Iran Polym J (2015) 24:41–50 DOI 10.1007/s13726-014-0298-8
ORIGINAL PAPER
Ultrasound‑assisted polymerization of methyl methacrylate using the reactive surfactant Hitenol BC10 in a semicontinuous heterophase process Citlalli Y. Vargas‑Salazar · Víctor M. Ovando‑Medina · Raquel Ledezma‑Rodríguez · René D. Peralta · Hugo Martínez‑Gutiérrez
Received: 10 June 2014 / Accepted: 3 December 2014 / Published online: 16 December 2014 © Iran Polymer and Petrochemical Institute 2014
Abstract Semicontinuous heterophase polymerization was used to polymerize methyl methacrylate (MMA) with the reactive surfactant Hitenol BC10 (polyoxyethylene(10) alkylphenyl ether ammonium sulfate, HBC10) in the presence of ultrasound at 50 °C. The effects of HBC10 concentrations and the monomer addition rate (Ra) on kinetics, colloidal behavior, and molar masses were studied. Latexes with polymer content between 20 and 24 % were obtained. Particle size distributions (PSD) of latexes without HBC10 were bimodal, whereas those obtained in the presence of HBC10 were mono-modal in all cases. The average particle diameters (Dp) were in the range of 39–63 nm decreasing with the HBC10 concentration and increasing with Ra. Polymerization rates (Rp) were decreased, by increasing the HBC10 concentration, which was ascribed to chain transfer events to HBC10. It was also observed that Rp increased
with Ra; however, monomer-starved conditions were favored at lower Ra values. Very high-average molecular weights were observed (1.63 × 106 ≤ Mw ≤ 2.34 × 106 g/ mol) which decreased when HBC10 concentration increased, and increased with Ra. The corresponding polydispersity indexes (Mw/Mn) were in the range of 1.55–2.30, showing relatively wide molar masses distributions. It was observed from differential scanning calorimetry that polymers with HBC10 presented two Tg (123 and 178 °C) which was ascribed to HBC10 incorporated to PMMA chain, corroborated by 1H NMR.
C. Y. Vargas‑Salazar · V. M. Ovando‑Medina (*) Departamento de Ingeniería Química, Coordinación Académica Región Altiplano (COARA), Universidad Autónoma de San Luis Potosí, Carretera a Cedral KM 5+600, San José de Las Trojes, 78700 Matehuala, SLP, Mexico e-mail:
[email protected]
Surfactants are widely used and find a very large number of applications because of their remarkable ability to influence the properties of surface and interfaces [1]. One of their most useful applications is the production of polymeric latexes by dispersion, emulsion, mini-emulsion and micro-emulsion polymerization systems [2]. They impact strongly the nucleation of latex particles, emulsification of monomer droplets, stabilization of polymer particles throughout polymerization and the shelf-life (stability) of the products [3–5]. Some negative effects of the presence of conventional surfactants in the latex are foaming and migration to interfaces during film formation, resulting in water sensitivity [6]. These deficiencies can be reduced or eliminated by covalent bonding of surfactant molecules into the latex particles [7]. A reactive surfactant is an amphiphilic molecule with an additional functionality that provides it with chemical
R. Ledezma‑Rodríguez Departamento de Materiales Avanzados, Centro de Investigación en Química Aplicada (CIQA), Blvd. Enrique Reyna 140, 25253 Saltillo, Coahuila, Mexico R. D. Peralta Departamento de Ingeniería de Reacciones de Polimerización, Centro de Investigación en Química Aplicada (CIQA), Blvd. Enrique Reyna 140, 25253 Saltillo, Coahuila, Mexico H. Martínez‑Gutiérrez Centro de Nanociencias y Micro y Nanotecnologías, Instituto Politécnico Nacional (IPN), Luis Enrique Erro S/N, 07738 Mexico, DF, Mexico
Keywords Nanoparticles · Ultrasound · Reactive surfactant · Heterophase polymerization
Introduction
Iran Polymer and Petrochemical Institute
13
42
Iran Polym J (2015) 24:41–50
