Cylindrical molecular brushes: Synthesis, characterization, and properties

In recent years, research on cylindrical polymer brushes (or molecular bottlebrushes) has received significant attention. In this article, we discuss various strategies for their synthesis and the unique properties arising from their regular multibranched structure. Some recent advances in the application of cylindrical polymer brushes are highlighted. Amphiphilic core– shell cylindrical polymer brushes, for example, have been successfully used as single molecular templates for inorganic nanoparticle formation. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3461–3481, 2005

https://onlinelibrary.wiley.com/doi/pdf/10.1002/pola.20900

Cylindrical polymer brushes

Syntheses and polymerizations of alpha-amino acid N-carboxyanhydrides (NCAs) were reported for the first time by Hermann Leuchs in 1906. Since that time, these cyclic and highly reactive amino acid derivatives were used for stepwise peptide syntheses but mainly for the formation of polypeptides by ring-opening polymerizations. This review summarizes the literature after 1985 and reports on new aspects of the polymerization processes, such as the formation of cyclic polypeptides or novel organometal catalysts. Polypeptides with various architectures, such as diblock, triblock, and multiblock sequences, and star-shaped or dendritic structures are also mentioned. Furthermore, lyotropic and thermotropic liquid-crystalline polypeptides will be discussed and the role of polypeptides as drugs or drug carriers are reviewed. Finally, the hypothetical role of NCAs in molecular evolution on the prebiotic Earth is discussed.

Polypeptides and 100 years of chemistry of alpha-amino acid N-carboxyanhydrides.

Since 1906, when Leuchs synthesized the first R-amino acid N-carboxyanhydrides (NCAs),1 later referred to as Leuchs’ anhydrides, a great number of publications dealing with the ring-opening polymerization (ROP) of these monomers (Scheme 1) has accumulated. This interest stems from the wide variety of polypeptides that this polymerization can generate. The synthetic polypeptides produced from the NCAs, although far from being monodisperse or constructed from a precise sequence and composition of R-amino acid residues, possess the ability, as their natural relative-proteins, to form R-helix and -sheet motifs. These secondary structures contribute significantly to the self-assembling character of polypeptide chains, leading to novel supramolecular structures with potential biomedical and pharmaceutical applications.2 As for their natural counterparts, it is important for such synthetic polypeptides to be well-defined with high molecular and structural homogeneity in order to favor their selfassembly into precisely defined nanostructures, a requirement for appropriate functionality. It was not until 1997, when Deming3 reported the first living initiating system for the ROP of NCAs, that the synthesis of well-defined polypeptides was achieved. Following this first report, other alternative living initiating systems or methods have also been developed. These living systems lead to well-defined homo-/copolypeptides and hybrids, with high molecular weight and structural homogeneity. Nevertheless, the earlier studies served as the springboard for developments in the whole area of polypeptide synthesis. Several excellent reviews4 have been dedicated to the ROP of NCAs, elucidating the mechanistic aspects of this polymerization. However, only a few have addressed the synthesis of polypeptide-based materials with different macromolecular architectures.4c,5,6 This review is divided into three parts. The first highlights the mechanistic developments of the ROP of NCAs from the conventional to the living initiating systems/methods; the second is dedicated to the synthesis of polypeptides and polypeptide hybrids with different macromolecular architectures; and the third deals with surface-bound polypeptides. Surface-bound polypeptides were incorporated in the review due to the great interest in biologically active surfaces for medical diagnostics and sensors.7

Synthesis of Well-Defined Polypeptide-Based Materials via the Ring-Opening Polymerization of α-Amino Acid N-Carboxyanhydrides

Telechelic polymers by living and controlled/living polymerization methods

Preparation of (p-vinylbenzyl)polystyrene macromer

Coupling Reaction between Living Polystyrene and Poly(chloromethylstyrene)

preparation par reaction d'α-lithio- et α,ω-dilithiopoly(vinyl-2 pyridines) avec le chlorure de p-vinylbenzyle. Copolymerisation avec le MMA

Preparation of (p-vinylbenzyl)poly(2-vinylpyridine) macromers

Living poly(tetrahydrofuran) (PTHF) was coupled with sodium p-vinylbenzyloxide quantitatively to prepare a macromer of p-vinylbenzyloxyl poly(tetrahydrofuran) (VBO-PTHF). The radical polymerization of the macromer with AIBN was performed. From the GPC measurement the conversion of the macromer to poly-macromer was shown to be high percentage, but the degree of polymerization of poly-macromer was much lower than that expected in the case of regular monomers such as styrene.

Syntheses and polymerizations of macromers

Monodisperse and pure macromers were synthesized by means of living polymers of cationic and anionic polymerizations The macromers obtained were polytetrahydrofuran-, polystyrene-, polyisoprene-, and poly(2-vinylpyridine)-macromers The radical homopolymerizations of these macromers were performed, and the high reactivity of the macromers was revealed The radical copolymerizations of macromers with common small monomers were performed and r1 and r2 values were estimated The radical copolymerizations between two kinds of macromers were carried out to prepare a unique double-colored multibranch-polymer

Mikio Takaki

Papers

Preparation of (p-vinylbenzyl)polystyrene macromer

Coupling Reaction between Living Polystyrene and Poly(chloromethylstyrene)

Preparation of (p-vinylbenzyl)poly(2-vinylpyridine) macromers

Syntheses and polymerizations of macromers

Synthesis of macromers by means of living polymers and their polymerizabilities