A water‐soluble supramolecular‐structured photoinitiator between methylated β‐cyclodextrin and 2,2‐dimethoxy‐2‐phenylacetophenone

A water‐soluble supramolecular‐structured photoinitiator (SSPI) was synthesized by supramolecular self‐assembling between methylated β‐cyclodextrin (MβCD) and hydrophobic 2,2‐dimethoxy‐2‐phenylacetophenone (DMPA). The structure of SSPI was characterized by X‐ray diffraction, FTIR, ¹H NMR, UV–vis, and fluorescence spectra. The results indicated that MβCD and DMPA had formed 1 : 1 inclusion complex in methanol solution. The binding constant (K) for the complex was 7.51 × 10²M^?1. SSPI could be dissolved in water easily and its water‐solubility was 15.3 g/100 mL. SSPI was the more efficient photoinitiator than DMPA for the photopolymerization of acrylamide (AM) in homogeneous aqueous system. The conversion for photopolymerization of trimethylolpropane triacrylate system initiated by SSPI was similar to that initiated by DMPA. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Efficiency of 4,4′‐bis(N,N‐diethylamino) benzophenone for the polymerization of dimethacrylate resins in thick sections

The efficiency of 4,4′‐bis(N,N‐diethylamino)benzophenone (DEABP) for the polymerization of dimethacrylate monomers in thick sections ( 1 – 2 mm) was studied. DEABP (λ_max = 365 nm) represents a complete initiating system as it contains both ketone and amine functional groups. During irradiation, DEABP photobleaches at a fast rate causing deeper penetration of light through the underlying layers, but the photoinitiation efficiency (rate of polymerization per photon absorption rate) is relatively poor. As a result, irradiation of methacrylate monomers at 365 nm results in a slow average polymerization rate and a reduced monomer conversion for thick sections due to the light attenuation caused by the high absorptivity of DEABP and photolysis products. These results highlight the inherent interlinking of light attenuation and photobleaching rate in polymerization of thick sections. Copyright © 2011 Society of Chemical Industry     

The effects of processing variables on stress development in ultraviolet-cured coatings

A cantilever deflection technique was used to monitor stress development during ultraviolet photo-cure of acrylate coatings to the glassy state. Two coating systems were studied: a trifunctional monomer (trimethylol propane triacrylate, TMPTA) and a tetrafunctional monomer (pentaerythritol tetraacrylate, PETA). Both were photoinitiated with 2,2-dimethoxy-2-phenylacetophenone (DMPA). Average in-plane stresses of up to 30 MPa were measured upon curing at room temperature. The rate and magnitude of stress development rose with the photoinitiator concentration and with light intensity. Curing with more strongly absorbed light had similar effects. Light absorption caused decreased stress magnitudes in thicker coatings. Somewhat unexpectedly, the rate and magnitude of stress development increased with monomer functionality even though the conversion fell. Moreover, curing thick coatings with high radical concentrations (strongly absorbing light and large photoinitiator concentrations) caused ripple defects to form. With the appearance of these defects, stress ceased to rise with the photoinitiator concentration. Fourier transform infrared spectroscopy was employed to monitor conversion and to help understand these stress development trends. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1267–1277, 1997     

Monomer conversion in a light‐cured dental resin containing 1‐phenyl‐1,2‐ propanedione photosensitizer

