Photografting of N‐isopropylacrylamide and glycidyl methacrylate binary monomers on polyethylene film: Effect of mixed solvent consisting of water and organic solvent

Photografting (λ > 300 nm) of N‐isopropylacrylamide (NIPAAm) and glycidyl methacrylate (GMA) binary monomers (NIPAAm/GMA) on low‐density polyethylene film (thickness = 30 μm) was investigated at 60°C using mixed solvent consisting of water and an organic solvent such as acetone. Xanthone was used as a photoinitiator by coating it on the film surfaces. A maximum percentage of grafting was observed at a certain concentration of acetone in the mixed solvent, which was commonly observed for both ratios of NIPAAm/GMA, 8/2 and 7/3. Based on the photografting of NIPAAm/GMA on xanthone‐coated film, monomer reactivity ratios of NIPAAm (r₁) and GMA (r₂) were calculated using the Fineman–Ross method. The values were 0.31 ± 0.1 and 4.8 ± 0.2 for the water solvent system, while they were 0.96 ± 0.1 and 4.9 ± 0.1 for the mixed solvent system. NIPAAm/GMA‐grafted films with a homogeneous distribution of grafted chains were formed by photografting using water and mixed solvents. The NIPAAm/GMA‐grafted films exhibited temperature‐responsive characters, whereas the grafted films showed a reversible change in the degree of swelling between 0 and 50°C, respectively. Epoxy groups in the grafted poly(NIPAAm/GMA) chains could be aminated with ethylenediamine in N,N′‐dimethylformamide at 70°C for 3 h. Complexes of the aminated NIPAAm/GMA‐grafted chains with cupric ion exhibited catalytic activity for the decomposition of hydrogen peroxide at 20 to 50°C. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2469–2475, 2005     

Spatial and temporal evolution of the photoinitiation rate for thick polymer systems illuminated by polychromatic light: selection of efficient photoinitiators for LED or mercury lamps

BACKGROUND: Four common free radical photoinitiators were evaluated for use in thick photopolymerizations illuminated with a medium‐pressure 200 W mercury–xenon arc lamp and a high‐intensity 400 nm light‐emitting diode (LED) lamp. For each photoinitiator/lamp combination, the spatial and temporal evolution of the photoinitiation rate profile was analyzed by solving the set of differential equations that govern the light intensity gradient and initiator concentration gradient for polychromatic illumination. RESULTS: The simulation results revealed that two of the four photoinitiators evaluated were ineffective for photoinitiating thick polymer systems. The photoinitiator bis(2,4,6‐trimethylbenzoyl)‐phenylphosphine oxide, in combination with the 400 nm LED lamp, was shown to be the most efficient photoinitiator/light source combination for photoinitiation of thick systems. CONCLUSION: The results show that some photoinitiators commonly used for photopolymerization of thin coatings are ineffective for curing thick systems. LED light sources provide advantages over traditional mercury lamps, and may have tremendous potential in the effective photoinitiation of thick polymer systems. Copyright © 2008 Society of Chemical Industry     

Photopolymerization of N,N‐dimethylaminoethylmethacrylate studied by photocalorimetry

Photopolymerization of dimethylaminoethylmethacrylate (DMAEMA) is studied in bulk and in solutions in the presence of different photoinitiators using differential photocalorimetry (DPC). The rate of DMAEMA photopolymerization is slow compared to that of alkylmethacrylates. Bimodal DPC curves of DMAEMA photopolymerization in bulk are obtained. The type I photoinitiators (IRGACURE® 651 and IRGACURE® 1700), which produce free radicals by homolytic fragmentation of photoexcited molecules, are more effective in promoting photopolymerization of DMAEMA. The type II photoinitiators (benzophenone and IRGACURE® 500), which initiate DMAEMA photopolymerization through an H‐abstraction mechanism involving an amino group from the monomer (polymer), are less efficient and favor the formation of partly crosslinked products. The effects of the photoinitiator concentration, temperature, and solvent on the kinetic data are evaluated and discussed. A scheme of photopolymerization of DMAEMA, including the formation of intermediate DMAEMA based macromonomers, is proposed. The main point of the suggested scheme is a high chain transfer to the DMAEMA monomer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 579–588, 2002     

