Surfactants polymeric initiator-based

Table 13.3 Polymeric initiator-based surfactants used to modify montmorillonite in PS-MMT nanocomposites. ... 

The polymeric material based on nonionic surfactant (Neodol 91-5) has diferent pore morphology (Figure5(f)) as compared to the anionic system. Even the polymeric material based on the anionic system with a different cosolvent, butyl cellosolve, shows a different morphology (Rgure5(g)). Figure5(h) illustrates the structure of polymers obtained from a microemulsion using a different nonionic surfactant (Emsorb 6916). Thus, the pore morphology depends on the initial microstructure of the microemulsion as determined by the type of surfactant and cosolvent in addition to composition and polymerization conditions. 

Most emulsion polymerization is based on free-radical reactions, involving monomers (e.g., styrene, butadiene, vinyl acetate, vinyl chloride, methacrylic acid, methyl methacrylate, acrylic acid, etc.), surfactant (sodium dodecyl diphenyloxide disulfonate), initiator (potassium persulfate), water (18.2MQ/cm), and other chemicals and reagents such as sodium hydrogen carbonate, toluene, eluent solution, sodium chloride, and sodium hydroxide. 

The physical picture of emulsion polymerization is based originally on the qualitative picture of Harkins [18] and the quantitative treatment of Smith and Ewart [19], followed by other contributions. Gilbert shaped the qualitative and quantitative picture of the emulsion polymerization process as it is now generally accepted [16]. The main components of an emulsion polymerization recipe are the monomer(s), dispersing medium (usually water), surfactant and initiator. 

CAS 9016-45-9 EINECS/ELINCS 248-293-6 Uses Detergent, wetting agent, emulsifier, dispersant, solubilizer for concrete mfg., agric. sprays, pesticides, solv. cleaners, paints, detergents, emulsion polymerization, leather, textiles, pulp/paper base surfactant for household and industrial detergents Properties Hazen 100 liq. sol. in water, benzene, ethyl acetate, ethyl Icinol, perchlorethylene, ethanol, veg. oil, olein sp.gr. 1.056 vise. 350 cps m.p. 0 2 C HEB 12.3 cloud pt. 30-34 C pH 6-8 (1% aq.) surf, tens. 29.4 dynes/cm (0.1%) wetting 4.1 s (0.1%) Ross-Miles foam 6.7 cm (0.1%, initial) nonionic 100% act. 

Fink synthesized a series of siUcone-based surfactants [39] and used these to examine the emulsion polymerization of vinyl pyrrolidone (VP) in CO2. These monomers are liquids under ambient conditions, and hence phase behavior in CO2 was measured to determine under what conditions one could operate in an emulsion polymerization mode (Fig. 7.7). As is the case with NVF, the phase behavior of 1-vinyl-2-pyrrolidone offers the possibility for distinct polymerization regimes. Above pressures of ca. 28 MPa at 338 K, VP is miscible with carbon dioxide in all proportions. Below 28 MPa, VP and CO2 will either phase split into monomer-rich and C02-rich phases, or exist as a single phase, depending upon the initial VP concentration and system pressure. Consequently, a polymerization can be conducted initially in the single phase regime above 28 MPa, leading to a purely dispersion mechanism, or initially within the two-phase dome in P-x space, leading to an inverse emulsion polymerization. Finally, a polymerization can be conducted where pressure and composition are chosen to initially... 

Monomer conversion can be adjusted by manipulating the feed rate of initiator or catalyst. If on-line M WD is available, initiator flow rate or reactor temperature can be used to adjust MW [38]. In emulsion polymerization, initiator feed rate can be used to control monomer conversion, while bypassing part of the water and monomer around the first reactor in a train can be used to control PSD [39,40]. Direct control of surfactant feed rate, based on surface tension measurements also can be used. Polymer quality and end-use property control are hampered, as in batch polymerization, by infrequent, off-line measurements. In addition, on-line measurements may be severely delayed due to the constraints of the process flowsheet. For example, even if on-line viscometry (via melt index) is available every 1 to 5 minutes, the viscometer may be situated at the outlet of an extruder downstream of the polymerization reactor. The transportation delay between the reactor where the MW develops, and the viscometer where the MW is measured (or inferred) may be several hours. Thus, even with frequent sampling, the data is old. There are two approaches possible in this case. One is to do open-loop, steady-state control. In this approach, the measurement is compared to the desired output when the system is believed to be at steady state. A manual correction to the process is then made, based on the error. The corrected inputs are maintained until the process reaches a new steady state, at which time the process is repeated. This approach is especially valid if the dominant dynamics of the process are substantially faster than the sampling interval. Another approach is to connect the output to the appropriate process input(s) in a closed-loop scheme. In this case, the loop must be substantially detuned to compensate for the large measurement delay. The addition of a dead time compensator can... 

