Supramolecular Self-assembly (supramolecular + self-assembly)

Distribution by Scientific Domains

Selected Abstracts

Supramolecular Self-Assembly: Self-Assembly of a Donor-Acceptor Dyad Across Multiple Length Scales: Functional Architectures for Organic Electronics (Adv. Funct.

More than the sum of its parts: by covalently coupling polycyclic donor and acceptor moieties, Samori and co-workers demonstrate on page 2486 that a donor,acceptor dyad, based on nanographene and perylene, self-assembles into highly ordered supramolecular architectures with nanosegregated coaxial donor and acceptor regions. The cover image features an atomic force microscopy image of mesoscopic ribbons along with the proposed crystallographic arrangement of the constituent molecules. [source]

Supramolecular Self-Assembly of Conjugated Diblock Copolymers

Hengbin Wang Dr.
Abstract This paper describes the synthesis and characterization of a novel series of copolymers with different lengths of oligo(phenylene vinylene) (OPV) as the rod block, and poly(propylene oxide) as the coil block. Detailed characterization by means of transmission electron microscopy (TEM), atomic force microscopy (AFM), and small-angle neutron scattering (SANS) revealed the strong tendency of these copolymers to self-assemble into cylindrical micelles in solution and as-casted films on a nanometer scale. These micelles have a cylindrical OPV core surrounded by a poly(propylene glycol) (PPG) corona and readily align with each other to form parallel packed structures when mica is used as the substrate. A packing model has been proposed for these cylindrical micelles. [source]

Supramolecular Self-Assembled Dendritic Nonlinear Optical Chromophores: Fine-Tuning of Arene,Perfluoroarene Interactions for Ultralarge Electro-Optic Activity and Enhanced Thermal Stability

Xing-Hua Zhou
Unprecedented electro-optic (EO) activity and excellent alignment stability at 85,°C are demonstrated through rational design of a new series of dendronized polyenic chromophores capable of supramolecular self-assembly directed by fine-tuned arene,perfluoroarene interactions. Analysis of the EO properties showed exceptional poling efficiency for these molecular glasses at high chromophore number density. [source]

Synthesis and supramolecular self-assembly of thermosensitive amphiphilic star copolymers based on a hyperbranched polyether core

Haiyan Hong
Abstract A novel amphiphilic thermosensitive star copolymer with a hydrophobic hyperbranched poly (3-ethyl-3-(hydroxymethyl)oxetane) (HBPO) core and many hydrophilic poly(2-(dimethylamino) ethyl methacrylate) (PDMAEMA) arms was synthesized and used as the precursor for the aqueous solution self-assembly. All the copolymers directly aggregated into core,shell unimolecular micelles (around 10 nm) and size-controllable large multimolecular micelles (around 100 nm) in water at room temperature, according to pyrene probe fluorescence spectrometry and 1H NMR, TEM, and DLS measurements. The star copolymers also underwent sharp, thermosensitive phase transitions at a lower critical solution temperature (LCST), which were proved to be originated from the secondary aggregation of the large micelles driven by increasing hydrophobic interaction due to the dehydration of PDMAEMA shells on heating. A quantitative variable temperature NMR analysis method was designed by using potassium hydrogen phthalate as an external standard and displayed great potential to evaluate the LCST transition at the molecular level. The drug loading and temperature-dependent release properties of HBPO- star -PDMAEMA micelles were also investigated by using indomethacin as a model drug. The indomethacin-loaded micelles displayed a rapid drug release at a temperature around LCST. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 668,681, 2008 [source]

A doubly responsive AB diblock copolymer: RAFT synthesis and aqueous solution properties of poly (N -isopropylacrylamide- block -4-vinylbenzoic acid)

Andrew B. Lowe
Abstract We describe herein the synthesis and self-assembly characteristics of a doubly responsive AB diblock copolymer comprised of N -isopropylacrylamide (NIPAM) and 4-vinylbenzoic acid (VBZ). The AB diblock copolymer was prepared via reversible addition-fragmentation chain transfer (RAFT) radical polymerization in DMF employing a trithiocarbonate-based RAFT agent. PolyNIPAM was employed as the macroRAFT agent. The NIPAM homopolymerization was shown to possess all the characteristics of a controlled process, and the blocking with VBZ was judged, by size exclusion chromatography, to be essentially quantitative. The NIPAM-VBZ block copolymer was subsequently demonstrated to be able to form normal and inverse micelles in the same aqueous solution by taking advantage of the stimuli responsive characteristics of both building blocks. Specifically, and as judged by NMR spectroscopy and dynamic light scattering, raising the temperature to 40 °C (above the lower critical solution temperature of the NIPAM block), while at pH 12 results in supramolecular self-assembly to yield nanosized species that are composed of a hydrophobic NIPAM core stabilized by a hydrophilic VBZ corona. Conversely, lowering the solution pH to 2.0 at ambient temperature results in the formation of aggregates in which the VBZ block is now hydrophobic and in the core, stabilized by the hydrophilic NIPAM block. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5864,5871, 2007 [source]

Amphiphilic star-block copolymers based on a hyperbranched core: Synthesis and supramolecular self-assembly

