Hexanediol Diacrylate Research Articles

Effect of polymer network on thermodynamic stability and switching behavior of the smectic-C_{α}^{*} phase.

A polymer-stabilized liquid crystal based on 4^{'}-(octyloxy)biphenyl-4-carboxylate 2-fluoro-4-((octyl-2-yloxy)carbonyl)phenyl (D16) and 1,6 hexanediol diacrylate as a monomer was prepared by in situ photopolymerization. The selected antiferroelectric liquid crystal contains a fast-switching smectic C_{α}^{*} phase (SmC_{α}^{*}), and the influence of the polymer network on the thermodynamic stability of this phase and its switching behavior under applying time-dependent electric field were studied. Using dielectric spectroscopy and polarizing microscopy, the liquid crystal materials were characterized, and subsequently with the use of the reversal current method (RCM) the current response, especially from the SmC_{α}^{*} phase was carefully analyzed. The current response is complex and also depends on the neighboring liquid crystal phases. In the liquid crystal-polymer system, as well as in the liquid crystal-monomer mixture, a significant shift of the temperature range of the SmC_{α}^{*} phase toward lower temperatures was observed; however, the thermodynamic instability related to the transformation to the crystalline phase was also noted and characterized. Because of the fuzzy phase transitions detected in the liquid crystal-polymer system by dielectric spectroscopy and also because of the lack of the characteristic dielectric signature of SmC_{α}^{*} after polymerization, we proposed the use of the RCM, as a complementary one, to identify the SmC_{α}^{*} phase even in such complex materials.

Photocuring of di-acrylate

Photocuring of multi-functional acrylate films for applications in large scale prints and 3D objects is a radical polymerization process under seriously changing conditions of liquid monomer to solid polymer network. Although a model is available describing this process and experimental data have been obtained for photocuring of hexanediol diacrylate (HDDA), measurements with widely varying light intensity to estimate the kinetic parameters in the model were still lacking. We have carried out such measurements with the aim of generating a proper set of parameters for the model, which then may be used for process optimization. We present results of the curing of thin HDDA films (10 μm) with initiator Irgacure 819, bis(acylphosphine oxide) under irradiation intensity varying in a range of 2–1350 W.m−2. Average conversion of vinyl groups in the films was registered by Fourier Transformed Infrared (FTIR) in transmission mode. A remarkable insensitivity of end conversion (range 78–85%) to light intensity was observed, but conversion rate varied strongly (0.1–6 s−1). Despite the large difference in irradiation and associated macroradical concentration level, a surprising similarity in the shapes of the conversion rate was observed.

Fluorinated photoinitiators: Synthesis and photochemical behaviors

Abstract Two fluorinated photoinitiators, named as 2959-IPDI-F and 2959-IPDI-F-HDDA, were successfully synthesized and characterized. The photochemical behaviors of 2959-IPDI-F and 2959-IPDI-F-HDDA were investigated through the photolysis and polymerization of 1, 6- hexanediol diacrylate. The oxygen inhibition was obviously decreased due to the migration of fluorinated photoinitiator to the surface, which was proved through XPS, SEM-EDS. The higher concentration of photoinitiator at top layer accelerated the polymerization rate and reduced the oxygen sensitivity. A fluorine element enriched and folded surface could be developed only through simple photopolymerization initiated by fluorinated photoinitiators.

Hyperbranched poly(ether amine) (hPEA) as novel backbone for amphiphilic one-component type-II polymeric photoinitiators

