Semicontinuous heterophase copolymerization of vinyl acetate and butyl acrylate

Vinyl acetate (VAc) and butyl acrylate (BuA) were copolymerized in heterophase by a semicontinuous process (unseeded) and compared with the seeded semicontinuous microemulsion polymerization of the same monomers. A mixture of sodium dodecyl sulfate (SDS) and poly(ethylene oxide) dodecyl ether (Brij‐35®) were used as surfactants. The effects of monomer addition rate (R_a) and surfactants concentrations (4 or 1 wt % with respect to the initial mixture of reaction) on polymer and latex properties were studied. High copolymer content latexes (24–36 wt %) with average particle diameters (D_p) from 38 to 55 nm and relatively narrow particle size distributions, high polymerization rates, weight ratios of polymer to surfactant (P/S) from 13.3 to 32.8 were obtained. The number‐average molecular weights (M_n) were between 96,000 and 188,000 g/mol. Homogeneous copolymer compositions were obtained throughout the reaction for both, seeded and unseeded processes, which is not possible by the usual batch microemulsion process. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis of poly(methyl methacrylate) nanoparticles initiated by azobisisobutyronitrile using a differential microemulsion polymerization technique

Nanosized poly(methyl methacrylate) (PMMA) particles with a high molecular weight of 10⁶ g mol^?1 and a polydispersity index of about 1–2 were synthesized, for which 2,2′‐azobisisobutyronitrile was used as the initiator and a differential microemulsion polymerization technique was employed. The kinetics of the polymerization, the glass transition temperature, tacticity, the particle size distribution, and the morphology of the nanosized PMMA synthesized were investigated. The dependence of the number of the polymer particles (N_p) and the number of the micelles (N_m) on the concentration of the surfactant was discussed. The molecular weight distribution was found to be nearly constant over the polymerization time, which was attributed to the significance of micellar polymerization. The resultant nanosized PMMA has a rich syndiotactic configuration (53–57% rr triads) with a glass transition temperature of about 125°C. A beneficial operation condition was discovered where the conversion reached a maximum at a high monomer‐to‐water ratio. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Narrow size‐distribution poly(methyl methacrylate) nanoparticles made by semicontinuous heterophase polymerization

The effect of surfactant (sodium dodecyl sulfate) concentration on particle size, molar masses, glass transition, and tacticity of poly(methyl methacrylate) (PMMA) nanoparticles synthesized by semicontinuous heterophase polymerization under monomer‐starved condition at constant monomer feeding rate is reported. Starved conditions are confirmed by the low amount of residual monomer throughout the reaction and by the fact that the instantaneous polymerization rate is similar to the feeding rate of monomer. Under these conditions, polymer particles in the nanometer range (20–30 nm) were obtained with narrow size distribution (1.07 < D_w/D_n < 1.18), depending of surfactant concentration. Final particle size diminishes as the surfactant concentration is increased. Glass transition temperatures and syndiotactic content (54%–59%) of the produced polymers are substantially higher than those reported for commercial and bulk‐made PMMA. Molar masses are much lower than those expected from termination by chain transfer to monomer, which is the typical termination mechanism in 0–1 emulsion and microemulsion polymerization of this monomer. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation of narrowly distributed nanoparticles of poly(n‐butyl methacrylate‐co‐vinyl pyrrolidone) through microemulsion polymerization

Narrowly distributed nanoparticles of poly (n‐butyl methacrylate‐co‐vinyl pyrrolidone) were prepared through microemulsion polymerization with a nonionic surfactant of Tween‐80 as emulsifier (6 wt % of the latex) and n‐butanol as coemulsifier. The polymerizations were initiated with benzoylperoxide (BPO), potassium persulfate (KPS), KPS/ferric sulfate (FeSO₄), and BPO/FeSO₄, respectively, where the initiation in the case of BPO/FeSO₄ took place mainly at the interphase between the oil phase and the reaction media. Namely, this interfacial‐initiated microemulsion polymerization resulted in larger particles with relatively narrower particle size distribution as well as higher limiting monomer conversion but lower polymerization rate compared with the polymerization initiated with KPS/FeSO₄. In this article, the influences of initiation method, monomer ratio, and addition of water‐soluble components on microemulsion polymerization and latex particle size were studied to discuss the mechanism of interfacial‐initiated microemulsion polymerization. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2334–2340, 2004     