Zhifeng Jia
Abstract Novel amphiphilic star-block copolymers, star poly(caprolactone)- block -poly[(2-dimethylamino)ethyl methacrylate] and poly(caprolactone)- block -poly(methacrylic acid), with hyperbranched poly(2-hydroxyethyl methacrylate) (PHEMA,OH) as a core moiety were synthesized and characterized. The star-block copolymers were prepared by a combination of ring-opening polymerization and atom transfer radical polymerization (ATRP). First, hyperbranched PHEMA,OH with 18 hydroxyl end groups on average was used as an initiator for the ring-opening polymerization of ,-caprolactone to produce PHEMA,PCL star homopolymers [PHEMA = poly(2-hydroxyethyl methacrylate); PCL = poly(caprolactone)]. Next, the hydroxyl end groups of PHEMA,PCL were converted to 2-bromoesters, and this gave rise to macroinitiator PHEMA,PCL,Br for ATRP. Then, 2-dimethylaminoethyl methacrylate or tert -butyl methacrylate was polymerized from the macroinitiators, and this afforded the star-block copolymers PHEMA,PCL,PDMA [PDMA = poly(2-dimethylaminoethyl methacrylate)] and PHEMA,PCL,PtBMA [PtBMA = poly(tert -butyl methacrylate)]. Characterization by gel permeation chromatography and nuclear magnetic resonance confirmed the expected molecular structure. The hydrolysis of tert -butyl ester groups of the poly(tert -butyl methacrylate) blocks gave the star-block copolymer PHEMA,PCL,PMAA [PMAA = poly(methacrylic acid)]. These amphiphilic star-block copolymers could self-assemble into spherical micelles, as characterized by dynamic light scattering and transmission electron microscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6534,6544, 2005 [source]

Direct synthesis of amphiphilic block copolymers from glycidyl methacrylate and poly(ethylene glycol) by cationic ring-opening polymerization and supramolecular self-assembly thereof

Wei Huang
Abstract Amphiphilic block copolymers composed of a hydrophilic poly(ethylene glycol) (PEG) block and a hydrophobic poly(glycidyl methacrylate) (PGMA) block were synthesized through cationic ring-opening polymerization with PEG as the precursor. The model reactions indicated that the reactivity of the epoxy groups was higher than that of the double bonds in the bifunctional monomer glycidyl methacrylate (GMA) under the cationic polymerization conditions. Through the control of the reaction time in the synthesis of block copolymer PEG- b -PGMA, a linear GMA block was obtained through the ring-opening polymerization of epoxy groups, whereas the double bond in GMA remained unreacted. The results showed that the molecular weight of the PEG precursor had little influence on the grafting of GMA, and the PGMA blocks almost kept the same length, despite the difference of the PEG blocks. In addition, the PGMA blocks only consisted of several GMA units. The obtained amphiphilic PEG- b -PGMA block copolymers could form polymeric core,shell micelles by direct molecular self-assembly in water. The crosslinking of the PGMA core of the PEG- b -PGMA micelles, induced by ultraviolet radiation and heat instead of crosslinking agents, greatly increased the stability of the micelles. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2038,2047, 2005 [source]

Basic forms of supramolecular self-assembly ­organized by parallel and antiparallel hydrogen bonds in the racemic crystal structures of six disubstituted and trisubstituted cyclopentane ­derivatives

Alajos Kálmán
A selection of stereoisomeric 2-hydroxy-1-cyclopentanecarboxamides, a 4- tert -butyl derivative and three tert -butyl derivatives of the respective carboxylic acid were subjected to X-ray crystallography. The optically active molecules (I),(VI) form racemic crystals. Each racemic structure is basically determined by two intermolecular hydrogen bonds of O,H,O=C,XH and O=C,X,H,OH types (X = O, NH). The partially similar patterns of close packing observed reflect five basic forms of supramolecular self-assembly. In the racemic crystals of chiral molecules, there are homo- and heterochiral chains of molecules formed by the principal (O,H,O=C) hydrogen bonds. These chains assemble either in a parallel or antiparallel mode. The parallel homochiral chains (hop) observed in structure (II), (1R*,2R*)-2-hydroxy-1-cyclopentanecarboxamide, demand the polar space group Pca21, while the parallel heterochiral chains (hep) are organized in antiparallel layers with space group P21/n in structure (VI), (1R*,2S*,5R*-5- tert -butyl-2-hydroxy-1-cyclopentanecarboxylic acid). Heterochiral chains in an antiparallel array (hea) are found in (I), (1R*,2S*)-2-hydroxy-1-cyclopentanecarboxamide, and (V) [(1R*,2S*4S*)-4- tert -butyl-2-hydroxy-1-cyclopentanecarboxylic acid, space group P21/c]. Structures (IV), (1R*,2S*,4R*)-4- tert -butyl-2-hydroxy-1-cyclopentanecarboxylic acid, and (III), (1R*,2R*,4S*)-4- tert -butyl-2-hydroxy-1-cyclopentanecarboxamide, reveal that homochiral chains in an antiparallel array (hoa; cross-linked by heterochiral dimers held together by the second hydrogen bonds) can be formed by either translation (space group P) or a screw axis (space group P21/c). These alternatives are denoted hoa1 and hoa2. Similarly, within each pattern (hea, hep and hop) two slightly different alternatives can be expected. The partial similarities in the identified five patterns of hydrogen bonding are described by graph-set notations. Structures (I), (IV) and (V) can be characterized by a common supramolecular synthon, while the highest degree of similarity is shown by the isostructurality of (I) and (V). [source]