Conducting polymer films fabricated by oxidative graft copolymerization of aniline on poly(acrylic acid) grafted poly(ethylene terephthalate) surfaces

A conductive polyaniline/poly(ethylene terephthalate) (PANI/PET) composite film was fabricated via the oxidative graft copolymerization of aniline (ANI) onto the plasma-induced poly(acrylic acid) (PAAc) grafted PET surface. The attenuated total reflectance Fourier transform infrared spectroscopy spectra (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) results confirmed that PANI was successfully grafted onto the surface of the PAAc-g-PET films. The effects of the experimental conditions on the percentage of PANI grafted onto the PAAc-g-PET films were extensively investigated. A very high grafting percentage of ANI can be obtained through the acid-base reaction between the aniline monomer and PAAc on the PAAc-g-PET surface at high temperature. As a result, the grafting percentage of PANI can be increased to as high as 12.18 wt %, which causes the surface resistance of the PANI-g-PAAc-g-PET film to be reduced to about 1000 Omega/sq. We predicted that this is because of the high flexibility of the PAAc molecular chains and high solubility of aniline, both of which facilitate the binding of aniline to PAAc during this high temperature acid-base reaction. It was observed by atomic force microscopy (AFM) that the PANI-modified PET surface exhibits higher size irregularity and surface roughness, which further indicated that a much greater number of aniline molecules can be reactively bonded to and distributed along the grafted AAc chains and that the PANI-g-PAAc-g-PET surface resulting from the sequential oxidative graft copolymerization can possess higher electrical conductivity.     

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.     

Gamma radiation synthesis of comb-type graft hydrogels based on poly(acrylic acid) and 4-vinylpyridine

A pH-sensitive comb-type hydrogel was obtained by gamma radiation polymerization and crosslinking of acrylic acid (AAc) in solution. The pH-sensitive 4-vinylpyridine (4VP) was then grafted to the poly acrylic acid (PAAc) hydrogel using gamma radiation from a ⁶⁰Co source. The comb type graft polymers obtained (net-PAAc)-g-4VP has been studied through determination of graft yield and swelling behavior. The critical pH value was found to be 5.6. The apparent mechanical properties appear to be qualitatively better than hydrogels of PAAc upon swelling. The new comb-type system presents faster swelling response (30 h) than the polyacrylic acid hydrogel (50 h). The increase in dose rate from 7.3 to 11.3 kGy h⁻¹, increase the radiation grafting percentage of 4VP in the system. Comb-type polymers were also characterized by DSC, TGA and FTIR-ATR.     

Cu(II) immobilization in AAc/NIPAAm-based polymer systems synthesized using ionizing radiation

Polymer systems based on the pH-responsive monomer acrylic acid (AAc) and the thermosensitive monomer N-isopropylacrylamide (NIPAAm) were synthesized using gamma radiation. Three systems were synthesized: a comb-type hydrogel structure (grafting of NIPAAm onto crosslinked PAAc), a binary graft of both monomers onto a polypropylene (PP) film synthesized by a one-step method and a binary graft prepared by a two-step method. The binary graft systems were characterized by swelling behavior and the reversibility of water uptake. The three systems were compared with respect to their Cu(II) adsorption quantity, reversibility and time response. The binary graft system synthesized in one step exhibited the best adsorption response. The comb-type hydrogel required 150 h to reach its maximum swelling percentage, and the binary graft systems on polypropylene (PP) prepared by the one- and two-step irradiation-based methods required 10 and 30 min, respectively. The optimum pH range for Cu(II) immobilization was 5-6 in the binary graft system synthesized in one step. The maximum adsorption capacity for Cu(II) in the (PP-g-(AAc/NIPAAm)) (45% graft) was found to be 337 mg g⁻¹, and the adsorption followed the Freundlich model.     

