Block Copolymers Containing Polypeptide Segments

Polypeptides have received much attention because they exhibit complex and versatile structures, and reversible transitions depending on external environments (pH, T, solvent, etc.) (Alberts et al, 1989). Much effort has gone into the synthesis of homo- and 

Polypeptides Polyisocyanates Aromatic polyamides Coil-Rod-Coil ABA 

Jenekhe and coworkers reported the synthesis of ABA triblock copolymers containing poly (9,9-dihexylfluorene-2,7-diyl)(PHF) and PBLG segments (17) by NCA polymerization from benzylamine end-functionalized PHF (Rubatat et al, 2008). The copolymers exhibited two different conformations (rod-rod-rod and coU-rod-coil) as a result of a controllable rod-to-coil transition of the polypeptide helices. X-ray scattering data showed that the coil-rod-coil form of the copolymer leads to lamellar ordering, whereas the rod-rod-rod form exhibits a clusterlike stmcture. These bioactive and fluorescent materials can be explored as 

Basically, intermediate polymeric anions were reacted with l-(3-bromopropyl)-2,2,5,5-tetramethyl-aza-2,5-disilacyclopentane, followed by spontaneous deprotection during workup to prepare well-defined in-chain- or core-functionalized star-branched polymers with primary amine group(s). These functionalized polymers could be used as macroinitiators for the living polymerization of NCAs. The success of those star-polymer syntheses may be derived from the 100% introduction of primary amino groups at the precise position and extremely clean media for NCA polymerization in completely sealed reactors based on the high-vacuum technique. 

Taton and Lecommandoux reported the self-assembly behavior of AB diblock copolymers and miktoarm AB2 star polymers comprised of PS (=A) and poly(glutamic acid) (=B) segments (Babin et al, 2005). AFM image and X-ray scattering data indicated that those polymers displayed hexagonally packed cylinders of helical rods within lamellar phase. 

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We assumed polypeptide microdomains would be formed in the matrix from vinyl polymer chains on the electrode (Figure 1), since multiphase materials including block and graft copolymers have been known in general to form microdomain structures in the solid state (72). In fact, some of those containing polypeptide segments were found to have microdomains composed of polypeptide (72-/<. In the present case, the segments from polypeptide was considered to form hydrophilic microdomains after hydrolysis. 

Although quite complex hybrid block copolymer architectures can now be synthesized, obtaining these materials in a state of high purity typically requires additional measures. As discussed above, many of the hybrid copolymers contain homopolymer impurities, which must be removed by selective solvent extractions or fractional precipitation when possible. Since conventional NCA polymerizations also usually give polypeptide segments with large chain length distributions, these samples are ideally also fractionated... 

When the polymer coated electrode was treated for 12 h with a ternary solvent of water, methanol, and 2-propanol (1 2 2, by volume) containing 0.5 wt-% KOH, the CV peaks have appeared at almost the same potential as, but of much smaller (oa. 30 %) current values than, those on the bare one. The alkaline treatment was made in order to hydrolyze the methyl ester group of the polypeptide to the carboxylate group. Thus, with the hydrolysis, the polypeptide segment of the block copolymer would be converted to hycfrophilic poly(L-glutamate) (PLG), which should allow the indicator ions to penetrate into the polymer layer. 

Recent progress in novel micellar structures, including micelles containing exotic blocks such as natural or synthetic polypeptides and metal-containing segments, micelles from ABC triblock copolymers, Janus micelles and other noncentrosymmetric micelles, micelles based on interpolyelectrolyte or other noncovalent complexes, and metallosupramolecular micelles, will be discussed in Sect. 7. 

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