Emulsion Polymerization Of N-butyl Acrylate Research Articles

Synthesis of Film-Forming Photoactive Latex Particles by Emulsion Polymerization-Induced Self-Assembly to Produce Singlet Oxygen.

The design of photoactive polymer substrates producing singlet oxygen under visible light irradiation has great technological potential. Aqueous dispersion of novel photoactive core-shell particles was synthesized by surfactant-free reversible addition-fragmentation chain transfer (RAFT) emulsion polymerization of n-butyl acrylate. The surface of the nanoparticles is directly decorated thanks to the polymerization-induced self-assembly process using a hydrophilic macromolecular chain transfer agent (macro-CTA) functionalized with the organic photosensitizer. The macro-CTA was synthesized by statistical copolymerization of acrylic acid and 2-Rose Bengal ethyl acrylate (RBEA) at 80 °C mediated with 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid. Monitoring polymerization kinetics of RAFT polymerization highlights that increasing amount of RBEA induces retardation, still more pronounced when using the vinylbenzyl Rose Bengal comonomer. The present work provides insight into the quantum yield of singlet oxygen production in water (ΦΔ = 0.2-0.6) for the three types of synthesized polymers (hydrophilic polymer, latex particles, and polymer film). The photoactive core-shell latex particles enabled the easy preparation of photoactive polymer film by simple casting.

Emulsifier-free polymerization of n-butyl acrylate involving trithiocarbonates based on oligomer acrylic acid

The effect of the chain length of oligomer acrylic acid obtained in the presence of a low-molecularmass trithiocarbonate and the position of trithiocarbonate fragment (within the chain or at the chain end) on the process of emulsion polymerization of n-butyl acrylate and characteristics of the resulting dispersions has been studied for the first time. It has been found that, when using an oligomer with trithiocarbonate group located within the chain in the emulsion polymerization of n-butyl acrylate in a wide range of monomer–water phase compositions, triblock copolymers self-organizing in aqueous medium to give stable particles with the core–shell structure are formed. Oligomers with Mn ∼ (5–10) × 103 are optimal for synthesis of stable dispersions. In this case, block copolymers with the controlled length of hydrophobic block and a rather narrow MWD may be obtained. Thin films formed from these copolymers retain the structure of the initial dispersions on solvent removal. If the trithiocarbonate group in the oligomer is located at the chain end, the main polymerization product is a diblock copolymer. In this case, the formation of polymer–monomer particles occurs during a longer period of time, the control of MWD is weakened, and the dispersions of particles lose the aggregative stability after thin film formation.

Effect of aqueous phase composition on particle coagulation behavior in batch emulsion polymerization of styrene

Previously, we studied the latex particle coagulation in the emulsion polymerization of n-butyl acrylate induced by an electrolyte (Colloid Polym Sci 291 (2013) 2385–2398). However, the evolution of particle size distribution vs. monomer conversion and reaction time, and the possibility for the manipulation of particle coagulation to control particle size and polydispersity were not studied. In this study, we investigated the evolution of particle size distribution vs. monomer conversion and reaction time during the emulsion polymerization of styrene. Moreover, the particle coagulation at different aqueous phase compositions was studied in details. The experimental results indicate that the particle size and polydispersity was controlled by particle coagulation, which was adjusted by varying the content of electrolyte or methanol in the aqueous phase. The final latex particle size increased in the range 89.2–265.9nm with increasing electrolyte or methanol. The effect of aqueous phase composition on the polydispersity index (PDI) of the final latex was also considered. The PDI of the final latex reached 0.005 at an appropriate aqueous phase composition. Interestingly, the demulsification phenomenon easily occurred at electrolyte concentration>1.2wt% or methanol/water ratio>30/70.

Soft Nanostructured Films with an Ultra‐Low Volume Fraction of Percolating Hard Phase

In this study, aqueous emulsion polymerization of n-butyl acrylate is performed in batch conditions without surfactants using a poly(acrylic acid)-trithiocarbonate macro-RAFT agent to control the polymerization and to stabilize the emulsion. According to the polymerization-induced self-assembly (PISA) approach, well-defined amphiphilic PAA-b-PBA diblock copolymers form and self-assemble during synthesis to yield highly stable core-shell particles with an extremely thin hard PAA shell. For the first time, we report here the specific properties of films obtained from these particular latexes. After drying the aqueous dispersion, tough and transparent films are obtained. Although the films are not chemically cross-linked, they do not dissolve in good solvents for PBA. Moreover, they remain transparent even after immersion in water. Rheology shows that the films are both stiff and ductile, thanks to the nanostructured but very low volume fraction (less than 3 wt%) of PAA forming a percolating network in the soft PBA. Compared with conventional core-shell-based films, this approach affords for the first time a route to a thin percolating honeycomb nanostructure with a sharp and strong interface between the two phases. The versatility of the synthetic procedure opens perspectives for a large range of functional materials.