reactivity [8]. Since the early 1990s, the application of reactive surfactants in heterophase polymerization has become a vast topic in its own right [9]. Reactive surfactants can be used in hetero-phase polymerizations as surfmers, inisurfs, or transurfs are covalently bonded to the polymer chains, avoiding migration of surfactants in the final application and preventing the formation of hydrophilic spots with higher water uptake in hydrophobic coatings [10]. The use of reactive surfactants in the polymerization of different monomers has been reported elsewhere [11– 13]. For example, Atta et al. [11] used the nonionic reactive surfactant Noigen RN20 (polyoxyethylene 4-nonyl2-propylene-phenol) in the preparation of amphiphilic gel nanoparticles (surfmer) by reacting Noigen RN20 with maleic anhydride followed by esterification with poly(ethylene glycol). The as-prepared nanogels showed a great reduction in interfacial tension values between formamide and styrene mixture to obtain cross-linked styrene-co-2-acrylamido-2-methylpropane sulfonic acid microgel in the presence of divinylbenzene and formamide as organic solvents. In a previous report, we studied the effect of MMA/ HBC10 weight ratio on kinetic parameters, colloidal and molar mass during semi-continuous heterophase polymerization (SHP) at constant Ra without the presence of ultrasound with the objective of developing the optimized conditions to obtain poly(MMA-co-HBC10) with low water sensitivity, resulting in increased performance of film formation [14]. However, latexes with bimodal particle size distributions (PSD) were obtained. Nanoparticles with monomodal and narrow PSDs are useful for some applications in which the specific surface area is determined, because this morphology and their greater surface/volume ratio allow them to access sites that cannot be reached otherwise. Ultrasound provides an unusual mechanism for generating high-energy chemistry and improves the reaction rate, and has opened up a new area of chemistry, i.e., sonochemistry [15]. The chemical effects of ultrasound (usually frequencies in the range of 20–1 MHz [16]) derive primarily from the acoustic cavitation phenomenon. Table 1 Experimental conditions used in the polymerizations and weight– average molecular weight and polydispersity index (PDI) of polymers and z-average particle diameters (Dp) of latexes
N.D. not determined
Iran Polymer and Petrochemical Institute
13
Implosive bubble collapse in liquids results in a highenergy concentration from the conversion of the kinetic energy of the liquid motion into heating of the contents of the bubble. Advantage can be taken from the high local temperatures and pressures, and the rapid cooling, to increase the efficiency of some chemical reactions [17]. Especially, shock wave of ultrasound not only can accelerate the heterogeneous liquid–liquid or liquid/ solid chemical reactions, but also can disrupt the agglomeration and decrease the resulting nanoparticle diameters due to its dispersion, crushing and emulsifying effect, and thus a better control on the morphology of particles can be achieved, especially on the polymeric nanoparticles [18]. In the present work, we polymerized MMA in SHP and in the presence of the reactive surfactant HBC10, using ultrasound to control particles’ morphology. The effects on kinetic parameters, colloidal behavior and molar masses that vary the Ra and MMA/HBC10 weight ratio were studied.
Experimental Materials Sodium dodecyl sulfate (SDS) was purchased from Hycel (Guadalajara, Mexico) (≥98 %). HBC10 was generously provided by Dai-Ichi Kogyo Seiyaku Co., Ltd. (Japan) (>98 %), through Montello, Inc. (Tulsa, USA). All the other reactants were purchased from Aldrich (Toluca, Mexico) (≥99 %) and were used as received. Distilled grade water and argon of ultrahigh purity from Infra™ were used in all experiments. The experimental conditions used in each reaction are given in Table 1. Methods Polymerization was carried out at 50 °C and 200 rpm in a two-neck 250-mL glass-jacketed reactor equipped with magnetic stirring. An ultrasonic processor (USA,
Run
MMA (g)
HBC10 (g)
Ra (g/min)
Mw × 10−6 (g/mol)
PDI (Mw/Mn)
Dp (nm)
