that the curing of reactive solution between two substrates is initiated by the surface freeradicals produced by aromatic ketones and surface-hydrogen of substrates. Using the new approach, two or more polymerfilms are bonded together by a grafted polymer network which is grafted to adjacent substrate surfaces. The technique hasbeen applied to film substrates of different polymers such as polyolefins, polyesters. and polyamides which have abstractablehydrogens 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.     

Controlled grafting of comb copolymer brushes on poly(tetrafluoroethylene) films by surface-initiated living radical polymerizations

Surface modification of poly(tetrafluoroethylene) (PTFE) films by well-defined comb copolymer brushes was carried out. Peroxide initiators were generated directly on the PTFE film surface via radio frequency Ar plasma pretreatment, followed by air exposure. Poly(glycidyl methacrylate) (PGMA) brushes were first prepared by surface-initiated reversible addition-fragmentation chain transfer polymerization from the peroxide initiators on the PTFE surface in the presence of a chain transfer agent. Kinetics study revealed a linear increase in the graft concentration of PGMA with the reaction time, indicating that the chain growth from the surface was consistent with a "controlled" or "living" process. alpha-Bromoester moieties were attached to the grafted PGMA by reaction of the epoxide groups with 2-bromo-2-methylpropionic acid. The comb copolymer brushes were subsequently prepared via surface-initiated atom transfer radical polymerization of two hydrophilic vinyl monomers, including poly(ethylene glycol) methyl ether methacrylate and sodium salt of 4-styrenesulfonic acid. The chemical composition of the modified PTFE surfaces was characterized by X-ray photoelectron spectroscopy.