Acrylate Mixture Research Articles

Photopolymerization without Light. Polymerization of Acrylates Using Oxalate Esters and Hydrogen Peroxide

We define the photopolymerization of acrylates without light as a process wherein the radical chain polymerization produced by photoinitiators are produced by nonphotochemical means. We use the chemical reactions of the chemiluminescent lightstick to accomplish this. An important potential application is in producing “photopolymers” in areas that are not light accessible as in the inside of a tube or behind a pipe. Polymerizable acrylate mixtures containing dissolved oxalate esters undergo radical chain polymerization when exposed to a flow of nitrogen gas saturated with hydrogen peroxide vapors. We propose aryloxyoxalyl hydroperoxides to be the reactive species.

Preparation of acrylate polymer/silica nanocomposite particles with high silica encapsulation efficiency via miniemulsion polymerization

Acrylate polymer/silica nanocomposite particles were prepared through miniemulsion polymerization by using methyl methacrylate/butyl acrylate mixture containing the well-dispersed nano-sized silica particles coupling treated with 3-(trimethoxysilyl)propyl methacrylate (MPS). The encapsulation efficiency of silica particles was determined through the elution and hydrofluoride acid etching experiments, and the size distribution and the morphology of the composite latex particles were characterized by dynamic light scattering and transmission electron microscopy. The coupling treatment of silica with MPS can improve the encapsulation efficiency of silica and the degree of grafting of polymer onto silica. When 0.10g MPS/g silica was used to modify silica, the encapsulation efficiency of silica was greater than 95%, and the degree of grafting of acrylate polymer onto silica was about 60%. Although the average size and the size distribution index of the composite latex particles increased as the weight fraction of silica increased, the stable latex containing the ‘guava-like’ composite particles was obtained. The grafting of polymer onto silica particles improved the dispersion of silica particles in the solvents for acrylate polymer and in the polymer matrix.

Segregation of silicone acrylate from acrylate mixture at resin–mold interface and its effect on UV embossing

When silicone diacrylate was added in small amount (<5wt.%) to ultraviolet (UV) curable formulations containing other oligomeric diacrylates, there was segregation of the silicone additive at the solid substrate–formulation interface. The amount was quantified by X-ray photoelectron spectroscopy measurement of the UV cured film surface composition. The effect of silicone diacrylate concentration, resin formulation and substrate polarity on silicone surface excess was systematically studied. Young's–Gibbs adsorption theory was applied to the prediction of the silicone surface excess at the solid substrate interface for these oligomeric mixtures. Further, we proposed a simplified Young's–Gibbs adsorption theory equation to predict the variation of surface excess from only formulation surface tension and substrate critical surface tension. The selective segregation is beneficial to demolding in UV embossing since only small amount of release added can result in large decrease of the mold–resin interfacial energy difference leading to easy demolding and high replication fidelity.

Synthesis of polymer/Laponite nanocomposite latex particles via emulsion polymerization using silylated and cation-exchanged Laponite clay platelets

Abstract We report the synthesis and characterization of polymer/Laponite nanocomposite latex particles through emulsion polymerization using organically modified Laponite clay platelets as seeds. Two approaches were adopted for the organic modification of Laponite. The first one is based on the grafting of either γ-methacryloyloxy propyl dimethyl-methoxysilane (γ-MPDES) or γ-methacryloyloxy propyl triethoxysilane (γ-MPTES) on the clay edges. The other strategy consists in exchanging the clay interlayer sodium ions by either a free radical initiator, 2,2-azobis(2-methyl propionamidine)hydrochloride (AIBA) or a cationic vinyl monomer, 2-(methacryloyloxy)ethyl trimethyl ammonium chloride (MADQUAT). The grafting was characterized both qualitatively using FTIR and quantitatively using elemental analysis or UV analysis. The results show that the degree of functionalization depends on the nature of the organic modifier. Before performing the emulsion polymerization reaction, the functionalized clay platelets were successfully dispersed in water. Nanocomposite latexes were then synthesized using a mixture of styrene (Styr) and butyl acrylate (BA) and sodium dodecyl sulphate (SDS) as anionic surfactant. An important result of the present work is that clay redispersion in water is a key step of the overall process. The larger the size of the clay aggregates, the poorer the stability of the resulting latex suspension. The morphology and mechanism of formation of the nanocomposite particles are discussed.