To make photoinitiators (PI) to be polymeric and water-soluble is an effective approach to develop the high efficient photoinitiator systems with low-migration, low-toxic and environment-friend. We developed a series of novel amphiphilic hyperbranched polymeric photoinitiators (hPEA-TXs, and hPEA-BPs) by introducing thioxanthone (TX) or benzophenone (BP) moieties into the periphery of the hyperbranched poly(ether amine) (hPEA) comprised of the hydrophilic poly(ethylene oxide) (PEO) short chain and coinitiator amine moieties in the backbone. Compared with their water-soluble low-molecular weight analogues, the resulting hyperbranched polymeric photoinitiators hPEA101-TX, hPEA211-TX, hPEA101-BP and hPEA211-BP could be dissolved very well not only in many organic systems including acrylate monomers, but also in water with high solubility of 10wt%. The photopolymerization kinetics of water-soluble monomer acrylamide (AM) and three hydrophobic multifunctional acrylate monomers initiated by these hyperbranched photoinitiators were investigated in detail by photo-differential scanning calorimetric (photo-DSC). Both hPEA-TXs and hPEA-BPs can initiate photopolymerization of AM as efficiently as their low-molecular weight analogues MGA-TX and MGA-BP, respectively. The final double bond conversion (DBC) of oil-soluble monomer hexanediol diacrylate (HDDA) photoinitiated by these hyperbranched photoinitiators can reach as high as 99%. Especially for photopolymerization of multifunctional monomers initiated by these hyperbranched polymeric photoinitiators, the final DBC of trimethylolpropane triacrylate (TMPTA) and pentaerythritol tetraacrylate (PETTA) can reach 80% and 60%, respectively, which is much higher than that of low-molecular weight photoinitiators.

Fabrication of strong and ultra-lightweight silica-based aerogel materials with tailored properties

Cross-linked silica aerogels are promising, strong, lightweight materials for photolithographic applications. The work presented here details the preparation of ultra-lightweight aerogel materials with tailored properties through the appropriate combination of silica and methacrylate polymer using laser-induced rapid photogelation fabrication technique. For fabrication, an ethanolic solution of hexanediol diacrylate, tetraorthosilicate, Eosin Y and a tertiary amine was prepared. The amounts of reactants were varied to prepare different compositions of aerogel monoliths. The solution was irradiated with a green beam from a low power laser source. The samples, after drying in supercritical ethanol, were characterized using FTIR, BET, SEM, TGA, and a mechanical testing instrument. FTIR data suggests that neither low nor high silica content has an effect on the reactivity of acrylate functionalities during polymer formation. SEM micrographs reveal that variation in silica or polymer content does not produce any phase-separated structures. Instead, uniformly distributed nano-sized polymer–silica structures were obtained for all compositions. Our results suggest that a variety of combinations of mechanical and other properties (such as densities, surface areas, pore sizes, and pore volumes) can be produced through appropriate combination for diverse applications. All these findings provide convincing evidence that the variation of silica and/or polymer content can be used to fabricate aerogels with a variety of properties, which have the depth needed for use in laser-based 3D printing technology of simple or complex structures with nearly any dimensions.

Poly(HDDA)-Based Polymers for Microfabrication and Mechanobiology

ABSTRACTMaterials processing and additive manufacturing afford exciting opportunities in biomedical research, including the study of cell-material interactions. However, some of the most efficient materials for microfabrication are not wholly suitable for biological applications, require extensive post-processing or exhibit high mechanical stiffness that limits the range of applications. Conversely, materials exhibiting high cytocompatibility and low stiffness require long processing times with typically decreased spatial resolution of features. Here, we investigated the use of hexanediol diacrylate (HDDA), a classic and efficient polymer for stereolithography, for oligodendrocyte progenitor cell (OPC) culture. We developed composite HDDA-polyethylene glycol acrylate hydrogels that exhibited high biocompatibility, mechanical stiffness in the range of muscle tissue, and high printing efficiency at ∼5 μm resolution.

Effect of nano-BaTiO3 on thermal, mechanical, and electrical properties of HDDA/TPA photopolymer prepared by a digital light processor RP machine

Abstract The acrylate-based photopolymer consists of tetra-functional polyester acrylate (TPA), and hexanediol diacrylate (HDDA) has been successfully composited with nano barium titanate (BaTiO3) and completely cured via a digital light processor RP machine. The degradation temperature, tensile strength, hardness, resistivity, and dielectric constant of samples were characterized by Thermo Gravimetric Analyzer Hi-Res TGA2950, Universal Tensile Machine JIA701, Hardness Shore D tester, Fluke 117 multimeter, and Agilent B1500A Semiconductor Device Analyzer, respectively. The morphology changes of the samples were also investigated using the JEOL JSM-6390LV scanning electron microscopy (SEM). The results show that the improvement of degradation temperature is not obvious. Furthermore, the modulus elasticity, hardness, and dielectric constant increase as the filler loading increases up to 2 phr, but the resistivity is vice versa. Interestingly, there is an inverse correlation between dielectric constant and resistivity of photopolymer/BaTiO3 nanocomposite.

