Polyethylene deuterated, melting temperature

As pointed out in Section 7.3.1, SANS studies of deuterium-labeled polymers were initially based on the assumption [8] that the molecular configurations and interactions are independent of deuteration, or alternatively that the Flory-Huggins interaction parameter for labeled and unlabeled segments of the same species, /hd. is zero. However, it was subsequently discovered that isotopic substitution can influence polymer thermodynamics, in that deuterated and protonated polyethylenes exhibit melting temperatures differing by 6 °C, so their mixtures can segregate in the solid state (see Section 7.5.2), due to differential-crystallization effects [103]. Also, the... 

A majority of the data collected using this cell has been with a polypropylene (PP) - polyethylene (PE) system, using a combination of two PP tacticities and a number of PE s of varying densities from linear low density PE (LLDPE) to high density PE (HOPE) [18,20,21], Deuterated isotactic PP (diPP) is semi ciystalline with a melt temperature of 157 C, while deuterated atactic PP (daPP) is amorphous. The melt temperatures of the LLDPE and HDPE used are 102 and 131 C, respectively. Reflectivity profiles from all the systems were obtained at temperatures well above the melt and ass transition temperatures of the polymers. Data from the diPP-HDPE system have been collected at 175, 200 and 225 C and the interfhcial widths obtained. The fitting revealed that in some cases the diPP does not folly wet the silicon [21], but the diPP layer was sufficiently thick to prevent complete dewetting... 

Variable-temperature NMR experiments provide information about the dynamic processes that occur in solids. It is well known that, for a semicrystalline polymer such as polyethylene (PE), a higher rate of cooling from the melt leads to lower crystallinity C CP/MAS NMR establishes that the cooling rate also affects the structure and motion of the amorphous domain [217]. Many of the dynamic properties of PE, such as jump rates and activation energy, can be explained in terms of chain diffusion between the phases, as detected by 2-D exchange C NMR [218]. Very slow motions in the crystalline a-form of deuterated poly(vinylidene fluoride) have also been detected by exchange NMR [219]. Double-quantum transitions can occur in materials in which spin pairs are only a few bonds apart this... 

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