Abstract

This work focused on the synthesis and aqueous self-assembly of a series of novel hyperbranched star copolymers with a hyperbranched poly[3-ethyl-3-(hydroxymethyl)oxetane] (HBPO) core and many linear poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) arms. The copolymers can synchronously form unimolecular micelles (around 10 nm) and large multimolecular micelles (around 100 nm) in water at room temperature. TEM measurements have provided direct evidence that the large micelles are a kind of multimicelle aggregates (MMAs) with the basic building units of unimolecular micelles. It is the first demonstration of the self-assembly mechanism for the large multimolecular micelles generated from the solution self-assembly of hyperbranched copolymers.

Bringt Farbe rein: Selbstorganisation eines amphiphilen, stark verzweigten Poly(amidoamins) auf einem festen Substrat liefert Filme mit Honigwabenmuster. Über die Konzentration der Polymerlösung lässt sich die Filmdicke im Bereich von Nano- bis Mikrometern einstellen. In unterschiedlichen Farben lumineszierende Filme werden durch Einschluss von Farbstoffen in das Polymer erhalten (siehe Bild, R=(CH₂)₁₄CH₃, rote Kugel=Farbstoffmolekül).

A film to dye for: Honeycomb-patterned films have been fabricated by the self-assembly of amphiphilic hyperbranched poly(amidoamine) on solid substrates. The film thickness can be varied from the nanometer to micrometer scale simply by changing the concentration of the polymer solution. Luminescent films of different colors can be prepared by encapsulating various dyes into the polymer (see picture, R=(CH₂)₁₄CH₃, red sphere=dye molecule).

Summary: Covalent surface functionalization of carbon nanotubes with polypeptides is promising for possible medical applications. This work presents a graft-from approach to perform the polypeptide modification of multiwalled carbon nanotubes (MWNTs). The raw MWNTs are first amine-functionalized. The amine-functionalized MWNTs are then used as the initiator to initiate the ring-opening polymerization of γ-benzyl-L-glutamate N-carboxyanhydride (BLG-NCA), to result in the polypeptide-grafted MWNTs. FT-IR, XPS, and TGA data demonstrate that the functionalization is successful. The TEM images of the products show that the thickness of the polypeptide shell of the PBLG-MWNT is about 4.5–22 nm. Using the facile route developed here, carbon nanotubes functionalized with other types of polypeptides can be easily fabricated using the corresponding NCAs.

Summary: This work reports a new type of poly(ε-caprolactone) (PCL) robust hollow sphere with controllable biodegradability, produced by grafting PCL shells from the surface of silica sphere cores and removing the template cores. Bis(ε-caprolactone-4-yl) (BCY) composed of two ε-caprolactone molecules was used as the crosslinker, which not only greatly strengthened the PCL hollow spheres but also brought hardly any non-biodegradable component into the system. Solubility experiments and biodegradation tests show that the crosslinked PCL hollow spheres were robust both in water and acetone, and were completely biodegradable with characteristics of controllable biodegradability according to the content of the BCY. The Rhodamine release test indicated that the release rate of encapsulated drugs in the PCL hollow spheres was controlled by diffusion and the biodegradability of the PCL molecules, and the latter mechanism will dominate when more enzymes are involved.

Eine supramolekulare Methode, um Polymerarchitekturen einzustellen, wird anhand der Synthese von unterschiedlich stark verzweigten Poly(sulfonamin)-Proben nur durch Variation der Menge an Wirt (β-Cyclodextrin) vorgestellt (siehe Bild). Mit weiter veränderten Polymerketten sind Kondensationspolymere mit ungewöhnlichen Topologien, Funktionalitäten und Eigenschaften zugänglich.

Isothermal and nonisothermal crystallization kinetics of even-odd nylon 10 11 were investigated by differential scanning calorimetry (DSC). Equilibrium melting point was determined to be 195.20°C. Avarmi equation was adopted to describe isothermal and nonisothermal crystallization. A new relation suggested by Mo was used to analyze nonisothermal crystallization and gave a good result. The crystallization activation energies have been obtained to be −583.75 and −270.06 KJ/mol for isothermal and nonisothermal crystallization, respectively. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1637–1643, 2005

Step heating melt polycondensation was adopted in the preparation of polyamides based on 1,16-octadecane diacid and α,ω(CH₂)_2n diamines (n = 1–6). The structure was confirmed by various spectroscopic techniques (IR, Raman, ¹H-NMR, and ¹³C-NMR). High molecular masses were obtained only in the presence of an excess of diamine and when the diamine possessed low volatility. The molecular masses were between (0.94 and 2.1) × 10⁴ Da for all polyamides under consideration. An excellent correlation between size exclusion chromatography and ¹H-NMR data was demonstrated in the measurement of the degree of polymerization. The melting temperatures of the polyamides decreased from polyamide 12 18 to polyamide 2 18 as the amide density along the molecular chain declined. No significant variation was observed in the glass-transition and decomposition temperatures of the polyamides that were obtained. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1565–1571, 2005

