Polyrotaxanes melt viscosity

Gibson and coworkers also found that the melt viscosity of a polymer is also altered by the formation of a polyrotaxane [19], Poly(ester rotaxane) 60 containing 42C14 as the cyclic component had a melt viscosity equivalent to that of the parent polyester with 2.5-fold higher molecular weight. This result clearly indicates that there is less chain entanglement in the polyrotaxane than in the backbone polymer by itself. 

Because of their novel topologies, polyrotaxanes have properties different from those of conventional polymers. Solubility, intrinsic viscosity, melt viscosity, glass transition, melting temperature and phase behavior can be altered by the formation of polyrotaxanes. The detailed changes are related both to the properties of the threaded cyclics and to the backbone and the threading efficiency. 

Despite the limited data in the area of viscosity, the results reported so far are encouraging they indicate possible applications of polyrotaxanes in rheology control and melt processability improvement. 

The last four entries of Table 43.1 represent a preformed polyurethane and polyrotaxanes derived by threading crown ethers onto it in the melt. Since the backbone molecular weight is constant, this series allows us to discern the effect of rotaxanation on the intrinsic viscosity. As can be seen in Fig. 43.2, in fact, the intrinsic viscosity increases linearly... 

---