Graft copolymerization kinetics of acrylic acid onto the poly(ethylene terephthalate) surface by atmospheric pressure plasma inducement

After one atmospheric pressure plasma treatment of poly(ethylene terephthalate) (PET) film, acrylic acid (AAc) in aqueous solution was successfully graft‐copolymerized onto PET films. The effects of reaction time, AAc monomer concentration and reaction temperature on grafting behavior of AAc were systematically studied. Possible reaction kinetics of plasma‐induced graft copolymerization, starting from initial hydroperoxide decomposition, were proposed. Through the Arrhenius analysis about graft copolymerization kinetics of AAc monomers on PET surface, it was revealed that the activation energies of decomposition, propagation and termination were 98.4, 63.5, and 17.5 kJ/mol, respectively. The temperature around 80 °C was favorable not only for the formation of oxide radicals through the thermal decomposition of hydroperoxide on PET surface but also for the extension of graft copolymer chain through direct polymer grafting. Poly(acrylic acid) (PAAc) grains grafted onto PET surfaces possessed relatively uniform size and both PAAc grain size and surface roughness increased with increasing the grafting degree of AAc. The increase of grain size with increasing grafting degree results from the possibility of forming long chain graft copolymers and their shielding of reactive sites. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1594–1601, 2008     

XPS analysis of the poly(ethylene terephthalate) film grafted with acrylamide

Graft polymerization of acrylamide (AAm) was performed onto the surface of a poly(ethylene terephthalate) (PET) film with the simultaneous UV irradiation method but using no photosensitizer and without degassing. To examine whether polyacrylamide (PAAm) was introduced into the bulk place of PET film by the surface graft polymerization, an x-ray photoelectron spectroscopic (XPS) study was performed on the PAAm-grafted PET films. The distribution of grafted PAAm chains on and in the PET films was estimated from the PAAm/PET ratio calculated from the XPS spectra of PET films with different amounts of grafted PAAm. The results clearly demonstrate that graft polymerization has actually occurred not merely on the outermost surface but also within the thin surface region of the PET film. In addition, the XPS analysis revealed that the PET component was always present in the grafted surface region by a mole fraction of 0.1 to 0.05 even when the amount of PAAm grafted was larger than 10 μg/cm².     

Thermo- and pH-responsive polypropylene microporous membrane prepared by the photoinduced RAFT-mediated graft copolymerization

Thermo- and pH-responsive polypropylene microporous membrane prepared by photoinduced reversible addition–fragmentation chain transfer (RAFT) graft copolymerization of acrylic acid and N-isopropyl acrylamide by using dibenzyltrithiocarbonate as a RAFT agent. Attenuated total reflection-Fourier transform infrared spectroscopy (ATR/FT-IR), X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscopy (FE-SEM) were used to characterize the structural and morphological changes on the membrane surface. Results of ATR/FT-IR and XPS clearly indicated that poly(acrylic acid) (PAAc) and poly(N-isopropyl acrylamide) (PNIPAAm) were successfully grafted onto the membrane surface. The grafting chain length of PAAc on the membrane surface increased with the increase of UV irradiation time, and decreased with the increase of the concentration of chain transfer agent. The PAAc grafted membranes containing macro-chain transfer agents, or the living membrane surfaces were further functionalized via surface-initiated block copolymerization with N-isopropyl acrylamide in the presence of free radical initiator, 2,2′-azobisisobutyronitrile. It was found that PNIPAAm can be grafted onto the PAAc grafted membrane surface. The results demonstrated that polymerization of AAc and NIPAAm by the RAFT method could be accomplished under UV irradiation and the process possessing the living character. The PPMMs with PAAc and PNIPAAm grafting chains exhibited both pH- and temperature-dependent permeability to aqueous media.     

Biodegradability of poly(3-hydroxybutyrate) film grafted with vinyl acetate: Effect of grafting and saponification

Radiation-induced graft polymerization of vinyl acetate (VAc) onto poly(3-hydroxybutyrate) (PHB) film was carried out. At a degree of grafting higher than 5%, the grafted films (PHB-g-VAc) completely lost the enzymatic degradability that is characteristic of PHB due to the grafted VAc covering the surface of the PHB film. However, the biodegradability of the PHB-g-VAc films was recovered when the films were saponified in alkali solution under optimum conditions. Graft chains of the PHB-g-VAc film reacted selectively to become biodegradable polyvinyl alcohol (PVA). The biodegradability of the saponified PHB-g-VAc film increased rapidly with time.     

