Batch Emulsion Copolymerization Research Articles

Tuning adhesion performance of an acrylic pressure‐sensitive adhesive using polysilsesquioxane‐acrylic core‐shell nanoparticles

AbstractSurface migration of unmodified inorganic or polymer core‐inorganic shell nanoparticles has limited their application for improvement of pressure‐sensitive adhesives (PSAs) properties. The efficiency of utilization of modified inorganic nanoparticles with sticky polymer brushes was investigated to overcome this problem. For this purpose, polymethacryloxypropylsilsesquioxane‐acrylic core‐shell (CS) nanoparticles were synthesized and added to poly(methyl methacrylate‐co‐butyl acrylate) (MBC) acrylic PSA through latex blending. Using CS nanoparticles, a concomitant increase in the peel and shear strengths of the acrylic PSA was achieved, and also the limitation of surface migration of nanoparticles at high volume fractions was overcome. Moreover, CS nanoparticles acted as a compatibilizer for MBC chains, rich in methyl methacrylate (MMA) or butyl acrylate (BA). These MMA‐rich and BA‐rich chains were formed during the synthesis of MBC latex through batch emulsion copolymerization method, due to the difference in the reactivity ratio of BA and MMA radicals. The compatibility of CS nanoparticles with each of the components of MBC was systematically investigated in terms of grafting density, swelling ratio, and thermodynamic affinity and was correlated to the final properties.

Emulsion Copolymerization of Vinyl Acetate and Vinyl Silanes: Kinetics and Development of Microstructure

AbstractThe batch emulsion copolymerization of vinyl acetate with different vinyl silane functional monomers (vinyl trimethoxysilane [VTMS], vinyl triethoxysilane [VTES], and vinyl silanetriol [VSTO]) is studied. The nature of the silane strongly affects the development of the microstructure and crosslinking ability of the latexes. A combination of techniques (Soxhlet extraction, centrifugation, assymetric‐flow field flow fractionation AF4/MALS/RI) shows that the factor controlling the molar mass and crosslinking density is the degree of hydrolysis of the alkoxysilane, producing higher molar masses and degrees of crosslinking when the degree of hydrolysis is high. Thus, the copolymer containing VSTO produced a very crosslinked latex, the one with VTMS produced a latex with a low degree of crosslinking in the wet state that can yield high degrees of crosslinking upon drying, and the latex with VTES do not produce significant amounts of crosslinking neither before nor after drying.

1,2,3-triazole functionalized polystyrene and perdeuterated polystyrene chelating latexes

Emulsifier-free polystyrene latexes with immobilized triazolic residues have been prepared by batch emulsion copolymerization of styrene with 1,2,3-triazole-based acrylic monomers containing diethylene or triethylene glycol monomethyl ether groups DEGTz and TEGTz, respectively. The effect of monomer structure and concentration on polymerization conversion, particle size, and morphology was investigated. Particle composition was also evidenced by 1H-NMR analysis. It was found that DEGTz monomer with the shorter pegylated chain allows the formation of the smaller particles with a better control of polytriazole water soluble oligomers formation. DEGTz and TEGTz were then used in batch and shot-growth polymerization of styrene-d8 in the aim to highlight the effect of deuterium isotope substitution. It was shown that the use of deuterated styrene significantly impacts the polymerization conversion as well as particle size and shape regardless of the monomer structure. Shot-growth process disadvantaged the copolymer particle formation in favor of obtaining water soluble polymers. This was confirmed from the NMR study and from the large values of surface charge density of latexes obtained from electrophoretic mobility.

Customizable 3D-printed stirrers for investigation, optimization and scale-up processes of batch emulsion copolymerizations

Diverse and cost-effective polyamide stirrers, printed by fused deposition modeling, were used in a 0.5L reaction calorimeter (Mettler Toledo RC1e) to principally investigate the suitability and performance of 3D-printed stirrers. Thermal-initiated batch emulsion copolymerizations of styrene and butyl acrylate were successfully carried out with monomer contents between 20 and 40 wt% and temperatures in the range of 60 to 85 °C. Further, precisely adjusted stirrers were designed and fabricated based on a constant volume related power input for scale-up processes in a 10L batch reactor. This scale-manufacturing concept enables a time-effective and inexpensive access to versatile and tailor-made 3D-printed stirrers, even for the implementation in already existing reaction systems. Inline turbidity was used as online monitoring tool to detect the mixing characteristics and control the course of emulsion polymerization processes. Analytical results of the 10 L resembled those of the 0.5 L scale and proved our main objective to produce comparable droplet dispersions (±2 nm). The resulting emulsions from 0.5 and 10 L scale were stable with Zeta potential values down to –90 mV. Neither product adhesion on nor deformation of the 3D-printed stirrers were found even at higher temperatures, monomer contents or scale-up processes.

