Effect of Temperature on the Supramolecular Tubular Structure in Oriented Fibers of a Poly(methacrylate) with Tapered Side Groups

Kwon, Yong Ku; Чвалун, С. Н.; Blackwell, John; Percéc, Virgil; Heck, J.

doi:10.1021/ma00109a029

Cited by 121 publications

(79 citation statements)

References 1 publication

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“…This effect manifests itself in the signif icant macroscopic elongation of the samples. For example, H12 ABG PMA samples are elongated by 30% upon heating from room temperature to t 2 = 90°С [38]. It is noteworthy that the second phase tran sition in the samples (isotropization) occurs at the same critical size of columns in all compounds under study (Fig.…”

Section: Self Assembling Of Wedged Dendrons Based On Gallic Acid Derimentioning

confidence: 85%

Self-assembling supramolecular systems of different symmetry formed by wedged macromolecular dendrons

et al. 2012

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The main stages of the self assembling of supramolecular ensembles have been revealed by study ing different functional wedged macromolecules: polymethacrylates with tapered side chains based on gallic acid, their macromonomers, and salts of 2,3,4 and 3,4,5 tris(dodecyloxy)benzenesulphonic acid. The first stage is the formation of individual supramolecular aggregates (long cylinders or spherical micelles) due to the weak noncovalent interactions of mesogenic groups and the subsequent ordering in these aggregates, which is accompanied by a decrease in the free energy of the system. Supramolecular aggregates, in turn, form 2D or 3D lattices. The shape of supramolecular aggregates and its change with temperature are delicate func tions of the mesogen chemical structure; this circumstance makes it possible to rationally design complex self assembling systems with the ability to respond smartly to external stimuli. X ray diffraction analysis allows one to study the structure of supramolecular systems with different degrees of order, determine the type of mesophases formed by these systems, and reveal the phase behavior of the material. Particular attention has been paid to the method for reconstruction of electron density distribution from the relative reflection intensity. The application of a suite of experimental methods, including wide and small angle X ray diffrac tion, molecular modeling, differential scanning calorimetry, and polarization optical microscopy, allows one to establish the relationship between the shape of the structural unit (molecule or molecular aggregate), the nature of the interaction, and the phase behavior of the material.

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Section: Self Assembling Of Wedged Dendrons Based On Gallic Acid Derimentioning

confidence: 85%

Self-assembling supramolecular systems of different symmetry formed by wedged macromolecular dendrons

et al. 2012

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“…X-ray analysis and optical microscopy [3,5] have shown that H12-ABG-4EO-PMA, H12-ABG-4EO-OH, and many of their homologues form columnar hexagonal (Col h ) phases. DSC heating scans for H12-ABG-4EO-PMA show two endotherms at~40 and~100 8C.…”

Section: Introductionmentioning

confidence: 99%

A second columnar liquid crystalline phase formed by polymers with highly tapered side chains

Чвалун

Blackwell²,

Cho

et al. 1999

Acta Polym.

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Previous work has shown that polymethacrylates with highly tapered side groups, such as poly{2-{2-[2-(2-methacryloyloxyethoxy)-ethoxy]ethoxy}ethyl-3,4,5-tris-(p-dodecyloxy-benzyloxy)benzoate} (H12-ABG-4EO-PMA), form columnar hexagonal (Col h , previously designated v h ) liquid crystalline structures. The small angle X-ray data for drawn fibers of H12-ABG-4EO-PMA, and also those of its hydroxy-terminated monomer precursor and decyloxy-homologue, contain several weak equatorial Bragg reflections in addition to those characteristic of the Col h phase. The intensities of these extra reflections decline progressively on heating and disappear before the temperature of the Col h -to-isotropic transition is reached. It is proposed that the as-drawn fibers contain a second phase, which is probably a columnar liquid crystalline structure in view of the decreases in the observed d-spacings with increasing temperature. The additional reflections are indexed by a two dimensional monoclinic lattice, which probably contains columns with elliptical cross-section. The lower symmetry is consistent with the formation of a tilted columnar phase analogous to those formed by certain low molecular weight discotic materials.

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“…At the macroscopic level the potential benefits of well-defined dendritic structures are also clear. Some dendritic materials have been identified as nanoscopic host molecules (Hawker et al, 1993;Ottaviani et al, 1995;Newkome et al, 1991;Jansen et al, 1994), dendritic catalysts (Bhyrappa et al, 1996;Brunner, 1995), liquid crystals (Kwon et al, 1995;Ponomarenko et al, 1996), gene vectors (Kukowska-Latallo et al, 1996), contrast agents for magnetic resonance imaging (Wiener et al, 1994) and as tools for immunoassay (Tam, 1996;Singh et al, 1996). Since the early 1980s the main emphasis in dendrimer research has been on their synthesis Tomalia and Durst, 1990;Issberner et al, 1995;Newkome et al, 1996;Fréchet and Hawker, 1996;Zeng and Zimmerman, 1997;Matthews et al, 1998;Voit, 1995).…”

Section: Introductionmentioning

confidence: 99%

Hydrodynamic properties of carbohydrate-coated dendrimers

Корнеева

Jumel

Harding

et al. 1999

Carbohydrate Polymers

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The hydrodynamic properties of poly(propylene imine) dendrimers, modified with outer-surface b-thiolactosyl residues (''lactodendrimers'') of generation number 1-5, have been investigated by velocity sedimentation, translational diffusion, and viscosity measurements in 0.165% NaCl aqueous solution. It has been demonstrated that apparent molecular weights (from the Svedberg equation) M sD of synthetic lactodendrimers, determined by sedimentation and diffusion experiments, are consistent with complete functionalization of initial poly-(propylene imine) dendrimers with sugar residues. The values of M sD range from 1900 to 45000 Da for generation numbers 1-5. Corresponding hydrodynamic (''equivalent Stokes'') radii range from ϳ10 to ϳ37 Å . Scaling relations of the conformation-dependent sedimentation coefficient, translational diffusion coefficient and intrinsic viscosity with molecular weight have been considered in detail and are all indicative of a spherical molecule with an inhomogeneous distribution of density (Mark-Houwink-Kuhn-Sakurada a, b and , coefficients of ϳ0.24, ϳ0.69 and ϳ0.31, respectively). ᭧

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Effect of Temperature on the Supramolecular Tubular Structure in Oriented Fibers of a Poly(methacrylate) with Tapered Side Groups

Cited by 121 publications

References 1 publication

Self-assembling supramolecular systems of different symmetry formed by wedged macromolecular dendrons

Self-assembling supramolecular systems of different symmetry formed by wedged macromolecular dendrons

A second columnar liquid crystalline phase formed by polymers with highly tapered side chains

Hydrodynamic properties of carbohydrate-coated dendrimers

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