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We explore the behavior of a supramolecular polymer subjected to repeated shear-startup runs. This interesting test was proposed 50 years ago as a measure of disentanglement kinetics in linear polymers. A key experimental finding was that the recovery time (originally attributed exclusively to the relaxation of partially disentangled state) decreased with increasing imposed shear rate. Recent modeling and simulations put the work in perspective by showing that the recovery time mainly reflects chain reorientation. However, for the present supramolecular polymer, the recovery time was found to be rate independent. This drastic difference is attributed to the different mechanism of stress relaxation, which involves a combination of bond breaking/recombination and reptation processes. Hence, the repeated shear-startup protocol may serve as a sensitive indicator of (supramolecular) polymer signatures and a tool to evaluate stress relaxation models.

The functional restoration of natural tissues in a variety of cardiovascular applications is the main objective of Endogenous Tissue Restoration (ETR). The recent progress in the development of biocompatible, biodegradable, and tunable biomaterials with unprecedented properties allow the next steps from laboratory studies to clinical studies. The independent control over mechanical properties and biodegradability provided by the combination of covalent and non-covalent bonds makes supramolecular polymers uniquely qualified for ETR. This paper will provide further details on the mechanism of ETR and will provide a perspective on the preclinical and clinical application of supramolecular polymers for ETR. In addition to various reports on chronic studies in large animal models, three world-first clinical studies are reported, demonstrating the potential of supramolecular technology in bringing ETR to patients.

Significance As the formation of quasicrystalline ordering in both metal alloys and soft matters reinforces the scale-invariance principle, however, it remains unknown that why metallic quasicrystals prefer decagonal quasicrystalline (DQC, 10-fold) ordering, and the condensed soft maters only exhibit dodecagonal quasicrystalline (DDQC, 12-fold) ordering. By tuning the self-sorting ability in a pair of giant molecules, the well-mixed binary blends generate a metastable DQC phase and corresponding unprecedent phase sequence (DQC → DDQC → Frank–Kasper σ) during thermal annealing. These peculiar assembling behaviors result from interplays of submesoatomic and mesoatomic packings. Reducing the self-sorting strength has induced an extra complexity in the sub-mesoatomic packings of giant molecules, which further influences the clustering on the mesoatomic level., The quasiperiodic structures in metal alloys have been known to depend on the existence of icosahedral order in the melt. Among different phases observed in intermetallics, decagonal quasicrystal (DQC) structures have been identified in many glass-forming alloys yet remain inaccessible in bulk-state condensed soft matters. Via annealing the mixture of two giant molecules, the binary system assemblies into an axial DQC superlattice, which is identified comprehensively with meso-atomic accuracy. Analysis indicates that the DQC superlattice is composed of mesoatoms with an unusually broad volume distribution. The interplays of submesoatomic (molecular) and mesoatomic (supramolecular) local packings are found to play a crucial role in not only the formation of the metastable DQC superlattice but also its transition to dodecagonal quasicrystal and Frank–Kasper σ superlattices.

Supramolecular glycopolymers exhibiting inherent dynamicity, tunability, and adaptivity allow us to arrive at a deeper understanding of multivalent carbohydrate-carbohydrate interactions and carbohydrate-protein interactions, both being essential to key biological events. The impacts of the carbohydrate segments in these supramolecular glycopolymers towards their structure, dynamics, and function as biomaterials are addressed in this minireview. Bottlenecks and challenges are discussed, and we speculate about possible future directions.

The synthesis and characterization of two chiral dendrimers, 1 and 2, in their racemic form is presented. The chirality is based on the construction of 4 constitutionally different, but chemically similar, branches to an achiral core. A multi-substituted pentaerythritol derivative is used as core and Frechet's aromatic-ether dendritic wedges of different generation are used as branches. The synthetic approach makes use of the fact that the 4 branches are attached consecutively by a selective deprotection of the core. Both chiral dendrimers of different size have been synthesized from the same precursor. 1H-NMR spectroscopy indicates an overall chiral shape for 1, while for both 1 and 2 stratified structures are observed. Several attempts to resolve both dendrimers into their individual enantiomers have not been successful so far, giving rise to a discussion on the degree of chirality of these dendrimers of nanometer dimensions.

In the past few decades, supramolecular polymers have emerged as novel materials with a wide variety of different functions. In this essay we reflect on the history of supramolecular polymers, their function in various applications and the challenges to be met in the near future.

Polar telechelic polymers with OH end groups were functionalized with a reactive synthon consisting of a ureidopyrimidinone unit connected to an isocyanate functionality. OH-telechelic polyethers, polyesters, and polycarbonates were functionalized with this synthon. The material properties of these low mol. wt. polymers (Mw=2.0 kg/mol-3.5 kg/mol) improve remarkably upon functionalization. Whereas the polyether with OH end-groups is a viscous fluid at room temp., the corresponding functionalized polymer is a soft, elastic solid. The semicryst. polycarbonate and polyester change from waxy and brittle solids to strong and slightly elastic materials upon functionalization. The polymers were studied with DSC, DMTA, and tensile tests

No abstract.

The dimeric structure of bis(acetylacetonato)(2-hydroxyphenolato)aluminium (I) has been elucidated using NMR spectroscopy and vapour phase osmometry. It has been shown that in solution the three geometrical isomers of the dimer are in equilibrium with monomeric species. At high concentrations even trimeric and/or polymeric species have to be considered in the equilibrium.