Anionic Polymerizable Surfactants and Stabilizers in Emulsion Polymerization: A Comparative Study

The feasibility of using commercially available anionic polymerizable surfactants (LatemulPD‐104 and SipomerPam‐200) and anionic polymerizable stabilizer (SipomerCops‐1) in the batch emulsion copolymerization of model acrylic latexes is studied. The effect of both surfactant type and surfactant concentration on the number of polymer particles and molecular weights is investigated. LatemulPD‐104 behaves as the conventional surfactant Dowfax2A1 and the dependence of the number of particles upon surfactant concentration is similar for both surfactants. However, when SipomerPam‐200 is used a higher dependence is observed, probably due to a substantial contribution of homogeneous nucleation. When the stabilizer SipomerCops‐1 is used polymer particles are only formed by homogeneous nucleation. The molecular weights of the final latexes are affected by the surfactant type and concentration used in the polymerization, and unexpectedly, gel is formed when SipomerPam‐200 is used.image

Mechanism of particle formation in radical emulsion copolymerization of styrene with α-tert-butoxy-ω-vinylbenzyl-polyglycidol macromonomer

In the batch emulsion copolymerization of styrene and α-tert-butoxy-ω-vinylbenzyl-polyglycidol macromonomer, carried out at macromonomer concentrations exceeding the critical micelle concentration (cmc), particles are formed by a two-step coagulative nucleation mechanism. This mechanism leaves its mark on morphology of particle interface, rate of polymerization and on molecular weight distribution of the obtained polymer. AFM studies revealed that the interface of particles is composed of objects with dimensions close to dimensions of the primary particles. Compartmentalization of styrene in the macromonomer micelles leads to the higher initial rate of styrene conversion than in the similar macromonomer free homopolymerization of styrene. The initial polymerization in the monomer-swollen macromonomer micelles, similar to the microemulsion polymerization, is responsible for the formation of the highest molecular weight component. In the mature particles there are two different polymerization loci: the interfacial layer and the core. This leads to bimodal molecular weight distribution of the formed polymer.

Study of the solution and aqueous emulsion copolymerization of vinylidene chloride with methyl acrylate in the presence a poly(ethylene oxide) macromolecular RAFT agent

The reversible addition-fragmentation chain transfer (RAFT) copolymerization of vinylidene chloride (VDC) with methyl acrylate (MeA) was studied in the presence of poly(ethylene oxide)-based macromolecular RAFT (macroRAFT) agents of the trithiocarbonate type (PEO-TTC) in solution and in aqueous emulsion. Firstly the formation of PEO-b-P(VDC-co-MeA) diblock copolymers was performed in toluene solution at 30 °C and a good control over the polymerization with high chain-end functionality was shown. A first aqueous emulsion copolymerization of VDC with MeA was performed using one of the amphiphilic PEO-b-P(VDC-co-MeA) diblock copolymers as macromolecular stabilizer. Then, in a series of experiments the PEO-TTC macroRAFT agents were directly tested as both chain transfer agents and stabilizing agents in similar conditions (aqueous batch emulsion copolymerization of VDC with MeA at 70 °C). The influence of the nature and concentration of the initiating system and the presence or not of a buffer were studied. We demonstrated that in simple conditions, nanometric latex particles composed of amphiphilic PEO-b-P(VDC-co-MeA) diblock copolymers formed by polymerization-induced self-assembly (PISA). It can thus be concluded that PEO-TTC macroRAFT agents are valuable non-ionic macromolecular stabilizers in the emulsion copolymerization of VDC and MeA and allow the formation of core–shell diblock copolymer particles in the absence of free surfactant. However, when rather high molar masses of the hydrophobic PVDC-based block were targeted, the determined molar masses deviated from the theoretical values.