Concentrated emulsion copolymerization of butyl acrylate and vinyl acetate initiated by a redox initiator at lower temperature

The concentrated emulsion copolymerization of butyl acrylate and vinyl acetate with an ammonium persulfate/sodium hydrogen sulfate mixture as a redox initiator, with a sodium dodecyl sulfate/cetyl alcohol mixture as a compound surfactant, and with poly(vinyl alcohol) as a liquid film reinforcer was carried out at lower temperature. In less than 3 h, the polymerization conversion was greater than 95%. The effects of the surfactant, the initiator, the volume fraction of the monomer, and the temperature on the stability of the concentrated emulsion, the kinetic process, and the average size of the latices were examined. The morphology of the polymer particles was observed by transmission electron microscopy, and the average size and distribution of the particle diameter were measured by photon correlation spectroscopy. The kinetic equation was R_p = k[M]^0.38[I]^0.89[E]^?0.80 at 30°C (where R_p is the polymerization rate, [I] is the initiator concentration, [M] is the monomer concentration, and [E] is the concentration of the compound surfactant), and the apparent activation energy was 22.69 kJ/mol. The thin‐layer polymerization of the concentrated emulsions, which enabled the removal of the heat of polymerization, was performed first. In comparison with test‐tube polymerization, thin‐layer polymerization provided a more regular morphology of the polymer particles. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 570–576, 2004     

Preparation of soap‐free cationic emulsion using polymerizable surfactant

A kind of polymerizable surfactant, methacryloyloxyethylhexadecyldimethylammonium bromide (DMHB) was used to synthesis soap‐free cationic emulsion with styrene (St), methyl methacrylate (MMA), and methacryloyloxyethyltrimethylammonium chloride (MATMAC) by emulsion polymerization using 2,2′‐azobis(isobutylamidine hydrochloride) (AIBA) as a cationic initiator. The effects of polymerizable surfactant concentration, initiator concentration, and reaction temperature on the conversion of monomer were investigated. The results indicated that the rate of polymerization could be expressed as R_p = k_p[AIBA]^0.42[DMHB]^0.45 and the apparent activation energy (E_a) was 83.42 kJ/mol. The particle size, ζ potential, and apparent charge density of cationic latices were also measured. The average diameter of copolymer particles decreased with increasing DMHB, MATMAC, and AIBA content; the charge properties of the particles were decided by the DMHB, MATMAC, and AIBA content. The polymerization mechanism is discussed. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1111–1116, 2006     

Polymerization of methyl methacrylate in micellar phase: A kinetic study

Polymerization of methyl methacrylate (MMA) using Ce(IV) as initiator in aqueous nitric acid solution in the presence of sodium lauryl sulphate (NaLS) has been studied kinetically at a temperature range of 25–35°C. The rate of polymerization (R_p) increases with increasing concentration of NaLS, and it was also proportional to [MMA]²; but, in the presence of NaLS, the change of R_p with respect to [Ce(IV)] and [H⁺] were not linear and similarly the rate of Ce(IV) disappearance was not proportional to its original concentration. The overall activation energy of the polymerization process in presence of 0.01M NaLS was found to decrease by ～ 7.0 kcal mol^?1. The monomer–micelle association constant has been calculated to be 5.135 × 10⁴ mol^?1 L. The polymer obtained in surfactant medium is sparingly soluble in benzene and DMSO. From infrared spectra clear evidence of vinyl polymerization was obtained.     