The efficiency of 1‐phenyl‐1,2‐propanedione (PPD) photosensitizer for the photopolymerization of a dental resin based on 2,2‐bis[4‐(2‐hydroxy‐3‐methacryloxyprop‐1‐oxy)phenyl]propane/triethylene glycol dimethacrylate was assessed. Experimental formulations containing PPD or/and camphorquinone (CQ) in combination with dimethylaminoethyl methacrylate (DMAEMA), ethyl‐4‐dimethylaminobenzoate (EDMAB), 4‐(N,N‐dimethylamino)phenethyl alcohol (DMPOH) and N,N‐3,5‐tetramethylaniline (TMA) at different concentrations were studied. The photopolymerization was carried out by means of a commercial light‐emitting diode (LED) curing unit. Near‐infrared spectroscopy was used to follow the consumption of double bonds versus irradiation time. No significant differences in the conversion values among formulations prepared with PPD in combination with DMAEMA, DMPOH and TMA were found. In contrast, the conversion was markedly increased by the presence of EDMAB. At low concentrations of photosensitizer, when used in combination with DMAEMA and EDMAB, PPD resulted in a final conversion equivalent to CQ. However, when DMPOH and TMA were used, PPD was found to be less efficient than CQ. In addition, at high photoinitiator concentration, the effectiveness of PPD was less than that of CQ independently of the co‐initiator used. The replacement of some CQ by an equivalent amount of PPD resulted in similar final monomer conversion as formulations having the same amount of CQ alone. The LED light source employed emitted in the wavelength range 410–490 nm with a peak around 470 nm, whereas the maximum molar absorbance of PPD was in the UV region. However, the small overlap of the spectral distribution of the LED curing lamp and the PPD absorption spectrum was compensated by the large extinction coefficient of PPD. Copyright © 2007 Society of Chemical Industry     

Wet‐spun,photoinitiator‐modified polyacrylonitrile precursor fibers: UV‐assisted stabilization

The role of dilute concentrations (～1 wt %) of a photoinitiator, 4,4 ′ ‐bis(diethylamino)benzophenone, on the processability and properties of the resulting wet‐spun polyacrylonitrile (PAN) fibers are reported. Rheology measurements show no adverse effect on the viscosities of solutions by the addition of the photoinitiator. Fibers containing photoinitiator were successfully wet‐spun from PAN – DMSO solution. FTIR results prove that 4,4 ′ ‐bis(diethylamino)benzophenone was retained in the fibers after coagulation and post‐stretching. SEM micrographs show no deterioration of the post‐stretched fiber microstructure due to the presence of photoinitiator. Tensile testing results show a small reduction in the strain‐at‐break of post‐stretched fibers containing photoinitiator when compared with pure (control) PAN fibers. After UV treatment, fibers with 4,4 ′ ‐bis(diethylamino)benzophenone display a higher tensile modulus compared with the other sets. Wide‐angle X‐ray diffraction results show no significant decrease in interplanar spacing and size of the crystals within the fibers containing photoinitiator, but such fibers retain a higher extent of molecular orientation after being UV treated. Conversion indices were measured from the WAXD spectra and compared with conventional thermal stabilized fibers. This correlation confirms that the addition of 1 wt % photoinitiator to PAN followed by 5 min of UV treatment leads to a conversion index that is observed in control fibers after more than an hour, which could reduce the conventional thermo‐oxidative stabilization time significantly. These results indicate the potential of the dual stabilization route in generating precursor fibers with higher molecular orientation, and possibly reducing the thermo‐oxidation time during carbon fiber processing. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2494–2503, 2013     

Hybrid organic–inorganic macromolecular photoinitiator system for visible-light photopolymerization

Hybrid organic–inorganic macrophotoinitiator bearing pendant tertiary amine groups (OI-AH) was prepared by hydrolytic condensation of a silane containing amino groups. The macromolecular amino-functionalized photoinitiator was used in combination with camphorquinone (CQ) for visible-light photo-polymerization. The OI-AH was incorporated into methacrylate resins at loadings between 1 and 10 wt.%. The photodecomposition of the CQ/OI-AH in methacrylate monomers under visible light irradiation (λ = 470 nm) was examined. The photolysis products of CQ/OI-AH were transparent at the irradiating wavelengths; consequently, the consumption of the CQ is accompanied by increased light intensity in the underlying lays. The clean and rapid photobleaching of CQ in combination with OI-AH makes this photoinitiator system very attractive for polymerization of thick sections. The evolution of monomer conversion versus irradiation time showed that the OI-AH is an efficient co-initiator of CQ because a fast reaction and high conversion of methacrylate groups result after 60 s irradiation with a LED source of 140 mW.     

