Homopolymerization of styrene

It has been emphasized in the copolymerization of styrene with butadiene or isoprene in hydrocarbon media, that the diene is preferentially incorporated. (7,9,10) The rate of copolymerization is initially slow, being comparable to the homopolymerization of the diene. After the diene is consumed, the rate increases to that of the homopolymerization of styrene. Analogously our current investigation of the copolymerization of butadiene with isoprene shows similar behavior. However, the... 

In the styrene (MJ-indene (Mz) system, rx increased with the field. This result shows that the dissociation of ion pairs at the growing chain ends, the terminal group of which is styrene, was enhanced by the field. As was mentioned above, the field has no effect on the homopolymerization of styrene by boron trifluoride etherate in nitrobenzene (see Fig. 5). This result of the homopolymerization seems to be inconsistent with that obtained for the copolymerization, but can be accounted for as follows. The field-accelerating effect decreases as kp/kp decreases, when an enhancement of the degree of dissociation with the electric field is given. The fact that no field effect was observed on the homopolymerization of styrene with boron trifluoride etherate in nitrobenzene may be attributed to a fairly small value of kp/kp, in addition to the factor af 1. On the other hand, the field enhanced the polymerization of indene by boron trifluoride etherate in nitrobenzene (16). The difference in the field effects of the two monomer systems suggests that the following relation must hold, ... 

An interesting effect of the ionic factors of the polymerization was found by Kuntz (59). He has shown that the homopolymerization of styrene using butyllithium catalysts is six times as rapid as that of butadiene. However, in copolymerization, butadiene polymerized initially at its own rate with relatively small amounts of the styrene being consumed. Only after 90% of the butadiene had been consumed, the styrene began to polymerize at its own rate. THF increased the rate of the polymerization but had little effect on the rate of butadiene to styrene which is polymerized. The butadiene structure is little influenced by copolymerization. The homopolymer contained 44% cis-1.4, 7% 1.2 and 49% trans-1.4 while the butadiene units of the butadiene copolymers contained 40% cis 1.4, 7% 1.2 and 53% trans-1.4 groups. 

A graph of equations (1) and (2) is shown in Figure 1 for the homopolymerization of styrene. The parameters used are given in the caption. In an independent study Sundberg and James (12)... 

Beside NdP (= Nd(P204)3) Xiu et al. and Liu et al. also describe the phosphorus-containing catalyst component Nd(P507)3 which is bis(2-ethyl-hexanol)phosphonate (Scheme 6) [262,263]. Xu et al. applied Nd(Pso7)3 as well as Nd(P204)3 in combination with the cocatalyst TIBA for the homopolymerization of hexylisocyanate [262]. The Nd-phosphonate-based catalyst system Nd(P507)3/TIBA/H2O is also used for the homopolymerization of styrene [263]. 

When both monomer and initiator are added simultaneously, the rate of monomer and initiator addition to the reaction doesn t appear to be very critical. This was shown in a study of homopolymerization of styrene (19) and appears to be true in this terpolymerization (Table IX). Variations in Mw/Mn appear small. However, there is a decrease in Mw... 

In the past the really well understood particle formation and kinetics involved the single-charge homopolymerization of styrene-like monomers in the presence of micellar surfactants and of water soluble initiators with long half lives. Even for these systems the theory was predictive only at relatively low conversions. Now the kinetics are well imderstood even at high conversions. 

Only a few papers have appeared dealing with LRP by DT [8], and the applications are almost completely limited to the homopolymerization of styrene. In this case, it was possible to obtain good control of the final CLD, with polydispersity values as low as 1.3-1.4. Better performances are difficult with styrene, mainly because of the limited transfer activity of the iodine atoms. This is the main reason for the very poor results obtained when applying this process to the polymerization of acrylates (e.g. n-butyl acrylate) and for the complete lack of control reported for other monomers [8]. 

While the majority of SBC products possess discrete styrene and diene blocks, some discussion of the copolymerization of styrene and diene monomers is warranted. While the rate of homopolymerization of styrene in hydrocarbon solvents is known to be substantially faster that of butadiene, when a mixture of butadiene and styrene is polymerized the butadiene is consumed first [21]. Once the cross-propagation rates were determined (k and in Figure 21.1) the cause of this counterintuitive result became apparent [22]. The rate of addition of butadiene to a growing polystyryllithium chain (ksd) was found to be fairly fast, faster in fact than the rate of addition of another styrene monomer. On the other hand, the rate of addition of styrene to a growing polybutadienyllithium chain (k s) was found to be rather slow, comparable to the rate of butadiene homopolymerization. Thus, until the concentration of butadiene becomes low, whenever a chain adds styrene it is converted back to a butadienyllithium chain before it can add more styrene. Similar results were found for the copolymerization of styrene and isoprene. Monomer reactivity ratios have been measured under a variety of conditions [23]. Values for rs are typically <0.2, while values for dienes (rd) typically range from 7 to 15. Since... 

