Dendritic Bromide Research Articles

Construction of Dendritic-Linear Brushes on Silica Nanoparticles by Electrostatic Assembly

Using dendritic bromide poly (benzyl ether), G2-Br, as macroinitiator, dendritic-linear polymer (G2-PS-NHSO3Na) was obtained via atom transfer radical polymerization and nucleophilic substitution of G2-PS-Br. G2-PS-NHSO3Na was constructed on cationic silica by both electrostatic attraction and steric effort coming from dendritic block of G2-PS-NHSO3Na. 1H-NMR and differential scanning calorimetry were used to characterize the structure and thermal behavior of G2-PS-NHSO3Na; thermo-gravimetric analysis and TEM were applied to analysis the assembly amount of G2-PS-NHSO3Na and the dispersibility of silica before and after assembly. The results show that G2-PS-NHSO3Na can be synthesized successfully and has exact structure; it can be constructed on cationic silica with 27% assembly amount; the aggregation of silica can be prevented effectively by the dendritic-linear brushes, but the molecular weight of linear segment and the generation of dendritic block will influence the assembly behavior and the amount of the dendritic-linear brushes.

Reactive Dendronized Copolymer of Styryl Dendron and Maleic Anhydride: A Single Molecular Scaffold

Novel dendronized copolymers bearing reactive anhydride groups along the backbones are reported in this paper. They were synthesized through copolymerizations of styryl macromonomers bearing Fréchet-type dendrons of the first to the fourth generation and maleic anhydride (MAn) through conventional radical polymerization. The dendritic macromonomers were prepared by an accelerated convergent approach, i.e., a reaction of the dendritic bromide of lower generation with a styrene derivative bearing a 3,5-dihydroxybenzyl group. The dendronized copolymers with rather high molar masses were obtained under mild conditions, even for the fourth-generation dendritic monomer as determined by static light scattering (SLS). For example, the degree of copolymerization for the third-generation monomer reached 487. Owing to the reactivity of the anhydride, functional groups, which were buried by the grafted dendrons along the backbone, could be easily introduced as follows: (1) by the hydrolysis under acid conditions, the amphiphilic copolymers with a structure of dendron-alt-2COOH were prepared; (2) by reacting with alkyl primary amine, the copolymers with dendron-alt-linear alkyl chain were obtained in a quantitatively yields; (3) when reacted with a primary amino dendron of its generation different from the pendent dendron, a series of new dendronized copolymers with their side dendrons grafted in an alternative generation structure were produced. Therefore, the novel reactive dendronized copolymer presented herein can be a single molecular scaffold to be applied in nanomaterials and nanotechnologies of one dimension.

Synthesis of axially chiral dendrimers containing meta-terphenyl peripheral groups and a chiral binol core

Fréchet-type poly(arylether) dendritic bromides carrying m-terphenyl peripheral groups were synthesised up to second generation by convergent methodology. Simple O-alkylation of chiral (S)-BINOL with the dendritic bromides afforded the corresponding axially chiral dendrimers. The molar optical rotation values of the dendrimers become increasingly negative as the dendrimer generation increases.

Synthesis and electrochemical properties of dendrimers containing meta-terphenyl peripheral groups and a 4,4′-bipyridinium core

Fréchet-type poly(arylether) dendrons carrying m-terphenyl peripheral groups were synthesized up to second generation by convergent methodology. Simple quarternisation of 4,4′-bipyridine with the dendritic bromides afforded the corresponding dendrimers containing a 4,4′-bipyridine core. The electrochemical parameters were obtained for all the dendrimers and the half-wave potentials of both the first and second redox processes shift to less-negative values as the dendrimer generation increases.

Investigation of self-assembled dendrimer complexes

Dendrimer complexes[(G-2) 4P and (G-3) 4P]with a porphyrin core have been prepared by self-assembling of sodium tetrakis(4-sulfonatophenyl) porphyrin with dendritic quaternary bromides (G-2 and G-3), which were synthesized by reaction of Frechet type dendritic bromides (G-2 and G-3) with triethylamine. The structure of dendrimer complexes was confirmed by 1 H NMR and element analysis. The stoichiometry rate between the dendritic quaternary bromide and porphyrin core was 4:1. Solvatochromism studies of the dendritic complexes showed that the (G-3) 4P dendritic complex is more stable than the (G-2) 4P dendritic complex. It is inferred that hydrophobic interactions play an important role in stabilizing these dendrimer complexes in addition to coulombic interactions.