1 2 3 4 5 6 7
40.0 39.2 38.4 37.6 36.8 39.2 39.2
0 0.8 1.6 2.4 3.2 0.8 0.8
0.4 0.4 0.4 0.4 0.4 0.2 0.5
1.63 1.93 1.91 1.84 1.75 1.73 2.34
2.30 2.00 1.55 1.70 2.00 1.80 1.55
63 50 41 40 52 39 54
8
39.2
0.8
0.6
N. D.
N. D.
58
Iran Polym J (2015) 24:41–50
Cole-Parmer Instruments, CPX 130) with a power output of 130 W and frequency of 20 kHz at 40 % of amplitude was connected to a probe (USA, Cole-Parmer, CV18) which was inserted in one neck of the reactor, and in contact with the reaction mixture since the beginning of reaction and throughout polymerization time. Then, SDS (2.0 g to form some initial micelles), water (130 g) and KPS (0.1 g) were charged to the reactor; afterwards, the system was cooled to 15 °C and purged with argon for 1 h to remove oxygen. Then, the mixture was brought to the reaction temperature by passing hot water through the reactor jacket during 10 min; at this point, the MMA/HBC10 mixture was added to the reactor using a gas tight 100 mL syringe adapted to a calibrated addition pump (USA, Kd-Scientific®) and using a constant monomer addition rate (Ra). After the semi-continuous addition period, the reactions were allowed to continue for 1 h to achieve higher monomer conversions. Conversion was followed gravimetrically: samples were withdrawn from the reacting system at given times and placed in vials (of known weight) immersed into an ice bath to stop polymerization. Then, the samples were weighed and dried at 60 °C in an oven by 48 h. Conversions were determined from a mass balance.
43
Water absorption ratio of polymer films was determined according to Huang et al. [19]. Accordingly, polymer samples were solubilized in THF, casted onto a glass dish and letting the solvent evaporate slowly at room temperature. Dimensions of the film samples were 2.0 cm length, 1.5 cm width, and 0.03 ± 0.01 mm thickness. The latex films were soaked in deionized water for 48 h, then the sample was taken out from the deionized water, excess water at film surfaces was gently removed using soft wipes and the films were weighed. Percentage of water absorption was calculated as follows:
Wabs (wt%) =
W1 − W0 × 100 W0
(1)
Characterization Particle size was determined by quasi-elastic light scattering (UK, Malvern, Nano S90 apparatus) at 25 °C. Polymer samples taken for gravimetry were purified, washed several times with hot water to remove surfactants and initiator, and dried at 40 °C for molar masses determinations. Average molar masses and molar masses’ distributions of polymers (previously dissolved in THF at 1 mg/mL) were determined in gel permeation chromatograph apparatus (USA, Alliance Waters, 2695) with two columns PLgel Mixed C 5µ and a flow rate of 1 mL/min, with a refraction index detector. Purified polymer samples were also analyzed by 1 HNMR at room temperature (Japan, JEOL, 300 MHz) with a 10 mg/mL solution of the polymer using CDCl3 and with TMS as the internal reference. Scanning electron microscopy (SEM) was made using a JEOL high-resolution microscope (JSM 7800F) in STEM mode at 28 kV of beam acceleration. Samples were prepared as follows: 1 g of sample was dispersed in 50 g of distilled water. Afterwards, a drop of the dispersed sample was poured onto a copper grid coated with Formvar™ resin and carbon film, and then it was allowed to dry overnight at room temperature. Differential scanning calorimetry (DSC) analyses were carried out in a simultaneous TGA-DSC SDT (USA, TA Instruments, Q600) apparatus. Samples of 5–10 mg were encapsulated in standard aluminum pans. Thermograms were recorded at a heating rate of 5 °C/min over a range of 25–270 °C.
