Comparative study of classical surfactants and polymerizable surfactants (surfmers) in the reversible addition–fragmentation chain transfer mediated miniemulsion polymerization of styrene and methyl methacrylate

Cationic and anionic amphiphilic monomers (surfmers) were synthesized and used to stabilize particles in miniemulsion polymerization. A comparative study of classical cationic and anionic surfactants and the two surfmers was conducted with respect to the reaction rates and molecular weight distributions of the formed polymers. The reversible addition–fragmentation chain transfer process was used in the miniemulsion polymerization reactions to control the molecular weight distribution. The reaction rates of the surfmer‐stabilized miniemulsion polymerization of styrene and methyl methacrylate were similar (in most cases) to those of the classical‐surfactant‐stabilized miniemulsion polymerizations. The final particle sizes were also similar for polystyrene latexes stabilized by the surfmers and classical surfactants. However, poly(methyl methacrylate) latexes stabilized by the surfmers had larger particle sizes than latexes stabilized by classical surfactants. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 427–442, 2006     

Reactive surfactants in heterophase polymerization for high performance polymers

 A variety of nonionic reactive surfactants have been prepared from block copolymer precursors. These precursors are formed from a commercially available polyoxyethylene glycol monomethylether as the hydrophilic sequence of the surfactant; this product is used as initiator of ring opening anionic polymerization of butylene oxide. Finally the reactive surfactants are obtained after proper functionalization of the precursor. The reactive surfactants are an inisurf with an asymmetric azo compound, a transurf with a thiol group, and a few surfmers with acrylic, methacrylic, styrenic and α-methyl styrenic reactive groups. These compounds have been engaged in styrene emulsion or dispersion polymerization. Several of them have been found to be useful for preparing stable latices. Received: 22 July 1997 Accepted: 11 December 1997     

Anionic surfmers in mini-emulsion polymerisation

Mini-emulsion polymerisation of styrene or methylmethacrylate, initiated with ammonium persulphate, have been carried out, in the presence of hexadecane or of polymethylmethacrylate as hydrophobic costabilizer, and the simple hemiester of linear dodecyl alcohol and maleic anhydride, or polymerisable surfactants (surfmers) derived from the condensation of succinic anhydride and either hydroxy propylmethacrylate (MAES), or hydroxyethylmethacrylate (ABS). While the pure surfmers have not so good surface activity, from surface tension measurements, stable mini-emulsion droplets are obtained using a mixture with low amounts of SDS, which have diameters of about 100–200 nm, which remain stable upon polymerisation. Most of the surfmers remain grafted onto the particle surface, thus conferring to these particles strong stability in the various tests. However, due to the high water solubility of the surfmers, another part remains in the serum as unconverted monomer or water-soluble polymers. To cite this article: A. Guyot et al., C.R. Chimie 6 (2003).     

Improving water sensitivity in acrylic films using surfmers

The water sensitivity of films obtained from high solids content acrylic latexes was investigated, with special focus on the role of the surfactant used in the synthesis step. The performance of films obtained from latexes stabilized by nonionic surfmers was compared to that of the acrylic latexes stabilized with conventional nonionic and anionic surfactants. It was seen that the latexes stabilized with reactive surfactants exhibited a remarkably better resistance to both water permeability and water vapor permeability and therefore enlarged the durability of the films. Atomic force microscopy images suggested that the defects created by surfactant migration in the latexes stabilized with conventional surfactants promoted the permeation of water by capillarity.     

EFFECT OF SURFACTANTS ON FILM FORMATION OF POLY (VINYL ACETATE) AND POLY (VINYL ACETATE-BUTYL ACRYLATE) LATEXES

Effect of ethoxylated nonyl phenol type non-ionic and alkyl sulfate type anionic surfactants on the film formation process of poly (vinyl acetate) and poly (vinyl acetate-acrylate) latexes are discussed. HLB value of non-ionic surfactant is shown to affect glass transition temperature, minimum film formation temperature and rate of film coalescence of vinyl acrylic latexes. Higher HLB non-ionic surfactant appears to be more compatible than the lower HLB ones with the fairly polar vinyl acrylic latex and form a well coalesced film. Presence of sodium lauryl sulfate in the latex is observed to result in incompatible regions on the latex film surface, typical of two phase morphology. Influences of surfactants on the film formation process in the polar vinyl acrylic latexes are compared and contrasted with the available data on the effects of surfactants in styrene butadiene latexes. The findings are discussed in terms of adsorption and interaction behavior of surfactants at polar vinyl acrylic latex surfaces and current theories of latex film formation mechanisms.     