Synthesis and characterization of acrylate–oxetane interpenetrating polymer networks through a thermal-UV dual cure process

In the present work, a thermal-UV dual-cure process was performed on acrylate–oxetane systems. A 1:1 molar mixture of difunctional acrylate–oxetane mixture was prepared starting from 2,2-Bis(4-(3-acryloxy-2-hydroxypropoxy)phenyl)propane (BPADA) and 3-ethyl-3-{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane ( OXT-221, DOX). Following a difunctional oxetane-acrylic monomer (OXAC) was synthesized. Starting from the 1:1 molar mixture a heterogeneous IPN is generated by dual cure process: the obtained material is characterized by DMTA curves with two maximum of tan δ peak; a broad damping effect can be expected. In the case of OXAC dual cured system a homogeneous material with no separation domain is obtained, as evidenced by a single tan δ peak in DMTA curves.

Mass transport phenomena during lithographic polymerization of nematic monomers monitored with interferometry

Photopolymerization of liquid-crystalline diacrylates is a versatile tool to make optical films for liquid-crystal display (LCD) enhancement. The constant drive towards LCD’s having an improved front-of-screen performance demands optical films with properties that can be adjusted on (sub) pixel level. Birefringent films made from liquid-crystalline diacrylates allow for the required adjustment of the optical property on (sub) pixel level. In this paper we report on the composition of the acrylate mixture that results in planarly aligned nematic films usable as optical retarder in transflective LCD’s as well as the mass transport phenomena that take place during heating of a mask-exposed birefringent film of liquid-crystalline diacrylates. The mass transport phenomena are studied by interferometry as a function of temperature and time. Upon heating a pronounced surface corrugation arises from the latent image formed during the mask exposure. The surface profile largely depends on lateral feature sizes. For 1×1-mm2 areas the exposed areas rise compared to the nonexposed areas, whereas the opposite is observed for 100×100-μm2 areas. Finally, the direction of the mass transport depends on the molecular orientation of the liquid-crystalline diacrylate. The protrusion formed by lengthwise diffusion is 1.7 times higher than that formed by sidewise diffusion.

Effects of Silicone Acrylate on Morphology, Kinetics, and Surface Composition of Photopolymerized Acrylate Mixtures

Films (ca. 150 microm thick) of twelve acrylate mixtures, which contained various proportions of hydrocarbon acrylates [mainly oligo(ethylene glycol) diacrylate, (OEGDA)] and small amounts of a silicone hexaacrylate (in proportion of 5% or less), were cured on a nickel substrate, and X-ray photoelectron spectroscopy analysis of the nickel-side surface compositions showed that for formulations with and without the silicone hexaacrylate, this surface was enriched with OEGDA and saturated (up to 50%) with the silicone hexaacrylate, respectively. The silicone hexaacrylate phase-separated and formed micelles which migrated to the resin-nickel interface. Silicone hexaacrylate, inherently less reactive, also significantly slowed the photopolymerization of the mixtures. The sequential homopolymerization of OEGDA and silicone hexaacrylate in a formulation was elicited using real-time Fourier transform infrared spectroscopy. The design-of-experiment approach was used to quantify the influence of the components on gelation time and the nickel-side surface composition as well as provide the statistical models to predict these two properties for new compositions.