Surface graft polymerization of acrylamide onto poly(ethylene terephthalate) film by UV irradiation

To improve the low water wettability of poly(ethylene terephthalate) (PET), graft polymerization of acrylamide (AAm) by UV irradiation was performed onto the surface of a PET film with the simultaneous irradiation method without using a photo sensitizer. The PET film immersed in a 10 wt % deaerated aqueous solution of AAm was found to become highly hydrophilic upon UV irradiation. Optical microscopy on cross sections of grafted films showed that localization of the graft polymerization was restricted to a thin surface region of the film. Both the low concentration of polymer radicals formed by UV irradiation and the monomer penetration limited to the film surface would be responsible for localization of the grafted layer to the film surface region. Pretreatment of the PET film with benzyl alcohol was effective for enhancement of the graft polymerization. Retention of high hydrophilicity of the surface even after rigorous extraction of homopolymer and a comparative study of polymerization without UV irradiation strongly suggested that UV irradiation of the PET film under immersion in the deaerated AAm aqueous solution would lead to formation of the true graft copolymer.     

甲基丙烯酸聚乙二醇单甲醚酯在聚(醚-氨酯)表面的臭氧化接枝

甲基丙烯酸聚乙二醇单甲醚酯在聚（醚 氨酯）表面的臭氧化接枝王晨晖王安锋车波周彩华苏琳丽林思聪（南京大学高分子科学与工程系生物材料分子工程与控制释放分子工程室南京２１００９３）王炳坤（南京大学环境科学系南京２１００９３）关键词臭氧化，表面接枝，大...     

Surface grafting polyethylene glycol (PEG) onto poly(ethylene-co-acrylic acid) films

Two reaction schemes were developed to covalently graft poly(ethylene glycol) (PEG) chains on poly(ethylene-co-acrylic acid) (EAA) surfaces. The schemes involved surface grafting of linker molecules L-lysine or polypropyleneamine dendrimer (AM64), with subsequent covalent bonding of PEG chains to the linker molecules. NHS and EDC were used to activate the carboxylic acid groups of the EAA in the outermost region of the film, estimated to be 20 nm by ATR-FTIR spectroscopy. XPS demonstrated that the conversion of this activation step was almost 100% in the detected region. After activation, L-lysine or dendrimer was grafted onto the EAA surface, followed by PEG grafting. Combining the data from ATR-FTIR, XPS, and contact angle goniometry, it was found that the PEG chains were grafted on the surface of the EAA film and larger surface coverage was achieved when the dendrimer was used as the intermediate layer. This surface also had the lowest water contact angle.     

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.     

Surface modification of SPEU films by ozone induced graft copolymerization to improve hemocompatibility

Surface modification of segmented poly(ether urethane) (SPEU) by graft copolymerization with N,N′-dimethyl-N-methacryloyloxyethyl-N-(3-sulfopropyl) ammonium (DMMSA), a zwitterionic sulfobetaine structure, was conducted. A simple two-step procedure for grafting of DMMSA onto the surface of SPEU film was used. The surface was first treated with ozone to introduce active hydroperoxide groups. The active surface was then exposed to the DMMSA solution in the sealed tube. Grafted SPEU film was characterized by ATR–FTIR, XPS and contact angle measurement. ATR–FTIR and XPS investigations confirmed the graft copolymerization. The monomer concentration, copolymerization temperature and time were varied to maximize the efficiency of DMMSA grafting. The equilibrium water content (EWC) and contact angle measurements showed that the hydrophilicity of the film had been greatly improved. The blood compatibility of the grafted films was evaluated by platelet adhesion in platelet rich plasma (PRP), deposits in blood control and protein adsorption in bovine fibrinogen using SPEU film as the control. No platelet adhesion and no thrombus were observed for the grafted films incubated in PRP for 300 min and in blood for 120 min, respectively. The protein adsorption was reduced on the grafted films after incubation in bovine fibrinogen for 120 min. These results proved that improved blood compatibility was obtained by grafting this new zwitterionic sulfobetaine structure monomer onto SPEU film.     

Gas transport in surface grafted polypropylene films with poly(acrylic acid) chains

This work describes the grafting reaction of poly(acrylic acid) (PA) onto the surface of polypropylene (PP) films carried out with ultraviolet radiation, using benzophenone as photoinitiator and water as solvent. By increasing the reaction time, graft percentages of 3.5, 6.5, 12.9, 19.8, 29.4, and 36.0% were obtained. Micrographs of the modified films show that grafting exclusively occurs on the PP films surface. The values of the permeability coefficient of oxygen, nitrogen, carbon dioxide, carbon monoxide, argon, methane, ethane, ethylene, and propane across the grafted films undergo a sharp drop. The interpretation of the permeation results suggest that radicals created in the tertiary carbons of the grafted chains by effect of UV light or by chain transfer reactions may highly crosslink the PA grafted layer. A rigid layer involving both strong hydrogen bonding and chains crosslinking is formed at grafting percentages of 3.5% that strongly hinders gas permeation across that layer. Destruction of hydrogen bonding by partially replacing protons of acrylic acid residues by sodium/silver cations increases the permeability of the surface grafted films. Finally, the films permselectivity is hardly affected by the grafted layer. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2421–2431, 2007     

