Tetrablock terpolymers

Fig. 24 SAXS pattern of PI-/7-PS-/ -P2VP- -PI tetrablock terpolymer. Sample geometry is edge view with incident X-rays parallel to film surface. Vertical thick bars at lower section denote calculated diffracted intensities based on non-centrosymmetric periodic structure shown in Fig. 23b solid curve domain scattering calculated using profile of two-step stairs. Vertical dotted bars calculated intensities based on centrosymmetric structure shown in (d) dashed curve domain scattering for symmetric profile in same figure. From [89]. Copyright 2003 American Chemical Society...

PEO-PSt-PBd-PEO tetrablock terpolymer was prepared by a multistep anionic polymerization method. First, an a,0-hydroxy PSt-Z -PBd was synthesized, using the protected initiator TBDMS and sequential monomer addition of St and Bd. The reaction was terminated by EO. After deprotection with tetrabutylammonium fluoride (TBAF), both OH ends were converted to potassium alkoxides and used to polymerize EO (Scheme 10). Depending on the length of the outer PEO segments, these ABCA amphiphilic terpolymers form vesicles or worm-like micelles in water. 

Stimulated by the finding of noncentrosymmetric superlattices in block copolymer blends also the possibility to generate this morphology by a pure A-B-C-A tetrablock terpolymer was investigated and found [247]. Here the difference between the interfacial tensions between A, B and A, C might be the major controlling parameter for the formation of this morphology. 

Takano et al. investigated an ABCA tetrablock terpolymer (ISVI) of isoprene, styrene, 2-vinylpyridine, and isoprene aiming for a periodic noncentrosymmetric lamellar morphology. They synthesized the tetrablock terpolymer by coupling two living diblock copolymers (IS and IV, respectively). This work was stimulated by the observation of a periodic noncentros)mimetric lamellar superstracture in a block copolymer blend, which will be discussed later. A hierarchical stmrture of lamellae was observed for a... 

While in triblock terpolymers core-shell structures can be obtained, these will be core double shell structures in the case of accordingly composed tetrablock quaterpolymers, as was shown by the example of cylindrical structures of a PS-b-PI-b-PDMS-b-P2VP copolymer synthesized by Takahashi et al. (Figure 17). °... 

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