Photopolymerization kinetics of hyperbranched acrylated aromatic polyester

The influences of the irradiation temperature, comonomer content, sample thickness, and photoinitiator concentration on the polymerization kinetics of hyperbranched acrylated aromatic polyester (HAAPE) were investigated with photo‐differential scanning calorimetry and IR measurements. The maximum photopolymerization rate increased with the temperature rising up to 110°C but decreased beyond 110°C. An activation energy of 16 kJ mol^?1 for the photopolymerization was obtained below 110°C from an Arrhenius plot, but it was negative beyond 120°C. A remarkable synergistic effect between HAAPE and the comonomer trimethylolpropane triacrylate with a molar fraction of around 0.4 was observed from a photopolymerization kinetic study of the resins. The final unsaturation conversion in an ultraviolet‐cured film decreased with the sample thickness, and this became more remarkable as the photoinitiator concentration increased. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1500–1504, 2003     

Water-absorbing characteristics of acrylic acid-grafted carboxymethyl cellulose synthesized by photografting

Cellulosic absorbents for water were synthesized by photografting (λ > 300 nm) acrylic acid (AA) onto fiberous carboxymethyl cellulose (CMC, degree of substitution [DS] = 0.1–0.4) at 30°C in the presence of N,N′-methylenebisacrylamide as a crosslinker. The CMC sample was pretreated with hydrogen peroxide in the presence of sulfuric acid to prepare CMC peroxides with a peracid type as a polymeric photoinitiator. The peroxides were active for the photografting and AA could be grafted onto CMC with percent graftings higher than 150% by photoirradiation of 10 min at 30°C. The amount of water absorbed increased with increasing percent grafting of AA and DS of CMC. The amount was reduced considerably when the absorbents were prepared by the photografting of AA onto crosslinked CMC in the absence of the crosslinker. Graft copolymers which display a decreasing water absorbency as a function of temperature were prepared by two methods: In the first synthesis method, AA and N-isopropylacrylamide (NIPAAm) binary monomers were graft-copoly-merized onto CMC samples using photoinitiation. In the second method, photografting of AA was followed by a second-step photografting of NIPAAm to produce a terpolymer with two types of side chains of differing repeat unit composition on the CMC substrate. Graft copolymers formed by both methods showed decreasing water absorbency as temperature increased with losses in water absorbency of up to about 60% as the temperature was increased above 30°C. Effects of NIPAAm composition and corsslinker content in the graft copolymers on the decreasing water absorbency as a function of temperature were also examined. © 1996 John Wiley & Sons, Inc.     

Degradation of poly(vinyl alcohol) in strongly alkaline solutions of hydrogen peroxide

The action of hydrogen peroxide and sodium hydroxide independently as well as in combination together with stabilizer formulation–consisting of magnesium sulphate (5 g/L), ethylenediamine tetraacetic acid (2 g/L), gluconic acid (2 g/L), and nonionic/anionic wetting agent (1.5 g/L)–on poly(vinyl alcohol) (PVA) was investigated at 30°C and 95°C. The effect of sodium hydroxide (5–25 g/L) alone was to bring about an enhancement in the viscosity of PVA most probably due to gel formation. The latter was favored at higher sodium hydroxide concentrations and longer duration (30 min) of treatment. The opposite holds true when hydrogen peroxide (35% w/v) was used alone at concentrations ranging from 2 to 20 mL/L. The viscosity of PVA decreased as the hydrogen peroxide concentration increased. Nevertheless, hydrogen peroxide alone could not cause complete dissolution of PVA even at 95°C for 30 min. On the other hand, complete dissolution of PVA could be achieved under the influence of stabilized alkaline solutions of hydrogen peroxide at 95°C in less than 10 min. It was postulated that, under the conditions used, oxidation of PVA by hydrogen peroxide prevailed over gel formation under the influence of sodium hydroxide.     

