Monomers methyl substituted styrene

OC-Methylstyrene. This compound is not a styrenic monomer in the strict sense. The methyl substitution on the side chain, rather than the aromatic ring, moderates its reactivity in polymerization. It is used as a specialty monomer in ABS resins, coatings, polyester resins, and hot-melt adhesives. As a copolymer in ABS and polystyrene, it increases the heat-distortion resistance of the product. In coatings and resins, it moderates reaction rates and improves clarity. Physical properties of a-methylstyrene [98-83-9] are shown in Table 12. 

Waters61 have measured relative rates of p-toluenesulfonyl radical addition to substituted styrenes, deducing from the value of p + = — 0.50 in the Hammett plot that the sulfonyl radical has an electrophilic character (equation 21). Further indications that sulfonyl radicals are strongly electrophilic have been obtained by Takahara and coworkers62, who measured relative reactivities for the addition reactions of benzenesulfonyl radicals to various vinyl monomers and plotted rate constants versus Hammett s Alfrey-Price s e values these relative rates are spread over a wide range, for example, acrylonitrile (0.006), methyl methacrylate (0.08), styrene (1.00) and a-methylstyrene (3.21). The relative rates for the addition reaction of p-methylstyrene to styrene towards methane- and p-substituted benzenesulfonyl radicals are almost the same in accord with their type structure discussed earlier in this chapter. 

The data in Table I are not directly comparable, since the viscosity of the 3-isomer was determined in benzene while the others were measured in DMSO. In addition, the first two polymers were prepared in bulk polymerizations, while the polymerization of methyl 3-vinylsalicylate was carried out with the monomer diluted 1 1 with benzene. Thus no certain conclusion can be drawn the data are, however, an indication of possible difficulty in radical polymerization of substituted styrenes bearing a phenol ortho to the vinyl group. 

In the 1960s, after Kennedy and Thomas [25] had established the isomerisation polymerisation of 3-methylbutene-l, this became a popular subject. From Krentsel s group in the USSR and Aso s in Japan there came several claims to have obtained polymers of unconventional structure from various substituted styrenes by CP. They all had in common that an alleged hydride ion shift in the carbenium ion produced a propagating ion different from that which would result from the cationation of the C C of the monomer and therefore a polymer of unconventional structure the full references are in our papers. The monomers concerned are the 2-methyl-, 2-isopropyl-, 4-methyl-, 4-isopropyl-styrenes. The alleged evidence consisted of IR and proton magnetic resonance (PMR) spectra, and the hypothetical reaction scheme which the spectra were claimed to support can be exemplified thus ... 

Monomers which can add to their own radicals are capable of copolymerizing with SO2 to give products of variable composition. These include styrene and ring-substituted styrenes (but not a-methylstyrene), vinyl acetate, vinyl bromide, vinyl chloride, and vinyl floride, acrylamide (but not N-substituted acrylamides) and allyl esters. Methyl methacrylate, acrylic acid, acrylates, and acrylonitrile do not copolymerize and in fact can be homopolymer-ized in SO2 as solvent. Dienes such as butadiene and 2-chloro-butadiene do copolymerize, and we will be concerned with the latter cortpound in this discussion. 

Wullf and Hohn recently described several new stereochemical results (93). They reported the synthesis of a copolymer between a substituted styrene (M ) and methyl methaciylate (M2) having, at least in part, regular. . . M,M M2M MiM2. . . sequences. Polymerization involves the use of a chiral template to which the styrene monomer is loosely bound. After elimination of the template, the polymer shows notable optical activity that must be ascribed to the presence of a chiral stmcture similar to that shown in 53 (here and in other formulas methylene groups are omitted when unnecessaiy for stereochemical information). This constitutes the first stereoregular macromolecular compound having a three monomer unit periodicity. 

Bevington has continued his studies of the initiation reaction and of the reactivities of monomers towards reference radicals (69—71). A study of the polymerization of substituted styrenes was recorded (72). In methyl methacrylate polymerization by ammonium trichloroacetate in the presence of copper derivatives, the complexities of the initiation and termination reactions were elegantly unravelled by Bamford and Robinson using two differently labelled trichloroacetates (73). Apparently cyclic processes involving alternate oxidation and reduction of copper may arise. 