Voltammetric and waveguide spectroelectrochemical characterization of ultrathin poly(aniline)/poly(acrylic acid) films self-assembled on indium-tin oxide

We report on the spectroelectrochemical characterization of conducting polymer (CP) films, composed of alternating layers of poly(aniline) (PANI) and poly(acrylic acid) (PAA), deposited on ITO-coated, planar glass substrates using layer-by-layer self-assembly. Absorbance changes associated with voltammetrically induced redox changes in ultrathin films composed of only two bilayers (ITO/PANI/PAA/PANI/PAA) were monitored in real time using a unique multiple reflection, broadband attenuated total reflection (ATR) spectrometer. CP films in contact with pH 7 buffer undergo a single oxidation/reduction process, with ca. 12.5% of the aniline centers in the film being oxidized and reduced. The ATR spectra indicate that during an anodic sweep, the leucoemeraldine form of PANI in these films is oxidized to generate both the emeraldine and pernigraniline forms simultaneously. A comparison of the behavior observed during anodic and cathodic sweeps suggests that the rate of oxidation is limited by structural changes in the polymer film originating in electrostatic repulsion between positively charged PANI chains.     

The study on grafting comonomer of n-butyl acrylate and styrene onto poly(ethylene terephthalate) film by gamma-ray induced graft copolymerization

Poly(ethylene terephthalate) (PET) film was successfully grafted with n-butyl acrylate and styrene comonomer through gamma-ray induced graft copolymerization. The degree of grafting (DG) and the composition of grafted side chain were characterized by ¹H NMR. It was found that St can inhibit the homopolymerization of BA effectively and increase the DG when the concentration of comonomer mixture is kept constant. The proportion of St to BA in grafted side chain has a positive dependence on the feed ratio of St, which ultimately approaches the feed ratio. The thermal properties of poly(ethylene terephthalate)-graft-poly(n-butyl acrylate-co-styrene) (PET-g-P(BA-co-St)) films were investigated by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). The T_g of PET decreases with the DG, indicating that the grafted P(BA-co-St) copolymer has good compatibility with PET backbone.     

Fabrication of shape-controllable polyaniline micro/nanostructures on organic polymer surfaces: obtaining spherical particles, wires, and ribbons

A novel strategy was developed in order to prepare various micro/nanostructured polyanilines (PANI) on polymer substrates. The strategy involved two main steps, i.e., a grafting polymerization of acrylate acid (AA) onto the surface of a polypropylene (PP) film and subsequently an oxidative polymerization of aniline on the grafted surface. By tuning the conformation of the surface-grafted poly acrylate acid (PAA) brushes, as well as the ratio of AA to aniline, the shape of the PANIs fixated onto the surfaces of the polymer substrate could be controlled to go from spherical particles to nanowires and eventually to nanoribbons. In these structures, the PAA brushes not only acted as templates but also as dopants of PANI, and thereby, the nanostructured PANIs could be strongly bonded with the substrate. In addition, the surface of the PP films grafted with polyaniline nanowires and nanoribbons displayed superhydrophobicity with contact angles for water of approxiamtely 145 and 151 degrees , respectively.     

Radiation synthesis of acrylic acid onto poly(tetraflouroethylene-perflourovinyl ether) film: Chemical modifications and electrical conductivity

Graft-polymerization of acrylic acid (AAc) monomer onto poly(tetraflouroethylene-perflouro vinyl ether) (PFA) copolymer film was carried out using gamma irradiation technique to synthesize grafted copolymer film PFA-g-PAAc (PFA-COOH). The effect of the dose on the degree of grafting of AAc onto PFA film was investigated. The results showed that the degree of grafting increases with increasing the irradiation dose. The grafted [PFA-COOH] film was chemically modified by reaction with aniline to produce modified [PFA-CO-NH-ph] film, followed by sulphonation reaction to introduce sulfonic acid (SO₃H) groups to get other modified [PFA-CO-NH-ph-SO₃H] film. The chemical structures of the grafted and modified films were identified by FT-IR, XRD, and SEM. It is of particular interest to measure the electrical conductivity of grafted and modified membranes as a function of degree of grafting. It was found that the conductivity of the grafted films increases with increasing the degree of grafting, however a slightly increase in conductivity was observed in [PFA-CO-NH-ph-SO₃H] sample. The electrical conductivity property of the modified PFA membranes suggests their possible use for fuel cell applications.     

