Other Aromatic Monomers

6-Trimethylstyrene has also been studied at —80 °C and evidence for the presence of the corresponding carbenium ions obtained by ultravicdet ctroscopy Both a-methylstyrene and p-methoxystyrene were studied at —80 °C by stop-flow spectrophotometry. They were ftwnd to polymerise so rapidly that the spectra taken were in fact those of species present at the end of the polymerisaticm . The polymerisation of p-methoxystyrene by perchloric acid in methylene chloride at room 

Acenaphthylene on the other hand polymerises with HQO4 in CH2CI2 with no detectable presence of carbenium ions. It seems that this stem is another example of a pseudocationic polymerisation Finally, in the case of N-vinylcarbazole it is difficult to establish the character of its pcJymerisation by perchloric acid in methylene chloride, since its very hi rate even with less than 10 M of acid did not permit a serious search of ptssible carbenium icms formed during the process The fact that this moncmer can be polymerised by dilute aquecus soluticais of perchloric acid in such nucleophilic scAvents as ethyl acetate and acetcme is hardly compatible with a cationic medianism. The nature of the chain carriers in this bizarre system is totally unclear. 

The only study of the polymerisation of a dienic moiomer perchloric acid is a brief report by Kohjiya et al. Reactions were carried out in tcduene and methylene chloride at -78 °C with acid concentrations ran g from 2 x 10 to 1.4 x 10 M. Asymptotic yields were observed and the pdymers diowed an appreciable amount of branching and crosslinking. The authors treatment of the results was optimistically based on Pepper and Burton s fast-initiation unimolecular-terminatitm kinetics. In fact, the evidence collected was extremely limited and any ctmclusion other than the obvious occurrence of a termination reaction seems totally unwarranted. 

Solutions of iodine in chlorinated hydrocarbons can be characterised by the existence of the double equilibrium  

Alkenes do not polymerise in the presence of iodine, but give instead the corresponding diiodides (see Sect. IIIC). Aromatic olefins and vinyl ethers on the other hand are susceptible to this initiator and readily give polymers in suitable media. Our present discussion of these processes will concentrate on work published after Plesch s second book, where previous investigations are thorou y reviewed. 

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The aromatic mono-olefins have been studied more extensively and intensively than any other class of monomers. Styrene, in particular, has received much attention, but nuclear and side-chain substituted styrenes are still largely unexplored, except in regard to copolymerization. The only other aromatic monomers which have been studied in any detail are a-methylstyrene [1] and 1,1-diphenylethylene and some of its derivatives [10]. It is strange that even readily available monomers, such as indene [80] and acenaphthylene [54b, 81], have hardly been investigated. 

Several chain transfer to polymer reactions are possible in cationic polymerization. Transfer of the cationic propagating center can occur either by electrophilic aromatic substituation or hydride transfer. Intramolecular electrophilic aromatic substituation (or backbiting) occurs in the polymerization of styrene as well as other aromatic monomers with the formation of... 

Biphenyl (and other aromatic monomers) Alkyl carbonates, UPF6 Overcharge protection 157- 159... 

In order to increase the solubiUty parameter of CPD-based resins, vinyl aromatic compounds, as well as other polar monomers, have been copolymerized with CPD. Indene and styrene are two common aromatic streams used to modify cyclodiene-based resins. They may be used as pure monomers or contained in aromatic steam cracked petroleum fractions. Addition of indene at the expense of DCPD in a thermal polymerization has been found to lower the yield and softening point of the resin (55). CompatibiUty of a resin with ethylene—vinyl acetate (EVA) copolymers, which are used in hot melt adhesive appHcations, may be improved by the copolymerization of aromatic monomers with CPD. As with other thermally polymerized CPD-based resins, aromatic modified thermal resins may be hydrogenated. 

Sodium naphthalene [25398-08-7J and other aromatic radical anions react with monomers such as styrene by reversible electron transfer to form the corresponding monomer radical anions. Although the equihbtium (eq. 10)... 

Polymerization. Spills of chemicals that are monomers or low-order polymers can be polymerized by adding a catalyst. Compounds that may be treated by polymerization include aromatics, aHphatics, and other oxygenated monomers such as vinyl chloride and acrylonitrile [107-13-1]. 

Some very peculiar features have been discovered in the microstructures of copolymers. Thus, Hanna et al. (1993) showed that a random copolymer of two aromatic monomers has chains in which random but similar sequences of the two monomers on distinct chains find each other and come into register to form a... 

Monomers employed in a polycondensation process in respect to its kinetics can be subdivided into two types. To the first of them belong monomers in which the reactivity of any functional group does not depend on whether or not the remaining groups of the monomer have reacted. Most aliphatic monomers meet this condition with the accuracy needed for practical purposes. On the other hand, aromatic monomers more often have dependent functional groups and, thus, pertain to the second type. Obviously, when selecting a kinetic model for the description of polycondensation of such monomers, the necessity arises to take account of the substitution effects whereas the polycondensation of the majority of monomers of the first type can be fairly described by the ideal kinetic model. The latter, due to its simplicity and experimental verification for many systems, is currently the most commonly accepted in macromolecular chemistry of polycondensation processes. 

