Peak melting temperatures block copolymers

Figure 3.12 Left Peak ciystallization and melting temperatures for the PLLA and PCL block for a wide range of PLLA-A-PCL diblock copolymers versus PLLA content Right PLOM micrographs for a) L32 C6s after 30 min. at 122 °C, b) the same sample after 15 min. additional time at 42 °C (modified from Ref. 107).

The DSC traces for these block copolymers exhibited a small transition at —5 °C corresponding to the glass-transition temperature of poly(l,3-phenylenevinylene-2,5-diethylhex-yloxy-1,4-phenylenevinylene) 22. An endothermic peak at 110 °C for block copolymer can be assigned to the melting of the octyloxy side chains of the first blocks. On cooling exothermic peaks for side-chain recrystallization were observed. The observation of transitions associated with both homopolymers 15, 22 in the DSC traces of block copolymers suggests that phase separation of the block copolymer is extensive. 

DSC cooling and heating scans of the nanostructured block copolymers presented here can be found elsewhere [207,208]. Figure 5.15 shows the peak melting and crystallization temperatures (T and T ) and the crystallinity degree (%XJ for the... 

Typical SAXS/WAXD spectra are shown in Figure 1 for the SEL-4,7/20/1.8 copolymers for a crystallization temperature of 313 K. The SAXS spectrum taken immediately before the T-jump indicated only a minor contribution from concentration fluctuations at 383 K. This is a result of the compatibility of PS and PCL in the melt state (8) and of the star architecture with PEO which further increases the intrinsic compatibility of the copolymer (9). After about 500 s the WAXD patterns develop peaks corresponding to the monoclinic unit cell of PEO. Notice that the crystallization of the shorter block is suppressed in the triarm star. At the same time the SAXS peaks develop signifying the formation of the PEO crystalline lamellar. 

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