Photo‐crosslinking of poly[ethene‐stat‐(methacrylic acid)] functionalised with maleimide side groups

BACKGROUND: Photo‐crosslinkable polymers are well known and commercially applied as photoresists. But so far they have not been applied as membrane materials for separation processes. They would offer certain advantages in membrane fabrication over conventional crosslinked polymer materials. Therefore, in this work, a poly[ethene‐stat‐(methacrylic acid)] (PEMAA) which is a potential membrane polymer for different separation problems was functionalised with photo‐crosslinkable maleimide side groups. RESULTS: It has been shown that PEMAA can be used as basic polymer material and a conversion with 3‐hydroxypropylmaleimide is possible in order to obtain a photo‐crosslinkable polymer. Investigation of the crosslinking mechanism was performed using stationary infrared and UV‐visible spectroscopy as well as nanosecond transient spectroscopy absorption measurements of a rotating film. Intense transient absorption of the maleimide‐esterified PEMAA occurs at 250 nm in the film pointing to maleimide anion formation and crosslinking via an ionic dimerisation mechanism. CONCLUSION: It is found that crosslinking reactions can be observed spectroscopically in situ using a maleimide‐functionalised PEMAA. Furthermore, experiments can be performed in the liquid phase (polymer in solution) as well as in the solid phase (polymer film) using a rotating polymer film sample. Maleimide anion formation and crosslinking via an ionic dimerisation mechanism can be investigated by variation of the polymer structure as well as the structure of the maleimide side groups. Copyright © 2009 Society of Chemical Industry     

Synthesis and characterization of thienyl‐ and terthienyl‐group‐bearing methacrylic polymers as precursors for grafting reactions of thiophene side‐chains

Acrylic and methacrylic monomers bearing pyrrolyl, thienyl and terthienyl groups, were synthesized and copolymerized with various amounts of butyl acrylate and butyl methacrylate. In the resulting copolymers the heterocycle side‐groups behaved as initiators in the oxidative polymerization of thiophene, allowing the polythiophene chains to grow from the side‐groups and leading therefore to graft copolymers. These last were collected mostly as insoluble fractions after extraction with chloroform. Processible polymers with polythiophene side‐chains were obtained when in the precursor polymer the heterocycle side‐group content was very low. The presence in the graft copolymers of a significant number of stiff polythiophene side‐chains was responsible for the rise in Tg values in comparison with the precursor polymers. The average number of grafted thiophene units, evaluated in the range 2–7.5, did not relate directly to measured conductivity values that were in the range 5.9 × 10⁻⁵–6.2 × 10⁻² S cm⁻¹. © 1999 Society of Chemical Industry     

UV crosslinkable microsphere pressure sensitive adhesives—influence on adhesive properties

In the following study, a synthesis and characterization of UV crosslinkable acrylic pressure sensitive adhesives are presented. Different amounts of unsaturated photoinitiator 4-acryloyloxy benzophenone (4-ABF) were added in t-butyl acrylate/2-ethylhexyl acrylate monomer mixture and then polymerized using a suspension polymerization technique. The adhesive suspension was coated on a pilot coating machine, dried by application of IR and subsequently crosslinked under UV light. The copolymerized 4-ABF photoinitiator will produce reactive radicals upon absorption of UV light, which are capable of initiating a rapid chain reaction with neighboring C-H positions of polymer side chains, what leads to formation of crosslinked polymer structures. UV crosslinking process was monitored by ATR-FTIR spectroscopic technique. Adhesion properties of the synthesized materials were determined using standard measurements of tack, peel and shear strength. Results have shown that all adhesive properties are strongly influenced by the degree of crosslinking of the microspheres, which increased with higher amounts of added 4-ABF photoinitiator. All the three measured adhesive properties showed a substantial decrease even at small amounts of added 4-ABF. The decrease in adhesion may be correlated with higher crosslinking density, what also resulted in higher gel phase amounts. Determination of glass transition temperature showed minor difference between adhesive coatings.     

