ИСТИНА

The complexity of thermal behavior of semirigid-chain semicrystalline polymers has been in the focus of scientific debate for a long time. In order to explain the origin of double, or, in some instances, even multiple, melting events visible in DSC of these polymers several models were put forward. In the "multiple-crystal-population-model" it is assumed that the structure of typical semirigid-chain polymers such as poly (trimethylene terephthalate) (PTT) contain several distinct crystals populations having different thermal stability. An alternative approach assumes that, due to the thermodynamically metastable structure of such polymers, the crystals can reorganize on heating by melting and recrystallization. With the advent of fast chip calorimetry, also sometimes referred to as nanocalorimetry, it becomes possible to not only study the melting behavior of such system, but also the reorganization process as a response to abrupt temperature changes in real time. In the presented work, we investigate the crystallization behavior of PTT using scanning nano-focus X-ray scattering combined with MEMS-based nanocalorimetry to explore the response of the crystallization process on fast temperature variations during melt crystallization, in-situ. In a complementary approach we apply scanning force microscopy combined in-situ with nanocalorimetry in order to probe the crystallization and melting of PTT undergoing variable thermal treatment. The high-resolution and non-destructive nature of the AFM technique provides the possibility to examine the morphological organization of PTT down to the lamellar level without altering the structure. Therefore, images of PTT semicrystalline structure were obtained with AFM/ Nanocalorimetry system in order to extract the size distribution of the crystalline and amorphous phases . AFM represents as well a complementary experimental method providing spatial resolution comparable with SAXS and allowing to assess the influence of the X-ray exposure on the sample.