Particle nucleation in high solids nitroxide mediated emulsion polymerization of n-butyl acrylate with a difunctional alkoxyamine initiator

In this work, we seek to understand the nature of the relationship between increasing alkoxyamine initiator concentration and increasing particle size for the SG1-mediated, two stage emulsion polymerization of n-butyl acrylate. Using a difunctional alkoxyamine, based upon the commercially available BlocBuilder MA, we studied the impact of various factors on the particle size in the 1st stage (particle nucleation) of the polymerization; these include ionic strength, pH, buffer (type and concentration) and surfactant concentration. The results suggest that superswelling of the particles during nucleation has significant influence on the behaviour of the system. In applying these strategies, we demonstrate that colloidally stable latexes can be created at 45 wt% solids with molecular weight >70 kg mol−1.

Soap-free emulsion polymerization of n-butyl acrylate in aqueous solution in the presence of α- and methylated β-cyclodextrin

Butyl acrylate, a relative hydrophobic monomer, was found to become completely water soluble simply by mixing with either α-cyclodextrin or methyl-β-cyclodextrin. The both cyclodextrins were found to form 1:1 host–guest complexes with butyl acrylate. The complexes formed exhibited similar supramolecular structures, i.e., butyl group of butyl acrylate included in the cavity of cyclodextrins, but the double bond of the monomer locating outside of the cavity. Association constant values for α-cyclodextrin and methyl-β-cyclodextrin were determined to be 407.3 and 45.8 L/mol, respectively, indicating the better fitting of butyl acrylate with α-cyclodextrin than with methyl-β-cyclodextrin. It was found that the addition of either α-cyclodextrin or methyl-β-cyclodextrin, even at very low concentration, could markedly improve the reaction rate, reduce the amount of coagulum, and narrow the molecular weight distribution and particle-size distribution, in which α-cyclodextrin exhibited a better effect on polymerizations because of its stronger interaction with the monomer.

Effect of Temperature on Emulsion Polymerization of n-Butyl Acrylate

Poly (n-butyl acrylate) was synthesized by emulsion polymerization using CHP-Ferrous sulfate redox system asinitiator. The effect of reaction temperature on the polymerization rate and particle size (D) was studied. The reaction showed a relatively high rate and reached high conversion in short time. The particle size was dependent on the reaction temperature. The size of particle reduced from 95nm to 65nm when the reaction temperature changed from 20°C to 70°C with fixed polymerization conditions. The activation energy is 29.80kJ/mol.

Seeded Emulsion Polymerization of Butyl Acrylate Using a Redox Initiator System: Kinetics and Mechanism

Seeded emulsion polymerization of n-butyl acrylate (n-BA) was initiated by a redox initiator system: cumene hydroperoxide/ferrous sulfate hexahydrate/ethylene-diaminetetraacetic acid monosodium salt/sodium formaldehyde sulfoxylate (CHP−Fe2+−EDTA−SFS). Final poly(n-butylacrylate) (PBA) particles with narrow size distribution were obtained. The kinetics and mechanism of seeded emulsion polymerization initiated by the redox initiator system were investigated. Special care was focused on effects of component concentration of the redox initiator system on the seeded emulsion polymerization kinetics. Particle growth and pH variation during the polymerization were also studied. It was found that the polymerization rate and the overall conversion increased with increasing CHP and SFS concentration. Interestingly, the optimal molar ratio of CHP/SFS was 1.10/3.81 rather than being equimolar in our work. In addition, an optimal molar ratio of EDTA to ferrous ions (2.19 × 10−5 mol/7.12 × 10−6 mol) was found. The polymerization rate increased first and then decreased with increases in ferrous ion concentration. The pH value in the system decreased as the polymerization proceeded. A limiting conversion phenomenon of conversion not being able to exceed 20% was found, and an explanation to the limiting conversion was proposed on the basis of the views of the practical cumulative formation constant log KMY and reaction rate comparison. When another activator solution (EDTA/FES/SFS (mol) 2.19 × 10−5/7.12 × 10−6/1.91 × 10−3) was added, the limiting conversion was removed and the final conversion reached 97%.