Control release of some pesticides from starch/(ethylene glycol‐co‐methacrylic acid) copolymers prepared by γ‐irradiation

Starch/(Ethylene glycol‐co‐Methacrylic acid) [Starch/(EG‐co‐MAA)] hydrogels were designed for controlled delivery of pesticides, such as Fluometuron (FH); Thiophanate Methyl (TF) and Trifluralin (TI) which are use in the agricultural field. The delivery device was prepared by using γ‐irradiation and was characterized by FTIR, DSC, and SEM. The swelling behavior of hydrogels as a function of copolymer composition and irradiation dose was detected. This article discusses the swelling kinetics of polymer matrix and release dynamics of Trifluralin from hydrogels for the evaluation of the diffusion mechanism and diffusion coefficients. The values of the diffusion exponent ‘n’ for both the swelling of hydrogels and the release of Trifluralin from the hydrogels have been observed between 0.56 and 0.86 when the MAA content in the polymers was varied from 20 to 80 wt %, respectively. It is inferred from the values of the ‘n’ that non‐Fickian diffusion mechanism has occurred for different EG/MAA compositions. The release rate from matrices prepared under different conditions was studied to determine which factors have the most affect and control over the hydrogel matrix release property. The preparation conditions such as EG/MAA hydrogel composition, pesticide concentration, type of pesticide and irradiation dose greatly affect the pesticide release rate, which also influenced by the pH and temperature of the matrix‐surrounding medium. The pesticide release rate decreased as the irradiation dose and pH increased, but it increased as the MAA content, pesticide concentration and temperature increased. The release rate of Trifluralin is the highest one, whereas the Fluometuron is the lowest. The properties of the prepared hydrogels may make them acceptable for practical use as bioactive controlled release matrices. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Photocrosslinking of halogen‐free flame‐retarded ethylene‐vinyl acetate copolymer by phosphorous‐nitrogen compound NP28

The photoinitiated crosslinking of halogen‐free flame‐retarded ethylene‐vinyl acetate copolymer (EVA) by the phosphorous‐nitrogen compound NP28 in the presence of photoinitiator and crosslinker and characterization of the related properties have been investigated by gel determination, heat extension test, thermogravimetric analysis (TGA), mechanical measurement, and thermal aging test. The photocrosslinking efficiency of EVA/NP28 blend and various factors affecting the crosslinking process, such as photoinitiator, crosslinker, NP28 content, and irradiation temperature, were studied in detail and optimized by comparison of gel content. The results show that the EVA/NP28 blend filled with 28.2 wt % NP28 with a thickness of 1.6 mm is homogeneously photocrosslinked to a gel content of above 80 wt % with 4.8 s UV‐irradiation under optimum conditions. The data from TGA, mechanical measurement, and thermal aging test give evidence that the thermal stability and mechanical properties of photocrosslinked EVA/NP28 blend are much better than those of the unphotocrosslinked one.© 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of UV‐curable difunctional silane monomer based on 3‐methacryloxy propyl trimethoxysilane (3‐MPTS) and its UV‐curing characteristics and thermal stability

In the present investigation, silicon containing UV‐curable difunctional monomer was synthesized by reacting 3‐methacryloxy propyl trimethoxysilane (3‐MPTS) with acrylic acid using anhydrous ether as a solvent under inert atmosphere. The synthesized acryloxymethacryloxy silane monomer was characterized by FTIR, ¹H‐NMR, and ¹³C‐NMR spectroscopy. The silane monomer along with 4 wt % photoinitiator (Darocure 1173) was cured under UV‐light for different exposure time. The curing characteristic of the monomer was investigated using FTIR spectroscopy. The conversion of the double bond due to curing has been evaluated from the peak intensity of the C?C double bond (at 1636 cm^?1) in the FTIR spectrum considering the peak intensity at 1720 cm^?1 due to C?O as internal standard. The maximum double bond conversion is observed to be 72%. The optimum cure time for the silane monomer has been estimated to be 7.8 sec. The UV‐cured sample decomposes at 440°C. The char residue is 35% at 700°C. The synthesized UV‐curable silane monomer may be useful for UV‐coating formulations, for fabrication of 3D‐objects by lithographic technique and as a precursor for organic–inorganic hybrid materials. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Ultraviolet‐curing behavior of an epoxy acrylate resin system

