Anionic dispersion polymerization

Fig. 51. Schematic illustration of the mechanism of microgel formation in the anionic dispersion polymerization of 1,4-DVB initiated by living PBS chains in heptane. [Reprinted with permission from Ref. 247, Copyright 1995, American Chemical Society].

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... 

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

Figure 10. Photomicrograph of polystyrene produced by anionic dispersion polymerization.

Characterization of the polystyrene produced by anionic dispersion polymerization by gel permeation chromatography shows a very narrow molecular weight distribution (Figure 12). This narrow distribution is reflected in its rheological characteristics as evidenced by the long Newtonian plateau at low shear rates as shown in Figure 13. 

As has been demonstrated, the polystyrene particles produced by anionic dispersion polymerization techniques contain accessible active carbanlons, i.e., they are "living" particles. They are therefore ideally suited to modification of the chemical character of the particle by a secondary reaction. 

Figure 15. Oxygen termination of anionic dispersion polymerization.

Muranaka M, Kitamura Y, Yoshizawa H. Preparation of biodegradable microspheres by anionic dispersion polymerization with PLA copolymeric dispersion stabilizer. Colloid Polym Sci 2007 285 1441-1448. 

The physicochemical mechanism of the polymer growth on catalyst particles is far from dear. As already mentioned, the anionic dispersion polymerization of EO produces a polymer insoluble in polymer diluents. As a result, the catalyst partides transform into polymer partides rapidly, within a few minutes after the start of the reaction. Hie size of the initial catalyst partides is in the 1-50 pm range. Hieir shape is not wdl defined. The relatively broad partide size distribution is due to the formation of a omerates. Hierefore, during the polymerization process, some manufacturers successfully apply ultrasound technique or surface-active compoimds as additives to destroy the a regates and to enhance the catalyst productivity. 

The reason for the very efficient reduction of transesterifica-tion in the anionic dispersion polymerization of s-caprolactone is not yet fully clarified. However, it is possible that the high... 

Figure 13 GPC trace of the anionic dispersion polymerization of s-caprolactone In 1,4-dioxane heptane (1 9 v/v) mixture. Polymerization conditions [s-caprolactone]o = 4.0 x 10 mol initiator [(CH3)3SiONa]o = 5.1 x 10" moM room temperature. From calibration on PCL samples with narrow molecular weight distribution Mn = 106 600, MJMn = 5. Reproduced with permission from Slomkowski, S. Sosnowski, S. Gadzinowski, M. Colloids Surf. A Physicochem. Eng. Aspects 1999, 153,111. ...

Okay, O. and Funke, W. 1990. Anionic dispersion polymerization of 1,4-divinylbenzene. Macromolecules 23 2623-2628. 

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