Emulsion polymerization is among the most popular synthetic routes to prepare vinyl-based pH-responsive polymers, especially microgel systems (Rao and Geckeler, 2011). This technique employs a radical chain polymerization methodology to form latexes of narrow particle size distributions. The emulsion polymerization systems are commonly composed of monomer(s), water, water-soluble initiator and surfactant (emulsifier). Colloidal stabilizers may be electrostatic, steric or electrosteric, or display both stabilizing mechanisms. When phase separation occurs, the formation of solid particles takes place before or after the termination of the polymerization reaction. 

Scheme 96 Star-shaped, amphiphilic block copolymers prepared by the polymerizations of TMC initiated with a three-armed PEG-based surfactant.

Emulsion Polymerizations, eg. vinyl acetate [VAc]/ABDA, VAc/ethylene [VAE]/ABDA, butyl acrylate [BA]/ABDA, were done under nitrogen using mixed anionic/nonlonic or nonionic surfactant systems with a redox Initiator, eg. t-butyl hydroperoxide plus sodium formaldehyde sulfoxylate. Base monomer addition was batch or batch plus delay comonomer additions were delay. 

Poly(alkylene oxide)-based (PEO-PPO-PEO) triblock and diblock copolymers are commercially successful, linear non-ionic surfactants which are manufactured by BASF and ICI. Over the last four decades, these block copolymers have been used as stabilisers, emulsifiers and dispersants in a wide range of applications. With the development of ATRP, it is now possible to synthesise semi-branched analogues of these polymeric surfactants. In this approach, the hydro-phobic PPO block remains linear and the terminal hydroxyl group(s) are esteri-fied using an excess of 2-bromoisobutyryl bromide to produce either a monofunctional or a bifunctional macro-initiator. These macro-initiators are then used to polymerise OEGMA, which acts as the branched analogue of the PEO block (see Figures 2 and 3). 

Emulsion Polymerization. Poly(vinyl acetate)-based emulsion polymers are produced by the polymerization of an emulsified monomer through free-radicals generated by an initiator system. An emulsion recipe, in general. contains monomer, water, protective colloid or surfactant, initiator, buffer, and perhaps a molecular weight regulator. 

All quantitative theories based on micellar nucleation can be developed from balances of the number concentrations of particles, and of the concentrations of aqueous radicals. Smith and Ewart solved these balances for two limiting cases (i) all free radials generated in the aqueous phase assumed to be absorbed by surfactant micelles, and (ii) micelles and existing particles competing for aqueous phase radicals. In both cases, the number of particles at the end of Interval I in a batch macroemulsion polymerization is predicted to be proportional to the aqueous phase radical flux to the power of 0.4, and to the initial surfactant concentration to the power of 0.6. The Smith Ewart model predicts particle numbers accurately for styrene and other water-insoluble monomers. Deviations from the SE theory occur when there are substantial amounts of radical desorption, aqueous phase termination, or when the calculation of absorbance efficiency is in error. 

Batch miniemulsion polymerization of MMA using PMMA as the costabilizer was carried out with SLS as the surfactant and KPS as the initiator. Solids content was kept at -30%. A low surfactant level was used with the miniemulsions to ensure droplet nucleation. The initiator concentration of the polymer-stabilized miniemulsion polymerizations was varied from 0.0005 to 0.02 Mjq, based on the total water content. An aqueous phase retarder, (sodium nitrite) or an oil-phase inhibitor (diphenylpicrylhydrazol [DPPH]), was added to both the miniemulsions and the macro emulsions prior to initiation. Particle numbers and rates of polymerization for both systems were determined. 

Latexes. Latexes were made in a monomer addition recipe described earlier (10). This is a seeded continuous monomer addition recipe using t-butylhydro-peroxide/hydroxylamine hydrochloride redox couple as initiator. Polymerizations were carried out in stirred glass reactors at 50°C. The only variation in the original recipe was in the surfactants. In the present procedvire, < 1/3 of the soap (- 1.5% based on total monomer) was used in the seed and the remainder fed to the reactor during polymerization. The monomer feed contained styrene and butylacrylate in a 40/60 ratio. This composition was selected because it is readily filmforming and is not affected chemically by the electrodeposition process. The polymer remains soluble and... 

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