Polymerization Of Acrylic Monomers Research Articles

Multifunctional Role of MoS2 in Preparation of Composite Hydrogels: Radical Initiation and Cross-Linking.

This paper describes the multifunctional effect of molybdenum disulfide (MoS2) that enables the rapid and accessible preparation of nanocomposite hydrogels via a bottom-up design. The MoS2 nanoplatelet forms radical species through a redox reaction with persulfate under aqueous conditions while initiating the polymerization of acrylic monomers and providing noncovalent cross-linking points without requiring external stimuli or extra cross-linkers, leading to the formation of hydrogels that are in situ embedded with inorganic flakes. Furthermore, the addition of MoS2 could induce more rigid and elastic networks compared to those in control hydrogels using a typical cross-linker at the same level; for example, 0.08 wt % MoS2 resulted in a composite hydrogel of which the elastic modulus was 2.5 times greater than that from a hydrogel using N,N'-methylenebis(acrylamide) as the showing phase transition during polymerization. The composite hydrogels are self-healable, taking advantage of reversible physical cross-links. Thus, two cut hydrogel strips could be readily rejoined by heating at 70 °C, and the resulting whole strip showed mechanical strength similar to that of the pristine sample before it was cut. This synthetic approach would give way to the modular design of MoS2-containing composite hydrogels.

Dimethyl Dihydroacridines as Photocatalysts in Organocatalyzed Atom Transfer Radical Polymerization of Acrylate Monomers

AbstractDevelopment of photocatalysts (PCs) with diverse properties has been essential in the advancement of organocatalyzed atom transfer radical polymerization (O‐ATRP). Dimethyl dihydroacridines are presented here as a new family of organic PCs, for the first time enabling controlled polymerization of challenging acrylate monomers by O‐ATRP. Structure–property relationships for seven PCs are established, demonstrating tunable photochemical and electrochemical properties, and accessing a strongly oxidizing 2PC.+ intermediate for efficient deactivation. In O‐ATRP, the combination of PC, implementation of continuous‐flow reactors, and promotion of deactivation through addition of LiBr are critical to producing well‐defined acrylate polymers with dispersities as low as 1.12. The utility of this approach is established through demonstration of the oxygen‐tolerance of the system and application to diverse acrylate monomers, including the synthesis of well‐defined di‐ and triblock copolymers.

Dimethyl Dihydroacridines as Photocatalysts in Organocatalyzed Atom Transfer Radical Polymerization of Acrylate Monomers.

Development of photocatalysts (PCs) with diverse properties has been essential in the advancement of organocatalyzed atom transfer radical polymerization (O-ATRP). Dimethyl dihydroacridines are presented here as a new family of organic PCs, for the first time enabling controlled polymerization of challenging acrylate monomers by O-ATRP. Structure-property relationships for seven PCs are established, demonstrating tunable photochemical and electrochemical properties, and accessing a strongly oxidizing 2 PC.+ intermediate for efficient deactivation. In O-ATRP, the combination of PC, implementation of continuous-flow reactors, and promotion of deactivation through addition of LiBr are critical to producing well-defined acrylate polymers with dispersities as low as 1.12. The utility of this approach is established through demonstration of the oxygen-tolerance of the system and application to diverse acrylate monomers, including the synthesis of well-defined di- and triblock copolymers.

Structural effect of oxazolone derivatives on the initiating abilities of dye-borate photoredox systems in radical polymerization under visible light.

Three photoinitiating systems based on new oxazolone derivatives have been developed and their performance in initiation of radical polymerization of acrylate monomers has been tested by differential scanning calorimetry. The absorption characteristics of the oxazol-5(4H)-ones is compatible with the emission characteristics of different light sources like diode pulse solid state lasers. Thus, the dyes were used as sensitizers which are photoreduced during a photochemical reaction in the presence of phenyltriethylborate salt. Results showed that the increase in the dimensionality of the molecule extends the range of light absorption and increases the efficiency of the photoinitiation process. The photoreduction of the oxazolone–borate complex was studied using steady-state and nanosecond laser flash photolysis. The dye singlet and triplet were found to be quenched by the electron donor via an electron transfer process. Rate constants for the quenching of the excited states were high and were found to depend on the dye structure.

Uncontrolled polymerization that occurred during photoinitiated RAFT dispersion polymerization of acrylic monomers promotes the formation of uniform raspberry-like polymer particles

Uniform raspberry-like polymer particles are prepared by a different type of photoinitiated RAFT dispersion polymerization.

