Siloxane-containing Bifunctional Epoxide Together with Multi-functional Acrylates to Improve the Performance of Holographic Gratings

Well-defined transmission holographic gratings with high diffraction efficiency were fabricated by irradiating a mixture of dipentaerythritol penta-/hexa-functional acrylates, 1-vinyl-2-pyrrolidone and 1,3-bis(3-glycidoxypropyl)-1,1,3,3-tetramethyldisiloxane or 1,3-bis[2-(1,2-epoxycyclohex-4-yl)ethyl]-1,1,3,3-tetramethyldisiloxane in the absence (photo-polymer systems, 30 : 10 : 60 in weight ratio; 80 or 55% efficiency) or presence (holographic polymer dispersed liquid crystal systems: 45 : 9 : 36 : 10 in weight ratio; 83 or 67% efficiency) of commercial liquid crystalline compound E7 with diphenyliodonium hexafluorophosphate and 3,3′-carbonylbis(7-diethylaminocoumarin) photo-initiating system by Nd:YAG laser (λ = 532 nm). When the ratio of dipentaerythritol penta-/hexaacrylate and 1,3-bis(3-glycidoxypropyl)-1,1,3,3-tetramethyldisiloxane was changed to 50 : 40 in photo-polymer system, the diffraction efficiency increased to 84%. They had smooth surface morphologies with regulated spacing. In polymer dispersed liquid crystal system, the same ratio of dipentaerythritol penta-/hexaacrylate and siloxane-containing epoxides gave the best results. 1,5-Bis(3-glycidoxypropyl)-1,1,3,3,5,5-hexamethyltrisiloxane and 1,5-bis[2-(1,2-epoxycyclohex-4-yl)ethyl]-1,1,3,3,5,5-hexamethyltrisiloxane gave high diffraction efficiency with 10% E7 (97% and 75%). The trisiloxane derivatives gave gratings with considerably or moderately reduced angular deviation (0.83, 0.66 degree for trisiloxane from 1.2, 0.7 degree for disiloxane derivatives, respectively for signal beam, and 0.76, 0.70 degree from 1.1, 1.0 degree for the reference beam at 32 degree of external incident angle) from Bragg profile, namely 5.2 and 4.5% volume shrinkage for trisiloxane, and 7.5, 5.6% for disiloxane derivatives, respectively. Gratings with diffraction efficiency over 95% with the narrowest angular selectivity of 4.0 degree was obtained when trimethylolpropane triacrylate was used together with 1,5-bis[2-(1,2-epoxycyclohex-4-yl)ethyl]-1,1,3,3,5,5-hexamethyltri-siloxane (50 : 40) and 5% E7. These gratings were actually used to store real images.     

Diffraction grating in a holographic polymer dispersed liquid crystal based on polyurethane acrylate

Diffraction modes of holographic grating were fabricated with polyurethane acrylates of various monomers, and with various film compositions, irradiation intensities, cell gaps and reading angles. An optimum monomer composition, LC content and irradiation intensity were obtained in terms of diffraction efficiency. Of the two types of multifunctional acrylate examined, dipentaerythritol penta-/hexa-acylate (DPHPA) gave better diffraction efficiency than the trimethylolpropane triacrylate (TMPTA) throughout the monomer compositions tested. This was interpreted in terms of high elasticity of the high functionality monomer. The existence of an optimum irradiation intensity at fixed resin composition was interpreted in terms of optimum rate of cure. A monotonic increases of diffraction efficiency with cell gap and interbeam angle were also noted, implying that the grating was formed uniformly as visualized by scanning electron microscopy.     

