Polyrotaxanes ester

The same types of polyrotaxanes were also prepared by a different method, Method 2 (Figure 6). In this method, a preformed polymer is used and the cyclic is threaded onto the polymer in a melt or in solution. A solution of 28 and polystyrene in THF under reflux afforded a polyrotaxane with an min value of 5.0X1CT4, much lower than those via Method 1 [69]. Threading 28 on to poly (butylene sebacate) afforded poly(ester rotaxane) 33 of Type 4 [70]. Although a laige excess of cyclic was used, 33 only had a min value of 0.0017. This value is 100-fold lower than that for the corresponding polyrotaxane prepared by Method 1 [19]. A possible reason is that the concentration of chain ends is very low and the random coiled-chain conformation of a polymer disfavors threading. 

Incorporating different amounts of 1,10-decanediol into the above system, copoly (ester rotaxane)s 64 were also obtained [22]. The m/n values for these polyrotaxanes were related to the amount of BG applied the m/n value linearly in-... 

Similar to that in copoly(ester rotaxane)s 64, min for these poly(urethane rotax-ane)s increased with increasing BG, i.e. higher x values [116,117]. However, compared with the copoly(ester rotaxane), the dethreading occurred to lesser extent in these polyrotaxanes this is attributed to the fact that the NH groups retard dethreading by hydrogen bonding with the threaded crown ether as in structure 67. A linear relationship between min values and x was revealed. 

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. 

Preparation of a Biodegradable Polyrotaxane with Ester Linkages and its Chemical Modification... 

Figure 7. Cumulative hydrolysis of ester group in the polyrotaxane. non-acethylated polyrotaxane ( ), ACRX-15 ( ), ACRX-32 (A), ACRX-100 (A), (n=3, Mean S. E. M.).

---