Surface Photografting Polymerization Research Articles

Cooperative enhancement of fungal repelling performance by surface photografting of stereochemical bi-molecules

Fungal contamination could increase exponentially on any convenient sites if without antifungal agents, thus seriously threatening human health. In this work, a cooperative fungal repelling coating has been fabricated by surface photografting polymerization of bi-molecules, polyethylene glycol diacrylate (PEGDA) and bornyl acrylate (BA), which combined amphiphilic feature with stereochemical fungal repelling strategy. ATR-FTIR and EDS were used to confirm the synthesized copolymers. The surface microstructures of the coating film were showed with AFM and SEM images. The cooperative enhancement of fungal repelling performance has been demonstrated through modulating the ratio between hydrophilic PEGDA and hydrophobic BA. When the ratio of monomers was 1:1, the coating exhibited the best cooperative effect on anti-adhesion of Aspergillus niger. Binary cooperation between PEG ring and bornyl cage is considered to play a crucial role in this coating system. Therefore, amphiphilic-stereochemistry is believed to be an effective strategy to prevent fungal adhesion.

Surface photografting polymerization of trimethylolpropane triacrylate onto LDPE substrate in tetrahydrofuran/water mixtures

AbstractA surface photografting polymerization (λ > 300 nm) of a multifunctional monomer which was trimethylolpropane triacrylate (TMPTA), was conducted with benzophenone (BP) as photoinitiator and LDPE as model substrate, in mixed solvents containing tetrahydrofuran (THF) and water. Proved by ATR‐IR, highly crosslinked grafted layer was generated rapidly under UV irradiation. Effects on percent conversion of grafting are detailed with, such as feed ratio of BP to TMPTA, mass percent of TMPTA in the reaction system, mass percent of water in the mixed solvents and addition of the second monomer, methyl methacrylate (MMA). As both verified by SEM and AFM, relatively planar grafted layer was produced when photografting was carried out merely in THF; adding water in the reaction system caused the formation of “craters” in the grafted layer. In addition, effects of mass percent of water in the mixed solvents, UV irradiation time, TMPTA concentration and addition of MMA on the size, shape and quantity of the “craters” were investigated by SEM. A plausible mechanism for the formation of “craters” is also proposed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

Surface photografting polymerization of vinyl acetate, maleic anhydride and their charge‐transfer complex. VII. Charge‐transfer complex (3)

AbstractIn the present article, a practically applicable method was developed, by which the compositions of the grafted chains achieved by UV‐irradiated photografting polymerization of vinyl acetate–maleic anhydride (VAC‐MAH)/low density polyethylene (LDPE) film systems can be determined. By measuring FTIR spectra of the films containing known amounts of VAC and MAH, standard working plots of the relationship between the ratio of the absorption peak area of MAH to that of VAC and the ratio of the content of MAH to that of VAC were set up. If the characteristic absorption peak areas of MAH and VAC on the grafted film are calculated, then according to the standard working plots, the ratio of MAH content to VAC content can be determined. It is proved that this method was effective in a wide range of MAH/VAC. Using this method, LDPE films containing different contents of MAH and VAC were characterized. The results show that the MAH content in the grafted film went up progressively, as the content of MAH in the monomer feed was raised; this phenomenon became more obvious when the total monomer concentration was increased, and the polymerization temperature was enhanced. These results should be attributed to the unique ability of MAH to abstract hydrogen when irradiated with UV light. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006

Surface photografting polymerization of vinyl acetate, maleic anhydride, and their charge‐transfer complex. VIII. Charge‐transfer complex (4)

AbstractIn view of the complexity of surface photografting polymerization of vinyl acetate/maleic anhydride (VAC/MAH) binary monomer systems, a novel method was adopted in the present article to obtain insight into the relevant grafting copolymerization mechanism. This method includes two steps: semibenzopinacol dormant groups were first introduced onto LDPE film by UV‐irradiation and then thermally reactivated to produce LDPE macromolecular free radicals, which initiated the grafting copolymerization of VAC and MAH. It was demonstrated that, in the first step, the solvent used to introduce benzophenone (BP) to LDPE film largely affected the subsequent grafting copolymerization, which was closely related to the affinity of the solvent toward the substrate. The monomer feed composition had considerable influence on both the grafting and nongrafting copolymerization; however, the maximum copolymerization rates did not appear in the polymerization system with [VAC]/[MAH] being 1 : 1, but, in the system with a bit more VAC than MAH, as the total monomer concentration was raised, the maximum copolymerization rates tended to appear in the system with [VAC] equal to [MAH]. The relationship between the total copolymerization rate (RP) and monomer concentration was determined to be LnRP ∝ [VAC + MAH]1.83. All of these results indicated that both charge transfer (CT) complex formed by VAC and MAH and free monomers took part in grafting copolymerization. This feature differentiated the surface grafting copolymerization of VAC/MAH from the well‐studied thermally induced alternating copolymerization of VAC/MAH. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006