A study of the effects of thiols on the frontal polymerization and pot life of multifunctional acrylate systems with cumene hydroperoxide

In an effort to create frontal polymerization systems with a “fail‐safe” curing mechanism, we studied the effects of thiols on the thermal frontal polymerization velocity and pot life of a mixture of a multifunctional acrylate, kaolin clay (filler), and cumene hydroperoxide with either trimethylolpropane tris(3‐mercaptopropionate) or 1‐dodecanethiol (DDT). The acrylates were trimethylolpropane triacrylate, trimethylolpropane ethoxylate triacrylate, 1,6‐hexanediol diacrylate, and di(ethylene glycol) diacrylate. Without a thiol, frontal polymerization did not occur. The front velocity increased with the concentration of either thiol, which has not been observed with peroxide initiators. The use of DDT yielded longer pot lives than the trithiol. The front velocities were inversely related to the pot lives. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3850–3855     

Effects of thiols,lithium chloride,and ethoxylated monomers on the frontal polymerization of a triacrylate

Thermal frontal polymerization is a process in which a localized reaction propagates through an unstirred system by the coupling of the thermal diffusion and the Arrhenius kinetics of an exothermic polymerization. With multifunctional acrylates, such as trimethylolpropane triacrylate (TMPTA‐n), front temperatures can reach 250 °C, resulting in smoke from unreacted peroxide. Addition of a thiol lowers the front temperature and the front velocity due the copolymerization between the thiol and the acrylate, with some formulations not sufficiently reactive to sustain frontal polymerization. The effects of molecular weight per thiol and functionality of thiol on front temperature and velocity were studied in the frontal copolymerization of TMPTA‐n/trimethylolpropane ethoxylate triacrylate and different thiols. We also investigated the front temperature and velocity for a system containing triacrylate and dodecyl acrylate. Finally, the effects of lithium chloride in the presence of thiol on the front velocity and front temperature were studied. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

紫外光快速固化的树枝状丙烯酸酯齐聚物的制备和性能

通过乙二胺(EDA)和三羟甲基丙烷三丙烯酸酯(TMPTA),以甲醇为催化剂,在30℃进行6小时Michael加成反应,可制得含多个双键的树枝状丙烯酸酯齐聚物(DAO).与相似分子量的线性丙烯酸酯齐聚物相比,DAO粘度低,用作紫外光固化树脂,其固化速度快,且固化产物硬度好,耐溶剂性好.     

Controlling final morphologies of two-step polymerization induced phase separated blends of trimethylolpropane triacrylate/acrylate copolymer through copolymer molecular weight

Effect of molecular weight of a thermoplastic copolymer on final morphology of polymerization induced phase separation of trimethylolpropane triacrylate/copolymer blends have been studied. Two acrylate copolymers, ACHM and ACLM, mainly based on methyl methacrylate, butyl acrylate and styrene were synthesized with high and low molecular weight, respectively. Final morphology of TMPTA/ACHM and TMPTA/ACLM blends were investigated by optical microscopic observation of ensemble of surface and bulk phase separation status points of view. Image analysis were done to provide related characteristic length scales.Polymerization induced phase separation of TMPTA/ACHM and TMPTA/ACLM resulted in different final morphologies with different characteristic length scales, which was attributed to the kinetic effect of the copolymer chains mobility during two-step phase separation induced during the thermal history and UV-irradiation periods.     

Photopolymerizable acrylated hyperbranched polyisophthalesters used for photorefractive materials : I. Synthesis and characterization

UV-curable acrylated hyperbranched prepolymers with different numbers of acrylic end-groups were synthesized by modifying the hyperbranched polyisophthalester (HPIPE) with hydroxyethyl acrylate and β-naphthol, and characterized by FT-IR, ¹H NMR and VPO measurements. The effect of naphthyl end-group concentration of the prepolymer on their refractive index (RI) was investigated by an Abel Refractive Apparatus. It was found that the RI increases gradually as naphthyl end-group concentration increases. The acrylate-modified HPIPEs with or without co-monomer trimethylolpropane triacrylate addition were photopolymerized rapidly in the presence of a photo-fragmenting initiator under UV irradiation. Thermal properties of the UV-cured films were also studied by DMTA and TGA measurements.     

Fast growing dendritic poly(ester-amines) from alternate reaction of EDA and TMPTA

Starting with ethylene diamine (EDA) as the core, dendritic poly(ester-amines) were prepared from directly alternate reaction of EDA and trimethylolpropane triacrylate (TMPTA) under mild conditions without protection-deprotection steps. Multiple reactive hydrogen atoms in EDA and acrylate groups in TMPTA led to fast growing of dendrimers and the number of their peripheral groups.     