Functionalizable composite nanoparticles as a dual magnetic resonance imaging/computed tomography contrast agent for medical imaging

A dual contrast agent for computed tomography (CT) and magnetic resonance imaging (MRI) was synthesized via microemulsion polymerization. This contrast agent consists of Fe₃O₄ particles (d = 7 nm) with an iodine-carrying nanopolymeric shell, with overall particle sizes ranging from 50 to 250 nm. 2-Methacryloyloxyethyl(2,3,5-triiodobenzoate) was used as the monomer. Sodium oleate was used as the surfactant and its amount was varied to control the overall particle size. The composite nanoparticles were mainly characterized via dynamic light scattering, with further analyses using transmission electron microscopy and atomic force microscopy. The particles provided a highly visible contrast in CT and MR images. A template for biomedical applications was created by adding a comonomer and the particles were further functionalized with the somatostatin analogue Tyr³-octreotate. The particles were tested for specific uptake into somatostatin receptor-positive AR42J cells. The additional uptake of the functionalized particles was investigated. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47571.     

Kinetics of polymerization and particle stabilization mechanism on dispersion copolymerization of styrene and divinylbenzene

Monodisperse highly crosslinked microspheres were prepared by dispersion copolymerization of styrene and divinylbenzene in an ethanol/water medium using poly(N‐vinylpyrrolidone) (PVP) as the stabilizer. The locus of polymerization and growth of particles were investigated. The polymerization kinetics, average particle diameter (D_n), polydispersity index (PDI), and numbers of particles (N_p) were presented. When the initial styrene concentration is below 20%, the results indicate that the polymerization occurs in the particles, and the particles grow to their final size by the diffusion of monomer and oligomer into the existing particles. The polymerization rate can be described by the equation R_p = k[l]^0.87 ([St]^1.91 + [DVB]^0.09) (1 + [PVP]^0.01) exp(? 45.35/RT). The data from infrared spectroscopy demonstrated that the graft stabilizer was present. The dissolution experiments show that the crosslinking reaction occurred irregularly in batch dispersion polymerization. Using the postaddition approach, up to 3% divenylbenzene (DVB) was successfully incorporated in the synthesis of coagulum‐free substance, and monodisperse crosslinked 5 μ m microspheres with a superior resistance to solvents have been prepared. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2230–2238, 2002     

Synthesis and structure of the poly(methyl methacrylate) microlatex

Microemulsion polymerization is a new approach for preparing nanosize polymer materials. In this article, a nanosize poly(methyl methacrylate) (PMMA) was prepared by a novel microemulsion polymerization. The kinetics of the polymerization and the effects of the temperature, the monomer, and emulsifier/water ratio on the polymerization were investigated by means of the conversion, the transmittance, and the refractive index measurements. The structure of the obtained PMMA microlatex was studied through transmission electron microscopy (TEM), nuclear magnetic resonance (¹H‐NMR), and differential scanning calorimetry (DSC). The results show that the polymerization exhibits typical kinetic characteristics of a microemulsion polymerization, i.e., there only exists two rate stages: a stage of increasing rate, and a stage of decreasing rate, and no constant rate stage is observed during the polymerization. The obtained PMMA microparticles are very uniform, regular, and small, being about 17–33 nm in the number‐average diameter. The polymer has higher molecular weight (1.71 × 10⁶ viscosity average molecular weight), higher tacticity (51% syndiotacticity), and higher glass transition temperature (127°C), much different from the commercial PMMA. Experimentally, a stable and transparent PMMA microlatex with higher polymer content (30–40 wt %), lower weight ratio of emulsifier to water (E/W ≤ 0.03) and emulsifier to monomer (E/M ≤ 0.05) as well as smaller particle size (d_p < 40 nm), has been prepared, which is very important for the industrialization of the microemulsion polymerization technique. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2839–2844, 2002     