Surface photografting polymerization of vinyl acetate, maleic anhydride, and their charge‐transfer complex. IX. Charge‐transfer complex (5)

AbstractThe two‐step method was employed to obtain insight into the grafting mechanism of (MAH‐VAC)/LDPE film in the preceding investigation, where photoreduction of BP (the first step) was investigated and the subsequent grafting polymerization (the second step) was studied from the viewpoint of kinetics. The present article is devoted to investigation of the living polymerization performance, the compositions of the grafted chains, and the relevant grafting copolymerization mechanism of the (MAH‐VAC)/LDPE system. Both grafting copolymerization and nongrafting copolymerization performed living polymerization characteristics to some degree. Regarding the nongrafting copolymerization at a monomer concentration, [MAH] = [VAC] = 2M, MAH and VAC mainly underwent alternating copolymerization, especially at low temperatures; however, the grafting copolymerization mostly exhibited random copolymerization, which became obvious with the elevation of temperature. The composition of the monomer feed largely affected the composition of the grafted copolymer and the nongrafted copolymer. When [MAH]/[VAC] was either 2.5/1.5, 2/2, or 1.5/2.5, MAH/VAC in nongrafted copolymers stayed approximately at 1/1; while when [MAH]/[VAC] was 2.5/1.5, MAH/VAC in the grafted copolymer was nearly 1/1; but in the case of [MAH]/[VAC] being 2/2 and 1.5/2.5, the content of MAH in grafted chains was somewhat lower than that of VAC. All these results demonstrated that the grafting copolymerization on the substrate occurred randomly, which was greatly affected by the affinity of the monomer toward the substrate. This performance of the grafting copolymerization was much different from the nongrafting copolymerization in the solution. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2230–2237, 2005

Surface photografting polymerization of vinyl acetate, maleic anhydride, and their charge‐transfer complex. VI. Charge‐transfer complex (2)

AbstractThe photografting copolymerization of a low‐density polyethylene/vinyl acetate (VAC)–maleic anhydride (MAH) binary monomer system was studied from the perspective of dynamics. The total conversion percentage (CP) and grafting conversion percentage (CG) were measured by gravimetry. On the basis of plots of CP and CG as functions of the polymerization time, the total polymerization rate (RP) and grafting polymerization rate (RG) were calculated. In addition, the apparent activation energy (Ea) and the reaction orders of the photografting polymerization under different reaction conditions, such as the total monomer concentration and the concentration of benzophenone (BP), were determined also. The results showed that, in comparison with the photografting polymerization of the two single monomers (VAC and MAH), RP and RG noticeably increased for the VAC–MAH binary monomer system. When the total monomer concentration was kept at 4M, the apparent Ea's of the three photografting polymerization systems were as follows: for VAC ([MAH]/[VAC] = 0/4), Ea's for the total polymerization and grafting polymerization were 41.00 and 43.90 kJ/mol, respectively; for MAH ([MAH]/[VAC] = 4/0, Ea's were 39.65 and 43.23 kJ/mol, respectively; and for the VAC–MAH binary monomer system, Ea's were 34.35 and 40.32 kJ/mol, respectively. These results suggested that the polymerization of the binary system occurred more readily than the other two. The reaction orders of RP with respect to the total monomer concentration of the monomers and the concentration of BP were 1.34 and 0.81, respectively. According to these investigations, it could be inferred that in the binary monomer system, both the free monomers and charge‐transfer complex took part in the polymerization; to the termination of the propagating chains, two possible pathways, unimolecular termination and bimolecular termination, coexisted in this binary monomer system. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 910–915, 2005

Surface photografting polymerization of vinyl acetate, maleic anhydride, and their charge‐transfer complex. V. Charge‐transfer complex (1)