Synthesis and photopolymerization kinetics of oxime ester photoinitiators

Oxime Ester (OXE) Photoinitiators were synthesized and characterized by HPLC, FTIR, UV–Vis spectra, and ¹H‐NMR. The UV–Vis spectra of these photoinitiators were similar to Benzophenone (BP) but showed large red‐shifted maximum absorption. OXE were not only soluble in many solvents and (meth) acrylate monomers but also could be dispersed easily in propylene glycol monomethyl ether acetate (PGMEA). The kinetics of polymerization of monomer using OXE as photoinitiator was studied by Real‐time infrared (RTIR) spectra. It showed that OXE were an efficient photoinitiator. The concentration of OXE, functionality of monomer, and light intensity had effect on the photopolymerization kinetics. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Photoinitiating behavior of bifunctional photoinitiator containing α‐hydroxyalkylphenone group on free‐radical polymerization

Photoinitiating behaviors of bis[4‐(2‐hydroxy‐isopropionyl)]ether photoinitiator on free‐radical polymerization have been investigated. The kinetics of photopolymerization initiated by the photoinitiator was studied by means of differential photocalorimetry. The bifunctional photoinitiator showed comparative performance with those commercial photoinitiators with monofunctional chromophoric group. The effect of UV intensity on the polymerization rate was investigated, and the value of exponential factor was found to be 0.5 at the beginning of polymerization, suggesting that the photopolymerization initiated by bis[4‐(2‐hydroxy‐isopropionyl)]ether followed biradical termination mechanism. Photosensitizer triethylamine improves the initiating efficiency while oxygen is shown to restrict polymerization in this system. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5297–5302, 2006     

Photopolymerization characteristics of bisbenzo[1,3]dioxol‐5‐ylmethanone as an initiator

Bisbenzo[1,3]dioxol‐5‐ylmethanone (BBDOM), a type of hydrogen‐abstraction photoinitiator, exhibited redshifted maximal absorption in comparison with benzophenone (BP) according to ultraviolet–visible absorption spectroscopy. The kinetics of photopolymerization of the photoinitiator in different systems was studied with real‐time infrared spectroscopy. The concentration of BBDOM, the components of the initiator, and the functionality of the monomer had great effects on the kinetics of photopolymerization. The results show that BBDOM is a more effective photoinitiator than BP. BBDOM consists of cyclic acetals that are widely distributed in nature, and with BBDOM, the use of large numbers of amines can be avoided in the system without the requirement of an additional hydrogen donor. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Thermoreversible hydrogel. V. Synthesis and swelling behavior of the N-isopropylacrylamide-co-trimethyl methacryloyloxyethyl ammonium iodide copolymeric hydrogels

A series of N-isopropylacrylamide/trimethyl methacryloyloxyethyl ammonium iodide (NIPAAm/TMMAI) copolymeric gels are prepared from the various molar ratios of NIPAAm, cationic monomer TMMAI, and N,N′-methylene bisacrylamide (NMBA) in this article. The influences of the amount of the cationic monomer in the copolymeric gels on the swelling behavior in water, various saline solutions, and various temperatures are investigated. Results show that the swelling ratios of copolymeric gels are significantly larger than those of pure homopolymer NIPAAm gel, and the more the TMMAI content, the higher the gel transition temperature. In the saline solution, results show that the swelling ratio of pure NIPAAm gel has not significantly changed with an increase of the salt concentration until the salt concentration is larger than 0.1M. The swelling ratios for the copolymeric gels NIPAAm/TMMAI decrease with increasing salt concentration. In various saline solutions, results show that the anionic effects are greater than cationic effects in the presence of common anion, different cations and common cation, and different anions for these hydrogels. Finally, we also tested the reversibility of the NIPAAm/TMMAI copolymeric gels. The deswelling and reswelling kinetics are dependent on the temperature, which is below or above the gel transition temperature. The gel with little TMMAI content has a good reversibility. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1793–1803, 1998     

Studies on preparation and properties of porous biodegradable poly(NIPAAm) hydrogels