Surfactant-Free RAFT Emulsion Polymerization Using Poly(N,N-dimethylacrylamide) Trithiocarbonate Macromolecular Chain Transfer Agents

Water-soluble poly(N,N-dimethylacrylamide)s (PDMAAm) with a reactive trithiocarbonate group exhibiting different structures were used as macromolecular RAFT (reversible addition−fragmentation chain transfer) agents in the surfactant-free emulsion polymerization of n-butyl acrylate and styrene, under ab initio, batch conditions. Independently of the structure of the RAFT group, the polymerizations were fast and controlled with molar masses that matched well the theoretical values and rather low polydispersity indexes. Monomer conversions close to 100% were reached and the polymerizations behaved as controlled systems, even when solids contents up to 40% were targeted. The system thus led to poly(N,N-dimethylacrylamide)-b-poly(n-butyl acrylate) and poly(N,N-dimethylacrylamide)-b-polystyrene amphiphilic diblock copolymers formed in situ and self-assembled upon chain extension. The stability of the aqueous dispersions, measured by the amount of coagulum formed, improved with increasing length of the stabilizing hydrophilic PDMAAm segments.

Surfactant-Free Controlled/Living Radical Emulsion (Co)polymerization ofn-Butyl Acrylate and Methyl Methacrylate via RAFT Using Amphiphilic Poly(ethylene oxide)-Based Trithiocarbonate Chain Transfer Agents

The RAFT-mediated, surfactant-free, ab initio, batch emulsion polymerization of n-butyl acrylate (nBA) and its copolymerization with methyl methacrylate (MMA) were studied. The control agent was a surface-active trithiocarbonate macromolecular RAFT agent composed of a hydrophilic poly(ethylene oxide) (PEO) block and a hydrophobic dodecyl chain. The homopolymerizations of nBA were fast with high final conversions, and the polymer chains were well-controlled with narrow molar mass distribution. The length of the PEO chain was shown to affect the particle size and the polymerization kinetics directly. We found the conditions to tune the particle size independently from the poly(n-butyl acrylate) chain length by playing with a mixture of macro-RAFT agents with long and short PEO segment or by adding a PEO-based nonionic surfactant. The copolymerizations of nBA and MMA exhibited features very similar to those of the nBA homopolymerizations provided that the molar percentage of MMA did not exceed approximately ...

Sulfonated Amphiphilic Block Copolymers: Synthesis, Self-Assembly in Water, and Application as Stabilizer in Emulsion Polymerization

Described is the synthesis of diblock copolymers generated via sequential atom transfer radical polymerization (ATRP) of poly(n-butyl acrylate) (PnBA) followed by chain augmentation with either sulfonated poly(2-hydroxyethyl methacrylate) (PHEMA) or poly(2-hydroxyethyl acrylate) (PHEA) blocks. ATRP of PHEMA or PHEA from PnBA macroinitiator was conducted in acetone/methanol 50:50 (v/v) and produced diblock copolymers of low PDI (<1.3). Hydroxyl functional groups were converted to sulfonate through esterification using excess 2-sulfobenzoic acid cyclic anhydride (SBA). TEM images of aqueous block copolymer solutions reveal an array of polymer micelle morphologies including monodisperse spheres, cylinders, and cylinder aggregates. Surface tensions and critical micelle concentrations appear to be dependent more on hydrophile structure as opposed to its length. Application of the synthesized block copolymers as stabilizers for batch emulsion polymerization of n-butyl acrylate showed the polymeric surfactant effectively stabilizes latex particles and produces a lower polydispersity when compared with commonly applied commercial emulsifiers.

Molecular Weight Distribution (Soluble and Insoluble Fraction) in Emulsion Polymerization of Acrylate Monomers by Monte Carlo Simulations

A Monte Carlo simulation model for the semibatch emulsion polymerization of acrylate monomers was developed. The model accounts for the complex kinetics of acrylate monomers (presence of chain-end and midchain radicals), the compartmentalization of emulsion polymerization systems and the development of the entire molecular weight distribution (MWD) as well as the branching density. It was found that the MWD produced in the semibatch process was bimodal (a sharp and extremely high Mw peak and a broad and lower Mw mode), the midchain radicals were predominant during the polymerization, and most of the branches were short and produced by the backbiting mechanism. Interestingly, the bimodality of the MWD could be avoided under certain experimental conditions (those who led to a decrease of particles with more than two radicals), but this did not prevent the formation of polymer chains of molecular weights above 107 g/mol (which are typically insoluble). The model also shows the importance of the presence of midchain radicals in the microstructure of the polymer formed. Thus, the fraction of termination by combination and disproportionation of the midchain radicals had a significant influence on the location of the high molecular weight peak. The predictions of the Monte Carlo model were in good agreement with experimental data and a previously developed deterministic mean-field theory model for the seeded semibatch emulsion polymerization of n-butyl acrylate.

