SYNTHESIS AND PRELIMINARY CHARACTERIZATION OF SOME POLYESTER ROTAXANES

A series of polyester rotaxanes containing polysebacate backbones [decamethylene, tri(ethyleneoxy), and 1,4-butylene] and ethylene oxide-based crown ethers [30-crown-10, 42-crown-14, 60-crown-20, and bis(p-phenylene)34-crown-10] was synthesized via step growth polymerizations using diacid chloride-diol and transesterification reactions. The polyrotaxanes were purified by multiple reprecipitations in good solvents for the crown ethers, and the physical linkage of the crown ether to the polymeric backbone was confirmed by a variety of experiments, including hydrolysis, NMR, GPC, and VPO. Up to 55 wt % macrocycle was incorporated, depending on the size and shape of the macrocycle and the feed ratios employed. In all cases, the solubilities of the polyrotaxanes were strongly influenced by the cyclic component; enhanced solubilities in polar solvents were observed relative to the simple parent polysebacates. Mark-Houwink K and a values were also strongly affected by rotaxane formation; in the case most thoroughly investigated, K decreased by almost 2 orders of magnitude and a doubled. Interpretation of this observation is complicated by the changes in solubility. Thermal behavior was also affected. In the tri(ethyleneoxy) system, T-g is lowered in the rotaxanes; in the 60-crown-20 system, the macrocycle crystallized! The poly(butylene sebacate) 60-crown-20 and 42-crown-14 systems also possessed two crystalline phases, a crown ether phase and a poly(butylene sebacate) phase. These exciting result demonstrate the mobility of the macrocycle along the polyester backbone in melt and solution states, allowing aggregation and crystallization without dethreading.