Monomer solution

Mayo and collaborators were among the earliest workers to clarify the relationship between copolymer and monomer solution compositions. 

As an alternative to the ratios ni/n2 and [Mi]/[M2] in Eq. (7.15), it is convenient to describe the composition of both the polymer and the feedstock in terms of the mole fraction of each monomer. Defining F as the mole fraction of the ith component in the polymer and fj as the mole fraction of component i in the monomer solution, we observe that... 

Table 7.5 also shows that increasing the percentage of Mj in the monomer solution flattens and broadens the distribution of sequence lengths. Similar results are observed for lower values of T1T2, but the broadening is less pronounced when the tendency toward alternation is high. 

Microemulsion Polymerization. Polyacrylamide microemulsions are low viscosity, non settling, clear, thermodynamically stable water-in-od emulsions with particle sizes less than about 100 nm (98—100). They were developed to try to overcome the inherent settling problems of the larger particle size, conventional inverse emulsion polyacrylamides. To achieve the smaller microemulsion particle size, increased surfactant levels are required, making this system more expensive than inverse emulsions. Acrylamide microemulsions form spontaneously when the correct combinations and types of oils, surfactants, and aqueous monomer solutions are combined. Consequendy, no homogenization is required. Polymerization of acrylamide microemulsions is conducted similarly to conventional acrylamide inverse emulsions. To date, polyacrylamide microemulsions have not been commercialized, although work has continued in an effort to exploit the unique features of this technology (100). 

The inverse emulsion form is made by emulsifying an aqueous monomer solution in a light hydrocarbon oil to form an oil-continuous emulsion stabilized by a surfactant system (21). This is polymerized to form an emulsion of aqueous polymer particle ranging in size from 1.0 to about 10 pm dispersed in oil. By addition of appropriate surfactants, the emulsion is made self-inverting, which means that when it is added to water with agitation, the oil is emulsified and the polymer goes into solution in a few minutes. Alternatively, a surfactant can be added to the water before addition of the inverse polymer emulsion (see Emulsions). 

Formaldehyde is noted for its reactivity and its versatility as a chemical intermediate. It is used in the form of anhydrous monomer solutions, polymers, and derivatives (see Acetal resins). 

Beaded polymeric supports are produced by a two-phase suspension polymerization in which microdrops of a monomer solution are directly converted to the corresponding microbeads. The size of a microdroplet is usually determined by a number of interrelated manufacturing parameters, which include the reactor design, the rate of stirring, the ratio of the monomer phase to water, the viscosity of both phases, and the type and concentration of the droplet stabilizer. 

Producing a polystyrene (PS)-DVB copolymer of increasing porosity has been accomplished by dissolving 50-80% styrene, 10-50% divinylbenzene, and 30-70% of an inert organic liquid. Toluene is a solvent for the monomer but is a nonsolvent for the polymerized polymer. The monomer solution is then incorporated into water to form a dispersion of oil droplets followed by the polymerization of the suspended oil droplets from the aqueous medium into the polymer (21). 

The reactor is loaded with a solution of emulsifier in an organic solvent and the aqueous monomer solution (20-60%) is dispersed in the organic phase by stirring. The obtained emulsion is deoxygenated by purging dry nitrogen or by multiple evacuation and thermostated at 30-60°C. Then, an initiator solution is introduced in the reaction mixture and the process is carried out at 30-60°C for 3-6 h, after which the reaction mixture is aged for 1-5 h. 

The particle size of the dispersed phase depends upon the viscosity of the elastomer-monomer solution. Preferably the molecular weight of the polybutadiene elastomer should be around 2 x 10 and should have reasonable branching to reduce cold flow. Furthermore, the microstructure of the elastomer provides an important contribution toward the low-temperature impact behavior of the final product. It should also be emphasized that the use of EPDM rubber [136] or acrylate rubber [137] may provide improved weatherability. It has been observed that with an increase in agitator speed the mean diameter of the dispersed phase (D) decreases, which subsequently levels out at high shear [138-141]. However, reagglomeration may occur in the case of bulk... 

These polymers are readily prepared by in-situ electropolymerization (from the monomer solution). The oxidation of the monomer proceeds according to... 