The Effects of Acrylate Impregnation of Black Spruce Timber as Connectors Strength

Chemical impregnation of black spruce was conducted to enhance the wood embedment capacity. The formulation was made of 1,6 hexanediol diacrylate, trimethylpropane triacrylate, and a polyester acrylate oligomer. A second formulation, same as the first but with 1% wt of SiO2 nanoparticles, was selected to investigate the potential of nanoparticles and to improve the efficiency of the treatment. The wood embedment capacity was carried out by a dowel-bearing test, which was performed for the two treatments and for an untreated wood group. Both treatments showed an increase of strength of nearly 50% when compared to untreated samples. Micrograph views revealed that the impregnation solution penetrated into the wood only up to 100 μm. Hence, with low chemical consumption, the structural bearing capacity can be significantly increased.

Preparation and Characterization of Halloysite Nanocomposites by Rapid Prototyping Technology

Rapid prototyping (RP) is a new technology to fabricate a prototype part layer-by-layer. This technique has been achieved in many industrial sectors, but parts fabricated using this technique exhibit low mechanical properties, this makes it difficult to apply to fast growing applications. This technology can not only effectively save production time and cost of the prototypes, but also produce complicated product. In this study, we investigate the effect of the addition of halloysite nanotubes on mechanical properties of nanocomposites made by the RP process. Test specimens were fabricated using tetrafunctional polyester acrylate (TPA) and 1, 6 hexanediol diacrylate (HDDA) photopolymer as a matrix material and halloysite nanotubes as a reinforcing material. The adhesion between TPA/HDDA and halloysite nanotubes has been improved by using surface modification of a silane coupling agent. When compared with neat photopolymer, the tensile strength of nanocomposites decreased by about 22%, because the halloysites had poor interfacial adhesion. Silane treatment of halloysites using 3-aminopropyl triethoxysilane was succeeded to improve tensile strength of nanocomposites (2 phr halloysite nanotubes) by 31%.

A kinetics study of diacrylic-styrene crosslinking copolymerization

Unsaturated acrylic resins such as hexanediol diacrylate (HDDA) are widely used in coating and adhesive materials because they provide excellent bonding properties and cosmetic surface finish. Styrene (St) monomer is often added to reduce the resin viscosity and facilitate acrylic reaction. In this study, we used an integrated analytical approach including differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectrometry, and rheometry, to monitor the kinetic and rheological changes of the diacrylic-styrene cross-linking polymerization at 100, 110 and 120 °C. Tert-butyl peroxybenzoate (TBPB) was used as initiator. It was found the reaction system gelled at <2 % conversion and overall conversions could only reach 94–95 % because of resin vitrification, suggesting most addition reactions were diffusion-controlled due to very low molecular mobility in the gel stage. Although conversions of HDDA and St, calculated from respective characteristic C=C absorption peak areas from isothermal FTIR sepectrum, followed the azeotropic co-polymerization pathway closely, styrene consumption was favored because of the lower molecular weight and higher mobility of styrene making it transfer comparatively faster than HDDA with pending double bonds.

Synthesis of ultrathin poly(methyl methacrylate) model coatings bound via organosilanes to zinc and investigation of their delamination kinetics.