A series of biodegradable porous hydrogels, based on thermosensitive N‐isopropylacrylamide (NIPAAm) and biodegradable crosslinker‐polycaprolactone diacrylate (PCLdA) that was synthesized from polycaprolactone diol with acryloyl chloride were prepared by photopolymerization at low temperature. The effect of the crosslinker content and gelation method on the swelling behaviors and physical properties for the poly(NIPAAm) hydrogels was investigated. Results showed that the swelling ratio of the gel in deionized water decreased with an increase of the content of polycaprolactone (PCL) segment in the poly(NIPAAm) hydrogels. The properties of the gels crosslinked with PCLdA were compared with those crosslinked with N, N′‐methylenebisacrylamide (NMBA). The results showed that the critical gel transition temperatures (CGTT) of the gels crosslinked with PCLdA were lower than those of the gels crosslinked with NMBA due to the hydrophobicity of the PCL segment. The results also showed that the gels crosslinked with PCLdA had higher mechanical strength and crosslinking density than those gels crosslinked with NMBA. Comparing the porous gels with nonporous gels, the results showed that the swelling ratio and CGTT of the porous gels were higher than those of the nonporous gels, and the transition temperature curve was smoother for the porous gels. The porous gels also exhibited more rapid thermal response and faster degradation rates. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Studies on the Redox State in Polyacrylamide Gels

Abstract

The oxidation-reduction properties of polyacrylamide gels were examined to test the possibility that persulfate-or other free radical donors-alter proteins during polyacrylamide gel electrophoresis. Polyacrylamide gels formed either by use of persulfate or riboflavin and light as catalysts were shown to oxidize sulfhydryl compounds. Electrophoresis of thioglycolate into the gel in amounts equivalent to persulfate resulted in reducing conditions (titratable SH groups) in the gel.

Acrylamide monomer and, therefore, presumably unreacted monomer in polyacrylamide react with the α-amino group of amino acids: the reaction with glycine proceeded slowly at pH 9 and at acrylamide concentrations comparable to that of amino acid. Acrylamide at high concentrations (0.5 M) also reacted with yeast enolase and, like the thiol groups of reduring agents, prevented the appearance of characteristic changes in the pattern of enolase in polyacrylamide gel electrophoresis, previously attributed to “persulfate damage” and now designated the “enolase band shift”.

The enolase band shift was demonstrated in gels photopolymerized by riboflavin in the absence of persulfate. Pattern changes resembling those of the enolase band shift were observed after direct incubation of enolase with persulfate at the high level used for polymerization (4 mM), although pattern changes indicative of drastic alteration of the protein result from such incubation. The enolase band shift was obtained whether or not gels were purified by pre-electrophoresis which should remove all persulfate. The pattern ascribed previously to persulfate damage only occurred in gels containing urea and was abolished by reaction of the protein with thioglycolate, hydroquinone, dithiothreitol, or acrylamide prior to the migration of the protein into the gel.

Under the conditions of the riboflavin-catalyzed photopolymerization of acrylamide the cyanmethemoglobin molecule was altered; illumination by itself had no such effect.     

Boronic acid–functionalized HEMA‐based gels for nucleotide adsorption

A gel matrix that could be used as a sorbent for the specific adsorption of nucleotides was prepared by the radical copolymerization of 2‐hydroxyethylmethacrylate (HEMA) with a relatively new boronic acid–functionalized monomer (4‐vinylphenylboronic acid, VPBA). The synthesis of a gel could be achieved at a reasonably low temperature (+4°C) by using potassium persulfate and tetramethylethylenediamine as the redox system and methylenebisacrylamide (MBA) as the crosslinker. To increase the diol binding affinity of boronic acid–carrying gels, two different amine‐containing monomers [N‐3‐(dimethylamino)propylmethacrylamide, DMAPM and 2‐(dimethylamino)ethylmethacrylate, DMAEM) were also included in the gel‐formation recipe. Then HEMA–VPBA–DMAPM and HEMA–VPBA–DMAEM terpolymer gels were obtained. The boronic acid–functionalized gel matrices with different swelling properties were produced by changing the feed concentrations of VPBA and of the amine‐containing monomers (DMAPM and DMAEM). To test the usability of produced gels as a sorbent in the nucleotide adsorption, β‐nicotinamide adenine dinucleotide (β‐NAD) was selected as a model compound. The results of adsorption experiments indicated that the β ‐NAD adsorption capacity of HEMA‐based gels increased with increasing VPBA feed concentration. Equilibrium adsorption capacities up to 33 mg β‐NAD/g dry gel could be achieved with the DMAPM‐containing boronic acid–functionalized HEMA‐based gels. An increase in the feed concentration of DMAPM resulted in an increase in the β‐NAD adsorption capacity of gels, while a decrease was observed with an increasing feed concentration of the other amine‐containing monomer (DMAEM). © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 268–277, 2000     