Functional and surface-active membranes from poly(vinylidene fluoride)-graft-poly(acrylic acid) prepared via RAFT-mediated graft copolymerization

Poly (vinylidene fluoride) (PVDF) with "living" poly (acrylic acid) (PAAc) side chains (PVDF-g-PAAc) was prepared by reversible addition-fragmentation chain transfer (RAFT)-mediated graft copolymerization of acrylic acid (AAc) with the ozone-pretreated PVDF. The chemical composition and structure of the copolymers were characterized by elemental analysis, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The copolymer could be readily cast into pH-sensitive microfiltration (MF) membranes with enriched living PAAc graft chains on the surface (including the pore surfaces) by phase inversion in an aqueous medium. The surface composition of the membranes was determined by X-ray photoelectron spectroscopy. The morphology of the membranes was characterized by scanning electron microscopy. The pore size distribution of the membranes was found to be much more uniform than that of the corresponding membranes cast from PVDF-g-PAAc prepared by the "conventional" free-radical graft copolymerization process. Most important of all, the MF membranes with surface-tethered PAAc macro chain transfer agents, or the living membrane surfaces, could be further functionalized via surface-initiated block copolymerization with N-isopropylacrylamide (NIPAAM) to obtain the PVDF-g-PAAc-b-PNIPAAM MF membranes, which exhibited both pH- and temperature-dependent permeability to aqueous media.     

Grafting of poly(ethylene oxide) to the surface of polyaniline films through a chlorosulfonation method and the biocompatibility of the modified films

Poly(ethylene oxide) (PEO) could be grafted on the surface of polyaniline (PANI) films by chlorosulfonating the films with chlorosulfonic acid followed by reacting the modified films with PEO in a pyridine solution. The modified PANI films were examined by X-ray photoelectron spectroscopy and water droplet contact angles. The surface of the PEO grafted to hydrophobic PANI films became hydrophilic and the amounts of bovine serum albumin and human blood plasma platelet adsorbed onto it were decreased by more than 80%. For comparison purposes, and because the water wetting angle can be used as a measure of biocompatibility, wetting angle experiments have been also carried out for Pluronic triblock copolymer grafted to PANI and PEO or Pluronic molecules entrapped on the surfaces of PANI films. PANI was selected as substrate because one can easily change its surface properties by PEO grafting and because being conductive can be used as a sensor.     

聚醚氨酯的氧化及其接枝共聚合的研究

本文研究了在聚醚氨酯表面上进行接枝共聚合的新方法。首先在聚醚氨酯薄膜上通过过氧化氢光氧化引入过氧化氢基,然后在还原剂亚铁盐或N,N-二甲基对甲苯胺的作用下引发丙烯酰胺接枝共聚合,反应具有低温快速的特点。产物经吸水性实验及扫描电子显微镜观察均证实了是一接枝共聚物。通过模型化合物的研究证明,接枝反应具有较高的选择性,接枝共聚占优势地发生在聚醚软段上,接枝地点很可能就在醚键旁的α-碳原子上。     

Synthesis and Biomedical Properties of Poly-[(Ethylene-Vinylalcohol)-g-Acrylamide]

This paper deals with the graft copolymerization of acrylamide (AM) onto ethylene-vinyl alcohol copolymer (EVAL) film initiated by cerium(IV) ion. It was found that both the chemical and diffusion factors had influences on the graft reaction. The reaction was initiated on the surface and then penetrated inward as the grafting percentage was increased. The permeability of urea through the grafted EVAL film was improved compared to that of the original film as was the blood compatibility.     

Degradation behaviour of poly (methyl methacrylate-g-3-hydroxybutyrate) polymer films

Poly(methyl methacrylate-g-3-hydroxybutyrate) films were prepared from new graft polymers synthesised by an anionic grafting reaction of 3-butyrolactone (3-BL) on poly(methyl methacrylate) (PMMA). The resulting graft polymers form a transparent film of a one phase system, as revealed by DSC measurements. A plasticisation effect was observed for film samples containing the PBL grafted chains. This effect increased with increasing amount of PBL in the graft copolymer. The mechanical properties of the films were investigated, and thermal, hydrolytic and enzymatic degradation behaviours were evaluated. Disintegration of the films was observed during their hydrolytic degradation in phosphate buffer.     

Functionalization of polyethylene surface using plasma-induced graft copolymerization of acrylic acid

Plasma-induced graft copolymerization of acrylic acid onto PE films was investigated. The influence of plasma treatment power, pressure, time, graft copolymerization time, and monomer concentration on polymerization yield was determined. A chemical shift of the Cls signal of Ar plasma treated and untreated PE films was revealed by ESCA, which also verified the presence of grafted PAAc. An increase in graft polymerization yield with plasma treatment time and power was found. Both the plasma treated film and the subsequently grafted film were shown to be hydrophilic. Only the grafted film, however, shows an invariably low contact angle. The decomposition of peroxides upon heating was followed by a simple first-order reaction. © 1993 John Wiley & Sons, Inc.