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 onto Wool. IX. Graft Copolymerization of Vinyl Monomers by Use of Vanadium Oxyacetylacetonate as Initiator

Methyl methacrylate (MMA), acrylic acid (AAc), and vinyl acetate (VAc) were graft copolymerized onto Himachali wool in an aqueous medium by using vanadium oxyacetyl acetonate as initiator. Graft copolymerization was studied at 45, 55, 65, and 75°C for various reaction periods. The percentage of grafting was determined as functions of concentration of monomers, concentration of initiator, time, and temperature. The maximum percentage of grafting with each monomer occurred at 55°. Several grafting experiments were carried out in the presence of various additives which include HNO3, DMSO, and pyridine. Nitric acid was found to promote grafting of MMA. All these additives had adverse effects on grafting of VAc and AAc. MMA, VAc, and AAc were found to differ in reactivity toward grafting and followed the order MMA > AAc > VAc.     

Surface structures of fluoropolymer,polyolefin and polyester films after modification by graft polymerization

Pristine and argon plasma pretreated polytetrafluoroethylene (PTFE), polystyrene (PS), high-density polyethylene (HDPE) and poly(ethylene terrephthalate) (PET) films have been subjected to near-UV light-induced graft polymerization with water-soluble acrylamide (AAm), the sodium salt of styrene sulfonic acid (NaSS), acrylic acid (AAc) and N,N-dimethylaminoethylmethylacrylate (DMAEMA) monomers. The structure and composition at the substrate surface with grafted polymer were studied by angle-resolved X-ray photoelectron spectroscopy (XPS). In most cases, the density of surface grafting is enhanced by plasma pretreatment. For each polymer substrate with a substantial amount of grafting, the hydrophilic graft penetrates or becomes partially submerged beneath a thin surface layer of dense substrate chains. This stratified microstructure is consistent with the static secondary ion mass spectroscopy (SIMS) and Ar⁺ beam depth profiling results. The two latter techniques also suggest that when the grafted polymer has a bulky substituent, there is less efficient penetration of the grafted polymer below the surface.     

Novel comb-type hydrogels of net-[PP-g-AAc]-g-4VP synthesized by gamma radiation,with possible application on Cu2+ immobilization

A novel comb-type grafted hydrogel system of net-[PP-g-AAc]-g-4VP was synthesized by gamma radiation in three steps. In the first step a pH sensitive graft copolymer of AAc onto PP film was obtained by radiation grafting of acrylic acid (AAc) onto polypropylene (PP) films in aqueous solution at radiation doses of 10 kGy with a ⁶⁰Co source. The grafted side chains of poly (acrylic acid) (PAAc) were then cross-linked with gamma radiation at different radiation doses to give net-[PP-g-AAc]. Finally, 4-vinylpyridine (4VP) was grafted into the net-[PP-g-AAc]. The comb-type grafted hydrogel obtained, net-[PP-g-AAc]-g-4VP, has been studied through determination of graft yield and swelling behavior at room temperature. Two critical pH values were found for net-[PP-g-AAc]-g-4VP at 4.5 and 7.2. Initial studies on the immobilization of Cu²⁺ ions from solution into net-[PP-g-AAc]-g-4VP films were performed.The comb-type grafted hydrogel, grafted onto PP was also characterized by differential scanning calorimetry (DSC), scanning electronic microscopy (SEM) and FTIR-ATR.     

γ-Ray-induced grafting of DMAEMA and AAc onto PP by two step method

Binary graft copolymerization of thermosensitive 2-(dimethylamino) ethyl methacrylate (DMAEMA) and pH sensitive acrylic acid (AAc) monomers onto polypropylene (PP) films was carried out by a two step method using a ⁶⁰Co gamma radiation source. The PP film was initially modified by grafting of DMAEMA through a direct method. The DMAEMA-g-PP film obtained was then subjected to radiation grafting of AAc by the pre-irradiation method to give (DMAEMA-g-PP)-g-AAc. The optimal conditions, such as reaction time, reaction temperature, monomer concentration, and dose were studied. The grafted samples were verified by the FTIR-ATR spectroscopy and swelling; thermal properties were analyzed by DSC and TGA.     

