Styrene, a-methyl

In cationic polymerization the active species is the ion which is formed by the addition of a proton from the initiator system to a monomer. For vinyl monomers the type of substituents which promote this type of polymerization are those which are electron supplying, like alkyl, 1,1-dialkyl, aryl, and alkoxy. Isobutylene and a-methyl styrene are examples of monomers which have been polymerized via cationic intermediates. 

Hydroperoxide Process. The hydroperoxide process to propylene oxide involves the basic steps of oxidation of an organic to its hydroperoxide, epoxidation of propylene with the hydroperoxide, purification of the propylene oxide, and conversion of the coproduct alcohol to a useful product for sale. Incorporated into the process are various purification, concentration, and recycle methods to maximize product yields and minimize operating expenses. Commercially, two processes are used. The coproducts are / fZ-butanol, which is converted to methyl tert-huty ether [1634-04-4] (MTBE), and 1-phenyl ethanol, converted to styrene [100-42-5]. The coproducts are produced in a weight ratio of 3—4 1 / fZ-butanol/propylene oxide and 2.4 1 styrene/propylene oxide, respectively. These processes use isobutane (see Hydrocarbons) and ethylbenzene (qv), respectively, to produce the hydroperoxide. Other processes have been proposed based on cyclohexane where aniline is the final coproduct, or on cumene (qv) where a-methyl styrene is the final coproduct. 

The first approach has been important commercially. The monomer most commonly used is a-methylstyrene (see Section 16.11), whose polymer has a Tg of about 120°C. The heat distortion temperature of the resultant-ABS type polymer will depend on the level of replacement of styrene by the a-methyl-styrene. (It may be noted in passing that a-methylstyrene-acrylonitrile binary copolymers have been available as alternatives to styrene-acrylonitrile materials but have not achieved commercial significance.)... 

Essentially the present procedure converted 1-methylindole to l-methyl-3-(N,N-dimethylaminomethyl)indole and a-methyl-styrene to o -(N,N-dimethylaminoethyl)styrene. ... 

Methyl styrene (all isomers except a-methyl styrene) a-Methyl styrene... 

Methyl propyl ketone, see 2-Pentanone a-Methyl styrene CT... 

Pure monomer. Nearly pure indene, a-methyl styrene, and vinyl toluene are polymerized to make pure monomer resins. These resins are an alternative to C9 resins. They offer nearly water white color and vastly reduced odor, but at higher cost. Softening points range as high as 155°C for polyindene, whereas C9 softening points are all below 120 C. 

The molecular weight of the continuous phase is an important parameter that affects the mechanics and the melt flow of the end product. It can be controlled by the use of a suitable chain transfer agent (e.g., /er/-dodecyl mercaptan Ct = 4.0) or their combinations (e.g., primary mercaptans Or = 26.0 and dimeric a-methyl styrene Ct = 0.1) [132]. 

An alternating copolymer of a-methyl styrene and oxygen as an active polymer was recently reported [20]. When a-methyl styrene and AIBN are pressurized with O2, poly-a-methylstyreneperoxide is obtained. Polymerization kinetic studies have shown that the oligoperoxides mentioned above were as reactive as benzoyl peroxide, which is a commercial peroxidic initiator. Table 1 compares the overall rate constants of some oligoperoxides with that of benzoyl peroxide. 

This method was first applied by McCormick27 and by Bywater and Worsfold11 to the system a-methylstyrene/poly-a-methyl-styrene, and the free energy, entropy and heat of polymerization as well as the ceiling temperature were determined. Similar studies concerned with the system styrene/polystyrene are being carried out in our laboratories. 

Prior to polymerization studies extensive model experiments have been carried out for guidance in selecting suitable preparative conditions. The next section concerns model experiments it is followed by two sections concerning polymerization of a-methyl-styrene and isobutylene, respectively. 

The latter seem to be more reactive than the former, and hence the shift of the equilibrium leads to an increase in the polymerization rate. This explanation was verified by investigating the polymerization initiated by monofunctional initiators31), as well as by difunctional poly-a-methyl styrene of DP 70 and 270 32). No curvature was observed in the first case, neither in the second provided that the DPn of the initiator was sufficiently large. 

Table 12. Comparison of the reactivities of styrene (I), a-methyl styrene (II) and 3-methyl styrene (III)...

Sequential addition of a second monomer (e.g., styrene,p-terbutyl styrene, p-methyl styrene, indene, -chloro styrene, isoprene, and a-methyl styrene) to make glassy outer-block... 

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