Crystallisation behaviour and crystal rearrangement of poly(ethylene oxybenzoate)

One complex fact of polymer crystallisation is that polymer crystals have a tendency to rearrange with time. In this paper, poly(ethylene oxybenzoate)s (PEOB) with different degrees of polymerisation ranging from 5 to 30 have been studied by differential scanning calorimetry and polarised microscopy. The samples showed a great tendency for crystal rearrangement during heating to the melting point, even at high heating rates. The relationship between melting point and crystallisation temperature was analyzed and the Hoffman–Weeks method was found to be unsuitable for determining the equilibrium melting point of these polymers. It is proposed that fast crystal rearrangement, which is a characteristic feature of poly(ethylene oxybenzoate), is the reason for the inadequacy of the Hoffman–Weeks method to obtain reliable estimates of the equilibrium melting point. Polarised microscopy showed, remarkably in view of the low molar mass of the polymers, the formation of perfect banded spherulites. Linear growth rate data suggested that the branched polymers crystallised more slowly than their linear analogues, presumably due to differences in the equilibrium melting point.