Polymer coatings are widely used to protect metals from corrosion. Coating adhesion to the base material is critical for good protection, but coatings may fail because of cathodic delamination. Most of the experimental studies on cathodic delamination use polymers to study the corrosion behavior under conditions where the interfacial chemistry at the metal(oxide)/polymer interface is not well-defined. Here, ultrathin linear and cross-linked poly(methyl methacrylate) [PMMA] coatings that are covalently bound to oxide-covered zinc via a silane linker have been prepared. For preparation, zinc was functionalized with vinyltrimethoxysilane (VTS), yielding a vinyl monomer-covered surface. These samples were subjected to thermally initiated free radical polymerization in the presence of methyl methacrylate (MMA) to yield surface-bound ultrathin PMMA films of 10-20 nm thickness, bound to the surface via Zn-O-Si bonds. A similar preparation was also carried out in the presence of different amounts of the cross-linkers ethylene glycol diacrylate and hexanediol diacrylate. Functionalized and polymer-coated zinc samples were characterized by infrared (IR) spectroscopy, secondary ion mass spectrometry (SIMS), ellipsometry, and X-ray photoelectron spectroscopy (XPS). Coating stability toward cathodic delamination has been evaluated by scanning Kelvin probe (SKP) experiments. In all cases, the covalently linked coatings show lower delamination rates of 0.02-0.2 mm h(-1) than coatings attached to the surface without covalent bonds (rates ∼10 mm h(-1)). Samples with a higher fraction of cross-linker delaminate slower, with rates down to 0.03-0.04 mm h(-1), compared to ∼0.3 mm h(-1) without cross-linker. Samples with longer hydrophobic alkyl chains also delaminate slower, with the lowest observed delamination rate of 0.028 mm h(-1) using hexanediol diacrylate. For the coatings studied here, delamination kinetics is not diffusion limited, but the rate is controlled by a chemical reaction. Several possibilities for the nature of this reaction are discussed; radical side reactions of the oxygen reduction are the most likely path of deadhesion.

Synthesis, photophysical and photochemical studies of benzophenone based novel monomeric and polymeric photoinitiators

Abstract Four novel benzophenone-containing photoinitiators (monomers PI-1 and PI-2 and their polymers PPI-1 and PPI-2) were prepared from alkyl α-hydroxymethacrylates. PI-1 was synthesized from reaction of tert-butyl α-bromomethacrylate and 4-hydroxybenzophenone followed by cleavage of tert-butyl groups using trifluoroacetic acid. PI-2 was synthesized from reaction of ethyl α-bromomethacrylate and 3-benzoylbenzoic acid. Thermal polymerization of PI-1 and PI-2 was performed using 2,2′-azobis(isobutyronitrile). PI-1 and PPI-1 show UV absorption (289 and 294 nm) which are red-shifted compared to benzophenone (252 nm), PI-2 (255 nm) and PPI-2 (252 nm). All of the photoinitiators give phosphorescence emissions from their n–π* states. The photopolymerizations of triethylene glycol dimethacrylate, 2-hydroxyethyl methacrylate and hexanediol diacrylate initiated by PI-1, PI-2, PPI-1, PPI-2 and benzophenone were studied by photo-differential scanning calorimeter using N,N-dimethyl-p-toluidine as coinitiator. Polymeric photoinitiators were found to have higher efficiencies than benzophenone and monomeric ones. Photopolymerization results are also compared to that of an alkyl α-hydroxymethacrylate-based photoinitiator previously reported by us; and the influence of monomer structure on polymerization efficiency is discussed.

Defined polymer shells on nanoparticles via a continuous aerosol-based process

A continuous aerosol-based process is described for the encapsulation of nanoparticles with a thin polymer shell. The process is essentially based on directed binary collisions between gas-borne core particles and liquid monomer droplets carrying opposite electrical charges, followed by photo-initiated polymerization. Once the two streams are mixed together, the process runs to completion on a time scale of about 2 min or less, required for coagulation and polymerization. Gold, silica, and sodium chloride nanoparticles were successfully coated by this technique with PHDDA [poly(hexanediol diacrylate)] and/or crosslinked PMMA [poly(methyl methacrylate)]. It was found that all core materials as well as agglomerates were wettable at room temperature and that the spreading kinetics of the monomer were fast enough to cover the core particles uniformly within the time scale provided for coagulation. The shell thickness depends on the volume ratio between core particles and monomer droplets. This was demonstrated for a combination of monodisperse silica spheres (d = 241 nm) and polydisperse methyl methacrylate droplets, resulting in a theoretical shell thickness of 18 nm. There was very good agreement between measurements by TEM and electrical mobility spectroscopy. The results revealed that about 90 % or more of the core–shell structures were formed from 1:1 collisions between a core particle and a single monomer droplet.

