Curable Polyurethane Acrylate Research Articles

Room Temperature Detachment Nanolithography Using a Rigiflex Polymeric Mold

We report on detachment nanolithography of an organic thin film at room temperature mediated by ultraviolet (UV) exposure. A nanopatterned, UV curable polyurethane acrylate (PUA) mold was placed on a spin-coated organic film made of 4,4'-bis[N-1-napthyl-N-phenyl-amino]biphenyl (NPB) under a low pressure (1-2 bar). A higher work of adhesion at the organic/mold interface induced detachment of the contacting layer on silicon or gold substrate, resulting in well-defined nanopatterns without a residual layer. The detachment was highly improved by a short-term UV exposure, rendering the film surface free from contaminant hydrocarbons with a lower cohesive force, as confirmed by Fourier transform infrared (FTIR) spectroscopy and measurements of contact angle of water.

Investigation of ultraviolet curable waterborne polyurethane acrylate dispersion based on hydroxyl-terminated polybutadiene

A new kind of ultraviolet (UV) curable waterborne polyurethane acrylate dispersion was synthesized based on hydroxyl-terminated polybutadiene (HTPB), poly-(propylene glycol) (PPG), isophorene diisocyanate (IPDI), 2-hydroxy ethyl acrylate (HEA) and dimethylol propionic acid (DMPA) after neutralizing by triethylamine (TEA). 2-Hydroxy-1-[4-2-hydroxyethoxy) phenyl]-2-methyl-1-propanone (Irgacure 2959) was used as a photoinitiator and deionized water as a diluent. Fourier transform infrared (FTIR) analysis was used to identify the chain structure of the UV-curable polyurethane prepolymer based on HTPB and the curing process. Effects of relative content of HTPB and PPG on emulsion stability, resistance to water and ethanol, thermal stability, compatibility of soft and hard segment, as well as the mechanical property of the cured film were investigated.

Fabrication of zinc oxide nanostructures using solvent-assisted capillary lithography

We present a simple solvent-assisted capillary molding method to fabricate zinc oxide(ZnO) nanostructures using an ultraviolet (UV) curable polyurethane acrylate (PUA)mold. A thin film of the ZnO sol–gel precursor solution in methyl alcohol was prepared byspin coating on a solid substrate and subsequently a nanopatterned PUA mold wasbrought into conformal contact with the substrate under slight physical pressure(∼3.5 bar). Afterannealing at 230 °C for 4 h, well-defined ZnO nanostructures formed with feature size down to∼50 nm, aided by capillary rise and solvent evaporation. It was found that the height ofcapillary rise depended highly on the applied pressure. A simple experimental setup wasdevised to examine the effects of pressure, revealing that the optimum pressure ranged from3.5 bar to 5 bar. Also, ZnO nanorods could be selectively grown on patterned regions usingthe seed layer as a pseudocatalyst when the width of the seed layer was larger than∼200 nm.

Pumpless, selective docking of yeast cells inside a microfluidic channel induced by receding meniscus

We present a simple cell docking method induced by receding meniscus to capture non-adherent yeast cells onto microwells inside a microfluidic channel. Microwells were fabricated either by capillary moulding of UV curable polyurethane acrylate (PUA) onto glass substrate or direct replica moulding of poly(dimethyl siloxane) (PDMS). A cell suspension of the budding yeast, Saccharomyces cerevisiae, was introduced into the microfluidic channel by surface tension driven capillary flow and a receding meniscus was subsequently generated by evaporation. As the meniscus progressed, one to multiple yeast cells were spontaneously captured onto microwells by lateral capillary force created at the bottom of the meniscus. Using this cell-based platform, we observed the response of yeast cells upon stimulation by a mating pheromone (alpha-factor) by monitoring the expression of green fluorescent protein (GFP) with time. It was observed that alpha-factor triggered the expression of GFP at 60 min after stimulation and the fluorescence intensity was sustained for an additional 60 min without changes.