In situ study of photopolymerization by fourier transform infrared spectroscopy

The Fourier transform infrared (FTIR) in situ method was developed for the investigation of photopolymerization. Ultraviolet (UV) cure of a mixture of a cycloaliphatic epoxide, a 2-ethylhexyl acrylate, and photoinitiators, which forms simultaneous interpenetrating polymer network (IPN), was monitored while the sample was irradiated with UV light. Triphenylsulfonium salt and benzoin ether were used as photoinitiators. For the sake of comparison, similar experiments were performed for the epoxide with the triphenylsulfonium salt photoinitiator and the acrylate with the benzoin ether photoinitiator. The epoxy photopolymerization was monitored using an epoxy CH stretching band at 3005 cm^?1 and a ring vibration band at 790 cm^?1. The acrylic photopolymerization was monitored using a C?C stretching band at 1637 cm^?1. The epoxy conversion was less than 60% when the acrylic polymerization was completed in the IPN.     

Uptake and removal of iron by immobilised persimmon tannin

Persimmon tannin was immobilised with formaldehyde (the aldehyde gel) and potassium peroxodisulfate (the persulfate gel). The resulting gels have high abilities to adsorb iron. The persulfate gel can adsorb iron from both iron(II) and iron(III) solutions with high efficiency. The adsorption of iron(III) by the persulfate gel was rapid and was affected by the solution pH, the concentration of iron in solution, and the mass of adsorbent. Adsorbed iron was easily desorbed with 0.1 mol dm⁻³ HCl solution. The gel can be repeatedly re‐used for iron recovery using the adsorption–desorption cycle. The persulfate gel could remove trace amounts of iron in a sake‐brewing water to facilitate the production of high quality sake. © 2000 Society of Chemical Industry     

Effect of intercalated hydrotalcite on swelling and mechanical behavior for poly(acrylic acid‐co‐N‐isopropylacrylamide)/hydrotalcite nanocomposite hydrogels

A series of nanocomposite hydrogels were prepared from acrylic acid (AA), N‐isopropylacrylamide (NIPAAm), and intercalated hydrotalcite (IHT) by photopolymerization. The influence of the intercalating content of 2‐acrylamido‐2‐methyl propane sulfonic acid (AMPS) in HT on the swelling and mechanical properties for poly(AA‐co‐NIPAAm)/IHT nanocomposite hydrogels was investigated. The results showed that the higher the content of the AMPS‐HT was, the higher the swelling ratio of the gels and the higher the content of the intercalating agent was, the lower swelling ratio. It was also demonstrated that the swelling ratio of the gel was not affected by the counterion in HT. The gel strength and crosslinking density were not enhanced by adding AMPS‐HT into the gel composition, but the maximum effective crosslink density and shear modulus of the nanocomposite hydrogels were increased with an increase of the content of the intercalating agent in HT. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1572–1580, 2005     

Preparation and characterization of poly(2‐acrylamido‐2‐methylpropane‐sulfonic acid) grafted chitosan using potassium persulfate as redox initiator

