Styrenes acid polymerization

With the improvement of refining and purification techniques, many pure olefinic monomers are available for polymerization. Under Lewis acid polymerization, such as with boron trifluoride, very light colored resins are routinely produced. These resins are based on monomers such as styrene, a-methylstryene, and vinyltoluene (mixed meta- and i ra-methylstyrene). More recently, purified i ra-methylstyrene has become commercially available and is used in resin synthesis. Low molecular weight thermoplastic resins produced from pure styrene have been available since the mid-1940s resins obtained from substituted styrenes are more recent. 

After epoxidation, propylene oxide, excess propylene, and propane are distilled overhead. Propane is purged from the process propylene is recycled to the epoxidation reactor. The bottoms Hquid is treated with a base, such as sodium hydroxide, to neutralize the acids. Acids in this stream cause dehydration of the 1-phenylethanol to styrene. The styrene readily polymerizes under these conditions (177—179). Neutralization, along with water washing, allows phase separation such that the salts and molybdenum catalyst remain in the aqueous phase (179). Dissolved organics in the aqueous phase ate further recovered by treatment with sulfuric acid and phase separation. The organic phase is then distilled to recover 1-phenylethanol overhead. The heavy bottoms are burned for fuel (180,181). 

Graft copolymers of nylon, protein, cellulose, starch, copolymers, or vinyl alcohol have been prepared by the reaction of ethylene oxide with these polymers. Graft copolymers are also produced when styrene is polymerized by Lewis acids in the presence of poly-p-methoxystyrene. The Merrifield synthesis of polypeptides is also based on graft copolymers formed from chloromethaylated PS. Thus, the variety of graft copolymers is great. 

This situation is somewhat reminiscent to that encountered in enzyme chemistry where the active biocatalyst is a combination of an apo-enzyme and a coenzyme, the components alone being complete inactive. Substrate specificity, which is so characteristic for enzymatic processes is also high in carbonium ion chemistry. For example styrene is polymerized by titanium tetrachloride—water, but not by titanium tetrachloride— alkyl chlorides 37) however, with stannic chloride catalyst alkyl chlorides are effective cocatalysts 88). In the same vein Plesch (93) showed that water is a better cocatalyst than acetic or chloroacetic acid in conjunction with titanium tetrachloride in isobutene polymerization, but Russel (94) found just the opposite with stannic chloride. 

Small amounts of carboxylic monomers (acrylic acid (AA) or methacrylic acid (MAA)) [86] or 2-hydroxyalkyl methacrylates [87] could be easily used in a styrene miniemulsion polymerization, using DMA or SMA as hydrophobe and SDS as emulsifier. 

The kinetics of acrylic acid polymerization in the presence of N-vinylpyrrolidone and acrylamide (up to 35%) or styrene (up to 20%) copolymers has been investigated. 

Also indicated in Figure 7.7 is the possibility of acid-catalyzed aromatization of DH to an unreactive dimer (DA). Under neutral conditions, only traces of DA are found. However, when a small amount of CSA is added to styrene undergoing polymerization by auto-initiation, significant levels of DA are formed along with polystyrene of higher than expected MW. We believe this is strong support for the Mayo mechanism since acid would have little affect on the Flory diradical intermediate. 

A typical mobile-phase composition is an acetonitrile-water gradient with a fixed concentration of trifluoroacetic acid (TFA), formic, or acetic acid (typically 0.05-0.5%). TFA acts as an ion-pairing agent and masks secondary interactions with the silica-based stationary phase. TFA may significantly suppress the ESI response in positive-ion mode. To avoid this, either formic acid is preferred or a mixture of 0.02% TFA and 0.5% acetic acid can be used. Some silica-based RPLC materials can be used with a lower TFA concentration (PepMap ). Alternatively, poly(styrene-divinylbenzene) polymeric materials (PS-DVB) can be applied. With a monolithic PS-DVB column, only a small decrease in separation efficiency on the monolithic column was observed when the TFA concentration was reduced from 0.2%to0.05%[51]. 

As various organic monomers, such as acrylamide, acrylonitrile, vinyl acetate, maleic acid and styrene, can polymerize at the same time as forming inorganic nanomaterials, various kinds of polymer-inorganic nanocomposites can be prepared at room temperature by a y-irradiation synthesis method. 

In addition to true ion exchange, other interactions can take place between the sample solutes and the resin. Adsorption is one of the commonest of these interactions. For example, the benzoate anion appears to be adsorbed somewhat by the poly-styrene-divinylbenzene polymeric matrix of organic ion exchangers. This may be due to an attraction of the k electrons of the aromatic polymer for the benzoate. Benzoic acid, which exists mostly in the molecular form, is absorbed to a much greater degree than benzoate salts. 

If trifluoroacetic acid (mixed with ethylbenzene) is added dropwise to styrene, no polymerization occurs. However, if styrene is added to the acid, high molecular... 

Using sealed-tube sample holders, Santoro and co-workers (32-35) investigated a wide variety of organic reactions. Examples are the cis - trans isomerization of stilbene and oleic acid, polymerization of styrene, Diels-Alder reactions, and others. Unstable intermediates in an organic reaction have been detected using DTA techniques by Koch (36). If a solution of an unstable compound is heated, temperature changes characteristic of reactions of the intermediate can be detected. Conversely, the absence of thermal effects indicates that no unstable product is present. 

In the nonaqueous polymerization processes that are conducted in organic solvent or diluent, many of the carboxyl-containing monomers cited have successfully been used in the preparation of ASNE and HASNE ASTs. Reactivity ratios, rates of reaction, monomer-polymer solubilities, economics, and degree of polymerization were among the criteria considered in monomer selection. However, in the important aqueous processes of suspension and particularly emulsion polymerization, the water solubility and hydrophilicity of the carboxylic monomer was found to be of considerable importance. Fordyce and Ham (13) observed that a significant portion of itaconic acid polymerized in the aqueous phase when emulsion polymerization was carried out with styrene. Fordyce et al. (9, 10) reported that... 

In order to prepare block copolymers by sequential monomer addition, the crossover reaction must be efficient. The order of monomer addition is therefore extremely important in anionic polymerizations, since the propagating anion of the first block must be nucleophilic enough to initiate polymerization of the second monomer. Since the reactivity of the propagating anion correlates with the pA a of its conjugate acid, any monomer listed in Table 13 (such as styrene) will polymerize any monomer listed... 

Pickering stabilizers, commonly used in styrene suspension polymerization, are inorganic solids, insoluble in the aqueous phase. Their main advantage is that they can be removed easily from the final particulate product (e.g., by dilute acid), which improves the clarity and transparency of the polymer. Also, the amount of polymer deposited on the wall and on other parts of the reactor decreases, which considerably improves the heat transfer rate from the reaction medium to the coolant. Finally, it should be mentioned that inorganic powders are usually cheaper [5]. 

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