Polystyrene initiation

Technical Information, Polystyrene Initiators for Styrene Polymeric tion Alc7o Chemie, Deventer, the Netherlands, Nov. 1985. 

Formation of block polymers is not limited to hydrocarbon monomers only. For example, living polystyrene initiates polymerization of methyl methacrylate and a block polymer of polystyrene and of polymethyl methacrylate results.34 However, methyl methacrylate represents a class of monomers which may be named a suicide monomer. Its polymerization can be initiated by carbanions or by an electron transfer process, the propagation reaction is rapid but eventually termination takes place. Presumably, the reactive carbanion interacts with the methyl group of the ester according to the following reaction... 

FIGURE 5.2 Synthesis of a peptide on a solid support according to Merrifield in 1964. PS = polystyrene. Initially, the protector was benzyloxycarbonyl, removed by HBr in CHjCOjH, followed by final deprotection with the same reagent at 78°C. The current protocol employs CF3C02H and HF, respectively. 

Suitably functionalised crown-ethers and cryptands have been synthesi -ed and reacted with chloromethyl polystyrene. Initially... 

Figure 2. Frequency distributions for polystyrene initiated with n-BuLi.

Figure 3. Intrinsic viscosity of polystyrene samples, irradiated in benzene solution in the presence of initiator I-III. Polystyrene concentration 7.69x10 2 M, photoinitiator concentration 2.31 x 10-3 Ml p Pure polystyrene initiator I initiator II A initiator III. (Reproduced with permission from Polym. Deg. Stability Ref. 21).

On the other hand, Ishizu et al. [58] reported the synthesis of cyclic polystyrene using interfacial condensation reaction of a/o-dibromopolyslyrcnc prepared from living polystyrene initiated with sodium naphthalene and terminated with 1,4-dibromobutane and then tetramethylenediamine as depicted in Fig. 11. The reaction was carried out in organic solvent/water to yield in more than 90%. The effect of solvent on the yield of cycUc polymer was observed, and the yield of cyclic product obtained in DMSO was higher than that in toluene. Since DMSO dissolves in both water and toluene, the reaction proceeded faster than that in toluene. 

Functionalised polystyrenes, initially used as ion-exchange resins and supports for solid phase peptide synthesis, have progressively expanded in importance as insoluble supports for catalysts and organic reagents1. Currently, most of these reactive polymers are prepared from polychloromethylstyrene, the so-called Merrifield resin, by a nucleophilic attack onto the chlorine atom. However, these supports present two main drawbacks ... 

Scheme 13 Polymerization of polystyrene initiated with 9-fluorenyllithium.

However, the partial volume is not independent of N, even for IV 103, as can be seen from Fig. 5.15, on which values of v(N), measured by Francois, Candau and Benoit16 for linear polystyrene initiated with cumyl-potassium, are plotted against 1/JV. We see that (5.2.9) is not realistic and must be replaced by a formula of the form... 

Such a "killing" procedure allows us to introduce desired end-groups into the prepared polymer and, if both ends are active, bifunctional polymers could be synthesized. For example, addition of CO2 to living polystyrene initiated by electron transfer yields... 

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