A grafted material based on chitosan and 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS) has been successfully prepared in homogenous solution using potassium persulfate as a redox initiator. The grafted copolymer was precipitated during the reaction polymerization. The effects of the reaction temperature and chitosan–potassium persulfate contact time as well as concentrations of AMPS, potassium persulfate, and acetic acid on grafting yield were investigated. The percentage of grafting is gradually increased with the increasing of the AMPS concentration. The extent of grafting can be controlled by setting the appropriate reaction conditions. The maximum percentage of grafting was about 180% under the optimum conditions (1% v/v acetic acid, 50°C reaction temperature, 10 min chitosan–potassium persulfate mixing period, 0.37 mmol of potassium persulfate, and 28.96 mmol AMPS). The grafted chitosan was insoluble in the acid of the grafting. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2314–2318, 2000     

Cationic photopolymerization of bisphenol A diglycidyl ether epoxy under 385 nm

The cationic photopolymerization of bisphenol A diglycidyl ether epoxy (DGEBA) at λ = 385 nm was conducted by the combination of a cationic photoinitiator PAG30201 (Bis (4‐isobutylphenyl) iodonium hexafluorophosphate) and a photosensitizer PSS303 (9,10‐dibutoxy‐9,10‐dihydroanthrance). The kinetic characterization was investigated by real‐time Fourier transform infrared spectroscopy. The enhancement of epoxy conversion of DGEBA was achieved by increasing temperature, adding alcohols, active monomers and radical photoinitiators. As a result, in the presence of 2 wt % PAG30201 and 1.2 wt % PSS303, the epoxy rings conversion of DGEBA has reached to more than 70% from 55.9% at room temperature; it could be increased to almost 80% if heated to 60°C. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3698–3703, 2013     

Effect of photosensitive groups on the photoefficiency of polymeric photoinitiators

The purpose of this paper is to determine the effect of photosensitive groups contained in the main chain of polymeric photoinitiator on photopolymerization. Through polycondensation of toluene-2,4-diisocyanate (TDI), different diamines and N-phenyldiethanolamine (PDEA), three novel polymeric photoinitiators containing in-chain benzophenone (BP) and coinitiator amine were synthesized in comparison with the corresponding side-chain ones. FT-IR, ¹H NMR and GPC analyses confirm the structures of all polymers. UV-Vis spectra showed that the maximal absorption and the molar extinction coefficient of polymeric photoinitiator can be greatly improved by the electron donating groups and the imino nitrogen that directly link to BP structure. The photopolymerization of trimethylolpropane triacrylate (TMPTA) and PU prepolymer, initiated by these polymeric photoinitiators, was studied by photo-DSC. The results indicate that the location of photosensitive group has an important effect on the photoefficiency of polymeric photoinitiators. The efficiency order of polymeric photoinitiators comprising in-chain BP is different from that of the side-chain ones: PUIBA-s and PUIBA-n are the most efficient for TMPTA and PU prepolymer, respectively.     

Effect of silane coupling agent on swelling behaviors and mechanical properties of thermosensitive hybrid gels

A series of organic–inorganic hybrid thermosensitive gels with three different structures were prepared from N‐isopropylacrylamide (NIPAAm), and N, N′‐methylenebisacrylamide (NMBA) and tetraethoxysilane (TEOS) [N‐IPN]; NIPAAm, 3‐(trimethoxysilyl) propyl methacrylate (TMSPMA) as coupling agent and TEOS [NT‐IPN]; and NIPAAm, TMSPMA, and TEOS [NT‐semi‐IPN] by emulsion polymerization and sol–gel reaction in this study. The effect of different gel structures and coupling agent on the swelling behavior, mechanical properties, and morphologies of the present gels was investigated. Results showed that the properties of the gels would be affected by the gel networks such as IPN or semi‐IPN and with or without existence of TMSPMA as the bridge chain between networks. The NT‐semi‐IPN gel had higher swelling ratio and faster diffusion rate because poly(NIPAAm) moiety in the semi‐IPN gels was not restricted by NMBA network. However, the IPN gels such as N‐IPN and NT‐IPN had good mechanical properties and lower swelling ratio, but had a poor thermosensitivity due to the addition of coupling agent, TMSPMA, into the gel system that resulted in denser link between organic and inorganic components. The morphology showed that IPN gels had partial aggregation (siloxane domain) and showed some denser phases. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009