Addition of styrene monomer

Funt et al. followed this work and have extended it in detail. When naphthalene was added to the tetrahydrofuran solution of NaAl(CaH6)4 and NaB(C6H8)4 without monomer, they found the green sodium naphthalene complex produced by electrolysis (11). Upon the addition of styrene monomer, generation of the orange living polystyryl anions was spectrophotometrically observed. 

The B values for addition of styrene, p-methylstyrene, and 2-vinylpyridine to living polystyrene demonstrate the importance of the polar character of the monomer. The addition of vinylpyridine is much faster than the addition of styrene, whereas addition of p-methylstyrene is slower. Hence, a decrease in the negativity of the C=C bond enhances the addition (vinylpyridine as compared with styrene), its increase having the opposite eflFect (p-methylstyrene as compared with styrene). On the other hand, the change in the polarity of the ion has a less pronounced effect as shown by the for the addition of styrene monomer to... 

Also, it has been reported that poly(styrene-co-maleic anhydride-b-styrene) could be obtained either by addition of styrene monomer to the styrene-maleic anhydride macroradicals or by the free-radical-initiated copolymerization of maleic anhydride with more than an equimolar proportion of styrene in benzene solution (7). However, the maximum amount of styrene present in these block copolymers was less than 35% of the weight of the original macroradical. This limitation on the yield of the block copolymer is now assumed to be related to the increased solubility of the styrene block in the benzene solvent, which permits termination of the new macroradicals by coupling. 

Figure 1. Rate of addition of styrene monomer to a styrene-maleic anhydride macroradical in benzene at 50° C...

Thus, an example of a condensation polymer would be a polyester, formed by the condensation reaction between a glycol and a dicarboxylic acid (with the evolution of water), whereas an addition polymer is exemplified by polystyrene, formed by the self-addition of styrene monomers. 

Also, according to the above definition, an example of an addition polymer can be polystyrene that is formed by addition of styrene monomers ... 

Polyester Resins. Reinforced polyester resins are thermosets based on unsaturated polyesters from glycols and dibasic acids, either or both of which contain reactive double bonds. The ratio of saturated to unsaturated components controls the degree of cross-linking and thus the rigidity of the product (see Polyesters, unsaturated). Typically, the glycols and acids are esterified until a viscous Hquid results, to which an inhibitor is added to prevent premature gelation. Addition of the monomer, usually styrene, reduces the viscosity to an easily workable level. 

In the absence of impurities there is frequently no termination step in anionic polymerisations. Hence the monomer will continue to grow until all the monomer is consumed. Under certain conditions addition of further monomer, even after an interval of several weeks, will eause the dormant polymerisation process to proceed. The process is known as living polymerisation and the products as living polymers. Of particular interest is the fact that the follow-up monomer may be of a different species and this enables block copolymers to be produced. This technique is important with certain types of thermoplastic elastomer and some rather specialised styrene-based plastics. 

The effect of penultimate units on the rate constants of anionic propagation is observed also in other systems. For example, the addition of styrene to the lithium salt of 1-phenyl-n-hexyl anion is 4 times faster than to polystyryl lithium 51). Similarly, the addition of monomer to the lithium salt of 1,1-diphenyl-n-hexyl lithium is faster than the addition to 1,1,3-triphenyl-n-octyl lithium or 2-poly-sty ry 1-1,1-diphenyl ethyl lithium, the latter two salts having comparable reactivities52 . See also Ref.53)... 

The observation of Tsuji et al. 148) concerned with copolymerization of 1- or 2-phenyl butadiene with styrene or butadiene illustrates again the importance of the distinction between the classic, direct monomer addition to the carbanion, and the addition involving coordination with Li4. The living polymer of 1- or 2-phenyl butadiene initiated by sec-butyl lithium forms a block polymer on subsequent addition of styrene or butadiene provided that the reaction proceeds in toluene. However, these block polymers are not formed when the reaction takes place in THF. The relatively unreactive anions derived from phenyl butadienes do not add styrene or butadiene, while the addition eventually takes place in hydrocarbons on coordination of the monomers with Li4. The addition through the coordination route is more facile than the classic one. 

Fig. T A shows the GPC traces obtained at wavelength 2 k and 3U0 nm for a 312 nm Dow latex sample. Note the response at 3 0 nm is at twenty-five times the sensitivity of the response at 25 nm and hence considerably exaggerated in comparison. At 25 nm two peaks are clearly noted, a polymer peak and a secondary peak whose retention volume corresponds to that of styrene monomer. At 3 0 nm, since neither monomer nor polymer absorb, the observed peak is attributable to the presence of additives such as emulsifier.

Sequential addition of different monomer charges to a living anionic polymerization system is useful for producing well-defined block copolymers. Thermoplastic elastomers of the triblock type are the most important commercial application. For example, a styrene-isoprene-styrene triblock copolymer is synthesized by the sequence... 

The % yield is calculated with respect to the total number of gram-molecules of both monomers added 2. The intervals between the start of the isobutene polymerisation and the addition of the styrene were about 3 minutes, those between the addition of styrene and the addition of water about 5 minutes ... 

At the end of the polymerisation, when species IA has disappeared and ions are present, the addition of styrene makes the ions vanish instantaneously and they remain absent whilst polymerisation proceeds. Moreover, this polymerisation has the same rate constant as the first. This means that it cannot have been initiated only by the acid that was free at that time and that the acid bound as ions must also have become available. These facts are represented by the reaction paths leading to esters IB and IC, which complete the cycle whereby eventually ions are formed again, and can be destroyed again by addition of more monomer. Of course, reaction of the freshly added monomer with the then free acid leads to formation of ester IA. The maximum concentration of carbonium ions increases after each addition because of the increasing double bond concentration, as the polymer concentration increases. Thus the final value of the equivalent conductance and... 

Berlin [69] also confirmed the importance of the presence of OH radicals in his investigation of the polymerisation of polystyrene in the presence of styrene monomer when he found the addition of water to the reaction solvent (benzene) greatly enhanced the yield of polymer. However, latterly it has been argued for these systems that the appearance ofwater decomposition products (e. g. H2O2) led to oxidation of the various impurities, which previously, may have acted as inhibitors in the polymerisation process. 

Starting from 1956, living ionic polymerizations became the major interest for the synthesis of well-defined polymers. Szwarc reported that in the anionic polymerization of styrene (St) the polymer chains grew until all the monomer was consumed the chains continued to grow upon addition of more monomer [16],... 

Fig. 3 a Immobilization of DPE initiator precursor and activation by addition of -BuLi. Monomer is eventually added and results in polymerization, b Specially made high-vacuum reactor with filter for handling LASIP of nanoparticles. The scheme shows the A ampule containing styrene, B ampule containing -BuLi, C ampule containing MeOH [28,29]... 

Consider three 10-m reactors operating at 70°C. Each contains 1000 kg of styrene monomer. Additional ingredients initially are as follows ... 

---