Dendritic block copolymers segment

Following the first papers of Tomalia et al. (1985) and Newkome et al. (1985) dealing with dendrimers, a large number of dendrimers have been presented in the literature ranging from polyamidoamine (Tomalia et al., 1991), polyethers (Hawker and Frechet, 1990 Padias et al., 1987), and polyesters (Miller et al., 1992 Ihre et al., 1996) to polysilane (van der Made and van Leeuwen, 1992). Copolymers of linear blocks with dendrimer segments (dendrons), block copolymers of different dendrons, and polymers with dendritic side chains (Frauenrath, 2005) have been described. 

The application of water-soluble, unmodified enzymes for practical purposes is often hampered by their protease susceptibility, thermal instability and inactivation by the intermediates, products formed or pH of the medium. One of the main thrusts in our research is the construction of micellar complexes of enzymes and amphiphilic block copolymers that contain linear and perfectly branched (dendritic) segments and their catalytic evaluation in aqueous media. Unique feature of these supermolecules is that the water-soluble biocatalyst, hydrophobic substrates and eventual mediator compounds are confined within the core of a normal micelle. The hydrophobic dendritic fragments have the primary function to serve as enzyme surface anchoring devices for the copolymer molecules while the hydrophilic linear portion of the copolymer will ensure the aqueous solubility and the stability of the entire construction. The complex is schematically presented in Fig. 1. 

It could be envisioned that one of the future trends in development of TPEEs will continue to be modification of chemical structure of these copolyesters. Continuation of the development of advanced materials with various molecular structures is important from a fundamental and industrial perspective. It can be expected that one of the future trends could be the introduction of hyperbranched and dendritic segments into these block copolymers. Also, some progress has been achieved in incorporation of liquid crystalline sequences into the backbone or as side chains. 

The liquid crystalline unit-containing polymers begin a timid entry in the TPE field. The liquid crystalline sequences can be part of the backbone or may be present as side chains. Nair et al. [200,201] carried out an abundant and very valuable work with both fundamental and applied aspects. These polymers are prepared by chain polymerization or by polycondensation and are discussed in Chapter 2. Some of them are blends and the morphology and properties of Rodrun LC3000 were the subject of two articles [202,203]. The first applications and patented products are very promising and their development should enjoy a rapid increase. This holds also for the introduction of hyperbranched and dendritic segments in block copolymers [204]. 

Numerous copolymers contain liquid crystalline segments either as the main chain [43-47] or as side chains [48-55]. They are prepared by chain polymerization [48-50] or by polycondensation [43,44,46,47,51-57]. In the same way, the introduction of hyperbranched and dendritic segments in block copolymers has a rapid development [54-56]. 

Dendritic Segment Block and Layer Block Copolymers [18b,38]... 

FIGURE 5.6 Schematic representation of dendritic copolymers with different polarities (a) segment-block dendrimer and (b) layer-block dendrimer. (From Klajnert, B. and Bryszewska, M., Acta Biochimica Polonica, 48, 199, 2001. With permission.)... 

FIGURE 11.3 Schematic architectures of polymers with semifluorinated segments (a) sf triblock copolymers (b) i/main chain polymers (c). side chain polymers (d) polymers with randomly distributed sf side chains (e) di- and triblock copolymers with one rf block (f) copolymers with dendritic segments. 

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