Radical polymerization behavior of dimethyl vinylphosphonate: Homopolymerization and copolymerization with trimethoxyvinylsilane

Dialkyl vinylphosphonates such as dimethyl vinylphosphonate (DMVP) and diethyl vinylphosphonate were quantitatively polymerized with dicumyl peroxide (DCPO) at 130°C in bulk. The polymerization of DMVP with DCPO was kinetically studied in bulk by fourier transform near‐infrared spectroscopy (FTNIR) and electron spin resonance (ESR) spectroscopy. The initial polymerization rate (R_p) was given by R_p = k[DCPO]^0.5[DMVP]^1.0 at 110°C, being the same as that of the conventional radical polymerization involving bimolecular termination. The overall activation energy of the polymerization was estimated to be 26.2 kcal/mol. The polymerization system involved ESR‐observable propagating polymer radicals under the practical polymerization conditions. ESR‐determined rate constants of propagation (k_p) and termination (k_t) were k_p = 19 L/mol s and k_t = 5.8 × 10³ L/mol s at 110°C, respectively. The molecular weight of the resultant poly(DMVP)s was low (M_n = 3.4 ? 3.5 × 10³), because of the high chain transfer constant (C_m = 3.9 × 10^?2 at 110°C) to the monomer. DMVP (M₁) showed a considerably high reactivity in the radical copolymerization with trimethoxyvinylsilane (TMVS) (M₂) at 110°C in bulk, giving an inorganic component‐containing functional copolymer with potential flame‐retardant properties; r₁ = 1.6 and r₂ = 0. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Kinetics of emulsion polymerization of styrene using the reactive surfactant HITENOL BC20

The effect of the reactive surfactant HITENOL BC20 (polyoxyethylene alkylphenyl ether ammonium sulfate; 20 U of ethylene oxide (EO)) on the emulsion polymerization of styrene was studied via reaction calorimetry (Mettler RC1; 70°C). For polymerizations carried out above the cmc of BC20, the reaction kinetics and evolution of the number of particles (N_p) resembled those reported using the conventional surfactant sodium lauryl sulfate, indicating that nucleation proceeded by a combination of micellar and homogenous nucleation (Interval I and Stage 2). The reaction rate (R_p) not only increased with increasing initiator (K₂S₂O₈) and surfactant concentrations, as expected, but the increase in rate in Stage 2 was dependent on the initiator concentration and independent of the surfactant concentration. This is consistent with the proposed nucleation mechanisms. The molecular weight increased with increasing surfactant concentration and decreasing initiator concentration as would also be expected for a conventional surfactant. The dependencies of R_p and N_p on the BC20 and initiator concentrations, however, were lower than the classical Smith‐Ewart values (R_p ∝ [E]^0.47–0.52; R_p ∝ [I]^0.21–0.25) although R_p was found to be directly proportional to N_p. Chain transfer to the reactive surfactant is considered a likely source of divergence. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis of substituted polymethylenes from acenaphthylene by radical polymerization and copolymerization

Radical polymerization of acenaphthylene (Ace) as a 1,2-disubstituted ethylene was investigated. It was found that the polymerization rate (R_p) was expressed as follows: R_p = k[Ace]^1.0[AIBN]^0.68, and that the overall activation energy was 113 kJ/mol for polymerization with 2,2'-azobisisobutyronitrile (AIBN) in benzene at 50–70°C. Poly(Ace) obtained was characterized by NMR spectroscopy and GPC. Some substituted copolymethylenes were also prepared by radical copolymerization of Ace with other 1,2-disubstituted ethylenes, that is, maleic anhydride, diisopropyl fumarate, and N-cyclohexylmaleimide. The monomer reactivity ratios were determined from comonomer–copolymer composition curves.     