Modeling of Polymerization Behavior of Mixtures of Acrylates and Olefins via Computer Simulation

Computer simulations are performed to study the polymerization behavior of olefins and acrylates in an effective solvent, a coarse description for vegetable oil derived macromonomers (VOMMs) in solution. Olefin (A) and acrylate (B) are represented by particles with molecular weights MA and MB and limited functionality (with a maximum of two covalent bonds each) on a cubic lattice. A set of interactions between these units, solvent (S) constituents and their relative concentrations (pA, pB, pS) are used to model the perceived behavior of VOMM. Before initiating the polymerization, the system is equilibrated using the Metropolis algorithm. The covalent bonding between monomeric units is implemented stochastically for different reaction probabilities. Growth of each bond type (\(\left( {{\text{A}} - - {\text{B,}}\;{\text{B}} - - {\text{B}}} \right)\)) is studied as a function of polymer concentration p = pA + pB for four different model systems appropriate for VOMMs. The fraction of bond growth as a function of polymer concentration (p) is consistent with laboratory data.

Photopolymerization of thiol–allyl ether and thiol–acrylate coatings with visible light photosensitive systems

The photoinitiated polymerization reactions of thiol–allyl ether and thiol–acrylate mixtures under visible light in the presence of several visible photoinitiating systems have been investigated. Remarkable high yield of conversions as well as fast rates of polymerization are observed; a photoinitiating system based on Rose Bengal/Ferrocenium salt/hydroperoxide is particularly efficient. The role of a large variety of photoinitiating systems and the mechanisms involved in the initiation step are discussed.

Toward the comprehensive spectrochemical imaging of painted works of art: a new instrumental approach

AbstractThis paper introduces novel technologies that will be instrumental in the development of new methods for the Raman spectrochemical imaging of painted works of art. We show that second‐derivative preprocessing diminishes interference from fluorescence. Normalization and mean‐centering of such second‐derivative spectra cast them in the form of unit vectors, the displacement of which from library standards serves as a basis for the instantaneous on‐line identification of artistic pigments and binders. Multivariate measures of displacement are shown to function well in difficult cases such as spectrally similar fatty acid media and pigments diluted to varying degrees in uncharacterized binders. A self‐calibrating technique for background subtraction extracts pure component spectra from pigment–acrylic mixtures. Copyright © 2004 John Wiley &amp; Sons, Ltd.

Thiol−Ene Photopolymerization Kinetics of Vinyl Acrylate/Multifunctional Thiol Mixtures

The photopolymerization of multifunctional thiol (trimethylolpropane tris(3-mercaptopropionate))/vinyl acrylate mixtures as a function of thiol content in the presence and absence of photoinitiators has been investigated using real-time FTIR, thin-film calorimetry, and 2D-COSY NMR. The addition of a multifunctional thiol to vinyl acrylate significantly enhances the conversion of the vinyl double bonds of vinyl acrylate due to the preferential addition of the thiyl radical to the vinyl group. Two separate free-radical polymerization processes, acrylate homopolymerization and thiol/vinyl ester copolymerization, occur simultaneously in thiol/vinyl acrylate mixtures. Thin-film calorimetry and 2D-COSY NMR results are consistent with real-time FTIR results, giving strong evidence for two simultaneous free-radical processes.

Modeling the polymerization behavior of vegetable‐oil‐derived macromonomers in solution by computer simulation

AbstractA computer simulation model was used to study the polymerization behavior of multifunctional, vegetable‐oil‐derived macromonomers. Mixtures of olefins (A) and acrylates (B) were initially randomly dispersed on a cubic lattice of size L3. Interactions between A, B, and the solvent sites were considered with respect to their relative proximity, mobility and some kinetics. The Metropolis algorithm was used to move each functional group (A and B). Stirred and equilibrated samples were prepared before reaction initiation. Reactions between the functional groups were implemented with a bonding probability kαβ, which was subject to the availability of unsaturated bonds. The conversion factor, that is, the growth of A–B bonds, was analyzed for a range of polymer concentrations (p = 0.2–0.8) with different reaction probabilities (i.e., kαβ). A stirred (nonequilibrium) sample did not allow sufficient time for the functional groups to arrange according to the interaction parameters. Therefore, the simulations were rerun with equilibrated samples and were found to be consistent with experimental observations. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1164–1172, 2004

Synthesis and characterization of a new acrylic adhesive mixture for use in ocular strabismus surgery