Synthesis of well‐defined responsive membranes with fixable solvent responsiveness

A versatile method is described to synthesize a new family of solvent‐responsive membranes whose response states can be not only tunable but also fixable via ultraviolet (UV) irradiation induced crosslinking. The atom transfer radical polymerization (ATRP) initiator 2‐bromoisobutyryl bromide was first immobilized on the poly(ethylene terephthalate) (PET) track‐etched membrane followed by room‐temperature ATRP grafting of poly(2‐hydroxyethyl methacrylate) (PHEMA) and poly(2‐hydroxyethyl methacrylate‐co‐2‐(dimethylamino)ethyl methacrylate) (P(HEMA‐co‐DMAEMA)) respectively. The hydroxyl groups of PHEMA were further reacted with cinnamoyl chloride (a photosensitive monomer) to obtain photo‐crosslinkable PET‐g‐PHEMA/CA membrane and PET‐g‐P(HEMA/CA‐co‐DMAEMA) membrane. The length of grafted polymer chains was controllable by varying the polymerization time. X‐ray photoelectron spectroscopy, Fourier transform infrared spectroscopy in attenuated total reflection and thermogravimetric analysis were employed to characterize the resulting membranes. The various membrane surface morphologies resulting from different states of the grafted chains in water and dimethylformamide were characterized by scanning electron microscopy. It was demonstrated that the grafted P(HEMA/CA‐co‐DMAEMA) chains had more pronounced solvent responsivity than the grafted PHEMA/CA chains. The surface morphologies of the grafted membranes could be adjusted using different solvents and fixed by UV irradiation crosslinking. © 2014 Society of Chemical Industry     

Rapid solid‐state photopolymerization of octadecyl acrylate: low shrinkage and insensitivity to oxygen

Mobility restrictions in solid‐state photopolymerization give extremely poor polymerization kinetics, but octadecyl acrylate can be rapidly photopolymerized in the solid state. The XRD, real‐time Fourier transform IR and DSC analyses prove that the hexagonal packing of monomer molecules is favorable for UV‐initiated solid‐state polymerization, and crystalline long alkyl chains of monomers were preserved as the crystalline long alkyl side‐chains of polymers. More importantly, octadecyl acrylate provides a chance to investigate the shrinkage and oxygen inhibition of UV‐induced solid‐state polymerization. This novel radical‐mediated solid‐state photopolymerization is insensitive to oxygen and lowers the volume shrinkage (1.48%). © 2013 Society of Chemical Industry     

Synthesis,characterization, and UV‐curing properties of silicon‐containing (Meth)acrylate monomers

Eight different silicon‐containing (meth)acrylate monomers are synthesized by the substitution reaction of chlorosiloxanes with 2‐hydroxyethyl methacrylate or 2‐hydroxyethyl acrylate. Their molecular structures are confirmed by IR, ¹H‐NMR, and ¹³C‐NMR spectroscopic analyses. The effects of silicon content on the UV‐curing behavior, physical, surface, and thermal properties are investigated. The UV‐curing behavior is analyzed by photo differential scanning calorimetry. The surface free energy of the UV‐cured film is calculated from contact angles measured using the Lewis acid‐base three liquids method. The silicon‐containing (meth)acrylate monomers perform much better than traditional (meth)acrylate monomers on UV‐curing. The silicon‐containing monomers have higher final conversions and fast UV‐curing rates in photopolymerization. The surface free energy decreases with increasing silicon content, because silicon in the soft segment is transferred to the surface, producing a UV‐cured film; this is confirmed by X‐ray photoelectron spectroscopy measurements. All these advantageous properties enable these synthetic silicon‐containing monomers to perform better in applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and characterization of poly[methyl methacrylate‐co‐2‐ethylhexyl acrylate‐co‐poly(propylene glycol diacrylate)] latices

The emulsion polymerization of the monomers methyl methacrylate (MMA) and 2‐ethylhexyl acrylate (EHA) was studied to investigate the effect of the crosslinkable monomer poly(propylene glycol diacrylate) (PPGDA). IR spectroscopy, NMR, differential scanning calorimetry, gel permeation chromatography, and scanning electron microscopy were used to characterize the synthesized polymers. These polymers were coated on glass panels and cured at appropriate temperatures to study the physical properties, swelling behavior, surface tension, and contact angle of these polymer latices. The results show that as the concentration of EHA monomer increased, the surface tension of the latices decreased. The copolymers were characterized by ¹H‐NMR spectroscopy to ensure the absence of unreacted monomer, and the results confirm the incorporation of EHA units in the copolymer. The contact angle of the latices on the glass substrate was smaller than that on the metal. The swelling mechanism of the film showed that the Fickian diffusion coefficient with 10 wt % PPGDA was at a minimum value and was the most highly crosslinked polymer among the samples. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Highly Efficient Fluorescent Interstrand Photo‐crosslinking of DNA Duplexes Labeled with 5‐Fluoro‐4‐thio‐2′‐O‐methyluridine