While there is a considerable body of research on CCT polymerizations of styrene itself, there are no reports of CCT in polymerizations of substituted styrenes. In the case of styrene as well as in the case of other vinylic monomers bearing no methyl group adjacent to the propagating radical, CCT always provides oligomers with an exclusively trans configuration of the double bond.28 368 Because there is no abstractable methyl hydrogen atom, the only site for... 

A topochemical condition for polymerization is the proper approach of successive monomers at the growing chain-end within the channels. In this respect, conjugated dienes like butadiene, isoprene, etc. possessing reactive atoms in terminal positions, are very suited to inclusion polymerization. However, even bulkier monomers such as substituted styrenes or methyl methacrylate can polymerize if the space available inside the channels permits a favorable orientation and/or conformation of the monomer. The most studied examples are butadiene, vinyl chloride, bromide and fluoride, and acrylonitrile in urea 2,3-dimethylbutadiene and 2,3-dichlorobutadiene in thiourea butadiene, isoprene, cis- and trans-pentadiene, trans-2-methylpentadiene, ethylene and propylene in PHTP butadiene, cis- and trans-pentadiene, cis- and trans-2-methylpentadiene in DCA and ACA butadiene, vinyl chloride, 4-bro-mostyrene, divinylbenzene, acrylonitrile and methyl methacrylate in TPP. 

It is very clear that if the initiator has hydroxyl groups, and if the termination takes place exclusively by recombination then a polymeric diol is obtained [2, 3], which is ideal for polyurethane. If the termination takes place by disproportionation, only monofunctional compounds are obtained, which cannot be used in PU. The vinylic and dienic monomers used in practice have various termination mechanisms. Some monomers give only recombination reactions, such as styrene, acrylates (methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethyl hexyl acrylate), acrylonitrile and butadiene. Other monomers give both mechanisms of termination, around 65-75% disproportionation and 25-35% recombination, such as methacrylates (methyl methacrylate, ethyl methacrylate, butyl methacrylate etc.), substituted styrenes and other monomers [2, 3, 4]. 

Certain types of reactions, such as polymerization, in the confined nanoscale channels/space may have different pathways compared with those in open space. Kitagawa and coworkers have utilized size-tunable MOFs as reactions hosts for radical polymerization of activated monomers, such as styrene, divinylbenzene, substituted acetylenes, methyl methacrylate, and vinyl acetate (Fig. 11) [32-35]. Fara-dicarboxylate linkers of different sizes, a-d, were used to link Cu " and Zn " centers to form 2D sheets which were further linked by triethylenediamine to form 3D frameworks 9a-d (for Cu " ) and lOb-d (for Zn " ) that possess 1-D channels (Fig. 12). 

A few monomers, like styrene and methyl methaciylate, will, after careful purification and presumably free from all impurities, polymerize at elevated temperatures. It is supposed that some ring-substituted styrenes act similarly. The rates of such thermal self-initiated polymerizations are slower than those carried out with the aid of initiators. Styrene, for instance, polymerizes only at a rate of 0.1 % per hour at 60 C, and only 14% at 127 C. The rate of thermal polymerization of methyl methacrylate is only about 1% of the rate for styrene.Several mechanisms of initiation were proposed earlier. The subject was reviewed critically. More recently, the initiation mechanism for styrene polymerization was shown by ultraviolet spectroscopy to consist of an initial formation of a Diels-Alder dimer. The dimer is believed to subsequently transfer a hydrogen to a styrene molecule and form a free radical ... 

Various substituted styrenes also anionically polymerize readily. These include methyl, methoxy, dimethylamino, t- butyl and other groups which are electron donating to the benzene ring and do not themselves react with carbanion centers. Substituents such as chloro or nitro can be anionically polymerized only at imder very carefolly controlled conditions. 2,3, or 4 vinylpyridine can also be anionically polymerized. Any aromatic or condensed aromatic compounds with a vinyl substituent is potentially anionically polymerizable, or co polymerizable with any other anionically polymerizable monomer. 

