Semicrystalline block

Hedrick et al. reported imide aryl ether ketone segmented block copolymers.228 The block copolymers were prepared via a two-step process. Both a bisphenol-A-based amorphous block and a semicrystalline block were prepared from a soluble and amorphous ketimine precursor. The blocks of poly(arylene ether ether ketone) oligomers with Mn range of 6000-12,000 g/mol were coreacted with 4,4,-oxydianiline (ODA) and pyromellitic dianhydride (PMDA) diethyl ester diacyl chloride in NMP in the presence of A - me thy 1 morphi 1 i nc. Clear films with high moduli by solution casting and followed by curing were obtained. Multiphase morphologies were observed in both cases. 

Effects of Variation of Composition and Block Sequence on Properties of Copolymers Containing Semicrystalline Block(s)... 

Weakly segregated systems, Todt > Tc < Tg with hard confinement. In this case, the crystallization of the semicrystalline block can overwhelm the microphase segregation of the MD structures even though the amorphous block is glassy at the crystallization temperature, because of the weak segregation strength [19]. 

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. 

The technique of self-nucleation [75] can be very useful to study the nucleation and crystallization of block copolymer components, as already mentioned in previous sections. In block copolymers, factors like the volumetric fraction and the degree of segregation affect the type of confinement and therefore modify the self-nucleation behavior. In the case of semicrystalline block copolymers, several works have reported the self-nucleation of either one or both crystallizable components in PS-fc-PCL, PS-b-PB-b-PCL, PS-b-PE-b-PCL, PB-fr-PIB-fr-PEO, PE-fr-PEP-fr-PEO, PS-fc-PEO, PS-h-PEO-h-PCL, PB-b-PEO, PB/PB-fc-PEO and PPDX-fc-PCL [29,92,98,99,101-103,134] and three different kinds of behavior have been observed. Specific examples of these three cases are given in the following and in Table 5 ... 

Fig. 5.10 Schematic of perpendicular and parallel chain folding in semicrystalline block copolymers.

Combination of Living Cationic and Anionic Ring-Opening Polymerization for the Synthesis of Semicrystalline Block Copolymers... 

Free radical promoted cationic polymerization was successfully employed [77] for the preparation of new classes of liquid crystalline (LC) block copolymers comprising a semicrystalline block, poly(cyclohexene oxide), and LC block of different structures ... 

Crystallization in block copolymers has a profound effect on their structure. This review article focusses on the morphology of semicrystalline block copolymers, and those containing two crystallizable blocks. The effect of crystallization on mechanical properties is briefly considered. The extent of chain folding upon crystallization is discussed, as is the orientation of crystal stems with respect to the microstructure. The effect of selective solvent on solution crystallization is also highlighted. Recent work on crystallization kinetics is summarized and finally the theories for crystallization in block copolymers are outlined. 

Crystallization has been investigated for other block copolymers, in particular those containing poly(e-caprolactone) (Tm=57 °C). Experimental results for these materials are also summarized here. The morphology in block copolymers where both blocks are crystallizable is also discussed. However, except in section 7, the remainder of this review concerns semicrystalline block copolymers. Elements of this review have appeared in an extended form elsewhere [ 1 ]. 

Crystallization in semicrystalline block copolymers can have a dramatic impact on mechanical properties, and hence is important to end use. There have been numerous studies, in particular of PE-containing block copolymers including industrial materials. A comprehensive overview of this work is outside the scope of this review. Instead, an illustrative example serves to illustrate the essential physics. 

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