Ultraviolet (UV)‐curing behavior of an epoxy acrylate resin system comprising an epoxy acrylate oligomer, a reactive diluent, and a photoinitiator was investigated by Fourier transform infrared (FTIR) spectroscopy. The conversion changes of the resin system containing 20 phr of 1,6‐hexanediol diacrylate as a reactive diluent and 2‐hydroxy‐2‐methyl‐1‐phenyl‐propan‐1‐one as a photoinitiator were measured under different UV‐curing conditions. The fractional conversion was calculated from the area of the absorption peak for the vinyl group vibration occurring at 810 cm^?1. The effects of photoinitiator concentration, total UV dosage, one‐step or stepwise UV irradiation, UV intensity, atmosphere, and temperature on the curing behavior of the resin system were investigated. The conversion of the resin system increased rapidly at the initial stage of the UV‐curing process but increased very slowly after that. The final conversion of the resin system was mainly affected by total UV dosage. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1180–1185, 2005     

Optimization and kinetic modeling of lipase catalyzed enantioselective N‐acetylation of ( ± )‐1‐phenylethylamine under microwave irradiation

BACKGROUND: Optically pure amines are used in the fine chemical industry as resolving agents, chiral auxiliaries, and chiral synthetic building blocks for pharmaceuticals as well as agrochemicals. Lipase‐catalyzed kinetic resolution of ( ± )‐1‐phenylethylamine with ethyl acetate as an acyl donor was achieved using immobilized lipase (Novozyme 435) as a biocatalyst under microwave irradiation. RESULTS: Response surface methodology was employed with a four‐factor‐three‐level Box‐Behnken design to evaluate the effect of synthesis parameters (speed of agitation, enzyme loading, temperature and acyl donor:amine molar ratio) on conversion, enantiomeric excess, enantioselectivity and initial rate. The optimum reaction conditions obtained were mole ratio of acyl donor:amine 1:1, temperature 49.86 °C, 0.03 g of catalyst loading and 345 rpm speed of agitation, giving 49.12% conversion, 78.83% enantiomeric excess and an enantioselectivity of 38.21. R‐stereopreference of lipase was analyzed in detail from the aspects of enzymatic kinetic mechanism and reaction activation energy of both enantiomers. CONCLUSION: Novozyme 435 was found to be the most active chiral catalyst for resolution of ( ± )‐1‐phenylethylamine under microwave irradiation. Statistical analysis was satisfactorily used to determine the optimum reaction conditions. It was found that lipase has R‐stereopreference and the reaction matches the Ping Pong Bi Bi mechanism with dead‐end inhibition of 1‐phenylethylamine. Copyright © 2011 Society of Chemical Industry     

Biodegradable and photocurable multiblock copolymers with shape‐memory properties from poly(ε‐caprolactone) diol,poly(ethylene glycol), and 5‐cinnamoyloxyisophthalic acid

Biodegradable and photocurable multiblock copolymers of various compositions were synthesized by the high‐temperature solution polycondensation of poly(ε‐caprolactone) (PCL) diols of molecular weight (M_n) = 3000 and poly(ethylene glycol)s (PEG) of M_n = 3000 with a dichloride of 5‐cinnamoyloxyisophthalic acid (ICA) as a chain extender, followed by irradiation by a 400 W high‐pressure mercury lamp (λ > 280 nm) to form a network structure. The gel contents increased with photocuring time, reaching a level of over 90% after 10 min for all copolymers without a photoinitiator. The thermal and mechanical properties of the photocured copolymers were examined by DSC and tensile tests. In cyclic thermomechanical tensile tests, the photocured ICA/PCL/PEG copolymer films showed good shape‐memory properties at 37–60°C, with both shape fixity ratio and shape recovery ratio over 90% at a maximum tensile strain of 100–300%. The water absorption of these copolymers and their rate of degradation in a phosphate buffer solution (pH 7.0) at 37°C increased significantly with increasing PEG content. The novel photocured ICA/PCL/PEG multiblock copolymers are potentially useful in biomedical applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Properties and degradation behavior of surface functionalized MWCNT/poly(L‐lactide‐co‐ε‐caprolactone) biodegradable nanocomposites

