Thermal crystallization of polytetrahydrofuran networks

The thermal crystallization behavior of cross-linked rubbers formed by endlinking monodisperse and bidisperse linear polytetrahydrofurans (PTHF) was investigated. The introduction of crosslinkages in PTHF inhibits the ability of chain units in proximity to the crosslinks to crystallize. From melting point depression measurements, it is estimated that the suppression in crystallizability extends as much as 15 chain units away from the crosslinkage. This estimate is consistent with the degree of equilibrium crystallinity measured in the various PTHF networks. The equilibrium melting point for uncrosslinked PTHF was deduced from melting point depression in the crosslinked rubbers to be 368 K. This is in satisfactory agreement with the T determined linear PTHF, 361 K, but significantly higher than previously reported values. The distribution in the lengths of network chains exerted a trivial influence on thermal crystallization behavior, at least under the present experimental conditions.