Rotaxane-type hyperbranched polymers are synthesized for the first time from A₂B type semi-rotaxane monomers formed in situ via complexation of bis(m-phenylene)-32-crown-10 dimethanol (1) and two paraquat ω-n-alkylenecarboxylic acid derivatives with tris(p-t-butylphenyl)methylphenylalkylene stoppers (8 and 9). Rotaxane and taco complexes exist in solutions of the hyperbranched polyesters in CD₃CN/CDCl₃ as confirmed by NMR spectroscopy, but the taco complexes, which derive from non-rotaxanated paraquat units, disappear in DMSO-d₆. NMR spectroscopy indicates the portion of rotaxanes strongly interlocked by the environment (inner rotaxanes) is larger in HP1•9, which has longer alkylene spacers, perhaps indicating a higher degree of polymerization. The molecular size increases upon formation of the hyperbranched polymers are confirmed by dynamic light scattering and by viscometry. As with covalent hyperbranched polymers a number of potential applications exist; the unique mechanically linked character and the presence of uncomplexed host and guest moieties foreshadow the use of such systems for their responses to external stimuli with the added benefit of providing molecular recognition sites useful as delivery vehicles. Use of other host-guest motifs to form the semirotaxane A₂B monomers is possible and complementary systems with higher binding constants will enable efficient syntheses of high molecular weight, mechanically linked hyperbranched polymers. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 1647–1658

New bis(ω-hydroxyalkyl)imidazolium and 1,2-bis[N-(ω-hydroxyalkyl)imidazolium]ethane salts are synthesized and characterized; most of the salts are room temperature ionic liquids. These hydroxyl end-functionalized ionic liquids are polymerized with diacid chlorides, yielding polyesters containing imidazolium cations embedded in the main chain. By X-ray scattering, four polyesters are found to be semicrystalline at room temperature: mono-imidazolium-C₁₁-sebacate-C₆ (4e), mono-imidazolium-C₁₁-sebacate-C₁₁ (4c), bis(imidazolium)ethane-C₆-sebacate-C₆ (5a), and bis(imidazolium)ethane-C₁₁-sebacate-C₁₁ (5c), all with hexafluorophosphate counterions. The other imidazolium polyesters, including all those with bis(trifluoromethanesulfonyl)imide (TFSI⁻) counterions, are amorphous at room temperature. Room temperature ionic conductivities of the mono-imidazolium polyesters (4 × 10⁻⁶ to 3 × 10⁻⁵ S cm⁻¹) are higher than those of the corresponding bis-imidazolium polyesters (4 × 10⁻⁹ to 8 × 10⁻⁶ S cm⁻¹), even though the bis-imidazolium polyesters have higher ion concentrations. Counterions affect ionic conduction significantly; all polymers with TFSI⁻ counterions have higher ionic conductivities than the hexafluorophosphate analogs. Interestingly, the hexafluorophosphate polyester, 1,2-bis(imidazolium)ethane-C₁₁-sebacate-C₁₁ (5c), displays almost 400-fold higher room temperature ionic conductivity (1.6 × 10⁻⁶ S cm⁻¹) than the 1,2-bis(imidazolium)ethane-C₆-sebacate-C₆ analog (5a, 4.3 × 10⁻⁹ S cm⁻¹), attributable to the differences in the semicrystalline structure in 5c as compared to 5a. These results indicate that semicrystalline polymers may result in high ionic conductivity in a soft (low glass tranition temperature, T_g) amorphous phase and good mechanical properties of the crystalline phase.