A new series of acrylic adhesive mixtures was specifically designed for use in strabismus surgery, more precisely to join the rectus muscles to the sclera. These two-part adhesives consisted of a mixture of ethyl cyanoacrylate (CN) and ethyl carboxyacrylate (ECA). ECA acted as a plasticizer imparting flexibility to the CN, and also as a nonreactive diluent, serving to reduce the exotherm in the reaction between CN and eye tissues. In this article, the synthesis of the ethyl carboxyacrylate is described, and the properties of different ethyl cyanoacrylate + ethyl carboxyacrylate mixtures were studied. The curing reaction of the adhesive mixtures was monitored using Fourier transform infrared (FTIR) spectroscopy and scanning differential calorimetry (DSC). The rheological properties of the cured CN-ECA adhesive films were studied using plate-plate rheometer experiments. To quantify the adhesion, single lap-shear tests produced between a rubber and the adhesive mixtures were performed and, to evaluate the adhesion to eye tissues, tensile strength measurements of superior rectus muscle/adhesive mixture/sclera joints were carried out. The 70CN-30ECA (v/v) adhesive mixture provided the most adequate balance between adhesion and mechanical properties in the joining of the superior rectus muscle to the sclera. The glass transition temperature of the CN-ECA adhesive mixtures linearly decreased with increase in the ECA content, and a lower degree of conversion during polymerization was obtained by increasing the ECA content. As a consequence, the CN-ECA mixtures were less stiff than CN, giving better performance in the joining of the rectus muscles to the sclera. Finally, the adhesion of CN was sufficiently decreased in CN-ECA mixtures, and the locus of failure was directed to the adhesive film in the joint between the rectus muscles and the sclera.

On gaseous C 4H 6O 2 compounds in the atmosphere: new insights from collision experiments of the protonated molecules in the laboratory and on aircraft

A variety of mass spectrometric methods and complementary theoretical calculations are used to assess the potential contributions of C 4H 6O 2 isomers to the m/ z=87 ion found in a recent atmospheric field study (Int. J. Mass Spectrom. 223/224 (2003) 733). The analysis of high- and low-energy collision experiments suggests that a ca. 1:1:1 mixture of crotonic acid, vinylacetic acid, and methyl acrylate can account for the experimental findings in the field study. For a more concise assessment, further field studies using complementary approaches for the characterization of atmospheric trace components are recommended.

Controlling the Color of Cholesteric Liquid‐Crystalline Films by Photoirradiation of a Chiroptical Molecular Switch Used as Dopant

AbstractUsing thin films of a cholesteric mixture of acrylates 2 and 3 doped with the chiroptical molecular switch (M)‐trans‐1, photocontrol of the reflection color between red and green is possible. This doped liquid‐crystal (LC) film can be used for photoinduced writing, color reading, and photoinduced locking (via polymerization) of chiral, optically written information.

Inorganic-Organic Cross-Linking in UV Curable Hard Coats Based Upon Vinyltriethoxysilane-Tetraethoxysilane-Polyfunctional Acrylate Hybrid Polymers: A Raman Spectroscopic Study

Hydrolysis, polycondensation and UV-induced radical polymerization processes in binary and ternary mixtures of vinyltriethoxysilane (VTEOS), tetraethoxysilane (TEOS), and several polyfunctional acrylates as reactive diluents were studied by means of FT-Raman and confocal micro-Raman spectroscopy. The study comprises measurements on sols, gels, xerogels, and thin films applied on top of glass slides and polymeric substrates. Characteristic Raman bands are utilized to gain information about the structural evolution, inorganic network connectivity, and organic cross-linking reactions. Supplementary, 29Si-NMR spectroscopic data are considered and correlated with Raman data. Structure-property correlations based on spectroscopic and mechanical data are outlined and discussed. It is demonstrated that thin hybrid polymer films may be studied in-situ by means of confocal micro-Raman spectroscopy.

Preparation of CuII-imprinted microspheres with imidazole groups at the surfaces by surface imprinting polymerization.

