Engineering long-range order in supramolecular assemblies on surfaces : the paramount role of internal double bonds in discrete long-chain naphthalenediimides

Achieving long-range order with surface-supported supramolecular assemblies is one of the pressing challenges in the prospering field of non-covalent surface functionalization. Having access to defect-free on-surface molecular assemblies will pave the way for various nanotechnology applications. Here we report the synthesis of two libraries of naphthalenediimides (NDIs) symmetrically functionalized with long aliphatic chains (C28 and C33) and their self-assembly at the 1-phenyloctane/highly oriented pyrolytic graphite (1-PO/HOPG) interface. The two NDI libraries differ by the presence/absence of an internal double bond in each aliphatic chain (unsaturated and saturated compounds, respectively). All molecules assemble into lamellar arrangements, with the NDI cores lying flat and forming 1D rows on the surface, while the carbon chains separate the 1D rows from each other. Importantly, the presence of the unsaturation plays a dominant role in the arrangement of the aliphatic chains, as it exclusively favors interdigitation. The fully saturated tails, instead, self-assemble into a combination of either interdigitated or non-interdigitated diagonal arrangements. This difference in packing is spectacularly amplified at the whole surface level and results in almost defect-free self-assembled monolayers for the unsaturated compounds. In contrast, the monolayers of the saturated counterparts are globally disordered, even though they locally preserve the lamellar arrangements. The experimental observations are supported by computational studies and are rationalized in terms of stronger van der Waals interactions in the case of the unsaturated compounds. Our investigation reveals the paramount role played by internal double bonds on the self-assembly of discrete large molecules at the liquid/solid interface

Combinatorial Selection Among Geometrical Isomers of Discrete Long-Carbon-Chain Naphthalenediimides Induces Local Order at the Liquid/Solid Interface

We report two families of naphthalenediimides (NDIs) symmetrically functionalized with discrete carbon chains comprising up to 55 carbon atoms (Cn-NDI-Cn, n = 39, 44, 50, and 55) and their self-assembly at the 1-phenyloctane/highly oriented pyrolytic graphite interface (1-PO/HOPG interface). The compounds differ by the presence or absence of two or three internal double bonds in the carbon chains (unsaturated and saturated Cn-NDI-Cn, respectively). Combinatorial distributions of geometrical isomers displaying either the E- or Z-configuration at each double bond are obtained for the unsaturated compounds. Analysis of the self-assembled monolayers of equally long unsaturated and saturated Cn-NDI-Cn by scanning tunneling microscopy (STM) reveal that all Cn-NDI-Cn tend to form lamellar systems featuring alternating areas of aromatic cores and carbon chains. Extended chain lengths are found to significantly increase disorder in the self-assembled monolayers due to misalignments and enhanced strength of interchain interactions. This phenomenon is antagonized by the local order-inducing effect of the internal double bonds: unsaturated Cn-NDI-Cn give qualitatively more ordered self-assembled monolayers compared to their saturated counterparts. The use of combinatorial distributions of unsaturated Cn-NDI-Cn geometrical isomers does not represent a limitation to achieve local order in the self-assembled monolayers. The self-assembly process operates a combinatorial search and selects the geometrical isomer(s) affording the most thermodynamically stable pattern, highlighting the adaptive character of the system. Finally, the antagonistic interplay between the extended carbon chain lengths and the presence of internal double bonds brings to the discovery of the lamellar "phase C" morphology for unsaturated Cn-NDI-Cn with n ≥ 50

Dispersity under Scrutiny: Phase Behavior Differences between Disperse and Discrete Low Molecular Weight Block Co-Oligomers

An experimental study is presented in which we compare the bulk phase behavior of discrete and (partially) disperse diblock co-oligomers (BCOs) with high χ–low <i>N</i>. To this end, oligomers of dimethylsiloxane (<i>o</i>DMS) and lactic acid (<i>o</i>LA) were synthesized, each having either a discrete number of repeat units or a variable block length. Ligation of the blocks resulted in <i>o</i>DMS–<i>o</i>LA BCOs with dispersities ranging from <1.00001 to 1.09, as revealed by mass spectroscopy and size exclusion chromatography. The phase behavior of all BCOs was investigated by differential scanning calorimetry and small-angle X-ray scattering. Compared to the well-organized lamellae formed by discrete <i>o</i>DMS–<i>o</i>LA, we observe that an increase in the dispersity of these BCOs results in (1) an increase of the <i>stability</i> of the microphase-segregated state, (2) a decrease of the overall <i>degree of ordering</i>, and (3) an increase of the <i>domain spacing</i>

A Versatile Method for the Preparation of Ferroelectric Supramolecular Materials via Radical End-Functionalization of Vinylidene Fluoride Oligomers