Synthesis and Structure of 1- and 2-Isomers of (Trimethoxysilylmethyl) and (Silatranylmethyl)benzotriazole

We have synthesized 1- and 2-(trimethylsilylmethyl)- and 1- and 2-(trimethoxysilylmethyl)benzotriazoles by reaction of 1,2,3-benzotriazolylsodium with trimethyl- or trimethoxy(chloromethyl)silane. We obtained 1- and 2-(silatranylmethyl)benzotriazoles by transesterification of the latter with triethanolamine.     

Beaded reactive polymers 3 effect of triacrylates as crosslinkers on the physical properties of glycidyl methacrylate copolymers and immobilization of penicillin G acylase

Various glycidyl methacrylate (GMA) copolymers were synthesized by suspension polymerization, using pentaerythritol triacrylate (PETA), trimethylolpropane triacrylate (TMPTA), and trimethylolpropane trimethacrylate (TRIM) as crosslinking comonomers. These copolymers were evaluated for the immobilization of penicillin G acylase. Broad pore-size distribution that was observed was in the range 5-300 nm. Both surface area and pore volume increased with increase in the mole fraction of crosslinking comonomer (increasing crosslink density). The pore volume of the copolymers was more than doubled by including lauryl alcohol as porogen. Binding of penicillin G acylase (PGA) was quantitative on highly crosslinked copolymers. The expression of bound PGA was better on the relatively more hydrophilic GMA-TMPTA and GMA-PETA copolymer supports compared to the GMA-TRIM copolymers. Among the different copolymers studied, GMA-TMPTA copolymer 7411 exhibited highest activity of immobilized penicillin G acylase (167.4 IU/g) with 35.1% expression.     

Reaction kinetics and microgel particle size characterization of ultraviolet‐curing unsaturated polyester acrylates

The free‐radical reaction kinetics and microgel formation of UV‐curing unsaturated polyester acrylates were studied in terms of the effects of internal maleic and terminal acrylate unsaturations. A triacrylate‐functional monomer, trimethylolpropane triacrylate, was used as the reactive diluent. A time‐resolved Fourier transform infrared technique was used to evaluate the consumption of double bonds and showed that internal (maleic) double bonds were involved in microgel formation at a rate similar to that of the more reactive terminal (acrylic) double bonds. Dynamic light scattering was used to measure the microgel particle size. The introduction of internal unsaturations caused smaller microgels, whereas terminal acrylate unsaturations resulted in larger particle sizes. These results were attributed to the higher tendency of the internal maleic double bonds toward intramolecular cyclization reactions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6544–6557, 2006     

The role of 1-octyl-3-methylimidazolium hexafluorophosphate in anticorrosion coating formula development

A hydrophobic ionic liquid (1-octyl-3-methylimidazolium hexafluorophosphate, C₈mimPF₆) with a function of inhibiting corrosion was encapsulated at different concentrations in the copolymer of poly (methyl methacrylate) and poly (butyl acrylate) through miniemulsion polymerization. These latexes were coated on steel samples whose corrosion properties were evaluated by electrochemical techniques. It was found that increasing the C₈mimPF₆ concentration from 0 wt% to 30 wt%, the corrosion inhibition efficiency was remarkably improved from 41% to 89% based on the charge transfer resistance and from 64% to 87% based on the corrosion current density, respectively. The ionic liquid did not attend the reaction during latex preparation but behaved as corrosion inhibitors on the steel surface. Such an anticorrosion effect could be ascribed to the physical adsorption of the C₈mim⁺ cation on the reaction sites and the hydrophobicity enhancement resulting from the hydrophobic PF₆^? anion.     

Two-photon microstructure-polymerization initiated by a coumarin derivative/iodonium salt system

Two-photon polymerization initiated by a bimolecular initiating system composed of 7-diethylamino-3-(2^′-benzimidazolyl)coumarin and diphenyliodonium hexafluorophosphate was investigated. The photosensitizer has been proven to possess large two-photon absorption cross-section for 800 nm femtosecond laser. The sensitizer/coinitiator system has high photosensitivity for the photopolymerization of methyl methacrylate. This photopolymer system has been demonstrated for fabricating three-dimensional microstructure.     

