Living supramolecular polymerization Mukhopadhyay, Rahul Dev; Ajayaghosh, Ayyappanpillai
Science (American Association for the Advancement of Science),
07/2015, Letnik:
349, Številka:
6245
Journal Article
Recenzirano
Greater control is achieved over the chain growth and properties of dynamic materials
Most polymers that we encounter, like those used in grocery bags and soda bottles, are formed from small ...molecules (monomers) held together by strong covalent bonds. In supramolecular polymerization, monomers bond through weaker reversible interactions, such as hydrogen bonds (H-bonds). Supramolecular polymerization usually proceeds through step-growth mechanisms (
1
), where both ends of each monomer are reactive and many smaller oligomers form before long polymers appear. To overcome this problem, a method developed for covalent polymers known as living polymerization has been adopted for supramolecular polymers to achieve better control and uniformity of chain growth and dispersity.
Self-Assembled Gelators for Organic Electronics Babu, Sukumaran Santhosh; Prasanthkumar, Seelam; Ajayaghosh, Ayyappanpillai
Angewandte Chemie (International ed.),
February 20, 2012, Letnik:
51, Številka:
8
Journal Article
Recenzirano
Nature excels at engineering materials by using the principles of chemical synthesis and molecular self‐assembly with the help of noncovalent forces. Learning from these phenomena, scientists have ...been able to create a variety of self‐assembled artificial materials of different size, shapes, and properties for wide ranging applications. An area of great interest in this regard is solvent‐assisted gel formation with functional organic molecules, thus leading to one‐dimensional fibers. Such fibers have improved electronic properties and are potential soft materials for organic electronic devices, particularly in bulk heterojunction solar cells. Described herein is how molecular self‐assembly, which was originally proposed as a simple laboratory curiosity, has helped the evolution of a variety of soft functional materials useful for advanced electronic devices such as organic field‐effect transistors and organic solar cells. Highlights on some of the recent developments are discussed.
All gelled together: Solvent‐assisted gelation of functional organic molecules leading to one‐dimensional fibers is an area of great interest. Recent developments in molecular self‐assembly‐assisted gelation of π systems into soft functional materials and their potential application in organic electronic devices, such as organic field‐effect transistors and organic solar cells, are reviewed (see picture).
Precise control of host-guest interaction as seen in biological processes is difficult to achieve with artificial systems. Herein we have exploited the thermodynamic benefits of a system in ...equilibrium to achieve controlled stepwise release and capture of cyclodextrin (guest) using a coordination polymer (Mg-CP) as the host and temperature as the stimulus. Since temperature is not a precision stimulus for artificial host-guest interaction, the present system is a distinct prototype that manifests temperature-controlled natural host-guest interaction. The described coordination polymeric host system, when incorporated into a hydrogel matrix, provides a microenvironment that facilitates the stepwise release of α-CD in response to temperature variation within a quasi-solid state. The work demonstrated here may pave the way towards thermally controlled delivery and monitoring of otherwise spectroscopically silent molecules such as cyclodextrins.
Functional differences between superhydrophobic surfaces, such as lotus leaf and rose petals, are due to the subtle architectural features created by nature. Mimicry of these surfaces with synthetic ...molecules continues to be fascinating as well as challenging. Herein, we demonstrate how inherently hydrophilic alumina surface can be modified to give two distinct superhydrophobic behaviors. Functionalization of alumina with an organic ligand resulted in a rose‐petal‐like surface (water pinning) with a contact angle of 145° and a high contact angle hysteresis (±69°). Subsequent interaction of the ligand with Zn2+ resulted in a lotus‐leaf‐like surface with water rolling behavior owing to high contact angle (165°) and low‐contact‐angle‐hysteresis (±2°). In both cases, coating of an aromatic bis‐aldehyde with alkoxy chain substituents was necessary to emulate the nanowaxy cuticular feature of natural superhydrophobic materials.
A new leaf: Surface‐functionalization and coordination‐polymer chemistry are utilized to create metal–organic framework (MOF)‐based nanoarchitectures on an alumina surface, which modify the surface's inherent superhydrophilicity to the distinctive superhydrophobic behaviors of rose petals and lotus leaves.
Spiraling into control: A photoresponsive supramolecular assembly demonstrates that light, along with heating (Δ) and cooling (), can cause chiral communication between molecules. This effect leads ...to bias in the helicity of the complex, causing a reversible switching of macroscopic handedness, as shown by a reversal of sign of the circularly polarized luminescence (CPL) that is emitted.