Living Radical ab Initio Emulsion Polymerization of n-Butyl Acrylate by Reverse Iodine Transfer Polymerization (RITP): Use of Persulfate as Both Initiator and Oxidant

Reverse iodine transfer polymerization (RITP) represents a new straightforward way to prepare controlled macromolecular architectures and relies on the use of molecular iodine (I2) as control agent. In this work, a one-step ab initio emulsion polymerization of n-butyl acrylate in the presence of molecular iodine has been successfully performed with potassium persulfate playing the dual role of radical initiator and oxidant. The polymerization was initiated by potassium persulfate at T = 85 °C with sodium 1-hexadecanesulfonate as surfactant, yielding a stable and uncolored latex. The hydrolytically disproportionated iodine was regenerated by potassium persulfate as oxidant (also serving as radical initiator), leading to the expected targeted molecular weight (e.g., butyl acrylate conversion = 99%, Mn,theoretical = 10 100 g mol-1, Mn,SEC = 9800 g mol-1, Mw/Mn = 1.8, particle diameter dp = 83 nm with a monomodal particle size distribution). The use of potassium persulfate as both radical initiator and oxidant offers a convenient way to overcome the upward deviation of the molecular weights due to hydrolytic disproportionation of iodine, which was a limitation for the implementation of the RITP process in dispersed aqueous media. The persulfate is able to regenerate iodine, and hence the molecular weight of the polymer chains can be accurately controlled by the concentration of iodine. Furthermore, a poly(butyl acrylate)-b-poly(butyl acrylate-co-styrene) block copolymer was synthesized in seeded emulsion polymerization, proving the living character of the polymerization.

Seeded semibatch emulsion polymerization of n‐butyl acrylate: Effect of the seed properties

The effect of the properties of the seed (molecular weight and gel content) on the kinetics and structural properties of the polymer produced by seeded semibatch emulsion polymerization of n-butyl acrylate with potassium persulfate as an initiator at 75 °C was studied. The amount of gel and the molecular weights formed in the process were independent of the initial gel contents present in the seed because the instantaneous generation rate of gel polymer is independent of the gel already present in the polymer particles. On the other hand, when the initial molecular weight of the seed was varied, the fraction of gel and the molecular weights formed were partially affected. A comparison between the experimental and model prediction results is also presented.

Polymerization rate and mechanism of ultrasonically initiated emulsion polymerization of n-butyl acrylate

The factors affecting the induction period and polymerization rate in ultrasonically initiated emulsion polymerization of n-butyl acrylate (BA) were investigated. The induction period takes only an instant in ultrasonically initiated emulsion polymerization of BA without any added initiator by enhancing the N 2 flow rate. Increasing temperature, power output and SDS concentration, decreasing the monomer concentration results in further decreasing induction period and enhanced polymerization rate. Under optimized reaction conditions the conversion of BA reaches 92% in 11 min. The polymerization rate can be controlled by varying reaction parameters. The apparatus of ultrasonically initiated semi-continuous and continuous emulsion polymerization were set up and the feasibility was first studied. Based on the experimental results, a free radical polymerization mechanism for ultrasonically initiated emulsion polymerization was proposed, including the sources of the radicals, the process of radical formation, the locus of polymerization and the polymerization process. Compared with conventional emulsion polymerization, where the radicals come from thermal decomposition of a chemical initiator, ultrasonically initiated emulsion polymerization has attractive features such as no need for a chemical initiator, lower reaction temperature, faster polymerization rate, and higher molecular weight of the polymer prepared.