Maleic diamide polymerizable surfactants. Applications in emulsion polymerization

A series of new polymerizable non-ionic and ionic surfactants (surfmers) with amides groups on both sides of the C=C double bonds have been prepared upon reaction of maleic isoimide carrying a long alkyl chain (or a benzyl group) with a hydrophilic amine derivative. Their critical micellar concentration (CMC) was measured with a surface tensiometer. They have been engaged in batch emulsion polymerization of styrene, and semi-batch seeded copolymerization of styrene and butyl acrylate, giving stable latexes during the polymerization process, and upon extraction with ethanol, showing a high rate of incorporation at the particle surface. However these surfmers do not confer good steric stabilization properties, which may be expected from the use of non-ionic surfactants. To cite this article: I. Klimenkovs et al., C. R. Chimie 6 (2003).     

The use of selected acrylate and acrylamide-based surfmers and polysoaps in the emulsion polymerization of styrene

Polymerizable surfactants (surfmers) 12-acryloyloxy-dodecanoic acid and 11-acrylamidoundecanoic acid and their respective sodium salts were prepared and then polymerized to form their corresponding oligomers using reversible addition-fragmentation chain transfer (RAFT). Different concentrations of both the surfmers, their sodium salts, and their RAFT oligomers were used as polysoaps in the emulsion polymerization of styrene. Stabilities of the pre-emulsions before polymerization were determined and compared. After polymerization, particle sizes and polydispersities of the resulting polystyrene latices were determined. Sodium dodecyl sulfate (SDS) was used as a reference surfactant to compare the particle sizes and stabilities of the pre-emulsions prepared using surfmers and polymeric surfactants (polysoaps) as particle stabilizers. Emulsion polymerization of styrene using these surfmers and polysoaps all led to latices which were stable for a period of more than six months, as indicated by constant particle sizes, whereas latices prepared using the conventional surfactant, SDS, were not as stable.     

Methacrylic maleic bifunctional stabilizer in emulsion polymerization

A new type of reactive surfactant, containing both a methacrylic and a maleic group, was prepared and engaged in batch and seeded emulsion polymerization of styrene and styrene-butyl acrylate. The stability of core-shell latexes versus electrolytes has been studied.     

Styrenic surfmer in emulsion copolymerization of acrylic monomers. II. Copolymerization and film properties

Polymerizable styrenic surfactants (surfmers) and nonreactive analogs, have been applied in emulsion copolymerization of acrylic monomers in a seeded semibatch process. Stable core-shell latexes with low levels of coagulum and controlled particle size have been obtained; some of them, with either steric or electrosteric stabilization, display excellent stability to electrolytes, freeze–thaw cycles, and shear flocculation. In addition, the reactive surfactants lead to films with superior performance due to reduced migration of surfactant to the surface (contact angle measurements) and dimensional stability when the films are dipped in water, as well as less water uptake. Some differences also appear in particle morphologies. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4205–4217, 1999     

Polymerisation of liquid crystalline phases in binary surfactant/water systems

The phase behaviour and polymerisation of a quaternary ammonium surfactant containing an ethylmethacrylate polymerisable moiety within the head group region has been investigated. The addition of this large flexible hydrophilic moiety alters significantly the inherent surface activity of the surfactant and the surfactant may be compared with the class of non-ionic polyethyleneoxide surfactants. Polymerisation of both self-assembled and non self-assembled states went to near completion with the resulting polymer being completely insoluble in water.     

LDH as Nanofiller: Organic Modification and Dispersion in Polymers

Summary: Layered double hydroxide (LDH) is a relatively new class of layered crystalline clay materials to be used as nanofiller in various polymer matrices. We report here the organic modification of LDH by anionic surfactants having different sizes and functionalities. Subsequently, their dispersion in polymer is discussed and finally the characteristics of the polymer/LDH nanocomposites are investigated. LDH has been modified using regeneration method, which shows that irrespective of size and functionality of the anionic surfactant, organic modification can be carried out efficiently. However, it has been observed that alkyl sulfonate are more efficiently intercalated within LDH layers than other surfactants giving well defined crystal structure of the modified LDH. These modified LDH, when dispersed in polymers like maleic anhydride grafted polyethylene shows that not only the size of the surfactant, but also the functionality of the surfactant influences their dispersion in a non polar polymer matrix.     

