Amphiphilic Homopolymers

This mechanism may account for the stability, in the absence of any external stabilising agent, of amphiphilic homopolymers in the fully collapsed/glo-bular state. The total free energy of a collapsed macromolecule includes a surface energy contribution in addition to the bulk free energy. Obviously, to form a stable particle, the outer shell of the particle should be hydrophilic enough. 

Amphiphilic polymers studied thus far for this purpose can be broadly classified into amphiphilic block copol5mers and amphiphilic homopolymers. We will discuss both of these types of linear polymer architectures. Another interesting class of polymeric amphiphiles is based on branched architectures, known as dendrimers. The most interesting aspect of dendrimers is that their molecular weight and polydisper-sity can be precisely controlled hence, these systems have the potential to be moved... 

Basu et al. (2004) reported a series of amphiphilic homopolymers in which the hydrophUic moiety is a carboxylic acid moiety and the hydrophobic moiety can be based on either an alkyl chain or an aromatic ring (Chart 2.7). These polymers self-assemble into either micelles or reverse micelles, depending on the solvent environment. Figure 2.7 represents the formation of a micellar assembly in a polar... 

Figure 2.7 Formation of micellar and inverted micellar assemblies from amphiphilic homopolymer.

Chart 2.9 Amphiphilic homopolymer containing an anthracene unit as a transducer. 

Basu S, Vutukuri DR, Shyamroy S, Sandanaraj BS, Thayumanavan S. Invertible amphiphilic homopolymers. J Am Chem Soc 2004 126 9890-9891. 

Sandanaraj BS, Bayraktar H, Krishnamoorthy K, Knapp MJ, Thayumanavan S. Recognition and modulation of cytochrome c s redox properties using an amphiphilic homopolymer. Langmuir 2007 23 3891-3897. 

Savariar EN, Aathimarukandan S V, Thayumanavan S. Supiamolecular assemblies from amphiphilic homopolymers testing the scope. J Am Chem Soc 2006 128 16224-16230. 

Fig. 24 The side-chain models of amphiphilic polymers a amphiphilic homopolymer (poly-A), b regular alternating HA copolymer, c regular multiblock HA copolymer, and d protein-like HA copolymer. Each hydrophobic monomer unit (H) is considered as a single interaction site (bead) each amphiphilic group (A) is modeled by a dumbbell consisting of hydrophobic (H) and hydrophilic (P) beads...

Figure 16 Application of amphiphilic homopolymers as nanoreactors for reactions in water. (Reproduced from Ref. 41. American Chemical Society, 2005.)...

Amphiphilic homopolymers containing both hydrophilic (carboxylic acid units) and lipophilic (benzyl moieties) functionalities in each repeat unit have been reported to assembly [180]. These polymers are soluble in both aqueous and organic solvents, where they assemble into micelle-like or inverse miceUe-Uke structures. All these solutions were optically clear. The hydrophilic carboxyhc acid unit and the hydrophobic benzyl moiety are placed on the opposite sides of the polymer backbone in solvents of different polarity. The observed solubUity characterishcs are the result of formation of a micehe-like structure in water, in which the hydrophihc carboxylate groups are exposed to the bulk solvent and the hydrophobic benzyl substituents are tucked in the interior of an assembly (Scheme 7). Similarly, an inverted micelle-like structure would be expected in apolar solvents, in which the functional group placements are reversed. 

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