Preparation of Covalently‐colored Polymer Latex via Batch Emulsion Polymerization

AbstractCovalently‐colored polymer latex was synthesized via batch emulsion copolymerization of styrene, butyl acrylate and methacrylic acid in the presence of red polymerizable dye monomer consisting of anthraquinone chromophore, alkyl spacer and acryloyl group, and the influences of the initiator, surfactant and polymerizable dye on the polymerization and the latex properties were investigated. Results showed that the initiator amount was a determinative factor for the monomer conversion, and a high conversion of the polymerizable dye could be achieved when the ammonium persulfate amount was equal to or more than 1 wt% to the total monomers. Most of the chromophores were covalently bonded to the polymer chains if the polymerizable dye was used in the range of 0–1.5 wt%. The light fastness of the resulting latex film was much better than that of the noncovalently‐colored polymer film.

Automated batch emulsion copolymerization of styrene and butyl acrylate

This article describes a method for carrying out emulsion copolymerization using an automated synthesizer. For this purpose, batch emulsion copolymerizations of styrene and butyl acrylate were investigated. The optimization of the polymerization system required tuning the liquid transfer method, sufficient oxygen removal from the reaction medium and setting a proper sampling procedure. The monomer conversion-time plots obtained with gas chromatography revealed a good reproducibility of the automated reaction kinetics. Furthermore, the particle size distributions and the properties of the final products were found to be highly reproducible. The performance of the automated reactions was subsequently compared with the conventional ones: similar reproducibility of either synthetic method was observed. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Influences of MAA on the porous morphology of P(St–MAA) latex particles produced by batch soap-free emulsion polymerization followed by stepwise alkali/acid post-treatment

Soap-free P(St–MAA) latex particles with variable styrene (St)/methacrylic acid (MAA) ratio were synthesized by batch emulsion copolymerization at 70 °C for 7 h, and the particles with porous structure were obtained after stepwise alkali/acid post-treatment. The effects of MAA amount on the particle morphologies after the alkali and the stepwise alkali/acid post-treatments were investigated by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Results indicated that the alkali-treated latex particles showed anomalous structure with rough surface, and no hollow was clearly identified inside them. When these alkali-treated particles were further treated with acid solution, the particle surface became much smoother, and porous morphology appeared. It was found that when the MAA amount was less than or equal to 4 mol%, no obvious morphological variation was observed; while the latex particles showed clearly porous structure as the MAA amount increased to 6 mol%; with the further increase of MAA amount to 8 mol%, the pore size decreased distinctly.

A Novel Estimation Method of the Distribution of Carboxyl Groups Within Copolymer Particles Using Isothermal Titration Calorimeter

AbstractSummary: A novel quantitative method using isothermal titration calorimeter (ITC) for the estimation of the distribution of carboxyl groups within polymer particles has been proposed. The method has been employed to clarify the difference in the distribution between the particles prepared by batch emulsion copolymerization of styrene and methacrylic acid under inefficient and efficient stirring conditions. At inefficient stirring, monomer was floating as a layer on the aqueous medium, whereas at efficient stirring, the monomer phase was dispersed as droplets. Under inefficient stirring, methacrylic acid (MAA) polymerized faster than styrene (S) due to a slower diffusion rate of S than MAA into the aqueous medium, while under efficient stirring, S and MAA copolymerized at similar rates. ITC measurement showed that under inefficient stirring, the carboxyl groups were distributed mainly in the center of the particles, and their number decreased toward the surface. On the other hand, under efficient stirring, carboxyl groups were distributed homogeneously inside the particle.

Monodisperse Particles Based on Copolymers of Methyl methacrylate or Styrene with N‐Vinylformamide

AbstractSammary: Various techniques of one‐step batch emulsion copolymerization of methyl methacrylate (MMA) or styrene (St) with N‐vinylformamide (NVF) initiated by 2,2′‐azobis(2‐methylpropanamidine) (AIBA) or 2,2′‐azobis[4,5‐dihydroimidazol‐2‐yl] (AIP) dihydrochlorides in the presence of dextran, cetyltrimethylammonium bromide (CTAB) or without any stabilizers were examined to obtain monodisperse submicron and nano‐ particles, having both positive surface charge and hydrophilic surface. After hydrolysis in acidic media, the particle surface contained amino groups originating from NVF units along with carboxylic groups from hydrolyzed initiator residues. The obtained particles were tested as building blocks of hierarchic structures. Owing to their amphiphilic surface, the particles were capable of self‐assembling from their dispersions into three‐dimentional (3D) ordered arrays.