AbstractIn previous studies, the photografting polymerization of vinyl acetate (VAC) and maleic anhydride (MAH) was investigated systematically. After that, to increase the grafting rate and efficiency and make the project more practicable, a VAC–MAH binary monomer system was employed for simultaneous photografting onto the surface of low‐density polyethylene film. The effects of several crucial factors, including the composition and total concentration of the monomer solution and different types of photoinitiators and solvents, on the grafting polymerization were investigated in detail. The conversion percentage (CP), grafting efficiency (GE), and grafting percentage were measured by gravimetry. The results showed that the monomer composition played a big part in this binary system; appropriately increasing the content of MAH in the monomer feed was suited for grafting polymerization. The growth of the total monomer concentration, however, made the copolymerization faster and was unfavorable for grafting polymerization. The three photoinitiators—2,2‐dimethoxy‐2‐phenylacetophenone (Irgacure 651), benzoyl peroxide, and benzophenone (BP)—led to only slight differences in CP, but for GE, BP was the most suitable. As for the different solvents—acetone, ethyl acetate, tetrahydrofuran (THF), and chloroform—using those able to donate electrons (acetone and THF) resulted in relatively higher CPs; on the contrary, the use of the other solvents made GE obviously higher, and this should be attributed to the charge‐transfer complex (CTC) that formed in this system. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 903–909, 2005

Surface Photografting Polymerization of Methyl Methacrylate in N,N‐dimethylformamide on Low Density Polyethylene Film

AbstractSummary: It was found that without additional photoinitiator, methyl methacrylate (MMA) dissolved in common solvent N,N‐dimethylformamide (DMF) could be photografted steadily on low‐density polyethylene (LDPE) film surface under UV irradiation. In short irradiation time (4 min) and at room temperature, high grafting efficiency (approaching 100%) and remarkable graft polymer amount (grafting percent is about 4.6%) was obtained. The possible reaction mechanism was based on the photosensitivity of DMF, which induced this photografting polymerization. This finding is useful to develop photoinitiator‐free grafting or photopolymerization system. Using SEM, special discrete globular structure was found on the MMA‐grafted LDPE film surface, and a possible model was proposed to interpret it.image

Promoting the cytocompatibility of polyurethane scaffolds via surface photo-grafting polymerization of acrylamide.

Polyurethane (PU) porous scaffolds were modified by grafting polymerization of acrylamide (AAm) initiated under UV light. A pre-adsorbing-monomer method was used beforehand. FTIR-ATR spectroscopy and X-ray photoelectron spectroscopy (XPS) measurements confirmed the presence of grafted PAAm on PU scaffolds. The measurement of water adsorption demonstrated the improvement of hydrophilicity after PU scaffolds were grafted with polyacrylamide (PAAm). The PAAm grafting degree related to the amount of AAm adsorbed, average pore diameter, and the degree of porosity. This study shows that higher degree of porosity and bigger porous areas yielded larger amounts of absorbed AAm and higher grafting degrees. In vitro human endothelial cell cultures of PU scaffolds modified with hydrophilic PAAm showed better cytocompatibility than the control matrix.

Surface photografting polymerization of vinyl acetate, maleic anhydride, and their charge-transfer complex. IV. Maleic anhydride

In general, it has been accepted that maleic anhydride (MAH) cannot be homopolymerized under normal conditions. However, MAH can be grafted onto substrates under UV irradiation rather easily. In this study, the photografting polymerization of MAH was examined with low-density polyethylene (LDPE) film as a substrate. The initiating performances of different photoinitiators, including benzophenone (BP), Irgacure 651, and benzoyl peroxide (BPO), were examined. The effects of some principal factors, such as the temperature, solvent, and UV intensity, on the grafting polymerization of MAH were also investigated. The results show that MAH can be smoothly grafted onto LDPE film by UV radiation. Enhancing the intensity of UV radiation and elevating the irradiation temperature facilitate the grafting polymerization of MAH. Among BP, Irgacure 651, and BPO, Irgacure 651 can initiate the polymerization of more MAH, but BP is more effective for the initiation of surface grafting polymerization. Solvents of MAH also have a great influence on the grafting polymerization; some of them even seem to take part in the reaction. The occurrence of photografting polymerization was verified with Fourier transform infrared and electron spectroscopy for chemical analysis spectra. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2318–2325, 2003

Self‐initiating performance of maleic anhydride on surface photografting polymerization

AbstractMaleic anhydride (MAH) was photografted onto low‐density polyethylene (LDPE) films with a grafting efficiency of about 70% in the absence of a photoinitiator. The self‐initiating performance was attributed to a mechanism of abstracting hydrogen atoms from LDPE chains by excited MAH dimers. The supporting experimental results were as follows: (1) the far‐UV radiation (200–300 nm) was indispensable for the graft polymerization and 2) the crosslinking reaction of LDPE inevitably accompanied the grafting of MAH. In addition, the initiation performance of MAH was further confirmed by surface photografting of acrylic acid in the presence of MAH, where MAH was used as the photoinitiator. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3246–3249, 2001

Auto-Initiating Performance of Styrene on Surface Photografting Polymerization

Investigating the surface photografting polymerization of styrene (St), it was found that in the absence of photoinitiator and at high temperatures, a remarkable amount of St-grafted polymer is formed. The initiation performance of St was further confirmed by surface photografting polymerization of acrylic acid, where St was used as the photoinitiator. This finding is useful to investigate the reaction mechanism of aromatic compounds under UV radiation and develop photoinitiator-free polymerization systems.