The formation of a fluorescent photoadduct between 5‐fluoro‐4‐thiouridine ( ^FS U ), in the sequence context 5′‐A ^FS U A‐3′ and incorporated into a synthetic oligonucleotide either at its 3′‐ or 5′‐end, and one of the thymines of the TAT motif in a complementary target DNA strand led to photo‐crosslinking of the two strands for several oligonucleotide constructs. Enzymatic digestion, MS, UV, and fluorescence spectral analyses of the interstrand crosslinked oligonucleotides revealed the identity of the thymidine that participates in the photo‐crosslinking reaction as well as the diastereomeric structures of the crosslinks. The proposed pathways of interstrand photo‐crosslinking are supported by experiments with isotopically labeled oligonucleotide constructs and visualized by means of molecular dynamics simulations.     

Synthesis,characterization and crosslinking of functional star‐shaped poly(ε‐caprolactone)

Star‐shaped low molecular weight poly(ε‐caprolactone)s (PCLs) were synthesized and functionalized with crosslinkable terminal groups for subsequent crosslinking. The ε‐caprolactone (CL) prepolymers were polymerized by ring‐opening in the presence of polyglycerine (PGL) as an initiator (1, 3 and 5 mol%) and Sn(II)2‐ethylhexanoate as a catalyst. Characterization of the prepolymer by ¹³C/¹H nuclear magnetic resonance (NMR) spectroscopy, size exclusion chromatography (SEC), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) revealed a six‐armed star‐shaped structure for the prepolymer with the molecular weight controlled by the ratio of PGL and CL. Functionalization of the hydroxyl‐terminated prepolymer was carried out with maleic or itaconic anhydride. In both cases, the characterization of the functionalized prepolymer showed that the hydroxyl groups were completely substituted. The functionalized PCLs were successfully crosslinked through the reaction of double bonds. The crosslinking was induced either thermally with organic peroxide or photochemically with a photosensitive initiator. Characterization of the crosslinked PCLs by Soxhlet extraction, DSC and FTIR showed that the itaconic double bond was much more reactive in thermal crosslinking than the maleic double bond. Thus, the crosslinked prepolymers that were functionalized with itaconic double bonds achieved a gel content of about 90%. A gel content of 100% was achieved with several compositions where crosslinking agents were employed. © 2002 Society of Chemical Industry     

Synthesis of new ionic crosslinked polymer hydrogel combining polystyrene and poly(4‐vinyl pyridine) and its self‐healing through a reshuffling reaction of the trithiocarbonate moiety under irradiation of ultraviolet light

A new ionic crosslinked polymer hydrogel was achieved by the strategy of ionically crosslinking α,ω‐dibromide terminated polystyrene (Br‐PS‐Br) with poly(4‐vinyl pyridine) (P4VP) which was synthesized by reversible addition‐fragmentation chain transfer polymerization using a chain transfer agent containing a trithiocarbonate moiety. The moiety of trithiocarbonate was introduced into the crosslinked network to show the self‐healing characteristics. The chain structure and components of Br‐PS‐Br and P4VP were characterized through ¹H NMR, gel permeation chromatography, Fourier transform IR spectroscopy and elemental analysis. The P4VP (M_n = 25 300 g mol^?1) chains were crosslinked with Br‐PS‐Br (M_n = 2000 g mol^?1) through the quaternization reaction to form a polymer network which was further crosslinked in acetonitrile by irradiation of UV light to fabricate a hydrogel. Such a hydrogel of P4VP/Br‐PS‐Br cut by a razor blade can be rapidly (1 h) and repeatedly (three times) healed through a reshuffling reaction of the trithiocarbonate moiety under irradiation by UV light. © 2018 Society of Chemical Industry     

Synthesis and UV curing kinetics of rapidly UV‐curable hyperbranched polycarbosiloxanes