Water vapour transmission in butadiene–MMA–methacrylic acid latex films

Batch emulsion copolymerizations of butadiene, methyl methacrylate (MMA), methacrylic acid (MAA) and hydroxyethyl methacrylate were performed in RC1e reactor, and the product vulcanized to form a film typical of those used for barrier products (gloves and condoms). The water vapour transmission (WVT) or breathability and physical properties (such as tensile strength and elongation at break) of the films were measured. Factorial design was used to vary the concentration of monomers in the copolymerizations. Methacrylic acid is a hydrophilic monomer and its distribution in or on the particles would be expected to affect WVT. Characterization by ultracentrifugation, nuclear magnetic resonance and infrared spectroscopy showed that most of the methacrylic acid units were buried inside the particles. This appears to be responsible for a relatively low WVT rate, probably due to the absence of hydrophilic (MAA-rich) domains inside the film. When centrifuged, the latex shows two particle-containing layers; characterization of the latex revealed the presence of MMA-rich domains in one layer, probably arising from secondary particle formation late in the polymerization. The butadiene-to-MMA ratio probably dominates tensile strength through vulcanization with sulfur. The elongation at break was independent of both the butadiene-to-MMA ratio and the MAA concentration over the range studied (ascribed to competing effects), but dependent upon the total crosslinker concentration.

Effect of carboxylic acid monomer and butadiene on particle growth in the emulsifier-free emulsion copolymerization of styrene–butadiene–carboxylic acid monomer

Carboxylated styrene–butadiene rubber (XSBR) latexes were prepared by emulsifier-free batch emulsion copolymerization of styrene and butadiene with different types of carboxylic acid monomers (AA, MAA, IA). It was found that the particle growth is dependent on the hydrophilic nature of carboxylic acid monomers. SEM studies showed that Np is almost constant in the particle growth stage (conversion above 10%). Through some calculations by data obtained from DLS technique, average diameter of monomer swollen polymer particles of all the XSBR latexes at the same conversion of 0.4 was obtained to be 368.91, 174.17 and 437.15nm for AA, MAA and IA, respectively. Several kinetic parameters related to the particle growth stage such as the average number of growing chain per particle were calculated to be 0.474, 0.370 and 1.685 for AA, MAA and IA, respectively. It was observed that these kinetic parameters increase with increasing average diameter of monomer swollen polymer particles, which is consistent with the emulsion polymerization kinetics. Moreover, results indicated that the polymerization rate per particle or equivalently the average number of the growing chain per particle (particle growth stage) decreases by replacing a part of styrene with butadiene in the emulsion copolymerization recipe of styrene–carboxylic acid monomer.

St–BA copolymer emulsions prepared by using novel cationic maleic dialkyl polymerizable emulsifier

A novel polymerizable cationic dialkyl maleic emulsifier with 12 carbon atomic hydrophobic chain lengths (R = C 12H 25) as well as a similar conventional cationic emulsifier, cetyltrimethyl ammonium bromide (CTAB) as comparison, were investigated in batch emulsion copolymerization of styrene and butyl acrylate. A series of emulsion samples have been prepared with two kinds of emulsifiers, and their properties have been characterized and compared. Compared with the emulsions prepared by using cationic CTAB emulsifier, the emulsions prepared by using maleic emulsifier have larger particle size, higher surface tension, generally more stable on certain electrolytes and less water absorption ratio as 34.87% after 30 days vs. 50.65% for the emulsion containing CTAB emulsifier. Whereas, the maleic emulsifier itself has lower CMC and surface tension compared with cationic CTAB emulsifier.

Investigation into the effect of carboxylic acid monomer on particle nucleation and growth in emulsifier-free emulsion copolymerization of styrene–butadiene–acrylic acid

Latexes of carboxylated styrene–butadiene rubber were prepared via batch emulsion copolymerization with different amounts of acrylic acid in the absence of emulsifier. The effect of acid monomer was investigated in the particle formation and growth. It was observed that the amount of acrylic acid strongly affected the particle formation. The number of particles and thus polymerization rate increased with increasing of the acid content. There was no significant difference in the polymerization rate per particle in all experiments. The results show that in this case particle growth process is less dependent on the acrylic acid amount in comparison with its influence on nucleation stage and then particle number. Several parameters such as polymerization rate and number of latex particle per unit volume of the aqueous phase were calculated. Attempt was made to evaluate the average number of growing chain per particle. Also average particle diameter of the above carboxylated SBR latexes was obtained through some calculations from the direct measurement of average particle diameter in the swollen state by light scattering technique for the first time.