Such investigations performed by the authors concerned nitration of cellulose-PS graft copolymer, PS isolated from this product and PS obtained by suspension homopolymerization of styrene. The grafted PS was isolated so as to preserve its molecular mass, chemical composition and supramolecular structure104 the homopolymer was reprecipitated from benzene into methanol. The molecular mass of grafted chains was 8 x 105—106 and that of the homopolystyrene 5 x 10s. 

The prinaples of latex reactor design, operation, and control will he illustrated by a consideration of the homopolymerization of styrene and vinyl acetate. Emulsion polymerization of vinyl acetate follows Case 1... 

The activation energy of anionic propagation in the homopolymerization of styrene was determined to be about 1 kcal. per mole. This value refers to the reaction proceeding in tetrahydrofuran solution. The activation energy for the same reaction in dioxane was reported (1, 2) to be 9 3 kcal. per mole. This is one of many examples which stresses the importance of a solvent in ionic polymerization. 

Since kp for the anionic homopolymerization of styrene in tetrayhdrofuran solution is / 600 liters per mole second and the respective activation energy is only 1 to 2 kcal. per mole, the entropy of activation is substantially more negative (by about 14 eu.) than AS for a radical polymerization of styrene. It is likely that the additional decrease in the entropy of activation is due to immobilization of the counterion in the transition state in the middle between the last unit of the growing end and the new unit being added, i.e. 

Table II. Effect of Counterion on the Rate of Anionic Homopolymerization of Styrene in Tetrahydrofuran at 25 C.

This relationship is shown (Figure 3) for the homopolymerization of styrene, where AHp = 300 B.t.u. per pound and Cp = 0.5 B.t.u. per ° F. per pound. The data show that the monomer entering the heat exchanger (Figure 2) will have to be heated or cooled depending on / and T2. With the monomer entering the exchanger at room temperature (taken as 30° C.), endothermic operation is involved when Tj > 30° C., exothermic when < 30° C., and adiabatic when Tj = 30° C. For a typical reactor temperature of 130° C., the monomer must be... 

Mono-Cp titanium catalyst systems are also suitable for the polymerization of polar and non-polar olefinic monomers. The reduction of a mixture of Cp TiMe3 and Ph3C[B(C6F5)4] with zinc produces a catalyst for the syndiotactic homopolymerization of styrene. The same catalyst mediates the polymerization of methyl methacrylate to poly(methyl methacrylate) (PMMA) with >65% of syndiotacticity. This system is also effective for the co-polymerization of styrene/methyl methacrylate upon optimal conditions. A new polymerization mechanism to explain the characteristics of the polymers is proposed based on sequential conjugate addition steps.541... 

The self-condensing copper-catalyzed polymerization of macromonomer of poly(tBA) with a reactive C—Br bond (H-6) affords hyperbranched or highly branched poly(tBA).447 Copolymerization of H-1 and TV-cyclohexylmaleimide induced alternating and self-condensing vinyl polymerization.448 The residual C—Cl bond was further employed for the copper-catalyzed radical homopolymerization of styrene to give star polymers with hyperbranched structures. Hyperbranched polymers of H-1 further serve as a complex multifunctionalized macroinitiator for the copper-catalyzed polymerization of a functional monomer with polar chromophores to yield possible second-order nonlinear optical materials.325... 

Emulsion homopolymerization of styrene Maximization of monomer conversion and minimization of deviation of average molecular weight and particle size from desired values. Adapted GA for MOO Model parameters were estimated based on experimental data. A decision support system was also developed to rank the Pxeto-optimal solutions. Massebeuf et al. (2003)... 

Massebeuf, S., Fonteix, C., Hoppe, S. and Pla, F. (2003). Development of new concepts for the control of polymerization processes multiobjective optimization and decision engineering. I. Application to emulsion homopolymerization of styrene, J. Appl. Polym. Sci, 87, pp. 2383-2396. 

The distinction suggested by the terms "reactive mononer and "unreactive monomer is not supported by the results obtained in the homopolymerization of styrene and of maleic anhydride (MAH) in the presence of a peroxyester undergoing rapid decomposition. Thus, the addition of 0.5 mmole di-sec-butyl peroxydicarbonate (t.. 1.3 hr) in 4 portions at 2 min intervals (total reaction... 

New macroradicals have been obtained by proper solvent selection for the homopolymerization of styrene, methyl methacrylate, ethyl acrylate, acrylonitrile, and vinyl acetate, and by the copolymerization of maleic anhydride with vinyl acetate, vinyl isobutyl ether, or methyl methacrylate. These macroradicals and those prepared by the addition to them of other monomers were stable provided they were insoluble in the solvent. Since it does not add to maleic anhydride chain ends, acrylonitrile formed a block copolymer with only half of the styrene-maleic anhydride macroradicals. However, this monomer gave excellent yields of block polymer when it was added to a macroradical obtained by the addition of limited quantities of styrene to the original macroradical. Because of poor diffusion, styrene did not add to acrylonitrile macroradicals, but block copolymers formed when an equimolar mixture of styrene and maleic anhydride was added. 