Scheme 1 Chemical structure of PMMA linked to HBC10
Fig. 1 1H NMR spectra of polymers obtained from Runs 1, 2 and 5
Iran Polymer and Petrochemical Institute
13
44
Iran Polym J (2015) 24:41–50
where W0 and W1 are the weight of the films before and after water absorption, respectively. Results and discussion The incorporation of HBC10 to PMMA was demonstrated by 1HNMR. Scheme 1 shows the chemical structure of the copolymer of poly(MMA-co-HBC10). The 1HNMR spectra corresponding to samples of Runs 1, 2 and 5 are shown in Fig. 1, where the signals corresponding to chemical structure of Scheme 1 can be seen. The singlet at 3.6 ppm corresponds to the protons of the –CH3 in PMMA (3); the signals observed at 1.6 ppm in the spectra of Runs 2 and 5 (in which HBC10 was used) are corresponding to protons of the aliphatic chain linked to the aromatic ring of HBC10 part (2). The peak around 3.65 ppm of polymers obtained from Runs 2 and 5 represents protons of the ethylene oxide units of the HBC10 structure (1). Thus, HBC10 units were chemically bonded to the PMMA structure. A semi-continuous hetero-phase polymerization (SHP) process was used in this work. In this process, usually reactants (water, surfactant and initiator) except monomer are charged to the reactor, thus only empty surfactant micelles are present initially. Monomer is fed continuously at a constant rate (Ra) to start polymerization. In this work, we charged water, SDS and KPS, and then the MMA/HBC10 mixture was fed at constant Ra to the reactor. The initially clear micellar solution in the reactor turned bluish and translucent at the beginning of addition of the monomer mixture indicating polymer formation. Figure 2 shows the instantaneous and global conversions observed at different HBC10 concentrations, as a function of relative time, τ. Relative time was defined as the ratio of polymerization time to total monomer addition time.
Fig. 2 Plots of instantaneous and global conversions obtained at different HBC10 concentrations
Iran Polymer and Petrochemical Institute
13
Final conversions between 80 and 90 % were obtained. It can be seen that using a low HBC10 concentration (Run 2), a higher conversion can be achieved; however, at higher HBC10 concentrations, conversion values decrease. The same behavior was observed in the corresponding polymerization rates (Rp) as can be observed in Fig. 3. It has been reported that high concentrations of reactive surfactants decrease polymerization rate by chain transfer to surfactant [14, 20, 21]. In a previous work [14] in which ultrasound was not used in the polymerization, conversions of only 70–85 % were reached. Then, ultrasound has an important effect on kinetics polymerization by facilitating monomer diffusion between phases and decreasing particles sizes, as will be
Fig. 3 Plots of polymerization rates obtained at different HBC10 concentrations
Fig. 4 Variation of instantaneous conversion as a function of relative polymerization time using only HBC10 as surfactant (SDS-free)
Iran Polym J (2015) 24:41–50
discussed later. Aguilar et al. [22] studied the effect of surfactant concentration in the heterophase polymerization of MMA using only SDS as surfactant, and found that instantaneous conversion increases with SDS concentration, which supports the assumption of chain transfer to HBC10 in our experiments. To compare the results of SDS-free polymerizations with those obtained in the presence of the mixture of HBC10/SDS surfactants, a reaction was conducted in similar conditions of Run 2 as shown in Table 1 but with 2.8 g of HBC10. Figure 4 shows the instantaneous conversion as a function of relative polymerization time. It can be observed that lower reaction rate and conversions are obtained, which can be ascribed again to chain transfer events. Moreover, kinetics is very similar to that observed for Run 4, in which high HBC10 concentration was used. On the other hand, the period in which Rp remains almost constant (beyond ca. 0.3 of relative time in Fig. 3) is known as the pseudo-steady state polymerization conditions (Rpss). It can be observed that Rpss for Run 2 was nearest to Ra, thus favoring monomer-starved condition in the system. The requisite for starved nucleation to occur is that the rate of polymerization should be tightly controlled by the rate of monomer addition and the absence of monomer droplets in the reaction system should be ensured [23]; in other words, if Ra is high enough to maintain monomer saturation concentration in the polymer particles, Rp becomes independent of Ra (flooded region). However, if the monomer concentration in the polymer particles falls below this value, Rp approaches a constant value which depends on Ra (monomer-starved condition) [24, 25]. Before polymerization can start, the added monomer has to be dissolved in the water phase and diffuse into the micelles. This imposes some delay time, which decreased with increasing Ra [22]. Figure 5 shows the kinetics of
Fig. 5 Plots of instantaneous and global conversions obtained at different values of Ra
45
polymerization at different Ra as a function of relative time. It can be seen that high conversions (about 90 %) can be obtained. As expected, polymerization rate increased with Ra (Fig. 6); however, Rpss approaches Ra as this variable decreases (Ra = 0.2 g/min). Dimitratos et al. [25] demonstrated that for emulsion polymerizations in the pseudo-steady state under monomer-starved condition, Rpss is related to Ra as follows: •
(2)
1/Rpss = 1/ K +c/Ra •
where K is a constant which indicates the capacity of the system to consume monomer, and is proportional to the number of particles, to the average radicals per particle and to the propagation rate coefficients; c is a constant which is theoretically equal to 1 [25].