We have reported the self-assembly of nucleotide-attached bolaamphiphiles in aqueous solutions1). On the other hand, π -conjugated oligomers are one of the attentions in electro-optical chemistry2). In this research, we have synthesized an oligo(p-phenylenevinylene) having a thymidylic acid at each end, and examined its self-assembly and binary self-assembly with complementary oligoadenylic acid (dA20). The self-assembled structures were examined by AFM, FE-SEM, UV and CD spectroscopy. We can find non-helical columnar structures by AFM and FE-SEM observations from the self-assembly of T-OPV-T with diameters of 3.8 nm, which well fits with the molecular length of T-OPV-T. Helical columnar structures are observed from the binary self-assembly of T-OPV-T and dA20, with 5.8nm diameters and 35nm helical pitches. The UV and CD measurements reveal that the formation of complementary A-T base pairs and π- π stacking interaction between the OPV moieties in the binary-self-assembly.

Three series of alternating donor-acceptor substituted co-oligomers (with different chain length), consisting of pyrrole or thiophene as the electron-rich unit and quinoxaline or 2,1,3,-benzobisthiadiazoles as the electron-deficient unit, were prepd. by Pd-catalyzed Stille coupling methodol. The incremental bathochromic shift of the absorption max. upon chain elongation of the three series of oligomers is less than that of the homo-oligomers of thiophene and pyrrole, which is caused by a diminished dispersion of the LUMO level upon chain elongation. The latter conclusion was drawn after comparing the oxidn.- and redn. behavior of the thiophene/benzothiadiazole oligomers with that of thiophene oligomers. The incremental bathochromic shift shows similarity for all three series of oligomers, which is used as a tool in the band-gap engineering of donor-acceptor substituted conjugated polymers

Supramol. polymers, in which the monomer units are linked together by non-covalent interactions, provide unique opportunities to design responsive materials, as the system remains in const. equil. with its environment. One of the most interesting aspects is the equil. between linear and cyclic structures formed in soln. and in bulk material, as this strongly influences soln. and material properties. Bifunctional mols. based on the strongly quadruple hydrogen bonding 2-ureido-4[1H]-pyrimidinone moiety form long supramol. polymers as well as small cyclic oligomers in soln. The equil. between the different aggregates is dependent on external conditions such as temp., but also on the geometry of the monomers. Here we report that small changes in the structure of the spacer between the hydrogen bonding units have a striking effect on the tendency of the mol. to form cyclic structures and, with that, on soln. viscosity.

A discussion on epoxy resin network formation and properties with emphasis on study of the mechanisms of epoxide polymn. via phosphorescence and NMR spectroscopic methods. [on SciFinder (R)]

Not available.

We have synthesized oligo-(p-phenylenevinylene) (OPV) having a thymidylic acid at each end (1) using phosphoramidite method. Self-assembly of the compound 1 was performed in an aqueous solution and examined by FE-SEM, AFM, UV, and CD spectroscopy. As a result, we can obtain non-helical nanofibers with diameters of 3.9 nm and lengths of several μm. The UV spectroscopy suggests that the nanofibers are stabilized by π-π-stacking interactions between the OPV moieties.

To study the ability of dendrimer-supported peptides to act as vaccines, four peptides based on the structure of malaria parasite Plasmodium falciparum CS protein were synthesized, modified with a 'click-tail' which will enable insertion of the peptide into a dendrimer via 'clicking' into the interstices between dendrimer end groups. CD spectroscopy of the four peptides showed random coil behavior in aq. soln. in the absence of dendrimer. The four peptides were Ac-P8, (P8 = Gly-Ala-Asn-Pro-Asn-Ala-Ala-Gly-), Click-P8 (Click = -NH(CH2)6NHC(O)NHCH2CO2H), Ac-P8-Click, and Click-P8-Click

Perfluoro-functionalized poly(propylene imine) dendrimers have been used as reactive extractants for anionic species and as phase transfer catalysts for two types of reactions. Different generations of dendrimers have been used for applications in carbon dioxide. First, the reactive extraction of the inorganic ions permanganate and dichromate, from an aqueous phase to a supercritical carbon dioxide phase, has been studied using the functionalized dendrimers. The yield for these extractions is rather low, indicating that the perfluoro-functionalized poly(propylene imine) dendrimers are not suited for oxidation reactions with these ions in carbon dioxide. Second, the poly(propylene imine) dendrimers have been used as a phase transfer catalyst for the halogen exchange reaction of benzyl chloride into benzyl bromide and for the esterification of oxalic acid with pentafluorobenzylbromide. In contrast with the low extraction yield for the inorganic permanganate and dichromate ions, a high reaction rate was obtained for the halogen exchange reaction with the functionalized dendrimers as phase transfer catalysts. It is found that the rate of reaction for both cases depends on the generation number of the dendrimer. For the higher-generation dendrimers, it is more difficult for the substrate to migrate from the bulk carbon dioxide phase to the interior of the dendrimer. This indicates that the mass transfer of the reagents from the organic phase into the interior of the dendrimer determines the reaction rate for the fourth and higher generation dendrimers. A model is proposed to describe the extraction and the phase transfer catalysis based on the fact that the modified dendrimers combine micellar properties with those of standard phase transfer catalysts. From the different experiments it can be concluded that the perfluoro-functionalized poly(propylene imine) dendrimers have great potential as multisite phase transfer catalysts.

A review with numerous refs. on the elec. conducting, ferromagnetic, and nonlinear optical properties of polymers in relation to their applications in optical and electronic devices. [on SciFinder (R)]