Hydrogen-bonded comb copolymers

Hydrogen-Bonded Comb Copolymers Nonmesogenic Side Chains. 129... 

Block Copolymer-Based Hydrogen-Bonded Comb Copolymers. 137... 

Hydrogen-Bonded Comb Copolymers Mesogenic Side Chains. 157... 

Hydrogen-Bonded Comb Copolymers Nonmesogenk Side Chains... 

Fig. 13 Illustration of the formation of hydrogen-bonded comb copolymers and subsequent micellization in a selective solvent. Reprinted with permission from [127]. 2005 American Chemical Society...

Finally, we will consider briefly the formation of multilayer thin films by layer-by-layer deposition of hydrogen-bonded polymer pairs [51,52]. In this way a multilayer structure is obtained from potentially miscible polymer pairs. The stability of these films very much depends on the presence of hydrogen bonds, and pH may be used as an external trigger to erase the layered structure [53,54] and selectively dissolve one of the components [25-27]. This procedure allows for the preparation of microporous films not unlike the nanoporous films obtained by dissolution of the hydrogen-bonded side groups from self-assembled block copolymer-based comb-shaped supramo-lecules [15,17,18]. 

The concept where amphiphihc molecules are hydrogen bonded to one block of a block copolymer to form specific comb-shaped supramolecules allows the production of nanoporous materials in a straightforward way. The concept is illustrated in Fig. 24. The procedure was first applied to a polystyrene-bZocfc-poly(4-vinylpyridine) diblock copolymer with a stoichiometric amount of pentadecylphenol hydrogen bonded to the P4VP block. The relative block lengths were selected to render a lamellar-m-cylindrical morphology, where the P4VP(PDP) comb-shaped blocks form the cylinders... 

In the following sections, we will review the various different ways in which comb copolymer-like architectures (supramolecular comb copolymers) mi t be obtained using noncovalent physical interactions, e.g., ionic, coordination complexation, or hydrogen bonding see Figure 8. 

As for any block copolymer, the self-organized structure formation in comb copolymers is based on the competition between the covalent attraction and the repulsion between the side chains and the backbone. The examples employing ionic attraction and coordination complexation demonstrate that the attractive interaction has to be sufficiently strong. In the case of hydrogen bonding, this is a much more delicate matter and the strength required to self-organize the supramolecular comb copolymers will be determined by a fine balance between attraction and repulsion. 

The possibility of obtaining comb copolymer structures via the supramolecular route, using physical matching interactions, such as ionic, coordination, or hydrogen bonding, was discussed in some... 

Ruotsalainen, T., Turku, J., Hiekkataipale, P. et al. (2007) Tailoring of the hierarchical structure within electrospun fibers due to supramolecular comb-coil block copolymers polystyrene-block-poly(4-vinyl pyridine) plasticized by hydrogen bonded pentadecylphenol. Soft Matter, 3,978-985. 

---