Fig. 6 Plots of polymerization rates obtained at different values of Ra
Fig. 7 Plot of reciprocal of the polymerization rate vs. reciprocal of monomer addition rate at the pseudo-steady state of polymerization
Iran Polymer and Petrochemical Institute
13
46
Iran Polym J (2015) 24:41–50
Fig. 8 Particle size distribution obtained by QLS at different HBC10 concentrations
Fig. 9 Particle size distribution obtained by QLS at different values of Ra
Figure 7 shows the reciprocal of the Rpss vs. Ra calculated from Fig. 6. It can be seen that by decreasing Ra, Rpss got nearest to Ra, nevertheless, the value of Ra would have to be very •low to achieve true monomer-starved condition; however, K value was high (0.037 mol/min) and c value was near to unity, which demonstrates the high capacity of monomer consumption under the studied conditions. Ledezma et al. [26] studied the semicontinuous polymerization of MMA under monomer-starved conditions at different Ra using a mixture of SDS/AOT (3/1 wt/wt) as surfactants and without employing ultrasound. From their results of instantaneous conversions, it was possible to calculate Rpss as a function of Ra (shown in Fig. 7). As can be
seen, their experiments were very near to true monomer• starved condition, and the corresponding values of K and c were 0.18 and 1.1 mol/min, respectively, which imply that their system has more capability for monomer consumption. The lower monomer consumption in our experiments can be ascribed to chain transfer events to HBC10. Figure 8 shows the PSD obtained from QLS analysis of final latexes at different HBC10 concentrations. It can be seen that monomodal PSD can be obtained except where HBC10 was not used (Run 1), in which case bi-modal PSD can be observed. Also, narrower PSD are obtained. The z-average particle diameter decreased from 63 to 40 nm with the increase in HBC10 concentration due to
Fig. 10 SEM micrograph of nanoparticles synthesized using only HBC10 as surfactant (SDS-free)
Fig. 11 PSD obtained from SEM micrograph corresponding to latexes synthesized using only HBC10 as surfactant (SDS-free)
Iran Polymer and Petrochemical Institute
13
Iran Polym J (2015) 24:41–50
47
higher particle stabilization; however, at very high HBC10 concentration (Run 5), Dp increased to 52 nm (Table 1) because higher chain transfer to HBC10 decreases monomer consumption in the system, thus flooded condition operates through polymerization favoring particle growth instead of particle nucleation. For the lower HBC10 concentration (Run 2) and for Ra between 0.2 g/min (Run 6) and 0.6 g/min (Run 8), monomodal and narrow PSD were observed in all cases (Fig. 9). Value of Dp decreases with Ra due to monomer-starved conditions, in which case particle formation is higher than particle growth, as can be seen in Table 1. The average Dp obtained in the present work was higher than that observed for the same system without using ultrasound [14]; however, narrower PSD are observed (Fig. 9) using ultrasound due to enhanced particles dispersion: crushing, emulsifying and lower particles agglomeration/coagulation. Figure 10 shows a representative SEM micrograph of nanoparticles synthesized using only HBC10 as surfactant (SDS-free). It can be observed that well-defined spherical nanoparticles were obtained. The number (Dpn) and weight (Dpw) average particle diameters were calculated from SEM micrograph counting at least 400 particles and using Eqs. 3 and 4: Dpn = ni Di ni (3)
Dpw =
ni Di4
ni Di3
(4)
where ni is the number of particles with diameter Di. Figure 11 shows the PSD obtained from SEM micrograph.