Compounds of the porphyrin series, like other aromatic compounds, have a strong tendency to aggregate in solution. In general, aggregation is favoured by increased concentration and by an increased proportion of the poor solvent in a mixed solvent system.67-70 The aggregate shows reduced fluorescence and reduced PDT activity with respect to the monomer.71... 

These experiments and similar ones with other monomers, to be described elsewhere, show that the explanation of the allegedly cationic polymerisations of aromatic monomers in terms of ions must be revised drastically, and that the interpretation of the rate-constants reported must be treated with the greatest circumspection. 

A number of other polar monomers have been polymerized with butyllithium, nominally in hydrocarbon or aromatic solvents. In almost all cases the monomer concentration was so high that the effective dielectric constant was much greater than in a pure hydrocarbon. All show rather complex behaviour. The degree of polymerization of the polymer formed is always much higher than the initial monomer-catalyst ratio so that a simple scheme involving only initiation and propagation reactions is not applicable. Only precipitable polymer was isolated, so it is not sure if the low initiator efficiencies are due to low polymer formation or to side reactions of butyllithium with the monomer. In addition most systems studied stop before complete conversion of the monomer. Evidently the small fraction of active polymer chains formed... 

Photoinitiation of polymerization can be obtained through a variety of photochemical reactions which produce reactive free radicals. These radicals then lead to the formation of the polymer chains through the addition of further monomer units to the end of a chain in a sequence of radical addition reactions (Figure 6.10). A photoinitiator of polymerization is therefore a molecule which produces free radicals under the action of light. Benzo-phenone and other aromatic ketones can be used as photoinitiators, since a pair of free radicals is formed in the hydrogen abstraction reaction. Some quinones behave similarly, for example anthraquinone in the presence of hydrogen donor substrates such as tetrahydrofuran. 

A large number of compounds related to styrene have been reported in the literature, Those having the vinyl group CH2=CH—attached to the aromatic ring are referred to as styienic monomers, Several of them have been used for manufacturing small-volume specialty polymers. The specialty styreme monomers that arc manufactured in commercial quantities arc vinyl toluene, /r, -methylstyrene, or-methylstyrene. and divinylbenzene. In addition, 4-fert-butylstyrene (TBS) is a specialty monomer that is superior to vinyltoluene and pnra-methylstyrene in many applications. Other styrenic monomers produced in small quantities include chlorostyrene and vinylbenzene chloride. With the exception of a-methylstyrene, which is a by-product of the phenol-acetone process, these specialty monomers are more difficult and expensive to manufacture than styrene... 

On the other hand, aromatic monomers containing a boronic acid function apart from a halide function, i.e. haloarene boronic acids, undergo coordination homopolycondensation in the presence of transition metal-based catalysts, which results in the formation of poly(arylene)s [2] ... 

The ethylbenzene recovery rate is usually over 95 per cent, and its purity greater than 99.8 per cent. The quality of the product obtained conditions that of its derivative, the styrene monomer, and its aptitude for polymeiizatioiL This depends on the presence of toluene or other aromatics in the feed, whose content must generally not exceed 0.3 per cent This fractionation can only be calculated conveniently on a computer. The theoretic cal number of trays is as high as 330 for 95 per cent recovery. Since the efiicieocy of these trays approaches 85 per Ccnu abotH 390 real trays must be used with reflux ratios up to 80 to 90. 

Instead of block copolymers, the use of pseudo-random linear copolymers of an aliphatic a-olefin and a vinyl aromatic monomer has been reported [20], where the styrene content of the polymer must be higher than 40 wt%. Preferred are styrene and ethylene copolymers. These blends may contain, amongst other things, an elastomeric olefinic impact modifier such as homopolymers and copolymers of a-olefins. Presumably the styrene-ethylene copolymer acts as a polymer emulsifier for the olefinic impact modifier. Using 5 wt% of an ethylene-styrene (30 70) copolymer and 20% of an ethylene-octene impact modifier in sPS, a tensile elongation (ASTM D638) of 25 % was obtained. 

Pyrolysis of polystyrene produces an oil very high in concentration of the monomer, styrene and also other aromatic compounds. Eigure 11.15 shows a typical gas chromatogram for the pyrolysis oil produced from the pyrolysis of polystyrene, showing... 

Polystyrene (PS). The thermal degradation proceeds again by C-C scission, which is then followed by a complex radical chain reaction. In the early stages of reaction and at low temperatures (290°C), the primary products are styrene, diphenylbutene, and triphenyUiexene. At higher temperature or longer residence times, the final stable products are toluene, ethylbenzene, cumene, and triphenylbenzene [47]. Fluidized-bed pyrolysis was applied successfully to pure PS more than 60% of monomer and 25% of other aromatics were obtained at a pyrolysis temperatnre of 515°C [25, 26]. 

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