Styrene oxide polymerization

In recent studies of styrene oxide polymerization reactions we found the phenyl substituent to have a significant Influence on the course of the polymerization process, too. In our particular case, however, the influence is due not only to steric factors, but also to the inductive effects of the phenyl ring, which Influences directly the course of the oxirane ring-opening reaction. 

The styrene oxide polymerization by the ZnEt2/H20 (1/0.8) catalyst was found to result in the formation of two polymer fractions, a partly crystalline fraction, I, and an amorphous fraction, II. The syntheses of poly(styrene oxide) starting from the R monomer showed both polymers were formed by almost exclusively... 

These results for styrene oxide polymerization indicate clearly that when a monosubstituted oxirane is polymerized, one can expect the occurrence of various active centers and of different polymerization mechanisms in the reaction. 

These results provide yet another example of an anionic ring-opening polymerization, in addition to that of styrene oxide polymerization, which can occur with formation of different active centers under the same reaction conditions. These results are in contradiction to those known until now, and to the general opinion that the anionic polymerization of 6-lactones proceeds by either the opening of alkyl-oxygen bond or an acyl-oxygen bond. 

ETHYLENE We discussed ethylene production in an earlier boxed essay (Section 5 1) where it was pointed out that the output of the U S petrochemi cal industry exceeds 5 x 10 ° Ib/year Approximately 90% of this material is used for the preparation of four compounds (polyethylene ethylene oxide vinyl chloride and styrene) with polymerization to poly ethylene accounting for half the total Both vinyl chloride and styrene are polymerized to give poly(vinyl chloride) and polystyrene respectively (see Table 6 5) Ethylene oxide is a starting material for the preparation of ethylene glycol for use as an an tifreeze in automobile radiators and in the produc tion of polyester fibers (see the boxed essay Condensation Polymers Polyamides and Polyesters in Chapter 20)... 

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). 

The radical mechanism is supported by a number of findings for instance, when the electrolysis is carried out in the presence of an olefin, the radicals add to the olefinic double bond styrene does polymerize under those conditions. Side products can be formed by further oxidation of the alkyl radical 2 to an intermediate carbenium ion 5, which then can react with water to yield an alcohol 6, or with an alcohol to yield an ether 7 ... 

There is much evidence" for this mechanism, including side products (RH, alkenes) characteristic of free-radical intermediates and the fact that electrolysis of acetate ion in the presence of styrene caused some of the styrene to polymerize to polystyrene (such polymerizations can be initiated by free radicals, see p. 978). Other side products (ROH, RCOOR) are sometimes found these stem from further oxidation of the radical R to the carbocation... 

Kmeshy et al. [96], for the first time reported recyclable catalyst based on polymeric Cr(lll)(X) salen complexes derived from (lR,2R)-(-)-cyclohexanediamine with 5,5 -methylene di-3- erf-butylsalicylaldehyde and X = Cl, NO3, and CIO4 67-69 (Figure 22). These complexes were used in regio-, diastereo-, and enantioselective aminolytic kinetic resolution (AKR) of fra 5-stilbene oxide, trans- S- methyl styrene oxide, and 6-CN-chromene... 

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. 

Lu and coworkers have synthesized a related bifunctional cobalt(lll) salen catalyst similar to that seen in Fig. 11 that contains an attached quaternary ammonium salt (Fig. 13) [36]. This catalyst was found to be very effective at copolymerizing propylene oxide and CO2. For example, in a reaction carried out at 90°C and 2.5 MPa pressure, a high molecular weight poly(propylene carbonate) = 59,000 and PDI = 1.22) was obtained with only 6% propylene carbonate byproduct. For a polymerization process performed under these reaction conditions for 0.5 h, a TOF (turnover frequency) of 5,160 h was reported. For comparative purposes, the best TOF observed for a binary catalyst system of (salen)CoX (where X is 2,4-dinitrophenolate) onium salt or base for the copolymerization of propylene oxide and CO2 at 25°C was 400-500 h for a process performed at 1.5 MPa pressure [21, 37]. On the other hand, employing catalysts of the type shown in Fig. 12, TOFs as high as 13,000 h with >99% selectivity for copolymers withMn 170,000 were obtained at 75°C and 2.0 MPa pressure [35]. The cobalt catalyst in Fig. 13 has also been shown to be effective for selective copolymer formation from styrene oxide and carbon dioxide [38]. 

Under optimized conditions regarding the choice of Br0nsted acid (mandelic acid 20), stoichiometry (1 1 ratio 9 and mandelic acid 20), solvent (the respective alcohol neat conditions), temperature (rt or 50°C), and catalyst loading (lmol% 9 and lmol% mandelic acid 20) electron-rich and electron-deficient styrene oxides underwent alcoholysis with simple aliphatic, stericaUy demanding as well as unsaturated and acid-labile alcohols. The completely regioselective (>99%) alcoholysis was reported to produce the corresponding P-aUcoxy alcohols 1-10 in moderate (41%) to good (89%) yields without noticeable decomposition or polymerization reactions of acid-labile substrates (Scheme 6.27). Notably, aU uncatalyzed reference experiments showed no conversion even after two weeks under otherwise identical conditions. 