Mono-modal PSD with diameters between 70 and 130 nm were observed. The resulting values of Dpn and Dpw were 101 and 107 nm, respectively. Polydispersity index in size can be defined as Dpw/Dpn; this value was 1.05 indicating a narrow PSD. Thus, even when bigger particle sizes were obtained using only HBC10 as surfactant, narrower PSD were obtained. Comparing our system with literature reports in similar conditions to Run 6, we found the work of Ledezma et al. [26] who obtained a Dpz value of 26 nm (Ra = 0.22 g/ min and polymer content of 24 %) using conventional surfactants (SDS/AOT 3:1) concentration of 3.7 %, achieving polymer to surfactant weight ratios (P/S) of 6.6. On the other hand, Aguilar et al. [22] found a Dpz value of 29 nm (Ra = 0.15 g/min and polymer content of 22 %) using only SDS as the surfactant in a concentration of 3 %; P/S was 10. The corresponding Dpz value obtained in the present work for Run 6 was 39 nm (Ra = 0.2 g/min and polymer content of 21 %) with P/S = 13 and surfactant concentrations of 1.6 %. Then, although comparable results in particle morphology can be obtained using conventional surfactants and without employing ultrasound, lower water absorption was observed for films made with the synthesized PMMA as will be discussed later. Further, in this work, the total amount of surfactant has been drastically reduced in relation to the reports mentioned above. Scheme 2 shows a proposed mechanism of particle formation using ultrasound. Before the addition of the mixture of MMA and HBC10, only SDS micelles are present in the reaction mixture. Upon monomer and HBC10 addition, MMA diffuses to the inner part of micelles and HBC10 molecules migrate to the interface of micelles, thus forming
Scheme 2 Proposed mechanism of particle formation when using ultrasound
Iran Polymer and Petrochemical Institute
13
48
Iran Polym J (2015) 24:41–50
Fig. 13 Molar mass distributions of the polymers at the end of reaction at different values of Ra
Fig. 12 Molar mass distributions of the polymers at the end of reaction at different HBC10 concentrations
mixed swollen micelles which are close to each other (some agglomeration), by applying ultrasound energy, swollen micelles and polymer particles separate due to the shock wave of the ultrasound disrupting the agglomeration and decreasing the resulting particle diameters due to its dispersive, crushing and emulsifying effect, and thus a better control on the size and morphology of particles is allowed, resulting in narrower PSD. The molar masses’ distributions (MMD) of the final polymers as a function of HBC10 concentration and Ra are depicted in Figs. 12 and 13, respectively. It can be observed that monomodal MMD were obtained in all cases, except for the higher Ra (Run 7) in which a small shoulder at high molar masses is observed. Polymer from Run 8 was impossible to analyze by GPC due to instrument resolution. As shown in Table 1, the weight–average molar masses obtained were in the range of 1.63 × 106–2.34 × 106 g/ mol, while polydispersity index was between 1.55 and 2.30, which indicate relatively wide MMD. Also, it can be inferred a close relationship between Dp and Mw. For example, for low HBC10 concentrations, Mw increases until a Iran Polymer and Petrochemical Institute
13