Visible macrophotoinitiators with Si-H: High efficient anti-oxygen inhibition and modified cured polymer materials

The development of multifunctional, highly antioxidant macromolecular visible light initiators has attracted great interest from chemists. This protocol has successfully designed and prepared a series of naphthalimide terminated polysiloxane photoinitiators (ND-HPSOs) containing silicon-hydride, with good compatibility in photopolymerization monomers. These photoinitiators could be generate silyl and carbon radicals under the visible LED light irradiation, demonstrated by the ESR spin-trapping experiment. The results of real-time infrared spectra (RT-IR) show that they could be server as efficient one-component visible photoinitiators with an ability to initiate the polymerization of acrylate monomers in the air. Moreover, the formation of reactive silyl radicals directly affects the reduction or elimination of oxygen inhibition. Meanwhile, the ND-HPSOs exhibited to excellent migration stability in the cured 1,6-hexanediol diacrylate films. Notably, employment the multifunctional photoinitiators ND-HPSOs in the photocuring of polyurethane acrylate (PUA) films could change the surface of photo-cured films from hydrophilicity to hydrophobicity and improve their thermal stability, water and ethanol repellency.

Impact of Catalyzed Radical Termination (CRT) and Reductive Radical Termination (RRT) in Metal‐Mediated Radical Polymerization Processes

Atom Transfer Radical Polymerization (ATRP), a metal‐catalyzed process, is a most powerful method for macromolecular engineering, producing polymers with targeted and low‐dispersity molar masses and with high chain‐end fidelity. This is due to the persistent radical effect, which dramatically reduces the spontaneous radical terminations, prolonging the lifetime of radical chains and the concurrent growth of all polymer chains. Two additional reaction modes that involve metals and organic radicals, however, may negatively affect the controlled polymerization. These are the Catalyzed Radical Termination (CRT) and the Reductive Radical Termination (RRT) and were shown to be particularly important for the polymerization of acrylate monomers. The scope and the mechanistic investigations carried out to elucidate how these processes interplay with ATRP and with each other are outlined in this Minireview.

UV-curable hybrid organic-inorganic membranes for the use as PEM in fuel cell

The series of membranes were prepared by UV-initiated polymerization of acrylic monomers (acrylonitrile AN, acrylic acid AA and potassium 3-sulfopropylacrylate SPAK) at the presence of photoinitiator (2,2-dimethoxy-2-phenylacetophenone (DMPA)) and cross-linker ethyleneglycole dimethacrylate (EGDMA), and simultaneous sol-gel process in TEOS-based sol-gel system. Characterization of the obtained nanocomposites includes measurements of proton conductivity, thermal behaviuor, water/methanol uptake, free surface energy. The synthesized membranes have high proton conductivity (10-2 Sm/cm) and other properties allowing to consider them as promising candidates for fuel cell application.

Colloidal silica bearing thin polyacrylate coat: A facile inorganic modifier of acrylic emulsions for fabricating hybrid films with least aggregation of silica nanoparticles

Novel nano-composite emulsions consisting of colloidal silica particles covered with thin polyacrylate coat (PreEm) were successfully prepared with the aid of a nonionic surfactant having a low cloud point (Tcp = 40 °C). This nonionic surfactant first deposited on the surface of colloidal silica particles above its Tcp to provide the sites for adsorption and the following polymerization of acrylic monomer. Scanning transmission electron microscopy of the colloidal particles obtained after the polymerization indicated the presence of very thin coat layer of polyacrylate (c.a., 1–3 nm nm in thickness) around silica nanoparticles. These PreEm particles were readily incorporated into the ordinary acrylic emulsions (AcEm) to obtain silica/ polyacrylate mixed emulsions (PreEm/ AcEm). It was revealed that the mixed emulsions can give transparent coating films at a silica/polyacrylate ratio below 150/100 in which the colloidal particles were distributed in the polymer matrix without aggregation. This morphology was in sharp contrast with the particle aggregation morphologies shown by the films obtained from the naked colloidal silica-AcEm mixed emulsion and the conventional nanocomposite emulsion consisting of silica particles covered with thick polyacrylate coat. The PreEm/ AcEm films exhibited increased hardness with increasing the silica contents to 150%. These data supported the effectiveness of PreEm in controlling the properties of silica-polyacrylate hybrid films.

