Sequence-controlled polymers polymerization

Sequence-controlled Polymers Prepared by Chain-growth Polymerization... 

Some examples of sequence-controlled polymers prepared by ring opening polymerization of cyclic esters have been reported. For instance, Thomas, Coates, and coworkers reported a very original method for the synthesis of alternating aliphatic polyesters.These authors used a stereoselective yttrium-based organometallic catalyst to control comonomer sequences. It had been previously shown that the polymerization of a racemic mixture of p-butyrolactone in the presence of this catalyst led to the formation of... 

Asides from chain-growth, step-growth, and multi-step growth strategies, sequence-defined polymers may also be prepared using polymerization concepts inspired by biological polymerizations such as replication, transcription, and translation. For instance, sequence-defined templates can be used for monomer sequence regulation in non-natural polymerizations. Alternatively, catalytic molecular machines inspired by biocatalysts such as enzymes and ribozymes have been tested for the synthesis of sequence-controlled polymers. These developments are summarized in this last section of the chapter. 

One can differentiate two main methods for obtaining polymer-polymer complexes 1) formation of complexes from pre-existing chemically and structurally complementary macromolecules 2) polymerization of monomers in the presence of matrix macromolecules introduced in the reaction media. Such matrix polymerization is accompanied by the formation of polymer complexes. In the first case, the chemical reaction proceeds via complex formation by random contacts between reacting chains. Then, these sequences of pairs of connected chains grow. In matrix polymerization, the complex is formed by the mechanism of consecutive addition of monomer along the chain leading to the formation of the so-called zip-up (double-stranded) structure, due to matrix control of polymerization. One can expect that the various mechanisms lead to the formation of complexes with a different structure and properties. Indeed, a difference in the composition and properties of complexes obtained by various methods has been found So, the comparison of complexes poly(methacry-lic acid)-poly(2-N,N-dimethylaminoethyl methacrylate), obtained by mixing of equimolar quantities of components in solution and also by the matrix polymerization of dimethylaminoethyl methacrylate in water in the presence of PMAA, shows a difference in composition. In the first case, the content of acid in the complex is always... 

In a third example of this methodology Mei et al. [65] produced a polymer containing the fibronectin-based peptide sequence GRGDS, a well-known cell adhesion sequence. This time, however, the polymerization of hydroxyethyl methacrylate was carried out on the sohd support in methyl ethyl ke-tone/propanol (7 3), resulting in a bio-hybrid with a polydispersity of 1.5. This peptide-polymer hybrid material was used as a support for the growth of mouse NIH-3T3 fibroblasts. It was shown that the cells adhered better to the polymer containing the peptide than to the unfunctionalized control polymer. This highhghts one of the many potential applications for protein-polymer hybrid materials. 

Polymer made by anionically initiated polymerization with MW, chain-end and chain-sequence control with defect-free chains... 

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