Complexation of anions, cations and even ion pairs is now an active area of investigation in supramolecular chemistry; unfortunately it is an area fraught with complications when these processes are examined in low polarity organic media. Using a pseudorotaxane complex as an example, apparent K_a2 values (=[complex]/{[salt]_o−[complex]}{[host]_o−[complex]}) for pseudorotaxane formation from dibenzylammonium salts (2-X) and dibenzo-[24]crown-8 (1, DB24C8) in CDCl₃/CD₃CN 3:2 vary with concentration. This is attributable to the fact that the salt is ion paired, but the complex is not. We report an equilibrium model that explicitly includes ion pair dissociation and is based upon activities rather than molar concentrations for study of such processes in non-aqueous media. Proper analysis requires both a dissociation constant, K_ipd, for the salt and a binding constant for interaction of the free cation 2⁺ with the host, K_a5; K_a5 for pseudorotaxane complexation is independent of the counterion (500 M⁻¹), a result of the complex existing in solution as a free cation, but K_ipd values for the salts vary by nearly two orders of magnitude from trifluoroacetate to tosylate to tetrafluoroborate to hexafluorophosphate anions. The activity coefficients depend on the nature of the predominant ions present, whether the pseudorotaxane or the ions from the salt, and also strongly on the molar concentrations; activity coefficients as low as 0.2 are observed, emphasizing the magnitude of their effect. Based on this type of analysis, a method for precise determination of relative binding constants, K_a5, for multiple hosts with a given guest is described. However, while the incorporation of activity coefficients is clearly necessary, it removes the ability to predict from the equilibrium constants the effects of concentration on the extent of binding, which can only be determined experimentally. This has serious implications for study of all such complexation processes in low polarity media.

An AA bisphenolic monomer (13), an AB activated fluoro-phenolic monomer (14), and an AB₂ alcohol-diester monomer precursor (17), all based on the isoquinoline nucleus, were prepared using Reissert compound chemistry. Additionally, model reactions established the efficiency of condensation of isoquinoline Reissert compounds with dihaloalkanes, providing evidence of the potential of this reaction to produce high molecular weight polymers, which was subsequently realized. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

MALDI-TOF MS of the heteroditopic compound 2-(benzylammoniomethyl)dibenzo-24-crown-8 hexafluorophosphate (4) revealed oligomeric “daisy chain” species up to the hexamer. Similar results were obtained for 2-(6′-hydroxyhexylammoniomethyl)dibenzo-24-crown-8 hexafluorophosphate (8). The complexations of two substituted dibenzylammonium salts, 2,2′-dimethyldibenzylammonium hexaflurophosphate (9a) and 2,2′,5-trimethoxydibenzylammonium hexafluorophosphate (9b), with dibenzo-24-crown-8 were examined as models for slippage systems; association constants are reported for these systems. A crystal structure is reported for the new dimethylbenzylammonoium pseudorotaxane. The trimethoxy analog is shown to be capable of slippage formation of a rotaxane, albeit in low yield. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 975–985, 2010

The chemistry of Reissert compounds has been used to synthesize activated difluorotetraketone monomers containing two coupled isoquinolyl moieties, linked at either the 1,1′- or 4,4′-positions. These monomers offer routes to novel families of poly(heteroarylene ether)s. New 4,4′-coupled bis(Reissert compound) 9 containing 4,4′-diketo moieties failed to afford the desired difluorotetraketo monomer upon attempted rearrangement. However, analogous bis(Reissert compound) 19 containing 4,4′-dibenzyl units did so, via aldehyde condensation, hydrolysis of the intermediate ester and oxidation of the four benzylic moieties to keto groups; thus the novel difluorotetraketone monomer 10 was prepared. Novel bis(Reissert compound)s 24, 28, and 35 were synthesized from diacid chlorides and 4-(p-fluorobenzyl)isoquinoline. Rearrangement of 24 to the diketone 29, followed by oxidation of the 4-benzyl moieties resulted in difluorotetraketone monomer 30 containing a 1,1′-linked bisisoquinoline. The 1,1′-linked bis(isoquinolylfluorodiketo) monomer 38, isomeric with 10, was prepared from 4-(p-fluorobenzyl) Reissert compound 36 by condensation with terephthaldehyde, ester hydrolysis to diol 37, and oxidation. In the course of this effort, a number of new isoquinoline Reissert compounds were synthesized as model systems. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3856–3867, 2010