The permeability tests for alkali metal ions in the aqueous solution were also conducted. When an aqueous salt solution moves to cell 2 through the membrane from cell 1, the apparent diffusion coefficient of the salt D can be deduced from a relationship among the cell volumes Vj and V2, the solution concentration cx and c2, the thickness of membrane, and time t6 . In Table 12, permeabilities of potassium chloride and sodium chloride through the 67 membrane prepared by the casting polymerization technique from the monomer solution in THF or DMSO are compared with each other and with that the permeability through Visking dialyzer tubing. The... 

Low Conversion Reactors. The major problem in temperature control in low conversion reactors is the orders cf magnitude increase in viscosity as the conversion increases. Fig.8 shows the viscosity of a polystyrene solution as the function of percent PS. The data are for polystyrene with a Staudinger molecular weight of 60,000 at 100 C and 150 C in a cumene solution, a satisfactory analog for styrene monomer solutions. As the polymer concentration increases from 0 to 60%, viscosity increases from about 1 cp to 10 cp. 

Instantaneous monomer feed flow-rate. Instantaneous initiator feed flow-rate. Time-averaged monomer solution flow-rate in oscillatory steady-state. 

Procedure. Concentration of n-BuLi in the feed was measured by titration (15). The reactor was filled completely with styrene monomer solution in toluene initially. Time was measured from the moment initiator and monomer feed was initiated. The reaction was... 

Another case in which bonds were made where none existed previously is that of irradiation of AsClj in benzene solution (76) which led to formation of PhAsCl2 and PhjAsCl, and even PhjAs. Yet another example 51) is the formation of FeCpj by irradiation of Fe(CO)j in cyclopentadiene (monomer) solution. While these examples may not tell us when the reaction does occur, they do show that initial bonding is not indispensable. 

Figure 12 and 13. ESCA spectra of polyethylene split film before. grafting (A), after presoaking in sensitizer-monomer solution (B) and after grafting with acrylic acid (8 sec., Figure 12) and acrylamide (6 sec., Figure 13) using the continuous method. 

Procedure To a dry Erlenmeyer flask of appropriate size, add one half of the reaction solvent. All reactants, including the dry mass of the hydroperoxide, should not constitute more than 23 weight percent of the reaction mixture or an insoluble product may be produced. Add dry lignin and dry calcium chloride to the reaction vessel and cap with a septum or rubber stopper. In a separate vessel, dissolve 2-propenamide in about one quarter of the DMSO solvent and, in a third vessel, dissolve the sulfonated monomer in the final one quarter of the solvent. Saturate both monomer solutions with by bubbling with the gas for 10 minutes. Saturate the lignin solution with for 10 minutes. Add the hydroperoxide to... 

If a monomer solution at a concentration of 1 mole/liter is fed to a CSTR at 0 °C, determine the space time necessary to achieve a conversion corresponding to 90% of the equilibrium value. If the reactor volume is 100 liters, what is the corresponding volumetric flow rate ... 

This process involves the suspension of the biocatalyst in a monomer solution which is polymerized, and the enzymes are entrapped within the polymer lattice during the crosslinking process. This method differs from the covalent binding that the enzyme itself does not bind to the gel matrix. Due to the size of the biomolecule it will not diffuse out of the polymer network but small substrate or product molecules can transfer across or within it to ensure the continuous transformation. For sensing purposes, the polymer matrix can be formed directly on the surface of the fiber, or polymerized onto a transparent support (for instance, glass) that is then coupled to the fiber. The most popular matrices include polyacrylamide (Figure 5), silicone rubber, poly(vinyl alcohol), starch and polyurethane. 

Epitaxial crystallization was accomplished by the immersion of a preheated substrate (the substrates for epitaxial crystallization were single crystals of alkali halides from Harshaw Chemical Co.) into the monomer solution followed by its in-situ cleavage to expose two fresh (100) surfaces. 

To produce novel LC phase behavior and properties, a variety of polymer/LC composites have been developed. These include systems which employ liquid crystal polymers (5), phase separation of LC droplets in polymer dispersed liquid crystals (PDLCs) (4), incorporating both nematic (5,6) and ferroelectric liquid crystals (6-10). Polymer/LC gels have also been studied which are formed by the polymerization of small amounts of monomer solutes in a liquid crystalline solvent (11). The polymer/LC gel systems are of particular interest, rendering bistable chiral nematic devices (12) and polymer stabilized ferroelectric liquid crystals (PSFLCs) (1,13), which combine fast electro-optic response (14) with the increased mechanical stabilization imparted by the polymer (75). 

---