The influence of silicon-containing acrylate as active diluent on the properties of UV-cured epoxydiacrylate films

A new silicon-containing acrylate, which can be a good active diluent for UV-curable epoxydiacrylate systems, was prepared by reacting N-cyclohexyl-γ-aminopropylmethyldimethoxysilane (CAMS) with trimethylolpropane triacrylate (TMPTA) by Michael-type addition reaction. The reactivity of -NH groups of CAMS with the acrylic groups of TMPTA was characterized by FTIR. The contents of the new active diluent in the UV-cured polymeric films were varied between 5% and 15% by weight. Mechanical, physical, and thermal characterizations of the UV-cured films were investigated: An increase in silicon-containing acrylate content caused a dramatic change of the surface properties of the films, and a decrease in mechanical properties besides the relative elongation. Thermogravimetric analysis of silicon-containing acrylate revealed that incorporating silicon into the structure resulted in a high char yield at 700 °C. Water absorption values of UV-cured films were also affected by the amount of silicon-containing acrylate.     

Reaction Kinetics and Reduced Shrinkage Stress of Thiol-Yne-Methacrylate and Thiol-Yne-Acrylate Ternary Systems

Thiol-yne-methacrylate and thiol-yne-acrylate ternary systems were investigated for polymerization kinetics and material properties and compared to the analogous pure thiol-yne and (meth)acrylate systems. Both thiol-yne-methacrylate and thiol-yne-acrylate systems were demonstrated to reduce polymerization induced shrinkage stress while simultaneously achieving high glass transition temperatures (T(g)) and modulius. Formulations with 70 wt% methacrylate increased the T(g) from 51 ± 2 to 75 ± 1 °C and the modulus from 1800 ± 100 to 3200 ± 400 MPa (44% increase) over the pure thiol-yne system. Additionally, the shrinkage stress was 1.2 ± 0.2 MPa, which is lower than that of the pure methacrylate, binary thiol-yne and thiol-ene-methacrylate control systems which are all > 2 MPa. Interestingly, with increasing methacrylate or acrylate concentration, a decrease and subsequent increase in the shrinkage stress values were observed. A minimum shrinkage stress value (1.0 ± 0.2 MPa) was observed in the 50 wt% methacrylate and 70 wt% acrylate systems. This tunable behavior results from the competitive reaction kinetics of the methacrylate or acrylate homopolymerization versus chain transfer to thiol and the accompanying thiol-yne step-growth polymerization. The crosslinking density of the networks and the amount of volumetric shrinkage that occurs prior to gelation relative to the total volumetric shrinkage were determined as two key factors that control the final shrinkage stress of the ternary systems.     

Photopolymerization of enzymatically synthesized methacrylated poly(caprolactone) with poly(ethylene glycol) macromonomer

Polycaprolactone (PCL) based α,ω-methacrylated macromonomer (DMPCL) was synthesized via enzymatic ring-opening polymerization (eROP) by using Novozyme 435 as the enzyme immobilized catalyst. DMPCL was further photopolymerized with monofunctional poly(ethylene glycol) methyl ether methacrylate (PEGMA-950) macromonomer and trimethylolpropane triacrylate (TMPTA) as tri-functionalized crosslinking agent in glass vials when CHCl₃ was the solvent and Irgacure 819 was the photoinitiator. Ultraviolet (UV) Light Emitting Diode (LED) bulbs enabled photoinduced reactions at room temperature with low heat generation and high reaction efficiency. The obtained gels were characterized with Fourier Transform Infrared Spectroscopy (FT-IR) and Differential Scanning Calorimetry (DSC). DMPCL participated as an effective crosslinking agent in the photopolymerization of PEGMA-950. Combined usage of DMPCL and PEGMA-950 resulted in significantly more effective polymerization than the separate photopolymerizations of these macromonomers.     