Potassium carboxylate groups introduced onto the surface of carbon fibers initiated anionic polymerization of epoxides (e.g., styrene oxide, epichlorohydrin, and glycidyl phenyl ethers) and cyclic acid anhydrides (e.g., maleic anhydride, succinic anhydride, and phthalic anhydride) in the presence of 18-crown-6 [41]. 

The catalytic activity of the metal complex on the oxidative reaction in solution is much influenced not only by the species and the structure of the complexes but also by the chemical environment around them. For instance, in the oxidative polymerization of phenols catalyzed by a Cu complex, the reaction rate varied about 102 times with changes in the composition of the solvent, and the highest rate was observed for polymerization in a benzene solvent162. Thus, we used the copolymer of styrene and 4-vinylpyridine(PSP) as the polymer ligand and studied the effect on the catalysis of the non-polar field formed by the polymer ligand163. ... 

Control of the electron-transfer step was also attempted by combining two metal species on a polymer ligand167. We prepared polymer-metal complexes involving both the Cu(II) and Mn(III) ions. The oxidative polymerization of XOH catalyzed by the PVP-Cu, Mn mixed complex or the diethylaminomethylated poly(styrene)(PDA)-Cu Mn mixed complex proceeded 10 times faster than the polymerization catalyzed by either PVP- or PDA-metal complex. The maxima of the activity observed at [Cu]/[Mn] = 1 and [polymer]/[Cu,Mn] moderately small where Cu and Mn ions were crowded within the contracted polymer chain. Cooperative interaction between Cu and Mn was inferred. The rate constant of the electron-transfer step (ke in Scheme 14) for Cu(II) -> Cu(I) was much larger than that for Mn(III) -> Mn(II). The rate constants of the reoxidation step (k0) were polymer-Mn ex polymer-Cu.Mn > polymer-Cu, so the rapid redox reaction... 

Diethyizinc is not an active catalyst for polymerization of ethylene oxide and propylene oxide, but gives a high molecular weight polymer from styrene oxide (78) and a copolymer from styrene oxide and propylene oxide (79). This behavior is interpreted by assuming that styrene oxide easily reacts with diethyizinc to give a catalytically active species Zn[OCH2CH PhEt]2 (79,80). 

Tsuruta,T., Inoue,S., Tsubaki,K. Polymerization of styrene oxide and butadiene monoxide by organozinc compounds. Makromol. Chem. Ill, 236 (1968). 

Samples collected in glass containers without headspace, refrigerated, and analyzed immediately. Because styrene undergoes polymerization, oxidation, and addition reactions, exposure to sunlight or air should be avoided,... 

Styrene is phenylethylene, c-C6Hu-CH=CH2, a compound important in a number of polymerizations. In the body, the cytochrome P450 enzyme in the liver can form styrene oxide, which then may react with the organisms DNA, i.e become a carcinogen. The use of MB in lipid fdms to oxidize styrene has been achieved by Rusling et al. (1997) in a series of reactions that can be written as follows ... 

Oligomer formation by a mechanism different from the polymerization mechanism has been proposed by Kern (7) for the tetramer formation from a number of epoxides and by Pasika (10) for styrene oxide dimer formation, although in the last case the initiation reactions are probably the same. However, in both cases degradation of polymer would be a possible alternative mechanism. 

The monomers of styrene oxide, 1,4-cyclohexene oxide, trioxane, and vinyl ether were polymerized at satisfactory rates. However, tetrahydrofuran, e-caprolactone, and cc-methylstyrene could not be polymerized7). 

Medvedev has reported work on the kinetics of polymerization of diolefins and other compounds, as influenced by the number of free radicals in the reaction (230). In the polymerization of styrene, two chain reactions are thought to take place the reaction of free radicals with oxygen leads to oxidation, and the reaction with styrene to polymerization (231). 

The use of SSL or lignosulphonates in other polymeric adhesive systems has also been examined [e.g., with polyacrylamide, proteins/aldehydes, polyethylene oxide, polyethylene imine, epoxides, melamine, styrene oxide, polyisocyanates (55)]. So far, these procedures, for different reasons, have not led to any major practical application (36). It would, however, be interesting to reexamine some of these processes using not crude spent sulphite liquors, but instead those purified by membrane filtration. 

Because ansa metallocenes had been found to be effective polymerization catalysts, exploration of chelating bis(arylimido) complexes has been undertaken, typical examples being (48-51). In general, these have distorted octahedral structures with mo-n in the range 1.73-1.75A and ZMo=N-R in the range 155-162°. Complex (51), which is chiral, catalyzed the kinetic resolution of styrene oxide with ane.e of 30%. 

Styrene readily polymerizes in air and it is therefore not surprising that there are a number of early obscure reports referring to its polymerization predating 1900. However, because the concept of polymerization had not yet been proposed (until Staudinger in 1920), many of these early reports referred to the oxidation or hardening of the styrene monomer. 

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