CuII-imprinted microspheres with imidazole groups at the surfaces were prepared from a seed emulsion with divinylbenzene as a matrix-forming monomer and CuII as a template by radical polymerization. The seed emulsion was prepared from the polymerization of 1-vinylimidazole, styrene, and n-butyl acrylate mixture by a radical initiator. The obtained microspheres were uniform-sized spherical particles and their average diameter was 0.44 μm based on scanning electron micrography. The adsorption of the CuII ion (0.05 mM) on these microspheres was studied, and compared to non-imprinted ones. The adsorption of CuII ion increased on both microspheres with increasing pH. The template effect was observed, that is, the pH giving 50% adsorption of CuII ion on CuII-imprinted resin was lower by one unit than that on non-imprinted resin. The template effect was also observed for the ZnII ion, but not observed for the CdII ion.

Kinetic Study and New Applications of UV Radiation Curing

AbstractHighly crosslinked polymers can be readily synthesized by photoinitiated polymerization of multifunctional monomers or functionalized polymers. The reaction can be followed in situ by real‐time infrared (RT‐IR) spectroscopy, a technique that records conversion versus time curves in photosensitive resins undergoing ultrafast polymerization upon UV exposure. For acrylate‐based resins, UV‐curing proceeds with long kinetic chains (7700 mol/radical) in spite of the high initiation rate. RT‐IR spectroscopy proved very valuable in assessing the influence of various parameters, such as initiation efficiency, chemical structure of the telechelic oligomer, light intensity, inhibitory effect of oxygen, on polymerization kinetics. Interpenetrating polymer networks can be rapidly synthesized by means of UV irradiation of a mixture of difunctional acrylate and epoxy monomers in the presence of both radical and cationic‐type photoinitiators. The same UV technology can be applied to crosslink solid polymers at ambient temperature, which bear different types of reactive groups (acrylate and vinyl double bonds, epoxy ring). UV radiation curing has been successfully used to produce within seconds weathering resistant protective coatings, high‐resolution relief images, glass laminates and nanocomposites materials.Photoinitiated crosslinking polymerization.magnified imagePhotoinitiated crosslinking polymerization.

A kinetic study in emulsion polymerization of polyurethane‐acrylate hybrids

Polyurethane (PU) anionomer having 2‐ethoxymethacrylate terminal groups was prepared in a methyl methacrylate/n‐butyl acrylate mixture as a reactive diluent, following a prepolymer mixing process. This prepolymer‐acrylic monomer mixture was chain extended in a water/surfactant solution using different dispersion speeds. Stability tests of PU‐acrylic monomer dispersions before polymerization were performed at different temperatures by following the particle size evolution. After the dispersion process the kinetics of batch emulsion polymerization at 70°C using different concentrations of initiator was investigated. Data are compared with published results of batch emulsion copolymerization of methyl methacrylate/n‐butyl acrylate. The effect of triethylamine, used in the prepolymer synthesis, on the emulsion polymerization of acrylic monomers was also studied. The kinetic results indicate that during emulsion polymerization of PU acrylic mixture, some coagulation takes place, mainly due to changes in ionic strength of the medium, before stable latex particles are formed. The presence of the PU prepolymer seems not to affect the kinetics of batch copolymerization of methyl methacrylate/n‐butyl acrylate monomers.

High-rate polymerization of acrylonitrile and butyl acrylate based on a concentrated emulsion

A mixture of acrylonitrile and butyl acrylate was polymerized starting from a concentrated emulsion in water. The polymerization was initiated at room temperature by a redox system, consisting of reductants dissolved in the water phase and an oxidant dissolved in the dispersed phase. The initial polymerization was carried out adiabatically with self-heating until a temperature of about 70 °C was reached; this was followed by additional heating in a water bath at a higher temperature, up to a total polymerization time of 30 min. The conversion thus achieved was higher than that obtained via the adiabatic process alone. An optimum temperature during the additional heating was observed. Because of the gel effect, the molecular weight of the product increased with time and the reaction rate became affected by diffusion. The additional heating enhanced the mobility of the species in the system, thus ensuring a final product with a composition near that of the feed.