Molecular weight distributions polyphosphazene

The two-step synthesis process shown in Figure 2 affords several possibilities for preparing new side-chain liquid crystal polymers. The polymerization process allows one to vary the molecular weight and molecular weight distribution (MWD), and potentially change the properties of the liquid crystalline state. Most of the polyphosphazenes reported in the literature, including the examples in this paper, are derived from the bulk uncatalyzed process this... 

Cationic polymerization of phosphoranimines initiated by small amounts of PCI5 in dichloromethane at ambient temperature offers a new route for the preparation of polyphosphazenes. Initiation of Me3SiNPCl3 gives poly(dichloro-phosphazene) with a narrow molecular weight distribution. The polymerization can be characterized as a living cationic polymerization. ... 

Anomalous changes are frequently noted for fractions across the broad molecular weight distribution(s). For example, k + k" / 0.5 —see references (3) and (4). Intrinsic viscosity parameters as a function of percent acetone in E2 solvent are plotted in figure 3 of reference (3) for several PNF fractions. Many other values are tabulated by Hagnauer and Schneider in this reference along with many other solution parameters. Recently, the solution properties of polyphosphazenes have been critically reviewed. Besides polymer quality, there have been problems with tailing" in the fractionation of fluorinated polyphosphazenes as pointed out in reference (15). The quality polymers s)mthesized since the should... 

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