Core-shell magnetic particles obtained by seeded suspension polymerization of acrylic monomers

Abstract Core-shell magnetic polymer particles were synthesized by seeded suspension polymerization. The core was made of poly(methyl methacrylate-co-divinylbenzene) and a mixture of magnetite, maghemite and goethite (P(MMA-co-DVB)-M). The shell was composed of poly(glycidyl methacrylate-co-divinylbenzene) (P(GMA-co-DVB)). These particles were characterized by infrared spectrometry (FTIR), thermal analysis (TG), scanning electron microscopy (SEM), dynamic light scattering (DLS) and vibrating sample magnetometry (VSM). The results showed the formation of core-shells with good magnetic properties (≈7.1 emu/g) and good thermal resistance (≈300 oC). The light scattering experiments showed that the particle size of these materials changed from 5-90 microns (core) to 5-120 microns (core-shell). Scanning electron microscopic images were useful to show the formation of P(GMA-co-DVB) shells on P(MMA- co-DVB)-M cores. The materials synthesized in this work have potential to be modified and employed in magnetic separation processes in the biotech and environmental fields.

Superhydrophobicity, conductivity and anticorrosion of robust siloxane-acrylic coatings modified with graphene nanosheets

The effects of low-cost graphene nanosheets in organic coatings were investigated. The hydrophobic organic siloxane-acrylic resin was synthesized by solution polymerization of acrylic monomers while the graphene nanosheets were modified using fluorosilane, and applied on LY12 aluminum substrate via spraying and a two-step coating system. The superhydrophobic, conductive, anticorrosion, self-cleaning, oleophilic and physical behaviors were comprehensively characterized. The results obtained revealed that addition of modified graphene increases the surface conductivity (≥ 2 μS/cm) and the water contact angle (≥ 152°) with low sliding angle (≤ 7°). The polarization measurement showed a positive shift in the corrosion potential signifying an inhibition of the cathodic reaction. Also, the two-step coated sample gave a good corrosion protection barrier as further confirmed by the electrochemical impedance parameters. The coating revealed good resistance to dirt adhesion, and its superhydrophobic-oleophilic property offered a promising application in oil-water separation. The physical integrity of the coatings was not extensively affected including after 120 days of outdoor exposure to snowing, de-freezing and surface wetting.

Surfactant-free emulsion Pickering polymerization stabilized by aldehyde-functionalized cellulose nanocrystals

Aldehyde-functionalized cellulose nanocrystals (CN) with two aldehyde contents were produced by periodate oxidation and gentle sonication. The aldehyde-functionalized CNCs were shown to be an effective stabilizer in the Pickering emulsion polymerization of acrylate monomers using potassium persulfate (KPS)/metabisulfite redox initiation system at 50 °C without any added surfactant. The effect of CNC content on the particle size, zeta-potential, colloidal stability and film properties were discussed. CNCs with the highest aldehyde content impart better colloidal stability to the polymer dispersion and lower particle size. The stabilization process was explained by the reaction of bisulfite with aldehyde groups borne by CNC, forming an adduct that contributes to the initiation of the polymerization and nucleation of polymer particles. This favors the effective attachment of CNCs onto the polymer particle, which is prerequisite for the effective Pickering stabilization process. The optical and mechanical properties of the nanocomposite films obtained by simple casting of the polymer dispersion and water evaporation were also investigated by transmittance and dynamic mechanical analysis (DMA). Better transparency was observed for films prepared in the presence of CNCs with the highest aldehyde content, while a reverse trend was noted for the mechanical properties.

Fabrication of porous carbon nitride foams/acrylic resin composites for efficient oil and organic solvents capture

This article reported novel porous carbon nitride foams (CNFs)/acrylic resin composites for effective removal of oils and organic solvents from water. The composites were fabricated by a facile and low-cost method: carbonization of melamine–formaldehyde foams to form CNFs with hierarchal porosity and large specific surface area, following by hydrophobic treatment and in situ polymerization of acrylic monomers. A variety of characterizations including XPS, FT-IR, Raman spectra, XRD, and SEM had been performed to record the preparation process of the composites. The results demonstrated that the hydrophobic oil-absorbing resins were chemically attached onto the external surface of CNFs pores, which was beneficial for oil capture. The oil capture tests revealed that the composites had adsorption capacities of ∼33.5 g g−1 to toluene and ∼20.6 g g−1 to DMF, when 15 wt% MCNFs were loaded. The excellent oil capture performances were owing to the combination of CNFs with oleophilic polymeric chains, which not only generated strong capillary and penetration interaction for oil absorption, but also provided large volume of space for oil storage. Despite of the high adsorption capacity, the composites also showed fast capture rate, good recyclability, and oil retention property, making them versatile candidates to satisfy the practical removal of oils and organic solvent from water.

