Acrylate nanolatex via self-initiated photopolymerization (original) (raw)
Related papers
Macromolecular Chemistry and Physics, 2011
ABSTRACT Two novel photoinitiator-free approaches to photopolymerize acrylic monomers with a conventional Hg lamp starting from an acrylates monomer miniemulsion are investigated. In one system the acrylate nanodroplet reaction is self-initiated and in the other the use of a photoactive di-Ph ether surfactant yields Ph and phenoxyl initiating radicals upon UV irradn. Photopolymn. kinetics are monitored in situ by real-time Fourier transform near IR spectroscopy (RT-FTNIR) and the colloidal properties are systematically investigated by dynamic light scattering (DLS). The up-scaling of these PI-free miniemulsion photopolymns. is carried out in an annular photoreactor. [on SciFinder(R)]
Radical Photopolymerization in Miniemulsions. Fundamental Investigations and Technical Development
Macromolecules, 2011
A photochemical means to convert acrylate monomer emulsions into polymer nanolatexes has been explored using radical miniemulsion photopolymerization. Our aim is to offer a complete overview through a stepwise mechanistic investigation, addressing first the key aspect of the electronic excitation of the photoinitiator in monomer miniemulsions and ending with the implementation of a photochemical reactor. In a first step, the photon flux absorbed by different photochemical initiators was investigated as a function of the miniemulsion droplet size. A series of miniemulsion polymerizations were also performed and the effects of the primary experimental parameters on the reactions kinetics, molar masses, and colloidal properties were assessed. As expected, droplet size, incident photon flux, and the nature of the photochemical initiator were found to be the primary reaction parameters. Finally, miniemulsion polymerizations were performed in an annular photochemical reactor in batch and semibatch processes.
Green Processing and Synthesis, 2014
We show the potential of miniemulsion photo polymerization for the continuous production of aqueous poly(acrylate) dispersions in a microreactor at room tem perature. While the starting acrylate nanoemulsions are amenable to limit scattering, their polymerization within a microreactor provides additionally small microchannels and short diffusion path enabling an efficient mixing in order to alleviate the constraints associated with non uniform throughcure in turbid medium. Two key features prove that this process design is highly ecoefficient: i) two types of energysaving and compact UV sources (fluo rescent or lightemitting diode) were employed; ii) high conversions were achieved using the fluorescent lamp with short residence times (10 min), low irradiance (3 mW cm 2 ) and without the need of solvent. The present study describes briefly the influence of various parametersflow rate, photoinitiator type/concentration, droplet size, solid content, UV source -on the photopolymeriza tion course (kinetics) and the properties of the nanolatex obtained (particle size and molecular weight).
Macromolecules, 2003
A systematic study on the effect of molecular structure on the photoinitiated polymerization of acrylates was undertaken. Initially, the research was focused on the effect of hydrogen bonding, and it was found that preorganization via hydrogen bonding enhances the maximum rate of polymerization (R p). This hydrogen bonding facilitated preorganization also affected the tacticity of the resultant polymer. Next, the effect of polarity as represented by the calculated dipole moment (µcalc) of a given monomer was investigated. A direct linear correlation between Rp and the calculated Boltzmann-averaged dipole moment (µcalc) was observed. The Rp-µcalc correlation holds for pure monomers, mixtures of monomers, and even mixtures of monomers with inert solvents. This correlation enables the rational design of monomers with a required reactivity. In addition, these studies suggest that the propagation step of polymerization is influenced by hydrogen bonding while the dipole moment influences the termination rate constant. These two mechanistic explanations can be regarded as complementary factors that influence the speed of acrylate polymerization.
Direct initiation of the photopolymerization of acrylates by short-wavelength excimer UV radiation
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2003
Investigations on the direct initiation of the photopolymerization of acrylates by irradiation with short-wavelength monochromatic UV light using the 222 nm emission of a KrCl à excimer lamp are reported. The reactivity of various acrylates was studied by real-time FTIR-ATR spectroscopy. Laser photolysis experiments and accompanying quantum chemical calculations were performed in order to propose a possible mechanism of initiation.