In this research, poly(L ‐lactide‐co‐ε‐caprolactone) (PLACL) reinforced with well‐dispersed multiwalled carbon nanotubes (MWCNTs) nanocomposites were prepared by oxidization and functionalization of the MWCNT surfaces using oligomeric L ‐lactide (LA) and ε‐caprolactone (CL). It is found that the surface functionalization can effectively improve the dispersion and adhesion of MWCNTs in PLACL. The surface functionalization will have a significant effect on the physical, thermomechanical, and degradation properties of MWCNT/PLACL composites. The tensile modulus, yield stress, tensile strength, and elongation at break of composite increased 49%, 60%, 70%, and 94%, respectively, when the concentration of functionalized MWCNTs in composite is 2 wt %. The in vitro degradation rate of nanocomposites in phosphate buffer solution increased about 100%. The glass transition temperature (T_g) of composites was decreased when the concentration of functionalized MWCNTs is 0.5 wt %. With further increasing the concentration of functionalized MWCNTs, the T_g was increased. The degradation kinetics of nanocomposites can be engineered and functionalized by varying the contents of pristine or functionalized MWCNTs. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and characterization of isocyanic acid,m‐phenylenediiso‐propylidene based poly(urethane‐urea) dispersions containing different amount of 2,2‐Bis(hydroxyl methyl)propionic acid

Isocyanic acid, m‐phenylenediiso‐propylidene (m‐TMXDI)‐based anionic poly(urethane‐urea) dispersions were prepared by the prepolymer mixing process. The equivalent ratio of NCO/OH was kept constant at 1.8, while 2,2‐bis(hydroxyl methyl) propionic acid (DMPA) used was varied from 3 to 10 wt %. The colloidal stability of poly(urethane‐urea) dispersions arose entirely from the presence of ionized carboxylic acid groups. The chemical structure of poly(urethane‐urea) dispersions with various amount of DMPA were identified by FTIR and ¹³C NMR analysis. The test results showed that the hydrophilicity of poly(urethane‐urea) dispersions were increased with increase in DMPA content. The degree of chain extension was much lower than the values predicted theoretically due to the side reaction of a small amount of hydrophilic isocyanate‐terminated prepolymer with water. The average particle size of poly(urethane‐urea) dispersions were decreased with an increase in DMPA content, and this lead to an increase in viscosity. Also, the thermal degradation behavior were measured and was shown that the initial degradation temperature shifted to lower temperature with an increase in DMPA content. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5737–5746, 2006     

Ultraviolet photopolymerization induced by a triazine derivative

2‐(3,4‐Methdioxyphenyl)‐4,6‐bis(trichloromethyl)‐ 1,3,5‐triazine (MBTTR) was used as a photoinitiator for the polymerization of acrylate monomer. Ultraviolet–visible absorption spectroscopy was used to investigate the photochemical behavior during the photophysical process. The photopolymerization kinetics were monitored by real‐time Fourier transform infrared spectroscopy. The polymerization rates of the acrylates were significantly higher than those of the methacrylates. When MBTTR induced the polymerization of trimethylolpropane triacrylate, there was an optimum polymerization rate and the final conversion was obtained at 0.1 wt % MBTTR. MBTTR was an inefficient photoinitiator for ethyl vinyl. The final conversions of tripropylene glycol diacrylate induced by MBTTR and triazine/1,3‐benzodioxole were similar. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Kinetics of Cationic Photopolymerizations of UV‐Curable Epoxy‐Based SU8‐Negative Photoresists With and Without Silica Nanoparticles

Summary: This paper reports on the photocuring kinetics of protonic‐acid‐initiated cationic polymerizations of UV‐curable epoxy‐based SU8‐negative photoresist systems with and without silica nanoparticles, as assessed using photo‐DSC, FTIR spectroscopy, UV‐vis spectroscopy, and SEM. Photo‐DSC analysis using an autocatalytic kinetic model demonstrated that the cross‐link density and cure rate increased as the concentration of silica nanoparticles with surface silanol groups increased to 2.5 wt.‐%. This result was confirmed by FTIR spectroscopy, and suggests that the presence of silica nanoparticles of up to 2.5 wt.‐% promoted the cure conversion and cure rate of the UV‐curable hybrid organic/inorganic negative photoresists due to the synergistic effect of silica nanoparticles acting both as an effective flow or diffusion‐aid agent and as a proton‐donor cocatalyst during the cationic photopolymerization process. The decrease in the cross‐link density that occurred when the silica content was higher than 2.5 wt.‐% was attributed to aggregation between silica nanoparticles due to their high surface energy.