Mid-Chain Radical Migration in the Radical Polymerization of n-Butyl Acrylate.

The occurrence of intramolecular transfer to polymer in the radical polymerization of acrylic monomers has been extensively documented in the literature. Whilst it has been largely assumed that intramolecular transfer to polymer leads to short chain branches, there has been some speculation over whether the mid-chain radical can migrate. Herein, by the matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry (MS) of poly(n-butyl acrylate) synthesized by solution polymerization under a range of conditions, it is shown that this mid-chain radical migration does occur in the radical polymerization of acrylates conducted at high temperatures, as is evident from the shape of the molecular weight distribution. Using a mathematical model, an initial approximation of the rate at which migration occurs is made and the distribution of branching lengths formed in this scenario is explored. It is shown that the polymerizations carried out under a low monomer concentration and at high temperatures are particularly prone to radical migration reactions, which may affect the rheological properties of the polymer.

Thermally conductive adhesives from covalent-bonding of reduced graphene oxide to acrylic copolymer

ABSTRACTThis work reports about the enhancement of the thermal conductivity of an acrylic pressure-sensitive adhesive (PSA) with the incorporation of functionalized and reduced graphene oxide (frGO) sheet in the composition. Bifunctional isocyanatoethylmetharcylate (IEMA) was intercalated (so-called ‘functionalization’) to the GO surface mainly at its –COOH sites. The remaining oxygenated groups on the GO surface were reduced by dimethyl hydrazine. The frGO was successfully incorporated into PSA matrix through in-situ polymerization of acrylic monomers and subsequently crosslinked under UV radiation. The conductivity and the peel strength of the PSA were studied as a function of filler content, filler modification (functionalization and/or reduction), UV-radiation dosage and mode of filler insertion (through in-situ polymerization or mechanical mixing). frGO/PSA showed much better properties than the PSA system with bare or IEMA-functionalized unreduced GO. In-situ polymerization was found to be more effective method for frGO insertion. Within the range of filler content (0.0–1.0) wt% and UV-radiation dosages of (400–3000) mJcm−2, the thermal conductivity and peel strength of the acrylic PSA-system under investigation varied in the range of 0.17–1.03 Wm−1K−1 and 2831–299 gf/25 mm. This is the first report on ‘reduced GO covalently bonded to polymer chain in an adhesive-composition’ providing novel idea to make PSA-system with balanced thermal conductivity and peel strength with perspective for application in miniature electronic industries.

A multifunctionalized macromolecular silicone-naphthalimide visible photoinitiator for free radical polymerization

Abstract Multifunctionalization strategy in the photoinitiator design keeps in step with the requirement of the green chemistry in photopolymerization techniques. Therefore, a multifunctional macromolecular silicone-naphthalimide visible photoinitiator (SND) has been designed and prepared by a convenient thermal polymerization process of 4-(1,3-dioxo-6-(piperidin-1-yl)-1H-benzo[de]isoquinolin-2(3H)-yl)phenyl acrylate (ND-PA) and 3-bis(trimethylsilyoxy)methylsiyl-propylmethacrylate (TSMSPM). Its structure has been confirmed by 1H NMR, 13C NMR, FT-IR and GPC analysis. On one hand, SND has been evidenced as a visible photoinitiator by its successfully initiating the free radical polymerization of acrylate monomers in the presence or absence of a hydrogen donor under the irradiation of different LEDs (405 nm, 455 nm and 470 nm). Furthermore, SND/MDEA (N-methyldiethanolamine) system shows higher photoinitiating activity than that of the commercial CQ (camphorquinone)/MDEA system. On the other hand, this multifunctionalization strategy also brings about some desired modification for cured-materials. After employing only 5 wt% SND as the photoinitiator, for example, a photo-cured film of urethane diacrylate prepolymer (PUA) increases its water contact angles from 70.1° to 101.2°, implying that SND could change the surface property of the PUA cured film from hydrophilic to hydrophobic. Meanwhile, the use of SND as an initiator could significantly improve the resistance against water and ethanol. When the mass fraction of SND increases to 15%, the water and ethanol absorption ratios of the cured PUA films decrease from 4.4% to 1.0% and 8.9% to 2.8%, respectively.