Controlled Radical Polymerization of Acrylates Regulated by Visible Light
ACS Macro Letters, 2014
The controlled radical polymerization of a variety of acrylate monomers is reported using an Ir-catalyzed visible light mediated process leading to well-defined homo-, random, and block copolymers. The polymerizations could be efficiently activated and deactivated using light while maintaining a linear increase in molecular weight with conversion and first order kinetics. The robust nature of the fac-[Ir(ppy) 3 ] catalyst allows carboxylic acids to be directly introduced at the chain ends through functional initiators or along the backbone of random copolymers (controlled process up to 50 mol % acrylic acid incorporation). In contrast to traditional ATRP procedures, low polydispersity block copolymers, poly(acrylate)-b-(acrylate), poly(methacrylate)-b-(acrylate), and poly(acrylate)-b-(methacrylate), could be prepared with no monomer sequence requirements. These results illustrate the increasing generality and utility of light mediated Ircatalyzed polymerization as a platform for polymer synthesis.
Photopolymerization of acrylate suspensions
Journal of Photochemistry and Photobiology A: Chemistry, 2012
Polymerization time parameters, induction time t 0 and t 50 obtained from Boltzmann sigmoidal fitting, were determined from photorheology experiments performed on diacrylate and glycol dimethacrylate suspensions with silicon dioxide, with varying photoactives concentration and in the presence of diluents. The experiments were performed at the intensity ∼23 mW/cm 2 . t 0 and t 50 are linearly proportional to reciprocal photoinitiator concentration 1/c P , dye concentration c D and inhibitor concentration c INH as predicted by modified inhibitor exhaustion model. Further, the effect of a reactive and an inert diluent is shown.
Journal of Photochemistry and Photobiology A: Chemistry, 2002
The goal of this study was to examine the possibilities of preparing thin surface spatial crosslinked polymer films by UV curing using 1,6-hexandioldiacrylate as a multifunctional monomer and 1-hydroxycyclohexyl acetophenone as a radical photoinitiator. Different UV light sources were used with different light spectral distributions and light intensities. It is found that the light source characterised at least by a particular overlap of its emission spectrum with the photoinitator's absorption spectrum is the best system used for effective cure. Low polymerisation rate achieved in the case of smaller overlap of spectrums is easy to regulate by extending the energy of the emitted light.
Dispersion Photopolymerization of Acrylated Oligomers Using a Flexible Continuous Reactor
Macromolecular Reaction Engineering, 2016
The photopolymerization of acrylated oligomers dispersed in an aqueous medium is successfully demonstrated using a simple continuous photoreactor designed with flexible tubing, which presents straightforward up-scaling and maintenance features. The performance of the continuous photoreactor is assessed by varying the length of the tube exposed to ultraviolet light as well as the flow rate of the aqueous dispersion thr ough the reactor. The insoluble nature of the dispersed particles after in-situ photo-crosslinking is particularly suitable for the estimation of the actual number of polymerized particles from static and dynamic light scattering data. The procedure is discussed in detail. Along with the overall acrylate double bond conversion of the particles determined by infrared spectroscopy, an estimation of the average conversion per polymerized particle is provided as a function of the exposure time to ultraviolet light. The sub-microscopic characterization by peak-force tapping atomic force microscopy of the particles after photopolymerization is also presented.
Polymer, 2002
The photoinitiated polymerization of multifunctional (meth)acrylic monomers was simultaneously monitored in real time by fluorescence and differential scanning calorimetry. As the curing proceeds, the fluorescence emission changes due to an increase in the viscosity of the microenvironment. A good correlation between fluorescence intensity and degree of conversion was established by using two different fluorescent probes, each having the same fluorophore, dialkylamino derivatives of 7-nitro-2-oxa-1,3-diazol. One of the probes contains an acrylic moiety which can react with the monomers labelling the formed network. The use of the first moment of fluorescence is presented as a suitable methodology to avoid experimental fluctuations. Furthermore, the influence of the length of the spacer between the acrylic groups in the polymerization reaction kinetics and fluorescence changes has been also discussed in terms of reaction diffusion controlled termination kinetics and free volume fraction. It was concluded that the fluorescence method is a powerful tool to study the kinetics of photopolymerization of multifunctional monomers. q