Batch and semicontinuous emulsion copolymerization of vinylidene chloride and butyl methacrylate. I. Kinetics in VDC–BMA emulsion polymerization and surface and colloidal properties of VDC–BMA latexes

Vinylidene chloride (VDC)—butyl methacrylate (BMA) comonomer mixtures with various composition (83 : 17, 60 : 40, 33 : 67 in mol %) were polymerized at 25°C using redox catalyst by batch and seeded semicontinuous emulsion copolymerization. The reactivity ratios determined in VDC (M₁)—BMA (M₂) emulsion copolymerization system were r₁ = 0.22 and r₂ = 2.41. Seven 35% solids (83 : 17 mol %) VDC–BMA copolymer latexes were prepared: one batch (G), one seeded batch (F), and 5 seeded semicontinuous polymerizations of 5 different monomer feed rates ranging from 0.27 (A) to 1.10 wt %/min (E). The kinetic studies of seeded semicontinuous polymerizations A-E showed that the rates of polymerizations (R_p) were controlled by the monomer addition rates (R_a). The conversion versus time curves for the polymerizations of 0 : 100–100 : 0 VDC–BMA mixtures by batch polymerization showed that the rate of polymerization (R_p) was a function of the number of particles, and that the rate of polymerization in a latex particle (R_pp) increased with increasing proportions of butyl methacrylate in the monomer mixture. All of the latexes had narrow particle size distributions. The greater particle number density in VDC polymerization and the greater water solubility of VDC suggest that the homogeneous nucleation mechanism is operative in VDC–BMA copolymerizations. The latex copolymers prepared by semicontinuous polymerization had lower number-and weight-average molecular weights than those of the corresponding batch copolymers, resulting from the monomer starvation occurring during the semicontinuous polymerization. The surface characterization study of the cleaned latexes showed that for the latexes by batch process, the surface charge density derived from strong-acid groups decreased with increasing proportion of VDC in the monomer mixture. On the other hand, for the latexes prepared by semicontinuous polymerization, the surface charge density derived from strong-acid groups did not depend on the monomer composition of the copolymers.     

Polymerization of vinyl acetate in ternary microemulsions stabilized with hexadecyltrimethylammonium bromide

The polymerization of vinyl acetate (VA) in three component o/w microemulsions stabilized with the cationic surfactant, CTAB, is presented. Initiation is achieved thermally with a water soluble initiator (V-50). Stable latex containing small particles (ca. 35 nm) with molecular weights (M_w) of around 4 × 10⁵ are obtained. Analysis of the molecular weight distribution suggests that chain transfer to monomer (and not to polymer, which is the typical termination mechanism in emulsion polymerization, specially at high conversions) is the dominant mechanism of termination. Received: 11. October 1996/Revised: 16 January 1997/Accepted: 21 January 1997     

The polymerization of acenaphthylene by sulphuric acid in methylenedichloride

Summary Acenaphthylene was polymerized in methylenedichloride at 273, 291 and 308 K by sulphuric acid. The initiation step takes place by addition of the proton of sulphuric acid to the monomer. The propagation step is through ion-pairs, and the propagation constants are first-order with respect to the monomer and initiator(k_p = 0.22 M^–1. s^–1(273K), k_p=0.88 M^–1. s^–1(291K), k_p = 2.81 M^–1. s^–1 (308K)). There is not appreciable loss of active centres, being this confirmed by experiments carried out with succesive additions of monomer. The molecular weights obtained confirm the importance of processes to monomer in this polymerization.     

Effect of sodium lauryl sulfate on the polymerization of acrylonitrile

Micellar catalyzed polymerization of acrylonitrile using ceric(IV)–glycerol redox system in aqueous sulfuric acid solution in the presence of sodium lauryl sulfate (NaLS) has been studied. The polymerization experiments were conducted between 15°C and 25°C, under conditions where no oxidation of sodium lauryl sulfate by ceric ion would we expected. The rate of polymerization (R_p) increases with increasing concentration of NaLS. The rate of monomer (AN) disappearance was proportional to [AN]^1.5 and [glycerol]^0.5, but, however, R_p changes in a nonlinear manner with increase in Ce(IV) concentration in the presence of the surfactant. The rate of Ce(IV) disappearance was not proportional to its original concentration. The chain length of the polymer could not be determined viscometrically, as the polymer obtained in presence of NaLS was insoluble in organic solvents. The activation energy of this polymerization process was calculated by conducting the experiment at different temperatures. The infrared spectra of the polymers in the presence and absence of surfactant have also been examined.     

