ABSTRACT:The structuring role of benzene-1,3,5-tricarboxamide (BTA) groups for the catalytic activity of single chain polymeric nanoparticles in water was investigated in the transfer hydrogenation of ketones. To this end, a set of segmented, amphiphilic copolymers was prepared, which comprised oligo (ethylene glycol) side chains to impart water solubility, BTA and/or lauryl side chains to induce hydrophobicity and diphenylphosphinostyrene (SDP) units in the middle part as a ligand to bind a ruthenium catalyst. All copolymers were obtained by reversible addition-fragmentation chain transfer (RAFT) polymerization and showed low dispersities (M w /M n 5 1.23-1.38) and controlled molecular weights (M n 5 44-28 kDa). A combination of circular dichroism (CD) spectroscopy and dynamic light scattering (DLS) showed that all copolymers fold into a single chain polymeric nanoparticles (SCPNs) as a result of the helical selfassembly of the pendant BTA units and/or hydrophilic-hydrophobic phase separation. To create catalytic sites, RuCl 2 (PPh 3 ) 3 was incorporated into the copolymers. The Cotton effects of the copolymers before and after Ru(II) loading were identical, indicating that the helical self-assembly of the BTA units and the complexation of SDP ligands and Ru(II) occurs in an orthogonal manner. DLS revealed that after Ru(II) loading, SDP-bearing copolymers retained their single chain character in water, while copolymers lacking SDP units clustered into larger aggregates. The Ru(II) loaded SCPNs were tested in the transfer hydrogenation of cyclohexanone. This study reveals that BTA induced stack formation is not crucial for SCPN formation and catalytic activity; SDP-bearing copolymers folded by Ru(II) complexation and hydrophobic pendants suffice to provide hydrophobic, isolated reaction pockets around Ru(II) complexes. V C 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52,[12][13][14][15][16][17][18][19][20]

A Ru(II)-based catalyst trapped within an amphiphilic, folded polymer is employed for the oxidation of secondary alcohols to their corresponding ketones using tBuOOH as the oxidant. Under the applied catalytic conditions, the polymer catalyst forms a compartmentalized structure with a hydrophobic interior. We selected secondary alcohols that differ in hydrophobicity, reactivity, and steric hindrance as substrates, with the aim to elucidate how this affects the rate and the end conversion of the oxidation reaction. Our investigations show that the Ru(II)-based catalyst is very efficient for oxidation reactions in water. Moreover, high selectivity toward the more hydrophobic substrate is observed, which originates from the hydrophobic interior of the compartmentalized catalyst system. This hydrophobic selectivity is also observed in the reverse reaction, the transfer hydrogenation.

We herein report the synthesis and characterization of ABC-type triblock copolymers containing two complementary association motifs and investigate their folding into well-defined polymeric nanoparticles under diluted conditions via intramolecular orthogonal hydrogen bonding. The precursor ABC-type triblock copolymers are prepared via reversible addition–fragmentation chain transfer (RAFT) polymerization bearing primary alkyl bromide on A, protected alkyne on B, and protected hydroxyl pendant groups on the C units. The dithioester groups of the RAFT polymers are quantitatively removed by radical-induced reduction before the side-chain functionalization. The complementary motifs, i.e., Hamilton wedge (HW, A block), benzene-1,3,5-tricarboxamide (BTA, B block), and cyanuric acid (CA, C block), are incorporated into the linear triblock copolymers side chains via post­functionalization. The self-assembly processes of the HW and CA supramolecular motifs are followed by nuclear magnetic resonance (1H NMR) spectroscopy at ambient and elevated temperature in various solvents. The helical BTA stack formation is monitored by circular dichroism (CD) spectroscopy. In addition, the final aggregates formed by these two orthogonal forces, namely HW-CA pseudo-cross-linking and BTA stacking, are characterized by static and dynamic light scattering (SLS and DLS) as well as atomic force microscopy (AFM).

Cataloged from PDF version of article.Cucurbituril homologues are multi-functional macrocycles that can find applications in many areas and have numerous interesting features setting them apart from the other macrocycles. Among them, the ability of one of the cucurbituril homologues, cucurbit[6]uril (CB6), to catalyze 1,3-dipolar cycloaddition in a regiospecific fashion is truly exceptional. Using this feature, small molecules can be clicked together to form complex structures in a very efficient way. Accordingly, in this article we review recent research involving the use of CB6-catalyzed 1,3-dipolar cycloaddition or the click reaction of CB6 in the construction of supramolecular assemblies including rotaxanes, pseudorotaxanes, polyrotaxanes, polypseudorotaxanes, molecular switches, machines, and nanovalves

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Ties us together: The selectivity and recognition behavior of cucurbit[n]uril (CB[n]) homologues (n=6,7,8) towards a ditopic guest containing two distinct binding sites is explored. CB6, CB7, and CB8 recognize and self‐sort the binding sites according to their size, shape, and chemical nature. In the presence of both CB6 and CB8 a hetero[4]pseudorotaxane is formed.

Achieving the perfection of Nature in forming ordered structures in three dimensions is one of the great challenges for supramolecular chemists.Recently, the merger of supramolecular and polymer chemistry resulted in the preparation of polymers with pendant supramolecular motifs that intramolecularly self-assemble in solution into structures of defined size and shape. This review summarizes the recent progress made in preparing and characterizing such compartmentalized structures in solution in which the internal structure arises from non-covalent bond formation, making the obtained particles dynamic and adaptable. In addition, the potential of these so-called dynamic single-chain polymeric nanoparticles (SCPNs) is explored. We highlight the potential of SCPNs for catalysis in water and sensing, functions that all arise as a result of the well-defined conformations that are attained by directional non-covalent interactions

The effects of cucurbit[n]uril on the dissolution and the photophysical properties of nonionic conjugated polymers in water are described. For this purpose, a fluorine-based polymer, namely, poly[9,9-bis{6(N,N-dimethylamino) hexyl}fluorene-co-2,5-thienylene (PFT) was synthesized and characterized by spectroscopic techniques including 1D and 2D NMR, UV-vis, fluorescent spectroscopy, and matrix-assisted laser desorption mass spectrometry (MALDI-MS). For the first time, it was demonstrated that a nonionic conjugated polymer can be made soluble in water through an inclusion complex formation with CB8. The structure of the complex was elucidated by NMR experiments including 1H and selective 1D-NOESY. This complex emits green and is highly fluorescent with fluorescent quantum yield of 35%. In contrast, CB6 or water-soluble CB7 although they are chemically identical to CB8 do not have any effect on the dissolution and photophysical properties of PFT. By preparing a protonated version of PFT, the optical properties of PFT in methanol, protonated PFT and PFT@CB8 in water have been studied and compared. It was also observed that the morphology of the polymer PFT was affected by the presence of CB8. Thus CB8-assisted self-assembly of polymer chains leads to vesicles formation; these structures were characterized by DLS, AFM, SEM, and TEM fluorescent optical microscopy. © 2010 Wiley Periodicals, Inc