Auto-Initiating Performance of Styrene on Surface Photografting Polymerization

Investigating the surface photografting polymerization of styrene (St), it was found that in the absence of photoinitiator and at high temperatures, a remarkable amount the St-grafted polymer is formed. The initiation performance of St was further confirmed by surface photografting polymerization of acrylic acid, where St was used as the photoinitiator. This finding is useful to investigate the reaction mechanism of aromatic compounds under UV radiation and develop photoinitiator-free polymerization systems.

Surface photografting polymerization of vinyl acetate (VAc), maleic anhydride (MAH), and their charge transfer complex (CTC). III. VAc(3)

AbstractVinyl acetate (VAc) was grafted onto low‐density polyethylene (LDPE) substrates by UV irradiation with benzophenone (BP) as the photoinitiator. BP preabsorbed film samples and BP precoated film samples were prepared in advance and applied as the substrates onto which VAc was photografted, together with the method in which BP was dissolved in VAc directly. In addition, the efficiency of the polymerizations applying the preirradiation technology was examined. The conversion percent, grafting percent, and grafting efficiency were determined by a gravimetric method. The contact angles of the grafted films against water were also measured. The results show that BP preabsorbing and precoating were favorable to grafting polymerization, especially the BP precoating method, which was due to its simple operation and the ease of controlling the amount of BP. The diffusion of BP and VAc through the substrates proved to be an important factor for grafting polymerization. Through UV irradiation, dormant groups can be introduced onto LDPE film, which may be activated again by UV irradiation or by heating, leading to the formation of free radicals. Grafting polymerization can be initiated during the activation process in the presence of monomer. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1426–1433, 2001

Molecularly imprinted polymer membranes for substance-selective solid-phase extraction from water by surface photo-grafting polymerization

Hydrophilized polyvinylidene fluoride microfiltration membranes were surface-modified in the presence of a template (terbumeton) in methanol with a graft copolymer of a functional monomer (2-acrylamido-2-methyl-1-propane sulfonic acid, AMPS, methacrylic acid, MAA, or acrylic acid, AA) and a cross-linker ( N, N′-methylene-bis-acrylamide) using UV irradiation and benzophenone as photoinitiator. As result, membranes covered with a thin layer of imprinted polymer selective to terbumeton were obtained. Blank membranes were prepared with the same monomer composition, but in the absence of the template. The membranes’ capacity to adsorb terbumetone from aqueous solution was evaluated yielding information regarding the effect of polymer synthesis (type and concentration of functional monomer, concentration of cross-linker) on the resulting membranes’ recognition properties. UV spectroscopic studies of the interactions with terbumetone revealed that AMPS forms a stronger complex than MAA and AA. In agreement with that finding, imprinting with AMPS gave higher affinities than with MAA and AA. The terbumeton-imprinted membranes showed significantly higher sorption capability to this herbicide than to similar compounds (atrazine, desmetryn, metribuzine). With the novel surface modification technology, the low non-specific binding properties of the hydrophilized microfiltration membrane could successfully be combined with the receptor properties of molecular imprints, yielding substance-specific molecularly imprinted polymer composite membranes. The high affinity of these synthetic affinity membranes to triazine herbicides together with their straightforward and inexpensive preparation provides a good basis for the development of applications of imprinted polymers in separation processes such as solid-phase extraction.

Surface photografting polymerization of vinyl acetate (VAc), maleic anhydride, and their charge transfer complex. I. VAc(1)

Photografting of vinyl acetate (VAc) onto LDPE films was carried out with lamination technology and simultaneous method, using BP as photoinitiator. Some principal factors affecting the grafting polymerization were investigated in detail. The experimental results showed that oxygen dissolved in monomer solution had great influence on grafting polymerization. Compared with other routine monomers (St, MMA, AN, AA, and AAm), VAc exhibited higher photografting reactivity. It was observed that the reaction temperature affected the graft polymerization markedly. To film samples with a given diameter, there exists optimum thickness of monomer solution. Adding a pertinent amount of water to the photografting polymerization system could accelerate the polymerization. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1513–1521, 2000