The effect of concentration of acrylic acid,dose rates and temperature on preirradiated graft of natural rubber-based thermoplastic elastomer

Grafting acrylic acid (AAc) onto thermoplastic elastomer (TE) films, a kind of product from natural rubber latex block-grafted by methyl methacrylate monomer was investigated. The preirradiated dose from a gamma Co-60 source for TE at 75 kGy was considered to be useful. Significant concentration of AAc aqueous solution for the grafting process is 20% (vol%). Dose rate of about 3.4 kGy/h is more effective for the graft. The temperature of around 90°C is suitable for obtaining a higher degree of graft. It is observed that the rate of grafting of AAc onto TE is proportional to 0.48 power of dose rate and 1.9 power of AAc concentration. The rate of grafting can be expressed as R_g=k·I^0.48·M^1.9. On the other hand, overall activation energy of the graft is estimated about 7.2 Kcal/mol. The FTIR spectrum analysis of TE and TE-g-AAc films was proceeded.     

Grafting of poly(acrylic acid) onto nonporous glass bead surfaces

The surface of glass beads were modified with covalently bonded poly(acrylic acid). The optimum reaction conditions were determined to graft poly(acrylic acid) effectively onto the glass surface. The dependence of the graft polymer molecular weight, grafting percentage and monomer weight conversion based on these reaction conditions were consistent with free radical kinetics. Grafting efficiency for azobisisobutyronitrile was more complex compared with the benzyl peroxide initiator system © 1997 John Wiley & Sons, Ltd.     

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.     

Radical grafting from glass fiber surface: Graft polymerization of vinyl monomers initiated by azo groups introduced onto the surface

This paper describes the radical graft polymerization of vinyl monomers from glass fiber surface initiated by alkylazo groups introduced onto the fiber surface. The introduction of azo groups onto the glass fiber surface was achieved by reaction of isocyanate groups which were previously attached onto the surface with two kinds of azo initiators, 4,4′-azobis(4-cyanopentanoic acid) (ACPA) and 2,2′-azobis(2-cyanopropanol) (ACP). The amounts of surface azo groups introduced by ACPA and ACP were both determined to be 1.3 × 10⁻⁵ mol g⁻¹ by nitrogen analysis. The radical graft polymerization of methyl methacrylate (MMA) was found to be initiated in the presence of the glass fiber having surface azo groups. During the polymerization, part of resultant poly(MMA) grafted onto the fiber surface through propagation of the polymer from the surface radicals produced by the decomposition of the azo groups. The percentage of grafting of poly(MMA) reached 48.1% after 24 h. The graft polymerizations of other monomers, such as styrene, N-vinylcarbazole, and acrylic acid, were also initiated by the surface azo groups, and the corresponding polymer effectively grafted onto the surface. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2121–2128, 1999     

Study of the effect of poly(vinyl alcohol) concentration on the gelation point of poly(vinyl alcohol) poly(acrylic acid) semi‐IPN systems as determined by viscoelastic measurements

We report on the determination of the gelation point of semi‐interpenetrating polymer networks (semi‐IPNs) composed of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAAc) formed by a sequential method. The evolution of the viscoelasticity during the gelation reaction of acrylic acid (AAc) in solutions of PVA has been monitored through the sol‐gel transition with dynamic mechanical experiments. The gelation time of the system increased with PVA concentration; however, the molecular structure of the gel, composed of swollen clusters, is rather independent of the presence of PVA. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1944–1949, 2005     

pH‐induced on–off switching of polycarbonate track‐etched membranes by plasma‐induced surface grafting

Surface functionalization of the plasma‐pretreated polycarbonate (PC) track‐etched membranes via plasma‐induced thermally graft copolymerization of acrylic acid (AAc) was carried out. The resulting PC membranes with grafted AAc side chains were characterized by X‐ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric (TG) analysis. The morphology of the PC membranes was studied by scanning electron microscopy (SEM). The results showed that the grafted PAAc polymers were formed uniformly inside the pores throughout the entire membrane thickness. With increase in the pore‐filling ratio, the pore diameters of PAAc‐grafted membranes became smaller. The PC‐g‐PAAc membranes exhibit rapid and reversible response of the flux to the environmental pH as pH is switched between 3 and 9. Between pH 3.5 and 5.5, the membranes demonstrate a pH‐valve function as the carboxyl group changes from neutral to charged with a corresponding variation in chain configuration. Copyright © 2009 John Wiley & Sons, Ltd.     

