Double-crystalline diblocks

There have been relatively few reports dealing with double-crystalline diblock copolymers [102-110,197-200]. The particular case of ABC triblock copolymers with two semicrystalline blocks will be presented in a separate section. Works pertaining to one of the most studied systems PCL-fo-PEO have already been previously reviewed [43]. Recently, probably the most comprehensive studies on double-crystalline diblock copolymer systems were performed on poly(p-dioxanone)-fc-PCL diblock copolymers, PPDX-fr-PCL, and therefore several important aspects of these works [102,103,107] will be summarized in this section. 

T, = 66.6°C for a PEO [18], The crystallization process is more complicated in the double crystalline diblock copolymers than in the homopolymeis. In the specific case of PEO-6-PCL diblocks, the crystallization of the first block occurs at supercoolings higher than in the correspondmg PEO homopolymer as a consequence of the diluent effect caused by the homogeneous melt. This effect becomes evident when comparing the crystallization temperature of PEO (Tc = 42.6°C) with that of the PEO block within = 36.2°C) ... 

As can be seen from the results presented above, the study of PEO-6-PCL has made evident the complexity of the crystallization and melting processes in double crystalline diblock copolymers that have the following characteristics their crystallization starts from a homogenous melt, crystallization and melting points of the blocks are very near to each other, and there is an absence of a nucleating effect of each block on the other. 

In this section, two examples of the use of self-nucleation are presented for block copolymers and nanocomposites. The first example shows how self-nucleation can help separate the coincident crystallization of a double crystalline diblock copolymer. In the second example, the efficiency scale based on self-nucleation helps to define supernucleation. 

Hamley IW, Parras P, Castelletto V, Castillo RV, Muller AJ, PoUet E, Dubois P, Martin CM. Melt structure and its transformation by sequential crystallization of the two blocks within poly(L-lactide)-WocA -poly(e-caprolactone) double crystalline diblock copolymers. Macromol ChemPhys 2006 207 941-953. 

Li S, Myers SB, Register RA. Sohd-state structure and crystallization in double-crystalline diblock copolymers of linear polyethylene and hydrogenated polynorbomene. Macromolecules 2011 44 8835-8844. 

Salim NV, Hanley T, Guo Q. Microphase separation through competitive hydrogen bonding in double crystalline diblock copolymer/homopolymer blends. Macromolecules 2010 43(18) 7695-7704. 

Crystallization within Strongly Segregated Double-Crystalline Diblock Copolymers and Triblock Copolymers, 355... 

Polyethylene-fi-poly(ethylene oxide) diblock copolymers (PE-6-PEO) represent an interesting double-crystalline diblock copolymer system since both blocks are strongly segregated and at the same time they have a marked tendency to crystallize in view of their highly flexible linear chains [20]. Hillmyer et al. [271] synthesized PE-6-PEO block copolymers of 2.1 and 2.8 kg/mol from hydroxyl terminated poly(l,4-butadiene) catalytically... 

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