UV curable waterborne polyurethane acrylate dispersions based on hyperbranched aliphatic polyester: effect of molecular structure on physical and thermal properties

AbstractA novel waterborne hyperbranched polyurethane acrylate for aqueous dispersions (WHPUDs) based on hydroxy‐functionalized hyperbranched aliphatic polyester Boltorn™ H20 was investigated. The effects of structural composition and crosslinking density have been studied in terms of swellability by water, thermal degradation, viscosity changes as well as transmission electron microscopy (TEM) morphology. The swell ratio showed an increasing trend with the higher concentration of ionic group, which is due to the increased total surface area of particles. The results of thermogravimetric analysis (TGA) for cured WHPUD films indicated good thermal stability with no appreciable weight loss until 200°C. The activation energies were evaluated and were found in the range 154–186 kJ mol−1. It was observed that an increase in hard segment content provoked the increases in thermal degradation temperature and activation energy of waterborne dispersions. The transmission electron photographs revealed that the average particle sizes of aqueous dispersions were in the range 30–125 nm. Owing to the enlargement of the stabilization site, the particle size decreased as the content of carboxyl group and degree of neutralization increased. The viscosity of WHPUDs increased rapidly with increasing the degree of neutralization. Moreover, water showed a favorable viscosity reduction effect. Copyright © 2004 John Wiley & Sons, Ltd.

Effect of polymer structure on the morphology and electro-optic properties of UV curable PNLCs

Polymer network liquid crystals (PNLC) were prepared from UV curable polyurethane acrylate (PUA) and a nematic liquid crystal mixture (E7) at a fixed film composition of 1.5/8.5 (polymer/LC) by weight. The polymer networks were obtained upon curing the reactive mixture of hydroxyethyl acrylate (HEA) terminated polyurethane prepolymer, monoacrylate and triacrylate (4/3/3). The effects of prepolymer molecular structure viz., length of polyurethane (PU) segment, molecular weight ( M n) and functionality ( f) of polyol(PPG), and type of hard segment were studied in terms of morphology, voltage–transmittance relationship, off-state transmittance–temperature relationship, and thermal properties of the films. Aromatic diisocyanate (TDI) segment of PU showed greater chemical affinity with aromatic LC molecules and gave smaller domain size resulting in higher threshold ( V 10) and driving ( V 90) voltages. The increase in prepolymer molecular weight gave larger polymer–LC phase separation and decreased V 10 as well as V 90, together with smaller nematic–isotropic transition temperature depression. Increase in functionality and decrease in M n of PPG gave smaller domain size, smaller decay time, greater V 10 and V 90, longer rise time, and greater depression of T NI in film.

Polymer network liquid crystals from u.v. curable polyurethane acrylate

Polymer network liquid crystals (PNLC) were prepared from u.v. curable polyurethane acrylate and a nematic liquid crystal mixture (BL001) at a fixed film composition of 2/8 (polymer/LC) by weight. The polymer networks were obtained upon curing the reactive mixture of hydroxyethyl acrylate terminated polyurethane prepolymer, monoacrylate and triacrylate (4/3/3 or 4/4/2). The effects of photoinitiator (PI) concentration, prepolymer molecular weight and cure temperature were studied in terms of morphology, off-state transmittance–temperature relationship, thermal and electro-optic performance of the films. It was found that an optimum PI concentration exists. Below and above the optimum concentration, phase separation is too slow and too fast, respectively, and proper morphology is not obtained regarding the electro-optic performance. The increase in prepolymer molecular weight gave larger phase separation and decreased threshold ( V 10) as well as driving ( V 90) voltages, together with reduced heating–cooling hysteresis and depression of nematic–isotropic transition temperature. Cure at and slightly below the isotropic temperature gave ideal morphology for PNLC giving rise to the lowest V 10 and V 90.

Preparation and properties of UV-curable polyurethane acrylate ionomers

Ultraviolet (UV)-curable polyurethane acrylate ionomer (PUAI) prepolymers were synthesized from isophorone diisocyanate (IPDI), poly(methylene ether) glycol (PTMG), 2,2-bis(hydroxymethyl) propionic acid (DMPA), triethylamine (TEA), 2-hydroxy ethyl acrylate (HEA), and dibutyl tin dilaurate (DBT) as a catalyst. UV-curable polyurethane acrylate ionomer aqueous dispersion was formulated from the prepolymers, water (30 wt %), and 1-hydroxycyclohexylhenyl ketone (Irgacure 184) as a photoinitiator. The films of UV-cured polyurethane acrylate ionomer were formed by curing the dispersion using a medium-pressure mercury lamp (80 W/cm; λ max = 365 nm). Gel content decreased with increasing water content in the aqueous dispersion. Effects of DMPA content and molecular weight of PTMG and the degree of neutralization on the physical properties were investigated. It was found that the storage modulus increased with increasing DMPA content. Tensile modulus and strength decreased with increasing the molecular weight of PTMG from 650 to 2000. The glass transition temperature shifted to a higher temperature as the content of DMPA increased. As the degree of neutralization increased, the tensile strength and modulus decreased. However, the elongation at break increased. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:2153–2162, 1998