Photopolymerization synthesis of polyacrylic acid dispersant with methoxysilicon end groups and its application in a nano‐SiO2 aqueous system

In order to improve the dispersity and stability of the nano‐SiO₂ aqueous system with high solid content, a kind of polyacrylic acid dispersant with methoxysilicon end groups (KH590‐PAA) was synthesized by photopolymerization of acrylic acid (AA) initiated with (3‐mercaptopropyl)trimethoxysilane (KH590). After adding KH590‐PAA into the nano‐SiO₂ aqueous dispersion system (20 wt% solid content), the viscosity and the curing time of the system were measured with a rotational viscometer and the inverted bottle method. Moreover, the dispersion mechanism of KH590‐PAA for the nano‐SiO₂ aqueous system was researched by measuring the adsorption capacity, the particle size and the zeta potential of the nanoparticles with a conductivity meter, dynamic light scattering, SEM and TEM, respectively. The results showed that the methoxysilicon groups in KH590‐PAA could react with hydroxyl groups on the surface of nano‐SiO₂ in the process of stirring, which enhanced the adsorption capacity of the dispersant and then increased the surface charge of the particles. Therefore, electrostatic repulsion and steric hindrance effects between the SiO₂ nanoparticles could be further enhanced by adding the KH590‐PAA dispersant, and then the nano‐SiO₂ aqueous system exhibited better dispersity and stability. Besides, the dispersion properties of SiO₂ nanoparticles in water were closely related to the addition amount and the molecular weight of the KH590‐PAA dispersant. © 2018 Society of Chemical Industry     

Environmentally friendly synthesis and photopolymerization of acrylated methyl ricinoleate for biomedical applications

In this study, we aimed to develop an efficient synthesis and photopolymerization of acrylated methyl ricinoleate (AMR) for biomedical applications. During the first step of the synthesis, methyl ricinoleate (MR) and boric acid were esterified via azeotropic distillation in toluene. Afterward, MR–boric acid ester was acrylated with acrylic acid at 165 °C via a boric acid ester acidolysis reaction. The bulk photopolymerization of AMR was performed in the presence of the photoinitiator 2,2-dimethoxy-2-phenyl acetophenone (DMPA) under 365 nm UV irradiation. Even with the use of 0.4% DMPA, a 35% monomer conversion was achieved within 30 min. Moreover, AMR, the plant-oil-based monomer, was also copolymerized with N-isopropyl acrylamide to obtain thermoresponsive hydrogels on the glass surface for biomedical applications. The synthesized materials were characterized by Fourier transform infrared (FTIR) spectroscopy, ¹H-NMR spectroscopy, and thermal characterization via thermogravimetric analysis (TGA) and differential scanning calorimetry techniques. The surfaces were characterized by FTIR and Energy Dispersive X-ray (EDS) spectroscopy. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47969.     

Synthesis and photosensitivity of acryloylmorpholine copolymers with a pendant (meth)acryloyl group

We have developed new photopolymers that have superior waterproof properties and that can easily interact with polyfunctional acrylate compounds, thus serving as hydrophobic photocrosslinking reagents. Acryloylmorpholine monomers whose homopolymers were less moisture absorbing than the usual water‐soluble polymers but were still water soluble to a good degree, were copolymerized with other acryloyl monomers. We then introduced the photosensitive (meth)acryloyl group to side chains of the resulting polymers. Among six copolymers examined, the copolymers composed of acryloyl morpholine, hydroxyethyl acrylate, ethyl, or methyl methacrylate, and methacryloyl isocyanate were found to have nicely balanced hydrophilicity and waterproof properties, in addition to good compatibility with hydrophobic photocrosslinking reagents. The composite polymers thus obtained were confirmed to be promising photopolymers usable even in a highly humid environment. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 684–692, 2003     

Synthesis and characterization of chitosan/poly(acrylic acid) polyelectrolyte complex

Polyelectrolyte complex based on chitosan and acrylic acid monomer by photoinitiated free‐radical polymerization in the absence of crosslinker showed a large transition in swelling in response to changes in pH of surrounding medium. Their ability to swell arises from polyelectrolyte interactions and molecular structure of the complex. The main properties of interest that related to the molecular structure, swelling volumes, glass transition temperature, and elastic modulus of the complex were investigated. The effect of water content, the only variable in the sample component, played an important role in molecular structure of the complex and as a consequence, the extent of intermolecular linkage, especially amide bonds which in turn governed the degree of swelling of the polyelectrolyte complex in this study. The decreased degree of swelling and higher temperature shift of glass transition temperature was found with increased water content, whereas increased modulus of elasticity of dry complex was found in lower water content of synthesis component. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1025–1035, 2002     

Photopolymerization of N,N‐dimethylaminoethylmethacrylate studied by photocalorimetry