A rather unexpected water- and alcohol-insensitive activator, namely boron trifluoride etherate, was developed by Sawamoto for the living polymerization of p-hydroxystyrene in combination with the water adduct of p-methoxystyrene as initiator [78], The polymerizations proceeded even in large excess of water, which is in large contrast with the absolutely dry conditions that are normally required for carbocationic polymerizations. It is proposed that acetonitrile, which is used as polymerization solvent, stabilizes the short-lived carbocationic propagating species. The same polymerization methodology could be applied for the preparation of statistical and block copolymers consisting ofp-hydroxystyrene and b-methoxystyrene [79], as well as for the homopolymerizations of styrene, p-chlorostyrene and p-methylstyrene in the presence of a proton trap [80]. 

Radical copolymerization of tetraphenylporphyrin monomers with the vinyl group in a benzene ring or pyrrole ring and their Cu(II), Co(II) and Zn(II) complexes with styrene or methylmethacrylate has been studied [47,48], Compared to the homopolymerization of styrene, the copolymerization decreases both the overall poljmierization rate and the molecular weight of the polymers formed. For example, the rate of chain transfer in the methylmethacrylate Co(II) porphyrin system is lO times greater than the homopolymerization of the methacrylate. 

Figure 19 (a-c) Several views of the Symyx CM2 synthesis platform encased in a glove box. (d) Libraiy design for the homopolymerization of styrene and f-BA. Adapted from Nasrullah, M. J. Webster, D. C. Macmmol. Chem. Phys. 2009, 210 (8), 640-650, and reprinted with permission from Wiley. 

In this communication we give preliminary results aimed at the elucidation of the mechanism and the estimation of the rate of radical generation in the spontaneous copolymerization of styrene and maleic anhydride. First, we show experiments that give order-of-magnitude estimates of the rate of radical generation in the copolymerization system, as compared with the homopolymerization of styrene. Second, we show additional results that give a preliminary estimation of the corresponding kinetic rate constant under some... 

Figure 5 shows the concentration profiles of the relevant species in the CDB-mediated copolymerization of styrene and maleic anhydride. This experiment was conducted at 70 °C, in the same fashion as the previously discussed experiments. The initialization in this experiment was extremely fast in comparison to the homopolymerization of styrene. Where the initialization period for a CDB-mediated styrene homopolymerization was 240 min-... 

It so happens that there is a way to exert FRRPP-based control over statistical copolymerizations/multipolymerizations early in the propagation reaction, and then continue chain extension after one of the monomers has been exhausted without having to alter reactor conditions. This is very attractive, because alteration of reactor conditions requires additional reaction time and steps and may even involve the use of extra equipment. For the S/AA copolymerization with excess S in the monomer eharge, ether is used as solvent/precipitant to facilitate FRRPP homopolymerization of styrene. However, we have established that poly(acrylic acid) precipitates in ether... 

Biscyclopentadienyl complexes and bridged metallocene complexes of titanium show lower polymerization activities than the monocyclopentadienyl complexes (39). The catalytic activity and S5nidiospecificity for bridged metallocenes does increase by decreasing the bite-angle (51). Although ansa-monocyclopentadienyl-amido titanium complexes are essentially inactive for homopolymerization of styrene, efficient sPS formation with nonbridged amido cylcopentadienyl complexes of titanium has been reported (52). 

Homopolymerization of styrene polystyrene PS Mixing with butadiene rubber (SBR) increasing impact strength (high impact PS or PS-HI) Mixing with poly(phenylene ether) (S/PPE) increasing temperature stability ... 

FeCl3.6H20 in methyl alcohol does not initiate homopolymerization of styrene, but it induces pyrrole and styrene to copolymerize [138] as seen in the data presented in Table 11.4. These copolymers were prepared by adding 0.1 mole of pyrrole and the required concentration of comonomer dissolved in 50 ml of solvents to a mixture of 0.4 M oxidant and 50 ml solvent with stirring. At the end of the reaction, the products were filtered, washed with methanol dried. F2 was determined from elemental analysis of the copolymers. 

The allyllithiums which are formed by addition of organolithiums add to butadiene, and tend to copolymerize with monomers such as styrene to give the block copolymers by forming the stable living polymers. Styrene polymerizes more easily than butadiene (the homopolymerization of styrene by w-butyllithium in n-heptane at 30 C is approximately six times faster than the homopolymerization of butadiene under the same condition [64]). However, in copolymerization of a mixture of the two monomers, butadiene is the more reactive comonomer. When 90% of the butadiene monomer has been converted to polymer, more than 80% of the styrene monomer present at the beginning of the reaction still remains. When the butadiene has all reacted a marked increase in the polymerization rate of styrene... 

---