Kinetic features of photocuring of oligomeric formulations in the presence of disperse dyes

The kinetics of consumption of double bonds, photoinitiators, and dyes in photocuring of formulations based on oligourethane methacrylate and trimethylolpropane triacrylate was studied. The kinetic parameters and quantum efficiencies of the processes were determined. The contributions from shielding and inhibition to the total polymerization deceleration by the dyes were estimated. The curing of dyed formulation and dye consumption were analyzed in relation to the structural features of the photoinitiators and dyes.     

A novel, neutral hydroxylated octadecyl acrylate monolith with fast electroosmotic flow velocity and its application to the separation of various solutes including peptides and proteins in the absence of electrostatic interactions

A neutral hydroxylated octadecyl monolith (ODM-OH) for reversed-phase capillary electrochromatography has been developed. The ODM-OH was prepared by the in situ polymerization of octadecyl acrylate and pentaerythritol triacrylate (PETA) in a ternary porogenic solvent. Pentaerythritol triacrylate possesses a hydroxyl functional group, which imparts the monolith with a hydrophilic group, thus the acronym ODM-OH. The ODM-OH column exhibited cathodal EOF over a wide range of pH and ACN concentration in the mobile phase despite the fact that it was devoid of any fixed charges. This ODM-OH monolith exhibited stronger EOF than its counterpart the ODM made from the in situ polymerization of octadecyl acrylate and trimethylolpropane trimethacrylate. Similar to ODM, it is believed that the EOF was due to the adsorption of ions from the mobile phase onto the surface of the monolith thus imparting the neutral monolithic column the zeta potential necessary to support the EOF. The higher EOF exhibited by ODM-OH was due to the presence of polar OH groups on its surface, which would favor stronger adsorption of ions from the mobile phase. The wide applications of the neutral ODM-OH column were demonstrated in the separation of a wide range of small and large solutes. As a typical result, the ODM-OH was able to separate proteins quite rapidly yielding 200,000 plates/m.     

Synthesis and characterization of ultraviolet light-curable resin for optical fiber coating

UV-curable polydimethylsiloxane epoxy acrylate (PSEA) and polyethylene glycol urethane acrylate (PGUA) were synthesized and characterized by ¹H-NMR and FTIR spectra. PGUA, PSEA and trimethylolpropane triacrylate (TMPTA) were mixed in different proportions to modify the properties of blends to prepare optical fiber coating. Formulation was optimized by the orthogonal table. When the proportion was PGUA:PSEA:TMPTA=10:4:3, it was used for a single coating (OFC-6). However, the proportion PGUA:PSEA:TMPTA=8:3:2 was used for a primary buffer coating. The rheological behavior and the selection of photoinitiators for OFC-6 were also discussed. The photopolymerization of OFC-6 was inspected by the FTIR spectrum. Results show OFC-6 film is completely cured after irradiated 5 s. The thermal behaviors of the cured film were also investigated by TGA, DMA, etc.     

One‐component thioxanthone‐based polymeric photoinitiators

The photochemical and photophysical properties of new polymeric photoinitiators (PPIs) containing pendant thioxanthone (TX) and amine moieties are studied. The PPIs are synthesized by copolymerization of tert‐butyl 2‐((9‐oxo‐9H‐thioxanthen‐2‐yloxy)methyl)acrylate (TX1) with N,N‐dimethylaminoethyl methacrylate (DMAEM) at two different ratios using free radical polymerization. UV–vis spectra indicate that PPIs possess similar absorption characteristics to TX1 in the violet range (～400 nm; absorption red‐shift 20 nm). The photochemical mechanisms are studied by electron spin resonance (ESR), steady state photolysis, laser flash photolysis, and cyclic voltammetry. ESR studies indicate formation of two different aminoalkyl radicals on the hydrogen donor amine. The triplet state of the PPIs is short‐lived compared to isopropyl thioxanthone and TX1, due to the built‐in amine functionality. Photopolymerization of trimethylolpropane triacrylate (TMPTA) initiated by these photoinitiators under LED exposure at 385 and 405 nm using real‐time FTIR spectroscopy shows that they exhibit higher efficiency than TX/N‐methyldiethanolamine (MDEA) and TX1/MDEA systems with the advantage of a much higher molecular weight that can be very helpful to overcome migration issues. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3370–3378