Photopolymerization of dimethylaminoethylmethacrylate (DMAEMA) is studied in bulk and in solutions in the presence of different photoinitiators using differential photocalorimetry (DPC). The rate of DMAEMA photopolymerization is slow compared to that of alkylmethacrylates. Bimodal DPC curves of DMAEMA photopolymerization in bulk are obtained. The type I photoinitiators (IRGACURE® 651 and IRGACURE® 1700), which produce free radicals by homolytic fragmentation of photoexcited molecules, are more effective in promoting photopolymerization of DMAEMA. The type II photoinitiators (benzophenone and IRGACURE® 500), which initiate DMAEMA photopolymerization through an H‐abstraction mechanism involving an amino group from the monomer (polymer), are less efficient and favor the formation of partly crosslinked products. The effects of the photoinitiator concentration, temperature, and solvent on the kinetic data are evaluated and discussed. A scheme of photopolymerization of DMAEMA, including the formation of intermediate DMAEMA based macromonomers, is proposed. The main point of the suggested scheme is a high chain transfer to the DMAEMA monomer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 579–588, 2002     

Local dynamics in epoxy coatings containing iron oxide nanoparticles by dielectric relaxation spectroscopy

Nanocomposites of photocurable epoxy resin and epoxy‐modified iron oxide magnetic nanoparticles were analyzed by dielectric relaxation spectroscopy to study the local dynamics at temperatures well below the glass‐transition temperature. Two secondary processes were detected, β and γ processes, but the second one was just detected at lower temperatures in the high‐frequency part of the spectra and moved out of the frequency range at higher temperatures. Data were fitted to the Havriliak–Negami and Arrhenius models, and the obtained parameters were analyzed. Relaxation times of the β secondary relaxation did not change with the nanoparticle content, but the relaxation strength increased. The increase could not be explained when we took into account the molecular origin of the relaxation. The presence of ferromagnetic nanoparticles enhanced the internal field and increased the relaxation strengths. Transmission electron microscopy images showed that the nanoparticles were well dispersed in the matrix, without magnetic agglomerates. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Dynamic photorheological analysis of photopolymerizable urethane dimethacrylate resins with varying diluent content and light fluence

The in situ measurement of dynamic changes in viscosity induced by illumination has been performed on a range of photosensitive urethane dimethacrylates (UDMA) evaluating the response at three different illuminations intensities (1, 2, and 5 W cm^?2) and at three different diluent concentrations (15, 30, and 50%), using 1,6‐hexanediol dimethacrylate (HDDMA). The initial viscosity value ranged between 1 and 10 Pa s for the mixtures with final viscosities approaching 1 × 10⁷ Pa s after illumination. The initial rise in viscosity was analyzed using an exponential model with an exponent ranging from 1.0 to 2.5 with time under exposure. Higher conversion rates were observed with both higher intensity and lower HDDMA content. The analytical approach taken here could aid in developing more sophisticated models that consider simultaneous flow and cure advancement in other thermosets. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Polymerization behavior and polymer properties of eosin-mediated surface modification reactions

Surface modification by surface-mediated polymerization necessitates control of the grafted polymer film thicknesses to achieve the desired property changes. Here, a microarray format is used to assess a range of reaction conditions and formulations rapidly in regards to the film thicknesses achieved and the polymerization behavior. Monomer formulations initiated by eosin conjugates with varying concentrations of poly(ethylene glycol) diacrylate (PEGDA), N-methyldiethanolamine (MDEA), and 1-vinyl-2-pyrrolidone (VP) were evaluated. Acrylamide with MDEA or ascorbic acid as a coinitiator was also investigated. The best formulation was found to be 40 wt% acrylamide with MDEA which yielded four to eightfold thicker films (maximum polymer thickness increased from 180 nm to 1420 nm) and generated visible films from fivefold lower eosin surface densities (2.8 versus 14 eosins/μm²) compared to a corresponding PEGDA formulation. Using a microarray format to assess multiple initiator surface densities enabled facile identification of a monomer formulation that yields the desired polymer properties and polymerization behavior across the requisite range of initiator surface densities.     

Preparation of Iron Filler-Based Photocomposites and Application in 3D Printing

The introduction of metallic fillers to polymers via the photopolymerization approach can endow the composite materials with some unique properties, but the relevant research is still scarce due to the issue of light penetration and inner filter effect. Herein, for the first time the fabrication of photocomposites based on fine iron powder (i.e., a typical kind of metallic filler) is reported in this work. The free radical polymerization of two different acrylate monomers, poly(ethylene glycol) diacrylate and trimethylolpropane triacrylate, is performed in the presence of iron filler under mild conditions (i.e., light emitting diode (LED)@405 nm irradiation at room temperature under air). And the real-time Fourier transform infrared spectroscopy reveals remarkable photopolymerization kinetics of acrylates with high final conversions and fast polymerization rates despite the increasing contents of iron filler in the composites. Interestingly, the 3D printing technique is applied to the iron filler-based composites to produce tridimensional patterns with excellent spatial resolution. This work not only paves the way for the investigation of photocomposites based on metallic fillers through photochemical methods, but also broadens the potential application prospects.