Graft Polymerization of Acrylic Monomers onto Lignin with CaCl2–H2O2 as Initiator: Preparation, Mechanism, Characterization, and Application in Poly(lactic acid)

Effective utilization of abundant industrial lignin has growingly attracted much attention besides potential environmental issues. Although chemical graft polymerization modification is one facile strategy for extending its applications, it remains an intractable challenge to select a highly efficient initiation system. We herein have attempt to understand the CaCl2–H2O2 system in initiating the graft polymerization of acrylic monomers onto acetic acid lignin (AAL) and biobutanol lignin (BBL). The initiation system is found to be highly efficient and selective, as proved by the successful graft of polyacrylates onto them, and a possible mechanism is also proposed. Thermal analysis shows that the graft modification results in a higher glass transition temperature and higher thermal stability of lignin. The graft modification make both AAL and BBL become more hydrophobic than before modification. Moreover, adding a small amount of lignin-graft-polyacrylate can considerably improve the UV blocking capability...

Dopamine-Triggered One-Step Polymerization and Codeposition of Acrylate Monomers for Functional Coatings.

Surface modification has been well recognized as a promising strategy to design and exploit diversified functional materials. However, conventional modification strategies usually suffer from complicated manufacture procedures and lack of universality. Herein, a facile, robust, and versatile approach is proposed to achieve the surface functionalization using dopamine and acrylate monomers via a one-step polymerization and codeposition process. The gel permeation chromatography, proton nuclear magnetic resonance, liquid chromatography-mass spectrometry, and UV-visible spectra results indicate that dopamine possesses the capability of triggering the polymerization of acrylate monomers into high-molecular-weight products, and the inherent adhesive ability of polydopamine can assist the polymerized products to deposit on various substrates. Besides, protein-resistant, antibacterial, and cell adhesion-resistant surfaces can be easily fabricated via the finely designed integration of corresponding acrylate monomers into the codeposition systems. This approach of in situ polymerization and codeposition significantly simplifies the fabrication process and provides more manifold choices for surface modification, which will open a new door for broadening the applications of polydopamine-based coatings.

The effect of tunable morphology on the potential application of p(acrylic acid-co-2-ethylhexyl acrylate)/silica nanohybrids

AbstractThe present study deals with the one-pot synthesis of acrylate copolymers/silica latexes through the use of simultaneous radical polymerization of acrylic monomers and a silica sol-gel precursor. In presence of 3-methacryloxypropyltrimethoxysilane (γ-MPS) and 3-aminopropyltriethoxysilane (APTS), compatibility of acrylate chains to the silica species was improved by the chemical bonds as revealed by Fourier transform infrared spectroscopy (FTIR) analysis. Transmission electron microscopy (TEM) demonstrated the successful formation of p(acrylic acid-co-2-ethylhexyl acrylate)/silica nanohybrids with core-shell morphology. The nanohybrids have been used to modify a glassy carbon electrode (GCE). Cyclic voltammetry and electrochemical impedance spectra were utilized to investigate the properties of the modified electrode in a 1.0mKCl solution that contained 1.0 mmK4[Fe(CN)6]/K3[Fe(CN)6], and the interface properties of electrode surfaces. The result showed a dramatic decrease in redox activity as compared to the bare GCE electrode. This revealed a slight increase in electron transfer resistance and the conductivity of the copolymer oligomers and silica species in the hybrid nanostructure. All the electrochemical results illustrated that the p(acrylic acid-co- 2-ethylhexyl acrylate)/silica nanohybrids could immobilize the selective analytes on the electrodes, which had electrochemical catalytic activity. The barrier properties of the hybrid films were also examined via ultraviolet (UV) absorption capacity of the films. It could be concluded that the adsorption capacity was a function of the silica content and uniform dispersion of the nanoparticles in the resultant films.

Enhancing the coating properties of acrylic/casein latexes with high protein content

Casein-derived materials are highly attractive as a consequence of their environmental friendliness and excellent film-forming properties. Due to the casein hydrophilicity, films containing a large protein content are highly susceptible to water, thus limiting their use in coating applications. A novel approach for synthesizing waterborne acrylic–casein latexes with large content of protein and high degree of compatibilization between both components is presented. The employed synthesis strategy involves the use of a highly methacrylated casein in an emulsifier-free emulsion polymerization of acrylic monomers with the aim of controlling both the fraction of grafted biomaterial and the amount of acrylic chains linked onto the protein backbone. The performance of the resulting materials was evaluated in a water-based coating application. The used methacrylation approach allowed the maximum compatibilization of 33% of casein in the hybrid polymer. The as-obtained casein-derived films were proven to exhibit superior water resistance, which would open a new possibility for designing biobased coatings in several fields.