Excess X-ray Scattering Observed at Low Angles during Melting of Crystalline-Amorphous Diblock Copolymers

Abstract

The heating process of a series of new crystalline-amorphous diblock copolymers, hydrogenated polynorbornene-blockhydrogenated poly(1,4-methano-1,4,4a,9a-tetrahydrofluorene) (hPNB-b-hPMTF), has been investigated using time-resolved small-angle X-ray scattering with synchrotron radiation. When the crystalline hPNB block was the major component in hPNB-b-hPMTF, the crystallization temperature of hPNB blocks at the maximum rate T c à (i.e., the peak temperature of DSC exotherms during cooling at À5 C/min) was found to be nearly the same to the glass transition temperature T g of amorphous hPMTF blocks. For these copolymers, the excess upturn scattering at low angles was transiently observed during the melting of hPNB blocks, which depended significantly on the composition and the thermal history applied to hPNB-b-hPMTF before heating. The crystallized lamellar morphology (i.e., an alternating structure consisting of hPNB lamellar crystals and amorphous hPNB + hPMTF layers), which had been gradually transformed from the molten microdomain structure by the crystallization of hPNB blocks, was responsible for the emergence of this scattering, because the excess X-ray intensity was proportional to the volume fraction of the crystallized lamellar morphology existing in the system. We discussed the possible origin of this excess scattering by considering the morphological change during melting.KEY WORDS: Crystalline-Amorphous Diblock Copolymer / Melting Process / Synchrotron SAXS / Excess X-ray Scattering /The morphology formation of crystalline-amorphous diblock copolymers is complicated depending on the relative position of the order-disorder transition temperature of block copolymers T ODT , the crystallization temperature T c of crystalline blocks, and the glass transition temperature T g of amorphous blocks.1-3 When T ODT > T g > T c , the molten microdomain structure is frozen at T c and eventually crystallization is effectively confined within this structure (confined crystallization), resulting in a crystallized microdomain structure.4-14 When T ODT > T c > T g , on the other hand, the microdomain structure is completely replaced with a crystallized lamellar morphology, an alternating structure consisting of lamellar crystals and amorphous layers, if the total molecular weight and the interaction between two blocks are not large enough (break-out crystallization).15-24 However, there are limited studies on the morphology formation of crystalline-amorphous diblocks with T ODT > T g $ T c . [25][26][27] Ho et al., for example, investigated the morphology of synpolypropylene-block-polystyrene (sPP-b-PS), 27 where T g of amorphous PS blocks partially overlapped with the T c range of crystalline sPP blocks. They observed confined or break-out crystallization according to T c they used. Thus, we can expect that the crystallization behavior and resulting morphology of crystalline-amorphous diblocks with T g $ T c depend significantly on T c and also the crystallization time t c , because the mobility of polymer chains is...

Fingerprint of semi-crystalline structure memory in the thermal and ionic conduction properties of amorphous ureasil–polyether hybrid solid electrolytes

“…It could be concluded from this that the longdistance period peak, found for the U-PEO hybrid host, had a backbone dependence similar to that reported for the PEO homopolymer. 55 In contrast, in this temperature range, no remarkable modication was observed in the SAXS curves for U-PEO:Li + , conrming the amorphous nature of the Li + -loaded hybrid (Fig. SI.3 †).…”

The Static and Dynamic Structure Factor of a Diblock Copolymer Melt via Small-Angle X-ray Scattering and X-ray Photon Correlation Spectroscopy

“…However, at low wavevectors ( q < 0.02 Å –1 ), they predict a relatively small scattering intensity. By contrast, a number of experimental scattering studies on BCP reveal unexpectedly large scattering intensities at low wavevectors. − Even in studies of polymer solutions, where the small-angle scattering is expected to be described by a Lorentzian, excess small-angle scattering is often reported . Koberstein et al attributed this excess scattering to long-range random heterogeneities, with correlation lengths several times the polymer radius of gyration.…”