SEM photograph at the film‐air interface of the UV‐cured hybrid organic/inorganic photoresist containing 10 wt.‐% silica nanoparticles.     

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     

3D‐Printing of High‐κ Thiol‐Ene Resins with Spiro‐Orthoesters as Anti‐Shrinkage Additive

Tri(ethylene glycol) divinyl ether and the spiro‐orthoester 2‐((allyloxy)methy)‐1,4,6‐trioxospiro[4.4]nonane can be formulated in different ratios and crosslinked by thiol‐ene reactions. The spiro‐orthoester is used as anti‐shrinkage additive, enabling shrinkage reduction of up to 39%. Addition of a radical photoinitiator for the thiol‐ene reaction and a cationic photoinitiator for the double ring‐opening of the spiro‐orthoester enables dual‐curing for application in 3D‐printing. The formulation free of the spiro‐orthoester shows gelation during the printing process and, correspondingly, low resolution. The formulations containing the spiro‐orthoester exhibit higher resolutions in the range of 50 µm. The resins containing mixtures of tri(ethylene glycol) divinyl ether and the spiro‐orthoester show permittivities as high as 10⁴. The dielectric loss factor of the resins is in the range of 0.5–7.6, and the conductivity in the range of 1.3?10^?11 to 2.0?10^?11 S cm^?1. These high‐κ materials can be 3D‐printed by digital light processing for the next generation of electronic materials.     

Controllable properties and microstructure of hydrogels based on crosslinked poly(ethylene glycol) diacrylates with different molecular weights

This work describes a comprehensive study of hydrogels based on polyethylene glycol diacrylates (PEGDAs) with the molecular weight (MW) range of 400–2000. The blends of low‐ and high‐molecular weight PEGDA macromers with different ratios were photopolymerized under visible light irradiation, using a blue light sensitive photoinitiator Irgacure819, at the total polymer concentration of 60 wt %. Swelling ratios, wetting property, elastic moduli, transparency, and the microstructure of the resulting hydrogels were investigated. Among them, equilibrium water contents, hydrophilicity, and mesh size of the hydrogels increased while the elastic moduli decreased when increased the PEGDA MW or the content of higher MW PEGDA in the blends. Most of the hydrogels possessed excellent transparency in visible region. The viability of L929 cells on the surface of hydrogel was also estimated. All the selected hydrogels exhibited a relatively high proliferation rate, which demonstrated this hydrogel system with photoinitiator Irgacure819 had good biocompatibility. These results show the properties of PEGDA hydrogel could be easily adjusted by varying PEGDA MW or the ratios of low‐ and high‐MW macromers in the composites. It could be helpful for the design of proper PEGDA hydrogels in the applications as tissue engineering or drug delivery system. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Rheological characterization of concentrated cellulose solutions in 1‐allyl‐3‐methylimidazolium chloride

The rheological properties of high concentrated wood pulp cellulose 1‐allyl‐3‐methy‐limidazolium Chloride ([Amim]Cl) solutions were investigated by using steady shear and dynamic viscoelastic measurement in a large range of concentrations (10–25 wt %). The measurement reveals that cellulose may slightly degrade at 110°C in [Amim]Cl and the Cox–Merz rule is valid for 10 wt % cellulose solution. All of the cellulose solutions showed a shear thinning behavior over the shear rate at temperature from 80 to 120°C. The zero shear viscosity (η_o) was obtained by using the simplified Cross model to fit experimental data. The η_o values were used for detailed viscosity‐concentration and activation energy analysis. The exponent in the viscosity‐concentration power law was found to be 3.63 at 80°C, which is comparable with cellulose dissolved in other solvents, and to be 5.14 at 120°C. The activation energy of the cellulose solution dropped from 70.41 to 30.54 kJ/mol with an increase of concentration from 10 to 25 wt %. The effects of temperature and concentration on the storage modulus (G′), the loss modulus (G″) and the first normal stress difference (N₁) were also analyzed in this study. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012