Mathematical Modeling of Batch Emulsion Copolymerization Processes

A general mathematical model for emulsion copolymerization processes in batch reactor is presented. The model predicts the time‐history of monomer conversion, average particle size, copolymer composition and number of particles. The model was tested and validated with experimental data of four different copolymerization systems: S/MMA (styrene/methyl methacrylate), S/BA (styrene/butyl acrylate), MMA/BA (methyl methacrylate/butyl acrylate) and MMA/VA (methyl methacrylate/vinyl acetate). The influence of several process variables, such as initiator concentration, emulsifier concentration, monomer‐to‐water ratio, and composition has been examined. Model predictions presented satisfactory agreement with the experimental data. Despite the model simplicity and the reduced number of adjustable parameters, the model accounts for the basic features of emulsion polymerization processes and can be useful for practical applications.

Preparation of multihollow polymer particles by the alkali/cooling method under partial neutralization conditionsa)

AbstractHeterogeneity in the formation of multihollow structure among submicron‐sized styrene‐methacrylic acid copolymer particles, which were produced by batch emulsion copolymerization, by the alkali/cooling method under partial neutralization of carboxyl groups was investigated. There was a threshold of the acid content to form the multihollow structure. The heterogeneity among the particles was based on the heterogeneity of the acid content among the original particles.

A Comprehensive Experimental and Theoretical Investigation of the Styrene/2‐Ethylhexyl Acrylate Emulsion Copolymerization

AbstractIn the present study an experimental and theoretical investigation on the styrene/2‐ethylhexyl acrylate emulsion copolymerization is reported. Kinetic experiments were carried out in a laboratory batch reactor, to analyze the effects of the initial styrene mole fraction, non‐ionic surfactant, and initiator concentrations on the reaction kinetics, copolymer composition and particle size distribution of the latex. All kinetic experiments were run through the full conversion. A comprehensive mathematical model was developed to describe the dynamic behavior of the styrene/2‐ethylhexyl acrylate batch emulsion copolymerization. The model includes a detailed kinetic mechanism, the thermodynamics of the emulsion mixture, dynamic molar species balances in the polymer and aqueous phases, the rate of particle formation, and growth and diffusion controlled phenomena. Detailed dynamic species mass balances are derived to follow the evolution of the particle nucleation rate, total number of particles, polymerization rate and particle size distribution in a batch reactor. The proposed particle nucleation mechanism accounts for both homogeneous and micellar particle nucleation. The capabilities of the present model are demonstrated by comparison of model predictions with the experimental data on conversion and particle size distribution (PSD). It is shown that the model is capable of correctly reflecting the time evolution of conversion, particle size and PSD over substantial variations of the process operating conditions.Comparison of model predictions and experimental measurements on average particle size.magnified imageComparison of model predictions and experimental measurements on average particle size.

Batch emulsion copolymerization of 3‐O‐methacryloyl‐1,2:5,6‐di‐O‐isopropylidene‐α‐D‐glucofuranose and butyl acrylate: Synthesis and properties of the sugar latices

AbstractTo obtain new polymer latices based on sugar derivative, batch emulsion copolymerizations of 3‐O‐methacryloyl‐1,2:5,6‐di‐O‐isopropylidene‐α‐D‐glucofuranose (3‐MDG) and n‐butyl acrylate (BA) were carried out at 70 °C, with potassium persulfate as the initiator. 3‐MDG polymerizes faster than BA because of its higher reactivity ratio, r(3‐MDG) = 1.94 versus r(BA) = 0.54. The effect of the initial monomer composition on the polymerization rate and the thermal properties of the end copolymers was investigated. The overall rate of polymerization increases by enhancing the sugar content in the initial monomer composition. The glass‐transition temperature is linearly related to the sugar content in the copolymer. The influence of the type of surfactant showed that the particle size increases by changing from ionic to nonionic surfactant. Furthermore, the effect of the added acrylic acid (AA) on the rheological properties suggests that the sugar latices exhibit different non‐Newtonian flows depending on the pH of the latex and on the AA concentration on the particle surface. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 788–803, 2003