Oligo(phenylenevinylene)s (OPVs) are extensively investigated π-conjugated molecules that exhibit absorption and fluorescence in the UV-Vis spectral region, which can be widely tuned by chemical ...functionalisation and external control (
e.g.
solvent, temperature, pH). Further modulation of the optoelectronic properties of OPVs is possible by supramolecular aggregation, primarily driven by hydrogen bonding or π-stacking interactions. In recent years, extensive research work has been accomplished in exploiting the unique combination of the structural and electronic properties of OPVs, most of which has been targeted at the preparation of molecules and materials featuring photoinduced energy transfer. This review intends to offer an overview of the multicomponent arrays and self-assembled materials based on OPV which have been designed to undergo energy transfer by means of a thorough choice of excitation donor-acceptor partners. We present a few selected examples of photoactive dyads and triads containing organic moieties (
e.g.
fullerene, phenanthroline) as well as coordination compounds (Cu(
i
) complexes). We then focus more extensively on self-assembled materials containing suitably functionalised OPVs that lead to hydrogen bonded aggregates, helical structures, gels, nanoparticles, vesicles, mesostructured organic-inorganic hybrid films, functionalised nanoparticles and quantum dots. In most cases, these materials exhibit luminescence whose colour and intensity is related to the efficiency and direction of the energy transfer processes.
The engineering of the nanostructure of OPV based self-assemblies allows control of photoinduced energy transfer processes, leading to materials exhibiting tunable luminescence colours, including white.
Trithienylenevinylenes having amide end functional groups form supramolecular gels in nonpolar solvents, comprised of self-assembled nanowires. These gels exhibit the unique property of solution ...phase epitaxy leading to the alignment of fibers on mica surface. FP-TRMC studies revealed high charge carrier mobility for xerogels from decane−chloroform whereas films obtained from chloroform solutions showed less mobility, highlighting the role of self-assembly and gelation on the electronic properties of semiconducting molecular gelators. This study opens the window for a new class of conducting gelators which may find wide application in organic electronic devices.
Excited state properties such as emission, exciton transport, electron transfer, etc., are strongly dependent on the shape, size and molecular arrangement of chromophore based supramolecular ...architectures. Herein, we demonstrate creation and control of distinct supramolecular energy landscapes for the reversible control of the excited‐state emission processes through cascade energy transfer in chromophore assemblies, facilitated by an unprecedented solvent effect. In methylcyclohexane, a tailor‐made Y‐shaped BODIPY derivative self‐assembles to form an unusual spherical architecture of 400–1200 nm size, which exhibits a single emission at 540 nm upon 475 nm excitation through a normal excitation deactivation process. However, in n‐decane, the same BODIPY derivative forms two‐dimensional supramolecular sheets, exhibiting multiple emission peaks at 540, 610, 650, 725 and 790 nm with 475 nm excitation due to cascade energy transfer. Further control on the morphology and excitation energy transfer is possible with variable solvent composition and ultrasound stimulation, resulting in enhanced near‐infrared emission with an overall pseudo Stokes shift of 7105 cm−1.
A designed Y‐shaped BODIPY exhibits a solvent‐dependent morphology transition with distinct excited‐state behavior. In methylcyclohexane, spherical assemblies are formed with normal emission in the visible region, whereas in n‐decane, 2D supramolecular sheets with multiple emission in the visible to NIR region are formed.
Ionic covalent organic nanosheets (iCONs), a member of the two‐dimensional (2D) nanomaterials family, offer a unique functional platform for a wide range of applications. Herein, we explore the ...potential of an ethidium bromide (EB)‐based covalent organic framework (EB‐TFP) that self‐exfoliates in water resulting in 2D ionic covalent organic nanosheets (EB‐TFP‐iCONs) for the selective detection of double‐stranded DNA (dsDNA). In an aqueous medium, the self‐exfoliated EB‐TFP‐iCONs reassemble in the presence of dsDNA resulting in hybrid EB‐TFP‐iCONs‐DNA crystalline nanosheets with enhanced fluorescence at 600 nm. Detailed steady‐state and time‐resolved emission studies revealed that the reassembly phenomenon was highly selective for dsDNA when compared to single‐stranded DNA (ssDNA), which allowed us to use the EB‐TFP‐iCONs as a 2D fluorescent platform for the label‐free detection of complementary DNA strands.
Feelin' single, seein' double: Self‐exfoliated nanosheets of an ionic COF were used as a fluorescent platform for the selective detection of double‐stranded DNA (dsDNA). DNA induced the reassembly of the 2D nanosheets, and the associated fluorescence changes facilitated the discrimination of dsDNA from single‐stranded DNA (ssDNA) and other phosphates.
PDF