Effect of partitioning of monomer on the reactivities of monomers in microemulsion

Copolymerization of styrene and 2‐hydroxyethyl methacrylate (2‐HEMA) was carried out in a microemulsion medium. The composition of the copolymers was estimated using proton ¹H‐NMR. The reactivity ratios of styrene and 2‐HEMA in ternary microemulsions were observed and were considerable different from those reported for solution and bulk polymerization. In monomer pairs with a considerable difference in polarity, partitioning of a monomer between the aqueous phase and the microemulsion droplets develops a concentration gradient, which can be calculated from the distribution coefficient of the monomer between the two phases. This approach has led to more reliable reactivity ratios for the monomers. The study of styrene–2‐HEMA copolymerization in a sodium dodecylsulfate‐based microemulsion resulted in r_S = 3.79 and r_H = 0.17 as apparent reactivity ratios and r_S = 0.57 and r_H = 23.24 as true reactivity ratios for styrene and 2‐HEMA, respectively. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1832–1837, 2002; DOI 10.1002/app.10401     

Interfacially initiated microemulsion copolymerization: One‐stage preparation of poly(n‐butyl methacrylate)–poly(N‐vinyl pyrrolidone) core–shell nanoparticles

Interfacially initiated microemulsion copolymerizations of n‐butyl methacrylate (BMA) and N‐vinyl pyrrolidone (NVP) by the redox initiation couple of benzoyl peroxide and ferrous sulfate were carried out with Tween 80 and n‐butanol as the surfactant and cosurfactant, respectively. Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy were recorded to analyze the chemical composition of the latex particles. Transmission electron microscopy was used to observe the particle morphology and dynamic light scattering to determine the particle size. The results demonstrated that interfacially initiated microemulsion polymerization prompted the copolymerization of the water‐soluble NVP monomer with the oil‐soluble BMA monomer to form core–shell nanoparticles. The influence of the surfactant concentration, BMA amount, and temperature on the particle size and polymerization rate was investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3751–3757, 2006     

Microemulsion polymerization of styrene using developed redox initiation system and study of rheological properties of obtained latices

Microemulsion polymerization of styrene was kinetically studied using a potassium persulfate (KPS)/P‐methyl benzaldehyde sodium bisulfite (MeBSBS) adduct as the developed redox pair initiation system. The rate of microemulsion polymerization of styrene was found to be dependent on the initiator, emulsifier, and monomer to the powers of 1.4, −0.77, and 0.83, respectively. The apparent Arrhenius activation energy (E_a) estimated for the microemulsion polymerization system was 6.5 × 10⁴ J/mol. Also, the morphological parameters were studied at different initiator concentrations. The rheological measurements for the prepared microemulsions were carried out to investigate the effect of the preparation parameters on the rheological behavior of the polystyrene microemulsions. The rheological flow curves of the polystyrene microemulsion latices prepared at different temperatures were carried out, and we found that the plastic viscosity and Bingham yield values of the flow curves increased with an increasing reaction temperature. That may be due to the cage effect of the prepared polymer particles, which trapped the medium molecules. The plastic viscosity increased with increasing emulsifier concentration while the Bingham yield value decreased. For the polystyrene microemulsion prepared in the presence of different initiator concentrations, the plastic viscosity and Bingham yield increased with increasing initiator concentration. This trend was found to be the same for the microemulsion latices prepared in the presence of different monomer concentrations. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1240–1249, 2000