Composite Polymer Nanoparticles via Transitional Phase Inversion Emulsification and Polymerisation

Summary: A new route was employed to produce composite polymer nanoparticles. First, a model polymer (a low molecular-weight polyisobutene) was dissolved in a model monomer (styrene) and then the solution was emulsified in water containing a pair of nonionic surfactants via a transitional phase inversion route. After phase inversion, which produced an oil-in-water miniemulsion, polymerisation of the vinyl monomer gave composite polymer particles. Low temperature emulsification was not practical because the inverted oil-in-water emulsions reinverted to water-in-oil emulsions upon raising the temperature to the reaction temperature. Miniemulsions prepared at the reaction temperature with low monomer content in the oil phase showed good stabilty in the course of polymerisation and produced latexes with a particle size similar to the size of drops in the initial miniemulsions.     

Synthesis,characterization, and utilization of itaconate‐based polymerizable surfactants for the preparation of surface‐carboxylated polystyrene latexes

Two polymerizable surfactants (surfmers), namely, monododecyl itaconate (MDDI) and monocetyl itaconate (MCI), were synthesized by reacting itaconic anhydride with 1‐dodecanol and cetyl alcohol, respectively. A series of uncrosslinked and crosslinked surface‐carboxylated latexes were prepared from styrene and styrene–divinylbenzene, respectively, using varying amounts of these two surfmers. The latexes were characterized by gravimetry, dynamic light scattering, and conductometric titration in order to obtain the conversion, particle size distribution, and concentration of surface carboxyl groups, respectively. The size of latex varied between 41–72 nm and was seen to depend inversely on the surfmer concentration. In the case of the soluble polystyrene latexes, solution ¹H NMR spectra provided conclusive evidence for surfmer incorporation into the polymer chain. Comparison of the incorporation levels determined by NMR with the surface carboxylic acid concentrations in the latexes, determined by conductometric titrations, revealed that the majority of the surfmers, as ancticipated, were present on the latex surface. The study of the stability of the latexes to varying salt concentrations clearly demonstrated that the smaller‐size latexes having higher surface carboxyl group density exhibited far improved stability when compared with the larger‐size ones having lower surface carboxyl group density. Similarly, enhanced freeze‐thaw stability was also observed for the smaller‐size latexes. MCI‐based latexes exhibited marginally improved stability compared with those prepared using MDDI, which again seems to be because of the higher surface functional group density in the former. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3257–3267, 2005     

Nonionic reactive surfactants. I. Synthesis and characterization

A procedure to prepare nonionic reactive surfactants with different polymerizable groups is described. The synthesis involves the initiation of living anionic ring-opening polymerization of ethylene oxide and propylene oxide (for the hydrophilic part and the hydrophobic part, respectively) by a potassium salt prepared from the stoichiometric reaction of potassium hydride and diethylene glycol monomethyl ether. The resulting anion is reacted with chloride compounds (methacryloyl, allyl, vinylacetoyl) and maleic anhydride, as well as with isobutanoyl chloride, leading to a nonpolymerizable compound having a similar structure. Then, it was possible to produce a range of reactive surfactants more or less reactive with the monomers. These surfactants are expected to be used further in emulsion polymerization processes (styrene and butyl acrylate). This procedure gives good control of both hydrophobic and hydrophilic parts, and the end reaction for the different functionality of surfmers is quite quantitative. All the surfactants were characterized by size-exclusion chromatography and ¹H NMR. Physicochemical properties, such as the critical micellar concentration and the specific area, were also measured.     

UV Polymerisation of Surfactants Adsorbed at the Nematic Liquid Crystal–Water Interface Produces an Optical Response

We have investigated the changes in crossed polariser optical textures produced by adsorption and UV polymerisation of a range of polymerisable surfactants at the interface between a nematic liquid crystal and water. Similar to non‐polymerisable surfactants, the adsorption of polymerisable surfactants with sufficiently long hydrophobic tail groups produces a transition from planar to homeotropic anchoring. UV polymerisation of surfactants with a polymerisable group located in the hydrophobic tail region changes the anchoring from homeotropic back to planar. Polymerisation in the hydrophilic headgroup region does not produce an optical transition. We demonstrate that these systems can be used to “write with light” in the interfaces and that they form the basis of a UV sensor device in which the optical response is visible to the naked eye.     