Preparation of a porous functional polymer and its application in the separation of small molecules in conjunction with HPLC

A porous functional polymer was prepared by in situ polymerization reaction. In this process, azobisisobutyronitrile was used as the initiator; hexanediol diacrylate (HDDA) and butyl methacrylate (BMA) as co-monomers; dodecyl alcohol as the porogenic solvent. The conditions of polymerization were optimized. The morphology of the polymer was investigated by scanning electron microscopy. Chemical groups in the monolith were assayed by infrared spectrometry. The pore size distribution was determined by mercury intrusion porosimetry and nitrogen adsorption–desorption. Finally, the functional polymer, a poly(HDDA-co-BMA-co-EDMA) monolith, was used as the stationary phase of high performance liquid chromatography (HPLC) to separate small molecules.

Fabrication of Ceramic Component Using Constrained Surface Microstereolithography

Microstereolithography (MSL) is one of the solid free form fabrication (SFF) techniques which involve fabrication of 3 dimensional (3D) objects by means of laser assisted photopolymerization of resin. The resolution and capability to fabricate high aspect ratio structures makes it suitable technique for the fabrication of Micro Electro Mechanical Systems (MEMS) and biomedical devices. Silicon micromachining technique on the other hand has the limitation in fabricating high aspect ratio structures. Also, the ability to fabricate 3D components using wide range of resins makes MSL a versatile technique. Recently resins loaded with ceramic particles have been used to fabricate sub millimetre ceramic devices for MEMS application. However challenge of processing ceramics lies in reducing the viscosity of the suspension for successful recoating and achieving the minimum layer thickness to improve resolution of the part. In the present study ceramic suspensions is prepared using carboxylic acid as dispersant and 1, 6 Hexanediol diacrylate resin. A ceramic structure containing three layers of 50 microns each was fabricated using constrained surface technique and merits and limitations of this technique were investigated.

Fast Proton Conduction Facilitated by Minimum Water in a Series of Divinylsilyl-11-silicotungstic Acid-co-Butyl Acrylate-co-Hexanediol Diacrylate Polymers

Studies of proton transport in novel materials are important to enable a large array of electrochemical devices. In this study, we show that heteropoly acids (HPAs) when immobilized in polymer matrixes have highly mobile protons. Divinyl-11-silicotungstic acid, an HPA, was copolymerized with butyl acrylate and hexanediol diacrylate at various weight percentage loadings from 25% to 85% using UV initiated polymerizations. The resultant films were tan colored flexible sheets of ca. 120 μm thickness. The morphology of these films varied with loading, showing phase separation into clustered HPA above a 50 wt % loading and lamella morphologies above an 80 wt % loading. Water uptake was strongly associated with the HPA clusters, which facilitated transport of protons. This was realized by proton conductivities as high as 0.4 S cm–1 at 95 °C and 95% RH and 0.1 S cm–1 at 85 °C and 50% RH. Pulse field gradient spin echo NMR measurements indicated that water self-diffusion was fast (1.4 × 10–5 and 4.4 × 10–5 cm2 s–1...

Characterization of “Bulk Lithography” Process for Fabrication of Three-Dimensional Microstructures