maximum where starts to decrease (due to chain transfer to HBC10) while Dp decreases until a negative effect is observed due to particle destabilization. However, a difference in Dp of 11 nm between Runs 1 and 5 implies that chain termination by radical annihilation will operate more in smaller particles, thus decreasing Mw. This also explains the Mw as a function of Ra, in which Mw increases with Ra (Fig. 1, 3; Table 1). DSC measurement gives the glass transition temperature (Tg) of the polymer. As shown in Fig. 14, only one Tg is observed at 120 °C for polymer corresponding to Run 1 (without HBC10) while two Tg values were obtained from polymer of Run 2 (small amount of HBC10) at 122 and
Fig. 14 Heat flow and the derivative vs. temperature obtained from DSC analysis of the polymers at the end of reactions corresponding to Run 1 (continuous curves) and Run 2 (dashed curves)
Iran Polym J (2015) 24:41–50
178 °C. Typical values of Tg reported for PMMA synthesized by microemulsion polymerization are around 120 °C; however, to the best of our knowledge, there were no Tg values reported about polymers of PMMA with HBC10. Thus, the second Tg value can be ascribed to the presence of reactive surfactant chemically bonded to PMMA. Water absorption experiments were made using polymers from Run 1 and Run 2, giving Wabs values of 9.2 and 1.9 %, respectively. This can be explained because the conventional surfactant is physically adsorbed onto the particle surface, which easily migrates to the surface of the polymer film, increasing water sensibility. HBC10 copolimerized with MMA and thus became covalently bonded and remains in the film when subjected to immersion in water. Therefore, water absorption is decreased. This result compares with those reported by Huang et al. [19].
Conclusion Nanoparticles of PMMA were obtained using HBC10 as polymerizable surfactant in a semicontinuous hetero-phase process, allowing the preparation of mono-modal PSD with average Dp around 50 nm. It was observed that Dp decreases with Ra whereas Mw increases. Also, contrary to expected, polymerization rate decreases with the amount of HBC10 present in the reaction mixture due to chain transfer events to HBC10. Lower water absorption was observed for films formed using polymers synthesized in the presence of a small amount of HBC10 which becomes covalently bonded to PMMA chains, thus giving lower water sensitivity. Acknowledgments This work was partially supported by Consejo Nacional de Ciencia y Tecnología, México, through grant CB—2011/168472 to RDP, and FAI UASLP 2012 (C13FAI-03-32.32) to VMOM. Special thanks are given to Camerina Janeth Guzmán Alvarez by her assistance in water adsorption tests. The author R.L.R acknowledges to J. Guadalupe Telles-Padilla and to Silvia Torres from CIQA by their help in NMR and GPC analysis, respectively.
References 1. Schramm LL (2000) Surfactants: fundamentals and applications in the petroleum industry. Cambridge University Press, Cambridge 2. Yang B (2014) Investigation of AGET-ATRP of methyl methacrylate in surface-active ionic liquid microemulsions. Iran Polym J 23:87–92 3. Asua JM (2004) Emulsion polymerization: from fundamental mechanisms to process developments. J Polym Sci Pol Chem 42:1025–1041 4. Zhang Y, Pan S, Ai S, Liu H, Wang H, He P (2014) Semi-continuous emulsion copolymerization of vinyl acetate and butyl acrylate in presence of AMPS. Iran Polym J 23:103–109