Surface photografting polymerization of vinyl acetate (VAc), maleic anhydride, and their charge transfer complex. II. VAc(2)

On the basis of our earlier work, extensive experiments were conducted to further investigate grafting vinyl acetate onto different films (10 types of films and 20 kinds of film combinations), using various photoinitiators, for example, BP, AQ, ITX, XAN, Irgacure 651 and 184, acetone, and cyclohexanone, irradiated by UV radiation. Several means were applied to confirm the grafted PE-g-PVAc film. The results showed that increasing UV radiation intensity is favorable for grafting polymerization and the far UV radiation plays a decisive role. Among the photoinitiators tested, BP is the best one, because it was found that BP initiates the grafting copolymerization efficiently, and other initiators are less effective. To various combined substrates, the affinity between the monomer and films, the reactivity of hydrogens on the substrates, and the transparence of the top film to UV radiation are main factors affecting polymerization. Both direct method (FTIR) and indirect methods (contact angle, color reaction, absorption of dye and water) verified the true product PE-g-PVAc. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1522–1531, 2000

Surface photografting polymerization of vinyl acetate (VAc), maleic anhydride, and their charge transfer complex. II. VAc(2)

On the basis of our earlier work, extensive experiments were conducted to further investigate grafting vinyl acetate onto different films (10 types of films and 20 kinds of film combinations), using various photoinitiators, for example, BP, AQ, ITX, XAN, Irgacure 651 and 184, acetone, and cyclohexanone, irradiated by UV radiation. Several means were applied to confirm the grafted PE-g-PVAc film. The results showed that increasing UV radiation intensity is favorable for grafting polymerization and the far UV radiation plays a decisive role. Among the photoinitiators tested, BP is the best one, because it was found that BP initiates the grafting copolymerization efficiently, and other initiators are less effective. To various combined substrates, the affinity between the monomer and films, the reactivity of hydrogens on the substrates, and the transparence of the top film to UV radiation are main factors affecting polymerization. Both direct method (FTIR) and indirect methods (contact angle, color reaction, absorption of dye and water) verified the true product PE-g-PVAc. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1522–1531, 2000

Surface photografting polymerization of vinyl acetate (VAc), maleic anhydride, and their charge transfer complex. I. VAc(1)

On the basis of our earlier work, extensive experiments were conducted to further investigate grafting vinyl acetate onto different films (10 types of films and 20 kinds of film combinations), using various photoinitiators, for example, BP, AQ, ITX, XAN, Irgacure 651 and 184, acetone, and cyclohexanone, irradiated by UV radiation. Several means were applied to confirm the grafted PE-g-PVAc film. The results showed that increasing UV radiation intensity is favorable for grafting polymerization and the far UV radiation plays a decisive role. Among the photoinitiators tested, BP is the best one, because it was found that BP initiates the grafting copolymerization efficiently, and other initiators are less effective. To various combined substrates, the affinity between the monomer and films, the reactivity of hydrogens on the substrates, and the transparence of the top film to UV radiation are main factors affecting polymerization. Both direct method (FTIR) and indirect methods (contact angle, color reaction, absorption of dye and water) verified the true product PE-g-PVAc. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1522–1531, 2000

Bulk surface photografting process and its applications. I. Reactions and kinetics

A bulk surface photografting process which is conducted in the interface between two polymer films was designed and investigated. The bulk surface photografting is a highly efficient process. With this method, the surface of hydrophobic polymers can be made hydrophilic in less than 2 s and a grafted layer 5 μm thick can be obtained in 30 s. The kinetic investigation shows that the bulk surface photografting polymerization involves a four-step reaction process: induction period, surface initiation, successive polymerization, involves a four-step reaction process: induction period, surface initiation, successive polymerization, and solid-phase crosslinking. The photoreduction of benzophenone (BP) takes place in the interlayer between the LDPE films and is a three-stage process: surface photoreduction, secondary photoreduction, and solid-state photoreduction. With regard to the photoreduction of the initiator caused by hydrogen abstraction, the kinetic studies show that the photoreduction rate has a first-order dependence on the BP concentration. The activation energy of the hydrogen abstraction reaction is about 28.5 KJ (6.8 kcal)/mol. With regard to the photografting polymerization reaction, the reaction order of the rate Rp with respect to the monomer is unity and 0.89 with respect to BP. This means that the termination reaction takes place mainly by combination of polymer chain free radicals and semipinacol free radicals from BP. The activation energy of the overall polymerization reaction is around 8.8 kJ (2.1 kcal)/mol. © 1996 John Wiley & Sons, Inc.