Kinetics and Polymer Microstructure of the Seeded Semibatch Emulsion Copolymerization of n-Butyl Acrylate and Styrene

The seeded semibatch emulsion polymerization of n-butyl acrylate, n-BA, with varying amounts of styrene as comonomer was investigated using potassium persulfate as initiator at 75 °C. The kinetics, the gel fraction, the molecular weight distribution, MWD, and the level of branches were determined. It was observed that the instantaneous conversion, the fraction of gel, the average molecular weights, and the level of branches were affected by the amount of styrene in the recipe. In particular, the fraction of gel decreased from 55% to almosnt nil and the level of branches decreased from 14 to 5 branches per 1000 carbons of the backbone when the amount of styrene increased from 0 to 10%. These results have technological implications because the amount of gel and the level of branches can be controlled; this is something that was not possible when initiator concentration or monomer feed rates were used as control variables. A mathematical model for predicting the kinetics, the fraction of gel, the level of branches and the MWD was used to analyze the effect of styrene on the seeded semibatch emulsion polymerization of n-BA. In addition, it is shown that the adhesive properties of these latexes can be modified by adding small amounts of styrene.

Seeded semibatch emulsion polymerization of butyl acrylate: Effect of the chain-transfer agent on the kinetics and structural properties

The effect of dodecane-1-thiol on the kinetics, gel fraction, level of branches, and sol molecular weight distribution of the seeded semibatch emulsion polymerization of n-butyl acrylate carried out at 75 °C was investigated. The gel fraction was strongly affected by the content of the chain-transfer agent (CTA). The sol weight-average molecular weights decreased with increasing CTA concentration, whereas no effect on the kinetics and the level of branches was observed. The experimental data were analyzed with a mathematical model of the process that was able to catch fairly well the effect of the process variable. In addition, adhesive tests were carried out to check the effect of the gel fraction on the adhesive properties. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1106–1119, 2001

Low Free Energy Surfaces Using Blends of Fluorinated Acrylic Copolymer and Hydrocarbon Acrylic Copolymer Latexes

Blends of small particle size fluorinated acrylic copolymer latexes with a large particle size styrene/acrylic copolymer latex were examined with regard to formation of low free energy surfaces, amount of incorporated fluorinated copolymer, particle size, and particle size asymmetry. The styrene/acrylic latex was prepared by emulsion polymerization of n-butyl acrylate and styrene. Several varieties of fluorinated latexes were prepared. One was prepared by copolymerization of n-butyl acrylate and the fluorinated monomer, FMA, H2CC(CH3)CO2(CH2)2(CF2)nF (n ≈ 7.7). Two types of copolymer core/fluorinated copolymer shell latex systems were prepared. One was comprised of a highly cross-linked core of poly(divinylbenzene) and a shell of poly(n-butyl acrylate-co-FMA). The other had a lightly cross-linked core of poly(n-butyl acrylate-co-divinylbenzene) and a shell of poly(n-butyl acrylate-co-FMA). Films cast from blends of styrene/acrylic and fluorinated copolymer latexes were examined by contact angle goniometr...

Seeded Semibatch Emulsion Polymerization ofn-Butyl Acrylate. Kinetics and Structural Properties

The seeded semibatch emulsion polymerization of n-butyl acrylate was investigated using potassium persulfate as initiator at 75 °C. The effect of initiator concentration and monomer feeding time (feed flow rate) on the kinetics, fraction of gel, molecular weight distributions, and level of branches were studied. It was found that the amount of gel formed was independent of initiator concentration and monomer feed flow rate if the process proceeded under starved conditions. On the other hand, the higher the initiator concentration and the feeding times, the higher the level of branches but the lower the molecular weights. A high level of branches was found, which was attributed to intramolecular transfer to polymer or backbiting.

Soap-free emulsion polymerization ofn-butyl acrylate: Copolymerization with 1,1-(dimethyl)-1- (3-methacryloxyethyl)-1-(sulfopropyl)ammonium betaine

Emulsifier-free emulsion polymerization of n-butyl acrylate has been performed in the presence of a polymerizable sulfobetaine monomer, 1,1-(dimethyl)-1-(3-methacryloxyethyl)-1-(sulfopropyl)ammonium betaine (SPE). An investigation of the effect of various salts (NaCl, NaHCO3, Na2CO3, and NaH2PO4) on the emulsifier-free emulsion polymerization of n-butyl acrylate revealed that the type and quantity of salt is important in determining the size and size distribution of the final latex particles. In the case of the copolymerizations, control of the monomer feeding protocol (batch vs. semicontinuous and unseeded vs. seeded reactions) and of the ionic strength of the reaction mixture via addition of electrolytes allowed the preparation of stable latexes at 10% solids content with controllable particle size distributions. The results indicate that the amphiphilic sulfobetaine is able to stabilize the latex in much the same way as a polymerizable surfactant or an ionic comonomer. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 227–236, 1998