Hyperbranched polycarbosiloxanes with peripheral photo‐crosslinkable groups were synthesized through controllable hydrosilylation reaction from A₂‐type and CB₃‐type monomers. The polymerization of the monomer pairs was monitored using Fourier transform infrared spectroscopy, from which it was found that vinyl silane and methacrylate groups reacted with hydride silane from the beginning of the reaction. The results thus suggest a step‐by‐step polymerization rather than a two‐step process for this system. The polycarbosiloxanes could be cured rapidly in either nitrogen or air atmosphere, this feature making them attractive for potential application as precursors of advanced ceramic devices with complex structures. The effects of light intensity, reaction temperature and atmosphere on the UV curing rate (R_p) and conversion (α) of the photo‐crosslinkable groups were characterized carefully, and the curing kinetics was also investigated systematically. The results show that R_p and α increased with an increase of light intensity or temperature, and that the inhibiting effect of oxygen in air could be suppressed by enhancing the irradiation intensity. Copyright © 2010 Society of Chemical Industry     

Synthesis and dynamic mechanical analysis of nanocomposite UV crosslinkable 100% solid acrylic pressure sensitive adhesives

A synthesis and characterization of nanocomposite solventless acrylic UV crosslinkable pressure sensitive adhesives is presented. Different prepolymers were synthesized using bulk polymerization procedure. The reaction mixture consisted of acrylic monomers (2-ethylhexyl acrylate, acrylic acid and t-butyl acrylate), azobisisobutyronitrile initiator, chain transfer agent n-dodecylmercaptan and unsaturated UV photoinitiator 4-acryloyloxybezophenone. Different formulations with different amounts of modified and unmodified montmorillonite (MMT) clays were tested and the prepolymer was characterized by viscosity measurements. UV crosslinking process was monitored using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. Gel phase amount in crosslinked samples was determined by Soxhlet extraction. Clay dispersion in polymer matrix was investigated by X-ray diffraction analysis (XRD). Three basic adhesive properties, the tack, peel and shear strength were measured and the viscoelastic properties of crosslinked adhesive films were characterized using dynamic mechanical analysis (DMA). Results of the study showed high increase in prepolymer viscosity, when hydrophobic types of MMT clays were added in the reaction mixture. The addition of clay had a negative effect on UV crosslinking process. XRD analysis confirmed complete exfoliation and/or intercalation of modified clays in polymer matrix, depending on modifier amount and type. Results of adhesive properties testing showed a major influence of clay addition on adhesive properties, especially on shear strength. DMA analysis showed an increase in storage modulus (G′) and a decrease of tan δ values for adhesives synthesized with clay what also concurs with higher shear strength and implies an improved cohesion of adhesive.     

Synthesis and characterization of novel photo‐crosslinkable fluorinated poly(phthalazinone ether)s for optical waveguides

A series of novel photo‐crosslinkable fluorinated poly(phthalazinone ether)s containing 1,1‐diphenylethylene segments in the polymer main chain, used for optical waveguide materials, were synthesized by polycondensation reaction of decafluorobiphenyl with a mixture of 4‐(4‐hydroxylphenyl)(2H)‐phthalazin‐1‐one (DHPZ), 4,4‐(hexafluoroisopropylidene)diphenol and 1,1‐bis(4‐hydroxyphenyl)ethylene (BHPE) as co‐reactant. The feed ratio of DHPZ to total bisphenols varied from 0 to 80 mol%, while that of BHPE remained at 20 mol% for all polymers. The obtained copolymers show good solubility in some common polar organic solvents. The resulting polymers were photo‐crosslinked after UV irradiation for 10 min in the presence of a photoinitiator. The cured polymers show good chemical resistance, high thermal stability (temperatures of 1% mass loss after curing of 472–496 °C under nitrogen) and high glass transition temperatures (160–249 °C) which could be further increased by about 10 °C after photochemical crosslinking. By adjusting the copolymerizing bisphenol content, the refractive indices of transverse electric and transverse magnetic modes (at 1550 nm) of films of the polymers were exactly tuned in the range 1.5029–1.5661 and 1.4950–1.5502, respectively. The propagation losses of the cured films were measured and found to be less than 0.3 dB cm^?1 at 1550 nm, indicating the promise of these materials for passive optical waveguide devices. Copyright © 2011 Society of Chemical Industry     

Synthesis,characterization, and thermal behavior study of methyl methacrylate polymers containing 4‐carbazole substitutes

