Covalent assembly

Use of this concept for the preparation of networks leads to unlimited architectures. It should facilitate and expand ordered (as well as random) network construction in the future. 

Principles of Polymer Chemistry, Cornell University Press, Ithaca, New York, 1953. 121 G. Odian, Principles of Polymerization, 3rd ed., Wiley, New York, 1991. 

Bastide, S. Candau, A. Coniglio, M. Delsanti, J. E. Mark, D. Stauffer, A. J. Sta-verman, in Polymer Networks, (Ed. K. Dusek), Springer, Berlin, 1982. 

Aharoni, S. F. Edwards, Rigid Polymer Networks in Advances in Polymer Science, Springer, Berlin, 1994. N. K. Mviller-Nedebock, S. M. Aharoni, S. F. Edwards, Macromol. Symp. 1995, 98, 701. 

161 Molecular Eletronic Devices, (Ed. F. L. Carter), Dekker, New York, 1982. 

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Amide bond is an effective anchor to connect CNTs to substrate surfaces. Lan et al. [52] covalently assembled shortened multi-walled carbon nanotubes (s-MWNT) on polyelectrolyte films. The shortened MWNT is functionalized with acyl chloride in thionyl chloride (SOCl2) before self-assembling. The FTIR spectrum of self-assem-bled MWNT (SA-MWNT) adsorbed on a CaF2 plate modified with PEI/(PSS/PEI)2 shows two characteristic absorption peaks at 1646cm-1 (amide I bond) and 1524cm-1 (amide II bond) resulting from the amide bond formed between the polyelectrolyte films and s-MWNTs. 

A rapid and versatile covalent assembly technique starting from DEE oligomers has provided the 11.9 nm long hexadecameric poly(triacetylene) rod 20.1481 With its linearly conjugated 16 double and 32 triple bonds spanning in-between the terminal silicon atoms, compound 20 is currently the longest linear, fully Jt-conjugated molecular wire without aromatic repeat units in the backbone. 

Ismaili, H., F.o. Lagugnei-Labarthet, and M.S. Workentin, Covalently assembled gold nanoparticle-carbon nanotube hybrids via a photoinitiated carbene addition reaction. Chemistry of Materials, 2011. 23(6) p. 1519-1525. 

Lukin, O., Kubota, T., Okamoto, Y., Kaufmann, A., Vogtle, F. Topologically chiral covalent assemblies of molecular knots with linear, branched, and cyclic architectures, Chem. Eur. J. 10 (2004), 2804-2810. 

The coupling chemistries that have been widely used in organic chemistry for producing chemical bonds have been applied to form irreversible and stable nanoparticle arrays on surfaces. Eychmriller et al. used the carbodiimide coupling chemistry to covalently assemble carboxylate-functionalized CdTe nanocrystals (NCs) onto amino-terminated glass surfaces, which resulted in densely covered nanoparticle films.14 The same principle was also applied to coat Si02 microparticles by CdTe NCs. 

Paraschiv et al. demonstrated a functionalized surface with locally isolated functional groups (Fig. 13.1).9 Au nanoparticles d 3 nm) stabilized with propanethiol and monofunctionalized with (mercaptopropyl)methyldimethoxysilane (MPMD) were first prepared by a place-exchange reaction. The Au nanoparticles were covalently assembled onto the surface via a single methyldimethoxysilane unit by reaction with Si-OH surface groups. AFM images revealed the attachment of Au nanoparticles... 

Small molecule imprinting in sol-gel matrices has received considerable interest in recent years, undoubtedly due to the flexibility offered by the sol-gel process.5 Two different approaches have been utilized covalent assembly and noncovalent self-assembly.9 In the covalent assembly approach, the polymerizable functional group (i.e., the silicon alkoxide group) is covalently attached to the imprint molecule. The functionalized imprint molecule is then mixed with appropriate monomers (i.e., TMOS) to form the imprinted materials. After polymerization, the covalent bonds are cleaved to release the template and leave the molecular recognition pocket. Figure 20.4 shows a diagram of this process. 

The noncovalent self-assembly method relies on less specific types of interactions, including electrostatic, hydrogen bonding, metal ion coordination, Van der Waals forces, and/or hydrophobic attractions.8 In this approach, the template and the polymerizable monomer (i.e., an organoalkoxysilane) are judiciously chosen so that they will have complementary interactions. Removal of the template is easier than in the covalent assembly approach and often involves simply washing the materials in a suitable solvent.8... 

Yang and coworkers also used a surface imprinting approach to prepare nanotube membranes that exhibit selectivity for the molecule estrone.77 In this study, the silica nanotubes with pore diameters of 100 nm were synthesized within the cylindrical pores of nanopore alumina membranes. A covalent assembly approach was used to prepare the imprint.77 Zhang and coworkers have also recently shown how silica nanotubes can be used as an imprinting scaffold.78 In this example, trinitrotoluene (TNT)... 

The covalent assembly of functional Jt-systems is a general synthetic principle and in some cases they can even be achieved in a multi-component fashion. One of the most impressive examples is the very elegant access to covalently linked donor-fullerene arrangements by 1,3-dipolar cycloadditions with in situ-generated azomethine ylids [59]. However, here only the multi-component de novo synthesis of the chromophore structures will be considered. The major developments have been achieved in condensation-based and cross-coupling strategies. 

Fig. 2.1.10. Energy minimized structures of self-assembled [Cu (all-Sa)-ll 2]+-complex (MMFF-minimized, left) and of analogous covalently assembled tetra (BINOL) substituted spirobifluorene (all-S0)-12 (MM2-minimized, right).

Far more attempts have been undertaken to covalently assemble multicomponent structures with at least one Pc moiety, which will be briefly described thereafter. In particular the C6o fullerene has been connected to the Pc by using different methodologies. Besides the Pc-C6o dyads presented above, the Pc scaffold has also been covalently connected through employment of Diels-Alder reaction onto the... 

Alternatively, dendrimers may be synthesized directly by our original II Divergent Core Proliferation method. This method may involve the exponential covalent assembly of monomer units around a multi-valent core to produce branch cells in situ or it may involve the direct use of pre-formed branch cell reagents. In either case the resulting covalent structure consists of precise numbers of dendrons organized around the initiator core. 

The covalent assembly of guest-encapsulating host species has long been an area of research interest. The first examples of host species binding their guests within a three-dimensional array of interactions were the class of compounds known as cryptands [26,27]. The cryptands were designed as hosts for alkali metal cations and are based on macrobicyclic-polyethers (Fig. 2). Typically, cryptands are synthesised by the addition of a diacyl-chloride to an azacrownether (Scheme 1). 

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