Diblock copolymers dendritic-linear

Table 4.5 Limiting area per molecule from extrapolation of the condensed-phase region of the isotherms for the modified linear-dendritic diblock copolymers. (From ref. [112])...

Kim and coworkers observed the formation of micelles in aqueous solutions by synthesizing a amphiphilic linear-dendritic diblock copolymer based on poly(ethylene oxide) (PEO) (Figure 5)50,62. In this case, the PEO can be considered as the core upon which the dendrimer was synthesized via a divergent process. In an aqueous phase, the hydrophilic... 

PEO prepared by anionic polymerization using the monofunctional initiator ((diphenylmethyl)potassium) has one -OH end group leading to the formation of linear-dendritic diblock copolymers (Scheme 102). 

Gitsov et al 10) produced a nanoreactor fi om laccase and linear poly(ethylene oxide)-dendritic poly(benzyl ether) diblock copolymers. A notable feature of this system is the presence of hydrophobic dendritic pockets that increase the local concentration of water-insoluble organic compounds near the active site where they are oxidized. Li and Hsieh (77) employed a hydrogel fiber membrane, with a large surface area and improved organic solvent solubility in order to facilitate lipase reactions. He (72) grafted lipase onto silica particles, which permitted him to carry out synthesis of polyesters, polycarbonates, polyphosphates, and their copolymers at temperatures up to 150°C. 

This chapter describes our recent advances on the utilization of polymer-modified laccase complexes in aqueous systems towards the oxidation/polymerization of naturally hydro-phobic steroidal compounds, Equilin (EQ) and 17-P-estradiol (P-EST). We elucidate the kinetic and synthetic aspects of the process with the model compoimd 5,6,7,8-tetrahydro-2-naphthol (THN). The nano-reactor system is composed of linear poly(ethylene oxide)-dendritic poly(benzyl ether) diblock copolymer (G3-PE013k) and laccase isolated from Trametes versicolor. Other advantages of the complex in comparison to the native enzyme are its recyclability, enhanced stability, activity, and overall simplicity in product harvesting and isolation. A principle of action of the complex is suggested based on these findings and is further supported by the biphasic solid-liquid nature of the reaction medium, which exhibits continuous influx of starting material and steady solid product expulsion. Comparative experiments with linear-linear poly(styrene)-Woc -poly(ethylene oxide) copolymer under identical conditions do not evince formation of a... 

Iyer, J., Fleming, K. and Hammond, P.T. (1998) Synthesis and solution properties of new linear-dendritic diblock copolymers , Macromolecules, 31,8757-8765. 

In order to explore the properties that may be obtained by hybridizing the linear and dendritic architectural states, both diblock and triblock copolymer... 

The addition of large linear blocks to dendrons with opposite polarity creates a desymmetrized structure predisposed to sequester insoluble components by aggregation rather than intramolecular hydrogen-bonding. Amphiphilic, linear-dendritic diblock (AB) and triblock (ABA) copolymers self-assemble into multimolecular micelles with CMC values that are well below those of low molecular weight surfactants. Typically, a hydrophilic linear block such as PEG is attached to the focal point... 

Although, there are many reviews on linear diblock chimeras, only a very few have addressed the synthesis of polypeptide-based materials with different macromolecular architectures (Hadjichristidis et al., 2009 Deming, 2006 Deming, 2000). In this chapter our discussion on the synthesis of well-defined complex chimeras, including linear multiblock co/ terpolymer, as well as nonlinear copolymer chimeras (e.g. star, graft, block-graft, dendritic), will hopefully enrich the current literature on macromolecular chimeras. This chapter will not address the self-assembly of these complex chimeras since this issue is discussed in another chapter of this volume. 

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