49 5. Lai Z, Sudol ED, Dimonie VL, El-Aasser MS (2005) Determination of the extent of incorporation of a reactive surfactant in polystyrene latex particles via GPC. J Polym Sci Pol Chem 43:2675–2678 6. Yan L, Ji J, Xie D, Li W, Zhang G (2008) Surfactant-free synthesis of amphiphilic copolymer of poly(styrene-co-acrylamide) in aqueous emulsion with the assistance of ultrasound. Polym Adv Technol 19:221–228 7. Lai Z, Sudol ED, Dimonie VL, El-Aasser MS (2008) Kinetics of emulsion polymerization of styrene using the reactive surfactant Hitenol BC20. J Appl Polym Sci 109:2275–2282 8. Tauer K (1997) In: Asua JM (ed) Polymeric dispersions: principles and applications, Springer, Netherlands 9. Guyot A, Tauer K (2001) In: Texter J (ed) Polymerisable and polymeric surfactants. Dekker, New York 10. Dufour M, Guyot A (2003) Nonionic reactive surfactants I. Synthesis and characterization. Colloid Polym Sci 281:97–104 11. Atta A, Dyab AKF, Allohedan HA (2013) A novel route to prepare highly surface active nanogel particles based on nonaqueous emulsion polymerization. Polym Adv Technol 24:986–996 12. Effect of polymerizable surfactants on particle size distribution, pH, viscosity, contents of solids and residual monomer of a styrene-butylacrylate resin (2013) Polímeros, São Carlos. 10.4322/ polimeros.2013.050. Accessed 09 Jun 2014 13. Wu L, Wang T, Jiang Z (2013) Formation of AgCl nanoparticle in reverse microemulsion using polymerizable surfactant and the resulting copolymer hybrid membranes. J Membr Sci 429:95–102 14. Ovando-Medina VM, Piña-García PS, Corona-Rivera MA, DíazFlores PE, Peralta RD, Martínez-Gutiérrez H, Lara-Ceniceros TE (2012) Semicontinuous heterophase polymerization of methyl methacrylate in the presence of reactive surfactant Hitenol BC10. Polym Bull 68:2313–2322 15. Xia H, Wang Q (2001) Synthesis and characterization of conductive polyaniline nanoparticles through ultrasonic assisted inverse microemulsion polymerization. J Nanopart Res 3:399–409 16. Korkut I, Bayramoglu M (2014) Various aspects of ultrasound assisted emulsion polymerization process. Ultrason Sonochem 21:1592–1599 17. Suslick KS, Price GJ (1999) Application of ultrasound to materials chemistry. Annu Rev Mater Sci 29:295–326 18. Selvaraj V, Sakthivel P, Rajendran V (2015) Effect of ultrasound in the free radical polymerization of acrylonitrile under a new multi-site phase-transfer catalyst—a kinetic study. Ultrason Sonochem 22:265–271 19. Huang H, Lu D, Shen L, Guan R (2008) Reactive surfactant in the emulsion copolymerization of methyl methacrylate and octyl acrylate. J Macromol Sci Pure 45:242–247 20. Dimonie VL, Sudol ED, El-Aasser MS (2008) Role of surfactants in emulsion polymerization polymers by design. Rev Chim (Bucureti) 59:1218–1221 21. Urquiola MB, Dimonie VL, Sudol ED, El-Aasser MS (1992) Emulsion polymerization of vinyl acetate using a polymerizable surfactant. I. Kinetic studies. J Polym Sci Pol Chem 30:2619–2629 22. Aguilar J, Rabelero M, Nuño-Donlucas SM, Mendizábal E, Martínez-Richa A, López RG, Arellano M, Puig JE (2011) Narrow size-distribution poly(methyl methacrylate) nanoparticles made by semicontinuous heterophase polymerization. J Appl Polym Sci 119:1827–1834 23. Chen Y, Jahanzad F, Sajjadi S (2013) Semicontinuous monomerstarved emulsion polymerization as a means to produce nanolatexes: analysis of nucleation stage. Langmuir 29:5650–5658 24. Ovando-Medina VM, Peralta RD, Mendizábal E (2009) Semicontinuous microemulsion copolymerization of vinyl acetate and butyl acrylate: high solid content and effect of monomer addition rate. Colloid Polym Sci 287:561–568
Iran Polymer and Petrochemical Institute
13
50
Iran Polym J (2015) 24:41–50
25. Dimitratos J, El-Aasser MS, Georgakis C, Klein A (1990) Pseudosteady states in semicontinuous emulsion copolymerization. J Appl Polym Sci 40:1005–1021 26. Ledezma R, Treviño ME, Elizalde LE, Pérez-Carrillo LA, Mendizábal E, Puig JE, López RG (2007) Semicontinuous
Iran Polymer and Petrochemical Institute
13
heterophase polymerization under monomer starved conditions to prepare nanoparticles with narrow size distribution. J Polym Sci Pol Chem 45:1463–1473