A synthetic method for the end-functionalization of vinylidene fluoride oligomers (OVDF) via a radical reaction between terminal olefins and I-OVDF is described. The method shows a wide substrate scope and excellent conversions, and permits the preparation of different disc-shaped cores such as benzene-1,3,5-tricarboxamides (BTAs), perylenes bisimide and phthalocyanines (Pc) bearing three to eight ferroelectric oligomers at their periphery. The formation, purity, OVDF conformation, and morphology of the final adducts has been assessed by a combination of techniques, such as NMR, size exclusion chromatography, differential scanning calorimetry, polarized optical microscopy, and atomic force microscopy. Finally, PBI-OVDF and Pc-OVDF materials show ferroelectric hysteresis behavior together with high remnant polarizations, with values as high as P-r approximate to 37 mC/m(2) for Pc-OVDF. This work demonstrates the potential of preparing a new set of ferroelectric materials simply by attaching OVDF oligomers to different small molecules. The use of carefully chosen small molecules paves the way to new functional materials in which ferroelectricity and electrical conductivity or light-harvesting properties coexist in a single compound.Funding Agencies|Dutch Polymer Institute (DPI) [765]; Dutch Ministry of Education, Culture and Science [024.001.035]; European Research Council [246829]</p

Supramolecular chemistry with ureido-benzoic acids

The controlled self-assembly of multiple molecules into predefined architectures requires highly directional and controllable non-covalent interactions with a high association constant. Here, we introduce the self-complementary ureido-benzoic acid (UBA) quadruple hydrogen-bonding motif. The dimerization constant is of the order of 109 M-1 in chloroform, which makes it an excellent candidate for supramolecular chemistry in dilute conditions. The self-complementary quadruple hydrogen bonding was confirmed in the solid state by a crystal structure. The applicability of the motif in supramolecular polymers was evaluated by bis-UBA telechelic poly(ethylene-butylene) polymers, which showed a dramatic increase in mechanical properties upon functionalization. The potential of the UBA motif in supramolecular chemistry was further evaluated in solution. One of the synthesized UBA molecules revealed hydrogen bonding to NaPy at high concentrations in chloroform. However, upon dilution, the UBA:NaPy hydrogen bonding is disrupted and UBA homodimers are obtained. This shows the potential of NaPy as a supramolecular protective group for the UBA molecule, which can be deprotected upon dilution. Furthermore, the dimerization of the UBA motif was reversibly switched between the 'off' and 'on' states using base and acid, demonstrating an alternative method of influencing the UBA dimerization. Switching of a UBA molecule in the presence of UPy revealed that UBA dimerization can be selectively switched 'off' and 'on' in the presence of UPy dimers. These results show the applicability and great potential of the self-complementary quadruple hydrogen-bonding UBA motif for supramolecular chemistry

Synthesis and Self-Assembly of Discrete Dimethylsiloxane–Lactic Acid Diblock Co-oligomers: The Dononacontamer and Its Shorter Homologues

Most of the theoretical and computational descriptions of the phase behavior of block copolymers describe the chain ensembles of perfect and uniform polymers. In contrast, experimental studies on block copolymers always employ materials with disperse molecular makeup. Although most polymers are so-called monodisperse, they still have a molecular weight dispersity. Here, we describe the synthesis and properties of a series of discrete length diblock co-oligomers, based on oligo-dimethylsiloxane (<i>o</i>DMS) and oligo-lactic acid (<i>o</i>LA), diblock co-oligomers with highly noncompatible blocks. By utilizing an iterative synthetic protocol, co-oligomers with molar masses up to 6901 Da, ultralow molar mass dispersities (<i><i>Đ</i></i> ≤ 1.00002), and unique control over the co-oligomer composition are synthesized and characterized. This specific block co-oligomer required the development of a new divergent strategy for the <i>o</i>DMS structures by which both bis- and monosubstituted <i>o</i>DMS derivatives up to 59 Si-atoms became available. The incompatibility of the two blocks makes the final coupling more demanding the longer the blocks become. These optimized synthetic procedures granted access to multigram quantities of most of the block co-oligomers, useful to study the lower limits of block copolymer phase segregation in detail. Cylindrical, gyroid, and lamellar nanostructures, as revealed by DSC, SAXS, and AFM, were generated. The small oligomeric size of the block co-oligomers resulted in exceptionally small feature sizes (down to 3.4 nm) and long-range organization

Supramolecular chemistry with ureido-benzoic acids

The controlled self-assembly of multiple molecules into predefined architectures requires highly directional and controllable non-covalent interactions with a high association constant. Here, we introduce the self-complementary ureido-benzoic acid (UBA) quadruple hydrogen-bonding motif. The dimerization constant is of the order of 109 M-1 in chloroform, which makes it an excellent candidate for supramolecular chemistry in dilute conditions. The self-complementary quadruple hydrogen bonding was confirmed in the solid state by a crystal structure. The applicability of the motif in supramolecular polymers was evaluated by bis-UBA telechelic poly(ethylene-butylene) polymers, which showed a dramatic increase in mechanical properties upon functionalization. The potential of the UBA motif in supramolecular chemistry was further evaluated in solution. One of the synthesized UBA molecules revealed hydrogen bonding to NaPy at high concentrations in chloroform. However, upon dilution, the UBA:NaPy hydrogen bonding is disrupted and UBA homodimers are obtained. This shows the potential of NaPy as a supramolecular protective group for the UBA molecule, which can be deprotected upon dilution. Furthermore, the dimerization of the UBA motif was reversibly switched between the 'off' and 'on' states using base and acid, demonstrating an alternative method of influencing the UBA dimerization. Switching of a UBA molecule in the presence of UPy revealed that UBA dimerization can be selectively switched 'off' and 'on' in the presence of UPy dimers. These results show the applicability and great potential of the self-complementary quadruple hydrogen-bonding UBA motif for supramolecular chemistry