Novel nonionic polymerisable surfactants based on sulfoxides. 1. Monomer synthesis and general surfactant behaviour

The synthesis, surface activity, and micellisation of a series of new nonionic polymerisable surfactants, often referred to as surfmers, are described. These monomers bear terminal vinyl groups or acrylic esters, and the nonionic sulfoxide moiety. Compared to many other nonionic hydrophilic fragments, the sulfoxide group behaves as a strongly hydrophilic fragment of small volume, that can balance up to an acryloyloxyundecyl hydrophobic chain. The incorporation of the polar acrylate moiety at the end of the hydrophobic chain seems to confer surfactant properties similar to the ones of bola amphiphiles to the monomers. Received: 22 March 2001 Accepted: 11 August 2001     

Emulsion polymerization of methyl methacrylate in the presence of novel addition–fragmentation chain‐transfer reactive surfactant (transurf)

Reactive surfactants allow the surfactant molecules to become covalently bound to the particles and thus provide added stability to the colloid particles, longer shelf life, better shear resistance, and polymer particles that can be redispersed. This article reports for the first time the use of a novel addition–fragmentation chain‐transfer reactive surfactant (transurf) in ab initio emulsion polymerizations of methyl methacrylate at 70 °C. It was found that the rate was lowered and average particle diameter nearly doubled when the transurf was used as compared with the SDS experiments (control). In addition the molecular weight distribution was very broad but had a lower Mn than observed in the sodium dodecyl sulfate experiment. Unfortunately because of the formation of many water‐soluble oligomers, the amount of transurf incorporated could not be obtained accurately. However, it was estimated theoretically that only a very small amount of transurf would be consumed, but for an alternative method to increase the incorporation of transurf into the particles, the ratio of monomer to transurf must be kept as low as possible. The best way to achieve this would be to carry the experiments out under starved‐feed conditions. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2813–2820, 2001     

Initialisation in RAFT-mediated polymerisation of methyl acrylate

Inhibition in Reversible Addition-Fragmentation chain Transfer (RAFT)-mediated polymerisations is currently a controversial issue; here we provide evidence that the slow "propagation" of the initiating and leaving group radicals during the early part (the period of consumption of the initial RAFT agent) of methyl acrylate RAFT-mediated polymerisation has characteristics similar to inhibition.     

Hemiesters and hemiamides of maleic and succinic acid: synthesis and application of surfactants in emulsion polymerization with styrene and butyl acrylate

Hemiesters and hemiamides of maleic acid with different chain lengths of the hydrophobic alkyl group (R = C₈H₁₇, C₁₀H₂₁, C₁₂H₂₅, C₁₆H₃₃) have been synthesized and used as surfactants in the emulsion polymerization of styrene and butyl acrylate. The same polymerization experiments were also carried out using nonreactive surfactants with an analogous succinic structure. The chemical structure of the surfactants was confirmed by 1H nuclear magnetic resonance. The melting point and critical micelle concentration of the reactive surfactants described herein were measured. All of the surfactants studied provided good stability of styrene/butyl acrylate latexes, when compared with a reference latex of a styrene/butyl acrylate copolymer prepared with a surfactant sodium dodecyl sulfate. The amount of surfactant grafted onto the particles of the final latex was estimated by conductimetric titration. Between 33 and 68% of surfactant used in emulsion polymerization was found on the surface of latex particles. Electrolyte addition at high concentration and freeze/thaw cycle cause flocculation of latexes. Copyright © 1999 John Wiley & Sons, Ltd.     

Controlled,radical reversible addition–fragmentation chain‐transfer polymerization in high‐surfactant‐concentration ionic miniemulsions

Living free‐radical polymerization of methacrylate and styrenic monomers with ionic surfactants was carried out with reversible addition–fragmentation chain transfer in miniemulsion with different surfactant types and concentrations. The previously reported problem of phase separation was found to be insignificant at higher surfactant concentrations, and control of the molar mass and polydispersity index was superior to that of published miniemulsion systems. Cationic and anionic surfactants were used to examine the validity of the argument that ionic surfactants interfere with transfer agents. Ionic surfactants were suitable for miniemulsion polymerization under certain conditions. The colloidal stability of the miniemulsions was consistent with the predictions of a specific model. The living character of the polymer that comprised the latex material was shown by its transformation into block copolymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 960–974, 2004