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.     

Preparation of pH- and thermo-sensitive hydrogel by two-step grafting of acrylamide and acrylic acid onto preirradiated polyethylene film

Two-step grafting reaction of acrylamide (AAm) and acrylic acid (AAc) onto preirradiated polyethylene (PE) film were performed. The effects of irradiation dose, reaction temperature and reaction time on the grafting yield were studied. The effect of reaction time of the first step grafting on the yield of the second step grafting was also evaluated. The original and the irradiated PE films were tested by Fourier transform infrared (FTIR) spectroscopy in the attenuated total reflectance mode (ATR). The AAm and AAc grafted PE film appeared thermo- and pH-sensitive which are similar to the interpenetrating polymer network hydrogel. This revised version was published online in July 2006 with corrections to the Cover Date.     

Swelling kinetics of poly(aspartic acid)/poly(acrylic acid) semi‐interpenetrating polymer network hydrogels in urea solutions

Semi‐interpenetrating network (semi‐IPN) hydrogels, composed of poly(aspartic acid) (PAsp) and poly(acrylic acid) (PAAc) with various ratios of PAsp to AAc, were prepared. In this work, swelling kinetics was investigated through calculating some parameters. The swelling ratios were measured at room temperature, using urea solutions as liquids to be absorbed. Compared to in deionized water, the hydrogels showed larger swelling ratios in urea solutions, which might be attributed to the chemical composition of urea. The equilibrium swelling ratio could achieve 600 g/g, and the equilibrium urea/water contents were more than 0.99. The diffusion exponents were between 0.5 and 0.7, suggesting that the solvent transport into the hydrogel was dominated by both diffusion and relaxation controlled systems. Therefore, the PAsp/PAAc semi‐IPN hydrogels were appropriate to carry substances in a urea/water environment for pharmaceutical, agricultural, environmental, and biomedical applications. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 666–671, 2010     

Kinetic study of preirradiation grafting of acrylic acid onto poly(tetrafluoroethylene–perfluorovinyl ether) copolymer

A kinetic study has been made on the preirradiation grafting of acrylic acid (AAc) onto poly(tetrafluoroethylene–perfluorovinyl ether) (PFA) film. The effect of grafting conditions was investigated. The dependences of the grafting rate on preirradiation dose and monomer concentration was found to be of the order of 0.5 and 1.3, respectively. The final degree of grafting was found to increase with dose and monomer concentration. However, it decreases as the grafting temperature increase. The overall activation energy for the graft polymerization was calculated from Arrhenius plots to be 5.6 kcal/mol. The activation energy for this grafting system was found to be independent of preirradiation dose used in the range from 10 to 100 kGy. The relationship between the grafting rate and film thickness gave a negative first-order dependence. The results suggest that the grafting proceeds by radical mechanism with bimolecular termination of growing chain radicals. It was reasonable concluded that this grafting proceeds from the surface to the center of film with progressive monomer diffusion through the grafted layer which swells in the monomer solution.     

接枝丙烯酰胺改善聚乙烯膜表面亲水性的研究

利用等离子体技术和紫外照射接枝相结合在聚乙烯膜表面接枝丙烯酰胺(AAm)以改善其亲水性。通过衰减全反射红外光谱(ATR-FTIR)、X射线光电子能谱(XPS)和接触角测定验证了在无光引发剂的条件下,将等离子体预处理和紫外照射接枝结合起来可以有效地提高AAm的接枝效果,很好地改善PE膜表面的亲水性。探讨了等离子体复合参数W/(FM)、等离子体预处理时间、AAm单体浓度以及紫外照射时间对改善PE膜表面亲水性的影响,确定改善PE膜表面亲水性的最佳实验条件。