A new polymerizable monomer, [4‐(9‐ethyl)carbazolyl]methyl methacrylate ( 2 ), was synthesized by reacting of methacrylic acid and 4‐hydroxymethyl‐9‐ethyl carbazole ( 1 ) by esterification procedure in the presence of N,N′‐dicyclohexylcarbodiimide. The resulting monomer was then polymerized free‐radically to form the poly(methyl methacrylate) containing 4‐(9‐ethyl)carbazolyl pend ent groups. Also, copolymerization of monomer 2 with various acrylic monomers such as methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, and n‐butyl acrylate by azobisisobutyronitrile as a free radical polymerization initiator gave the related copolymers in high yields. The structure of all the resulted compounds was characterized and confirmed by FTIR and ¹H NMR spectroscopic techniques. The average molecular weight of the obtained polymers was determined by gel permeation chromatography using tetrahydrofurane as the solvent. The thermal gravimetric analysis and differential scanning calorimeter instruments were used for studying of thermal properties of polymers. It was found that, with the incorporation of bulky 4‐(9‐ethyl)carbazolyl substitutes in side chains of methyl methacrylate polymers, thermal stability and glass transition temperature of polymers are increased. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4989–4995, 2006     

Two‐component photoresists containing thermally crosslinkable photoacid generators

Bis{4‐[2′‐(vinyloxy)ethoxy]phenyl}‐4‐methoxyphenylsulfonium triflate (TPS‐2VE‐Tf) and tris{4‐[2′‐(vinyloxy)ethoxy]phenyl}sulfonium triflate (TPS‐3VE‐Tf) were synthesized as thermally crosslinkable photoacid generators (PAGs) and used in a two‐component chemically amplified photoresist system. The photoresist films formulated with poly(p‐hydroxystyrene) (PHS) as a binder polymer and a thermally crosslinkable PAG are insolubilized in aqueous base by prebaking due to the thermal crosslinking reaction between PHS and the PAG. The insolubilization temperature of the resists and conversion of vinyl ether groups are greatly influenced by the PAG concentration and prebaking temperature, respectively. Upon exposure to deep UV and subsequent postexposure bake, the crosslinks are cleaved by photogenerated acid, leading to effective solubilization of the exposed areas. Photoresists containing TPS‐2VE‐Tf and TPS‐3VE‐Tf exhibited sensitivities of 12 and 45 mJ/cm², respectively. Positive‐tone images were obtained using a 2.38 wt% aqueous tetramethylammonium hydroxide developer.     

Synthesis of a photo‐crosslinked stable nonlinear optical polymer and application to external electro‐optic measurement

A photo‐crosslinked side‐chain second‐order nonlinear optical polymer was synthesized with bis‐phenol‐A as the polymer backbone, p‐nitroaniline as the chromophore and cinnamyl group as the photo‐sensitizer. The characterization of the polymer was made by nuclear magnetic resonance, infrared, ultraviolet‐vis, and dynamic mechanical analysis methods. An electro‐optic film was obtained by spin coating of the polymer and corona poling then photo‐crosslinking reaction. An external electro‐optic measurement system was established based on the film and reflective light path configuration, and successfully applied to measure the electrical signals propagating on the under‐test circuits. The poled and crosslinked film showed high glass transition temperature (160°C) and improved chromophore orientation stability. The measuring principle was analyzed by electro‐optic tensor matrix and index ellipsoid methods. The results showed that the designed polymer film had the linear electro‐optic effect, the voltage sensitivity of the system was measured to be 5 mv/ at the condition of 1 kHz input signal. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1506–1512, 2000     

Synthesis and photo‐curing behaviors of silicon‐containing (vinyl ether)–(allyl ether) hybrid monomers

A series of silicon‐containing (vinyl ether)–(allyl ether) hybrid monomers used in nano‐imprint lithography resists were synthesized and subjected to photo‐initiated polymerization. The surface energies of the monomers and the resulting polymer films were then investigated. The surface energies of the monomers were very low at less than 15 mJ m^–2. The photo‐curing behaviors of the five hybrid monomers were investigated using real‐time Fourier transform infrared spectroscopy. The monomers were sequentially initiated with cationic (PAG201) and mixed (cationic initiator PAG201, radical initiator ITX or TPO) initiators. The vinyl ether double bond polymerized both rapidly and completely, whereas the allyl ether double bond remained when PAG201 was used as the photo‐initiator and polymerized completely with mixed initiators. The different double bonds of the silicon‐containing (vinyl ether)–(allyl ether) hybrid monomer increased the efficiency of the polymerization and overcame the intrinsic limitations of the free radical and cationic polymerization processes, including strong oxygen inhibition, large volume shrinkage and high humidity sensitivity. The five monomers with low viscosity, low surface energy, good thermal stability and good photo‐polymerization properties were suitable for nano‐imprint photoresists. © 2013 Society of Chemical Industry     