Various ways of fabricating a three-dimensional (3D) component in a single-layer exposure using spatial variation of exposure dose have been presented in the literature. While some of them are based on dynamic mask process, more recently, a process based on varying intensity of a scanning Gaussian laser beam termed as “bulk lithography” has been proposed. In bulk lithography, the entire varying depth 3D microstructure gets fabricated because of spatial variation of intensity of laser imposed at every point in single layer scan. For the bulk lithography process, this paper first presents experimental characterization of unconstrained depth photopolymerization of resin upon exposure to Gaussian laser beam. Experimental characterization carried out for two resins systems: namely 1,6 hexane diol-diacrylate (HDDA) and trimethylolpropane triacrylate (TMPTA), over relatively wider range of Ar+ laser exposure dose and time, show behavior well beyond Beer–Lambert law. A unified empirical model is proposed to represent the nondimensional depth variation with respect to the time and energy of exposure for both resins. Finally, using these models, successful fabrication of several microstructures including micro-Fresnel lens, textured curved surface, otherwise difficult or impossible to fabricate, is demonstrated. Several advantages of the bulk lithography as compared to other similar processes in the literature are highlighted.

Synthesis and characterization of positively charged interpenetrating double-network hydrogel matrices for biomedical applications

In this study, positively charged interpenetrating double-network (DN) hydrogels of polyvinyl alcohol/polyacrylamide (PVA/PAm) were prepared using bifunctional cationic salt as a crosslinker. The cationic salts were synthesized by the Michael-addition of piperazine (PZ) with butanediol diacrylate (BDDA)/hexanediol diacrylate (HDDA) separately followed by the methylation of the products. The chemical characterization of the quaternary salts was performed using ATR-FTIR and NMR (1H, 13C, DEPT) spectroscopy. The zeta potential of the cationic salts was found to be in the range of 17.6±8.03–20.3±10.1mV for various monomers. Chemical crosslinking (free radical polymerization) and physical crosslinking (freeze–thaw) techniques were employed to crosslink PAm and PVA, respectively. The quaternized salt of BDDA and PZ was used to crosslink the PAm hydrogel network. The thermal stability and the compression modulus of the hydrogel increased, while the displacement value and the water absorption capacity decreased when crosslinker concentration was increased from 1.0 to 4.0mol%. The excellent cell viability (⩾94%) and gel content (⩾92%) suggest that these matrices can be utilized as future biomaterials for biomedical applications.

Fluorinated polymerizable phosphonium salts from PH3: Surface properties of photopolymerized films

An array of highly fluorinated polymerizable phosphonium salts (HFPPS) were synthesized from PH3 and utilized in UV-curable formulations. Inclusion of these salts at very low loading (0.1–1 wt %) into hexanediol diacrylate (HDDA) resulted in hydrophobic surfaces. The water repellency was achieved with short C4F9 fluorocarbon appendages in the monomer as opposed to the bioaccumulative C8F17 appended polymers. The physical properties of these new monomers were also characterized. The molecular architecture of the monomers had a pronounced effect on both their physical properties along with the degree of hydrophobicity imparted in the polymer. Salts utilizing the bis(trifluoromethylsulfonyl)imide anion displayed excellent compatibility with HDDA, while the chloride salts were insoluble. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) confirmed the presence of the HFPPS at the surface of the polymer coating. For the first time this demonstrates how these salts may be used to functionalize the surface of a UV-cured film with ionic species. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2782–2792

Photo‐curable highly water‐repellent nanocomposite coatings

Modification and use of natural products have gained a lot of interest in recent years due to their environmental friendliness and their availability from different sources. In this study, (castor oil)‐based photo‐curable highly hydrophobic coatings were prepared and characterized. Castor oil was first modified with 3‐isocyanatopropyltriethoxysilane and then hydrolyzed prior to the coating preparation. The resulting precursor was mixed with norbornyl acrylate and hexanediol diacrylate, and highly roughened hydrophobic coatings were prepared with the aid of fluorinated/nonfluorinated alkoxysilane coupling agents and hydrophobic fumed nanosilica particles. The coatings were applied on borofloat glass. The addition of fluorine and nanosilica showed a significant impact on the properties of the coatings. As the fluorine and nanosilica contents were increased in the formulations, flame retardancy and the contact angle values of the coatings increased. The surface roughness of the coatings increased with the addition of hydrophobic fumed nanosilica particles. Also, the relation between the surface energy and the contact angle values of the coatings was investigated. J. VINYL ADDIT. TECHNOL., 19:31–38, 2013. © 2013 Society of Plastics Engineers