An Alternative Synthetic Approach toward Dendritic Macromolecules: Novel Benzene-Core Dendrimers via Alkyne Cyclotrimerization

An Alternative Synthetic Approach toward Dendritic Macromolecules: Novel Benzene-Core Dendrimers via Alkyne Cyclotrimerization

An accelerated, improved synthetic route for the preparation of polyether-based dendritic fragments

An accelerated, improved synthetic strategy for the rapid construction of two different series of polyether-based dendritic fragments is described. Several modifications to the original method for the preparation of these dendritic fragements are detailed. A new branching agent, 5-(3-hydroxypropyloxy)-1,3-resorcinol 4, instead of 5-benzyloxy-1,3-resorcinol 2, is employed in this new synthetic protocol. As a result, the number of synthetic operations in each of the iterative cycle is reduced from three to two, as compared to the original procedure. Each iterative synthetic cycle involves two reactions: a bis- O-alkylation reaction of the brancher 4 with a dendritic bromide [Gn]-O(CH 2) 3Br to give a dendritic alcohol of the next generation [G(n+1)]-O(CH 2) 3OH; followed by a functional group conversion of the dendritic alcohol into the corresponding dendritic bromide [G(n+1)]-O(CH 2) 3Br of the same generation. The reaction yields of each iterative cycle are consistently higher than those of the previously reported three step cycle. Using this new protcol, the preparation of a 5th generation dendritic alcohol 15a could be realized in 10 steps and 23% overall yields from 1,3-dibromopropane.

Chiral dendrimers with axial chirality

The synthesis and optical activity of novel chiral dendrimers with axial chirality are reported. The dendrimers were constructed by coupling of the polyether dendritic bromides with (R)-(+)-1,1′-bi-2-naphthol (1). The uniform (2, 3, 4) and non-uniform double-O-alkylated (8, 9, 10) as well as mono-O-alkylated (5, 6, 7) products were thus obtained. These chiral molecules were characterized by 1H- and 13C-NMR, elemental analysis, optical rotation, adsorption spectra, and circular dichroism. It was found that the specific rotation decreases with the increase of the number of generation for each group of dendrimers (2–4, 5–7, and 8–10, respectively). In terms of the molar rotation, it was quite different; the molar rotation increased sharply for dendrimers, 2–4, but only slightly for dendrimers 5–7. The dihedral angle change of bi-naphthyl in the synthesized dendrimers was discussed based on the CD spectra. Chirality 10:661–666, 1998. © 1998 Wiley-Liss, Inc.

Dendrimers with anthyridine-based hydrogen-bonding units at their cores: Synthesis, complexation and self-assembly studies

Generation 1–4 Fréchet-type dendritic bromides were covalently linked to anthyridine ( 6) to give “sticky” dendrons 7a–7d. The binding constants of 1:1 complexes between 7 and benzamidinium salt 8 were measured to assess their ability to act as building blocks for self-assembly. A 2:1 complex of 7 and pentamidine 9 formed in 1% CD 3 CN CDCl 3 indicating the utility of these compounds for constructing larger dendritic assemblies.

Poly(methacrylates) with different kinds of dendritic moieties as side groups

AbstractAlkyl methacrylate monomers with three kinds of dendritic fragments as alkyl groups, two kinds of Fréchet‐type and a new type with 3,5‐diphenoxybenzyl as first generation, were prepared by reaction of the corresponding dendritic bromides with methacrylic acid in good yield and were homopolymerized with a radical initiator. Polymers with side groups in first generation had a degree of polymerization (P̄n) of 17–24, markedly higher than those with side groups in second generation, P̄n ≈ 6–7.

Synthesis and properties of novel linear-dendritic block copolymers. Reactivity of dendritic macromolecules toward linear polymers

The reactivity of benzylic dendritic polyethers toward linear polymers was investigated using coupling reactions of preformed dendritic and linear blocks in solution and in the melt. It was found that the rate constants for the Williamson reaction of poly(ethylene oxide)s (PEO) or poly(ethylene glycol)s (PEG) with dendritic bromides of various sizes increased with the length of the linear block and the generation of the dendrimer. Tits anomalous behavior is attributed to the increased reactivity of the PEO and PEG alcoholate anions due to the solvation of the counterion by the linear block and to the conformation changes occurring after attachment of the first dendritic block to PEG

‘Caged’ porphyrin: the first dendritic molecule having a core photochemical functionality

Alkali-mediated reaction of 5,10,15,20-tetrakis(3′,5′-dihydroxyphenyl)porphine with dendritic bromide gives the novel porphyrin covalently encapsulated into a huge dendritic cage (‘caged’ porphyrin).