Other furan monomers which polymerize cationically include 2-furfuryl vinyl ether, 2-vinyl furoate (albeit through a polyalkylation mechanism giving a polyester incorporating the ring into the pol5mer backbone), F and MF as co-monomers in conjunction with substituted styrenes and vinyl ethers, as well as 2-furfurylidene methyl ketone (obtained by the base-catalyzed condensation of F with acetone) and its homologues [4d]. 

Through the years other monomers have been investigated. The diene commonly employed is 1,3-butadiene, although isoprene, 2-ethyl butadiene, 2,3-dimethyl butadiene, piperylene, and other substituted dienes have been investigated. The nitrile commonly employed is acrylonitrile. It has been reported that when part of the acrylonitrile is replaced by methacrylo-nitrile or ethacrylonitrile, the cement-making properties of the rubber are improved. Small proportions of a third monomer may also be used in conjunction with the two principal components. Hycar 1072, which employs methacrylic acid as the third monomer, is occasionally used in adhesive applications. Other monomers including ethyl acrylate, methyl methacrylate, styrene, vinylidene chloride, acrylic acid, N-vinyl-2-pyrrolidone, and vinyl acetate have been employed in varying amounts to adjust the adhesive and elastomeric properties. 

In the early composition of matter, process and product patents that IKC had filed, reference and claims to all types of substituted styrene homopolymers and copolymers in the syndiotactic configuration had been made. These became the practical basis for the development of film and fiber grade products with improved (in this case reduced) crystallization rates from the melt. The incorporation of small amounts of alkyl-substituted styrene monomers led to a new line of products for these markets and applications. The almost complete random copolymer of para-methyl styrene and styrene with these catalysts is the basis of this technology. Once it was discovered that this was effective, it was only a matter of optimizing the melt crystallization rate with... 

A drastic change of nitroxide stmcture was witnessed with the use of the commercially available DBNO (27). In particular, Moad and Rizzardo showed that the dissociation rate constant of a DBNO-based alkoxyamine was higher than any similar alkoxyamines based on cyclic nitroxides bearing tetra-methyl alkyl groups on the vicinity of the aminoxyl function. The first experimental studies were performed by the group of Catala where it was shown that the polymerization of styrene and substituted styrene monomers could be carried out at 90 ° C with all the criteria of control/livingness. However, the polymerization rate was independent of the alkoxyamine concentration and remained governed by the production of thermal radicals in the medium. The tert-butyl-tert-amyl nitroxide 28 was tested by Moad et to control the polymerization of MMA and appeared to be inefficient. 

Styrene derivatives with a bulky substituent at the a or P position to the vinyl group cannot be made into high polymers because of the steric hindrance of the substituent. Consequently, these monomers give dimers exclusively at high temperatures irrespective of the kind of initiator few studies, however, deal with the dependence of the structure of these dimers on reaction conditions and on the nature of counteranions. This section briefly discusses cationic dimerization of a-methylstyrene ( MS) and anethol (P-methyl-p-methoxystyrene) as a- and P-substituted styrenes, respectively. 

In addition to providing fully alkyl/aryl-substituted polyphosphasenes, the versatility of the process in Figure 2 has allowed the preparation of various functionalized polymers and copolymers. Thus the monomer (10) can be derivatized via deprotonation—substitution, when a P-methyl (or P—CH2—) group is present, to provide new phosphoranimines some of which, in turn, serve as precursors to new polymers (64). In the same vein, polymers containing a P—CH group, for example, poly(methylphenylphosphazene), can also be derivatized by deprotonation—substitution reactions without chain scission. This has produced a number of functionalized polymers (64,71—73), including water-soluble carboxylate salts (11), as well as graft copolymers with styrene (74) and with dimethylsiloxane (12) (75). 

Other commercially relevant monomers have also been modeled in this study, including acrylates, styrene, and vinyl chloride.55 Symmetrical a,dienes substituted with the appropriate pendant functional group are polymerized via ADMET and utilized to model ethylene-styrene, ethylene-vinyl chloride, and ethylene-methyl acrylate copolymers. Since these models have perfect microstructure repeat units, they are a useful tool to study the effects of the functionality on the physical properties of these industrially important materials. The polymers produced have molecular weights in the range of 20,000-60,000, well within the range necessary to possess similar properties to commercial high-molecular-weight material. 

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