Pervaporation separation of 1,1,2‐trichloroethane–water mixture through crosslinked acrylate copolymer composite membranes

The separation of a chlorinated hydrocarbon from a dilute aqueous solution through a crosslinked acrylate copolymer–porous substrate composite membrane by pervaporation was investigated. Poly(n‐butyl acrylate‐co‐acrylic acid) and poly(n‐butyl acrylate‐co‐2‐hydroxyethyl acrylate) were synthesized and composite membranes were prepared, which were made from the crosslinked polymer and a porous substrate. Pervaporation measurement was carried out for a dilute aqueous solution of 1,1,2‐trichloroethane at 25°C and under a vacuum on the permeate side (below 10 mmHg). The separation factor, overall flux, 1,1,2‐trichloroethane concentration in the membrane, and the degree of swelling decreased with increase in the acrylic acid or 2‐hydroxyethyl acrylate content of the acrylate copolymer. The influence of the crosslinking agent content on the pervaporation performance was small, and the separation factor and the overall flux showed a convex curve. The structure of the crosslinking agent had no effect on the separation. The influence of the pore size of the substrate and the thickness of the polymer layer on the separation of 1,1,2‐trichloroethane was observed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 983–994, 1999     

The diacetone acrylamide crosslinking reaction and its control of core‐shell polyacrylate latices at ambient temperature

Self crosslinkable core‐shell polyacrylate latices (PAs) cured at ambient temperature were synthesized by semicontinuous‐seeded emulsion polymerization with diacetone acrylamide (DAAM) and adipic dihydrazide (ADH) as crosslinkable monomers. The influences of DAAM monomer mass content, neutralizer, and curing temperature on the properties of self crosslinkable core‐shell latices and the keto‐hydrazide crosslinking were discussed. The spectroscopic techniques such as Fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter (DSC), atomic force microscopy (AFM), transmission electron microscopy (TEM), and contact angle instruments were used to determine the structure and properties of PAs. The water evaporating rate during the film‐forming process of self crosslinkable core‐shell latices was also investigated. FTIR analyses demonstrate that the keto‐hydrazide crosslinking reaction does not occur in the latex environment but occurs at ambient temperature with the evaporation of water during the film‐forming process. The results of DSC show that the core‐shell crosslinkable PAs have two glass transition temperatures (T_g), and T_gs of crosslinked film are higher than that of non crosslinked fim. Moreover, the keto‐hydrazide reaction is found to be acid catalyzed and favored by the loss of water and the simultaneous decrease in pH arising from the evaporation of ammonia or amines during film‐forming process. Hence, in the volatile ammonia or amines neutralized latices, the latex pH value adjusted to 7–8, which not only ensure the crosslinkable latex with good storage stability but also obtain a coating film with excellent performances by introducing the keto‐hydrazine crosslinking reaction. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Polymerization Kinetics and Characterization of Dual Cured Polyurethane‐Acrylate Nanocomposites for Laminates

Summary: Four different types of montmorillonites have been dispersed by sonication at 50 °C into a propoxylated aromatic epoxy diacrylate oligomer to achieve interlayered or exfoliated nanocomposites. A thermally‐induced crosslinking reaction, forming a polyurethane network in the presence of 7 wt.‐% of a montmorillonite, has been promoted by addition of an allophanate modified polyisocyanurate based on hexamethylene diisocyanate. The kinetic behavior of the network formation has been studied at 25, 40 and 60 °C by following the disappearance of the isocyanate vibrational band found at 2 270 cm^?1. A tight crosslinked polyurethane acrylate network has been achieved by a subsequent dual UV curing promoted by a photoinitiator mixture (0.6 wt.‐%) added to the reactive mixture because of further reactions occur to the acrylate double bonds. The photopolymerization kinetic has been investigated on the different thermally treated polyurethane nanocomposite networks by Real Time FTIR spectroscopy monitoring the changes of the IR band at 810 cm^?1 assigned to the acrylate double bond vibrations. The influence of the different montmorillonite clays on the final nanocomposite morphology has been investigated by using XRD and SEM. Finally, the use of these mixtures as internal layer between two modified surface PET films has been also studied for the laminate production. The based‐PET laminate films have been characterized by determining the bending resistance and optical properties as a function of different nanofillers.

Bending resistance of the dual cured nanocomposite laminates containing 7 wt.‐% as a function of nanofiller types.