Styrene anionic dispersion polymerization

J.-H. Jiang, Y. Ozaki, M. Kleimann and H.W. Siesler, Resolution of two-way data from on-line Fourier-transform Raman spectroscopic monitoring of the anionic dispersion polymerization of styrene and 1,3-butadiene by parallel vector analysis (PVA) and window factor analysis (WFA), Chemom. Intell. Lab. Syst., 70, 83-92... 

Styrene-1,3-butadiene-styrene (SBS) or styrene-isoprene-styrene (SIS) triblock copolymers are manufactured by a three-stage sequential polymerization. One possible way of the synthesis is to start with the polymerization of styrene. Since all polystyrene chains have an active anionic chain end, adding butadiene to this reaction mixture resumes polymerization, leading to the formation of a polybutadiene block. The third block is formed after the addition of styrene again. The polymer thus produced contains glassy (or crystalline) polystyrene domains dispersed in a matrix of rubbery polybutadiene.120,481,486... 

A recent paper by Wenger (35a) deserves some comments. This careful worker proved again that mono-dispersed polystyrene can be produced through an anionic polymerization. Most unfortunately, however, he confused some issues and their clarification is therefore necessary. Wenger found, in agreement with Waack (Ph. D. Thesis, Syracuse, June 1959), that polymerization of styrene initiated by sodium naphthalene at —78° C produces polystyrene having a broad molecular distribution. In our opinion this results from an incomplete solution of sodium naphthalene in tetra-hydrofuran at —78° C, whereas Wenger assumes that this indicates the unfavorable position of the equilibrium... 

Schwab FC, Murray JG (1985) Anionic dispersion polymerization of styrene. In Culbertson BM, McGrath JE (eds) Advances in polymer synthesis. Plenum, New York... 

Similar results are also observed in PS nanocomposites [56], which were prepared by free radical polymerization of styrene monomers in the presence of ZnAl and MgAl LDHs intercalated with 4,4 -azobis(4-cyanopentanoate) anions (LDH-ACPA). An intercalated-exfoliated morphology is observed for the composites of ZnAl-ACPA, whereas MgAl-ACPA shows microcomposite formation. The cone calorimetry results show good correlation between the reduction in PHRR and dispersion, in which the reduction in the peak heat release rate for 10% ZnAl-ACPA is 35% relative to the pristine polymer, whereas a 24% reduction is recorded for MgAl-ACPA at a similar loading. 

In the dispersion polymerization of styrene in alcohol solution, PVP, and a variety of anionic and nonionic surfactants have been used. It was found that the formation of monodispersed particles by this procedure was not always reproducible [97]. It may be that the two observations discussed above should be taken into consideration in such dispersion polymerization procedures. 

Domingo et al. [193] presented an interesting smdy in which transmission and Raman-IR spectra were used to monitor the polymerization of silicon-based repellents and consolidants in stones in situ and in real time. Jiang et al. [194] used online FT Raman spectroscopy to monitor dispersion anionic polymerizations of styrene and 1,3-buta-diene. Sapk et al. [195] and Souza et al. [196] used IR-Raman spectroscopy and transmission NIRS to monitor the evolution of aniline polymerizations. Spectral data were used to detect the formation of water soluble products in the first case and for building of a kinetic model, in the second case. 

Calculate the ultimate number average degree of polymerization for the anionic polymerization of styrene in benzene at 25°C initiated by butyl lithium. The initial concentration of styrene was 10 mol m" and that of butyl lithium was 0.5 mol m . Account for the observation that even though this is a living polymer system a poly disperse sample is produced. 

An example of the grafting from strategy is the treatment of SWNTs with sec-butyllithium, which generates carbanions on the nanotube surface. These carban-ions serve as initiators of anionic polymerization of styrene for in situ preparation of polystyrene-grafted NTs [50]. This procedure allows the debundling of SWNTs and produces homogeneous dispersions of NTs in polystyrene solutions. 

There are some indications that the situation described above has been realized, at least partially, in the system styrene-methyl methacrylate polymerized by metallic lithium.29 29b It is known51 that in a 50-50 mixture of styrene and methyl methacrylate radical polymerization yields a product of approximately the same composition as the feed. On the other hand, a product containing only a few per cent of styrene is formed in a polymerization proceeding by an anionic mechanism. Since the polymer obtained in the 50-50 mixture of styrene and methyl methacrylate polymerized with metallic lithium had apparently an intermediate composition, it has been suggested that this is a block polymer obtained in a reaction discussed above. Further evidence favoring this mechanism is provided by the fact that under identical conditions only pure poly-methyl methacrylate is formed if the polymerization is initiated by butyl lithium and not by lithium dispersion. This proves that incorporation of styrene is due to a different initiation and not propagation. 

When a relatively water-insoluble vinyl monomer, such as styrene, is emulsified in water with the aid of anionic soap and adequate agitation, three phases result (see Fig. 6.17) (1) aqueous phase in which a small amount of both monomer and emulsifier are dissolved (i.e., they exist in molecular dispersed state) (2) emulsified monomer droplets which are supercolloidal in size (> 10,000 A), stability being imparted by the reduction of surface tension and the presence of repulsive forces since a negative charge overcoats each monomer droplet (3) submicroscopic (colloidal) micelles which are saturated with monomer. This three-phase emulsion represents the initial state for emulsion polymerization. 

One method is based on determining the refractive indexes of the two phases by interference microscopy. However this technique, which gives semi-quantative information, can be applied only if the particles of the dispersed phase are not too small (I, 2). We therefore prepared by anionic polymerization different copolymers of PS-PI containing a fluorescent group like styrene-9-phenyl-10-anthracene (see Structure 7 for structure of fluorescent copolymers). In such a PS-PI blend, the PI phase can be detected first by phase... 

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