Copolymerization of a-methylstyrene

G-5—G-9 Aromatic Modified Aliphatic Petroleum Resins. Compatibihty with base polymers is an essential aspect of hydrocarbon resins in whatever appHcation they are used. As an example, piperylene—2-methyl-2-butene based resins are substantially inadequate in enhancing the tack of 1,3-butadiene—styrene based random and block copolymers in pressure sensitive adhesive appHcations. The copolymerization of a-methylstyrene with piperylenes effectively enhances the tack properties of styrene—butadiene copolymers and styrene—isoprene copolymers in adhesive appHcations (40,41). Introduction of aromaticity into hydrocarbon resins serves to increase the solubiHty parameter of resins, resulting in improved compatibiHty with base polymers. However, the nature of the aromatic monomer also serves as a handle for molecular weight and softening point control. 

The monomer units in I are linked tail to tail and not in the normal head-to-tail manner. Therefore I is not comparable with a normal dimer. In substance II a dimer lies to the right of the tail-to-tail linkage. In the copolymerization of a-methylstyrene with, for example, methyl methacrylate, the addition of one molecule of a-methylstyrene corresponds to substance I,... 

Figure 2. Copolymerization of a-methylstyrene (Mt) and methyl methacrylate (Mt). Curves calculated using Equation 5.

One can describe the copolymerization of a-methylstyrene and methyl methacrylate with Equations 5 and 33. Equation 5 reflects only a mathematical approach, whereas Equation 33 takes into account the polymerization-depolymerization equilibrium investigated in the homopolymerization of a-methylstyrene. 

Figure 6. Copolymerization of a-methylstyrene and methyl methacrylate. Curves calculated by Equation 37 for 20°, 50°, 60°, 80°,...

Table VII. Copolymerization Parameters Used To Describe tbe Copolymerization of a-Methylstyrene (Mi) and Acrylonitrile (M2)...

Vitamin B12 is known for its ability to catalyze molecular rearrangements. A variety of cobalt chelates are logical models for vitamin B12, and their stoichiometric and catalytic activities in a variety of reactions,403 particularly olefin isomerizations, were studied intensively.404-411 Noncatalytic isomerization reactions based upon the synthesis of alkylcobalt chelates as model intermediates were favored. A variety of catalytic oxidations of substrates such as hydroquinone, azo compounds, phosphines, and olefins were also investigated.412-415 Copolymerization of a-methylstyrene and other monomers with oxygen in the presence of CoTPP led to alternating polyperoxides.416 418 Cobaloximes were found to catalyze... 

Also examined was the copolymerization of a-methylstyrene and 4-bromo-styrene [169], again with similar effect, here using a small Buehler-type probe of 25 kHz. This did not produce any sonochemically induced polymerization of the monomer over a 24-hour period without the application of an electric potential, representing an important control experiment since ultrasound is well known to produce radical species which could themselves influence polymerization. 

Copolymerization of a-methylstyrene with tetraoxane produced, besides the linear products, 4-methyl-4-phenyl-l,3-dioxane 54). 

Figure 18 - Electroinitiated copolymerization of a-methylstyrene and isoprene. (a) isoprene content of polymer (b) overall conversion (open symbols with ultrasound full symbols without ultrasound)...

Table 5 lists some selected copolymerization reactivity ratios. It is clear from the data that the monomer yielding the more stable carbocation dominates the copolymerization. Considering the importance of carbocation stability, it is not surprising that in some instances reasonable correlation was obtained between log(l/ri) and Hammett s a or Brown s ct+ values of the substituents of the second monomer. Examples are the copolymerization of a-methylstyrene with substituted styrenes (169) or styrene with substituted 1- and 2-phenylbutadienes (172). It is thus expected that ideal copolymerization (ri = T2 = 1) in carbocationic systems is imlikely— the only reported ideal system is the copolymerization of... 

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