The complexation between dibenzo-24-crown-8 (1) and diquat (2) was investigated in detail by NMR, MS and X-ray analysis. It was found that dibenzo-24-crown-8 and diquat formed a 1:1 complex 1·2 in acetone with K_a=2.0×10² L·mol⁻¹, but, as shown by X-ray analysis, a crystalline 2:1 host:guest inclusion complex 1₂·2 was isolated, in which a single molecule of diquat is enclosed in the concave cavity provided by two dibenzo-24-crown-8 host molecules. Both results are different from the previously assumed stoichiometry of the complexation between dibenzo-24-crown-8 and diquat. This result enriches the range of host-guest complexes based on dibenzo-24- crown-8 and provides new opportunities for developing more complicated structures and chemosensors for diquat.

Dibenzo-24-crown-8-terminated polystyrene (5) was chain extended to “dimeric” 8 by pseudorotaxane formation with a ditopic guest, α,ω-bis[p-(N-benzylammoniomethyl)phenoxy]heptane bis(hexafluorophosphate) (7). The three-armed star polymer 11 was similarly formed by complexation of the dibenzo-24-crown-8-terminated polystyrene (5) with a tritopic secondary ammonium salt, 1,3,5-tris[p-(benzylammoniomethyl)phenyl]benzene tris(hexafluorophosphate) (10). Another three-armed star polymer 13 was self-assembled from dibenzo-24-crown-8-terminated polystyrene (5) and a tetratopic paraquat compound, 1,2,4,5-tetrakis{p-N-[(N′-methyl-4,4′-bipyridinium)methylphenyl]}benzene octakis(hexafluorophosphate) (12). The above chain extension and star polymer formation processes seemed to be cooperative; that is, the second and third complexation steps proceed with stepwise higher efficiencies than statistically expected. Dibenzo-24-crown-8-terminated polystyrene (5) was chain extended with secondary ammonium terminated polystyrene 14, forming 16, and also self-assembled with a secondary ammonium ion terminated polyisoprene 15 to form supramolecular block copolymer 17. These processes were examined by NMR, mass spectrometry and viscometery. Thus, although binding in these systems is not particularly strong (association constants <10⁴ M⁻¹), these examples provide proof-of-principle that pseudorotaxane formation is a viable concept for chain extension and self-assembly of novel types of block copolymers and star polymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3518–3543, 2009

Multitopic dibenzylammonium derivatives (4) of C₆₀ were prepared by Bingel reactions of C₆₀ with a malonate diester (2) containing two t-BOC protected dibenzylamine moieties, followed by deprotection and protonation. Self-assembly of model pseudorotaxanes 5 from the multidibenzylammonium C₆₀ derivatives with dibenzo-24-crown-8 was studied by ¹H NMR spectroscopy and mass spectrometry. Self-assembly of linear and star-shaped pseudorotaxanes 8 with up to 12 arms based on polystyrenes bearing terminal DB24C8 host units (7) and the guest functionalized C₆₀ salts was demonstrated by ¹H NMR spectroscopy and solution phase viscometry. These studies provide further evidence of the potential of supramacromolecular chemistry in construction of complex polymeric architectures. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6472–6495, 2009

A small cyclophane, bis(5-carbometh-oxy-1,3-phenylene)-14-crown-4 (BCMP14C4, 3) and its diacid, bis(5-carboxy-1,3-phenylene)-14-crown-4 (4), were synthesized and characterized. The solid-state molecular structures of 3 and 4 were determined by X-ray crystallography as ladder or stepped conformations in which the two aromatic rings are antiparallel to each other without overlap and the ethylene tethers both take trans-conformations. Diester 3 is formed in the lowest cyclization yield (under the same reaction conditions) and exhibits the highest melting point compared to its larger ring (20-, 26- and 32-membered) analogs. In CD₂Cl₂ solution, diester 3 exists predominantly as a nonplanar gauche–gauche structure as deduced by H NMR studies. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:48–54, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20393