Crystallization of block copolymers

The technique of self-nucleation can be very useful to study the nucleation and crystallization of block copolymers that are able to crystallize [29,97-103]. Previous works have shown that domain II or the exclusive self-nucleation domain disappears for systems where the crystallizable block [PE, PEO or poly(e-caprolactone), PCL] was strongly confined into small isolated MDs [29,97-101]. The need for a very large number of nuclei in order to nucleate crystals in every confined MD (e.g., of the order of 1016 nuclei cm 3 in the case of confined spheres) implies that the amount of material that needs to be left unmolten is so large that domain II disappears and annealing will always occur to a fraction of the polymer when self-nucleation is finally attained at lower Ts. This is a direct result of the extremely high number density of MDs that need to be self-nucleated when the crystallizable block is confined within small isolated MDs. Although this effect has been mainly studied in ABC triblock copolymers and will be discussed in Sect. 6.3, it has also been reported in PS-fc-PEO diblock copolymers [29,99]. 

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 ... 

In this chapter, structure formation in semicrystalline diblocks containing PE, PEO and other crystalline blocks is discussed in Section 5.2. Section 5.3 is concerned with theories for the equilibrium crystallization of block copolymers, whilst Section 5.4 summarizes recent experimental work on the kinetics of crystallization. There have been few studies of crystallization in thin block copolymer films, and consequently Section 5.5 is correspondingly short. Finally, structure formation in glassy diblocks is considered in Section 5,6. 

Table 3.6 presents some representative examples of the wide range of copolymers eontaining PLA units that have been prepared in recent literature. We will foeus in this section on a few selected works that have dealt with the crystallization of PLA-based copolymers. Several reviews on the crystallization of block copolymers have also been published. ... 

Olley RH, Mitchell GR, Moghaddam Y (2014) On row-structures in sheared polypropylene and a propylene-ethylene copolymer. Eur Polym J 53 37 9 Organ SJ, Keller A (1985) Solution Crystallisation of Polyethylene at high temperature Part 1 lateral crystal habits. J Mater. Sci. 20(5) 1571-1585 Perret R, Skoulios A (1972a) Study of crystallization of block copolymers having sequence poly (epsilon-caprolactone)-poly(oxyethylene). 1. Copolymers with sequences of very different lengths. Makromolekulare Chemie 162 147... 

Folkes, M.J., Keller, A., and Scalisi, F.P. (1973) An extrusion technique for the preparation of single-crystals of block copolymers. Colloid and Polymer Science. 251, 1-4. 

When of crystalline-amorphous diblock copolymers is sufficiently large, the soft microdomain structure is stable against the subsequent crystallization. Therefore, this structure is preserved through the crystalUzation process, that is, constituent blocks crystallize within the soft microdomain stmcture, to yield a crystalline microdomain structure (lower route in Fig. 10.7). Amorphous domains in the crystalline microdomain structure are not hard in this case, so that crystalline domains can deform moderately during crystalUzation in order to get a larger crystalUnity and/or favorable crystal orientation, which is criticaUy different from the crystallization of block copolymers with high-T amorphous blocks, as described in Section 10.3.2. 

The basic research on the crystallization in more complicated systems started recently to find ouf unique morphologies formed in polymer systems. The crystallization of block copolymers is a striking example of such crystallization, which is intimately dependent on the molecular characteristics of crystalline block copolymers. For example, the crystallization of crystalline-amorphous diblock copolymers yields the lamellar morphology or crystalline microdomain structure depending on xN of block copolymers, Tg of amorphous blocks, crystallization conditions, and so on. These kinds of crystallization have the possibility of developing new crystalline polymer materials. Therefore, we strongly anticipate future advances in this research field. 

Nojima S, Kato K, Yamamoto S, Ashida T. Crystallization of block copolymers. 1. SmaU-angle X-ray scattering study of an e-caprolactone-butadiene diblock copolymer. Macromolecules 1992 25 2237-2242. 

Crystallization of Block Copolymers from Homogeneous or Weakly Segregated Melts, 340... 

In semicrystalline block copolymers, the crystallization behavior is often more complex than that observed in statistical copolymers because the solid-state morphology adopted by block copolymers can be driven either by block incompatibility or by crystallization of one or more blocks [5-8]. In this chapter, we will cover only block copolymers with homogeneous or weakly segregated melts, such that crystallization is always the dominant factor in determining solid-state morphology. Crystallization of block copolymers from strongly segregated melts is covered in Chapter 12. Furthermore, the... 

CRYSTALLIZATION OF BLOCK COPOLYMERS FROM HOMOGENEOUS OR WEAKLY SEGREGATED MELTS... 

Nojima S, Ono M and Ashida T (1992) Crystallization of block copolymers II. Morphological study of poly(ethylene glycol)-(poly(e-caprolactone) block copolymers. Polymer J 24 1271-1280. 

---