The crystal structures of the odd–odd nylons X 11 (X = 3, 5, 7, 9, and 11) under different conditions, including solution-crystallized samples and melt-crystallized samples, were investigated by wide-angle X-ray diffraction (WAXD) and electron diffraction (ED). For the melt-crystallized samples of the odd–odd nylons under consideration, the strong diffraction at 0.42 nm, which is typical of the hexagonal lattice, was found in the WAXD patterns. As for the solution-crystallized samples, nylon 11 11 presents the monoclinic crystal structure characteristic of the two strong diffractions at about 0.42 and 0.40 nm of the WAXD and ED patterns, while nylons 9 11, 7 11, 5 11, and 3 11 show the hexagonal crystal ones typical of the same diffraction patterns as those of the melt-crystallized samples. The model of hydrogen bonds in crystal structures of the odd–odd nylons under study is discussed. POLYM. ENG. SCI., 45:1673–1679, 2005. © 2005 Society of Plastics Engineers

Amphiphilic block copolymers composed of a hydrophilic poly(ethylene glycol) (PEG) block and a hydrophobic poly(glycidyl methacrylate) (PGMA) block were synthesized through cationic ring-opening polymerization with PEG as the precursor. The model reactions indicated that the reactivity of the epoxy groups was higher than that of the double bonds in the bifunctional monomer glycidyl methacrylate (GMA) under the cationic polymerization conditions. Through the control of the reaction time in the synthesis of block copolymer PEG-b-PGMA, a linear GMA block was obtained through the ring-opening polymerization of epoxy groups, whereas the double bond in GMA remained unreacted. The results showed that the molecular weight of the PEG precursor had little influence on the grafting of GMA, and the PGMA blocks almost kept the same length, despite the difference of the PEG blocks. In addition, the PGMA blocks only consisted of several GMA units. The obtained amphiphilic PEG-b-PGMA block copolymers could form polymeric core–shell micelles by direct molecular self-assembly in water. The crosslinking of the PGMA core of the PEG-b-PGMA micelles, induced by ultraviolet radiation and heat instead of crosslinking agents, greatly increased the stability of the micelles. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2038–2047, 2005

A novel sulfonated aromatic diacid, 3,3′-disulfonyl-4,4′-dicarboxyldiphenylsulfone (DSDCDPS), was successfully synthesized from 4,4′-dimethyldiphenylsulfone by sulfonation and further oxidation. A series of sulfonated polybenzimidazoles (sPBI-SS) with various sulfonation degrees was prepared from DSDCDPS, 4,4′-sulfonyldibenzoic acid and 3,3′-diaminobenzidine by solution copolycondensation in poly(phosphoric acid). The chemical structure of the resulting sPBI-SS was confirmed by FTIR and ¹H NMR. The DSDCDPS-based sPBI-SS with the number-average molecular weights of 32,000–55,000 were easy to dissolve in polar aprotic solvents such as DMF, DMSO, and DMAc, and could be cast into transparent, tough, and flexible membranes. The membranes presented good thermal stabilities (5% weight loss temperatures higher than 430 °C), and the thermal degradation activation energies of the sulfonic group of sPBI-SS40 evaluated under N₂ by both Ozawa and Kissinger methods were 266.06 and 264.79 kJ/mol, respectively. The membranes also exhibited high storage moduli, glass transition temperatures (above 238 °C) and tensile strengths (∼80 MPa), in addition to water uptakes (22.3–25.2%) and low swelling degrees (<14.0%). © 2005 Wiley Periodicals, Inc. J Polym Sci A: Polym Chem 43: 4363–4372, 2005

The crystal structures of nylons X 11 under different conditions (X = 2, 4, 6, 8, 10, and 12) were investigated by wide-angle X-ray diffraction (WAXD) and electron diffraction (ED). Both the solution- and melt-crystallized samples of nylon 2 11 possess the hexagonal lattice (named γ-form). Nylons 4 11 and 6 11 exhibit the monoclinic unit cell (termed as α-like form) for both samples characteristic of two strong diffractions at 0.44 and 0.38 nm. For nylons 8 11, 10 11, and 12 11, the α-like form are obtained for the solution-crystallized samples while the β-like ones are obtained in the case of the melt-crystallized ones, with typical strong diffractions at 0.42 and 0.40 nm. The quenched nylon 12 11 samples annealing at different temperatures were also studied in this work to illustrate the various crystal forms obtained under different conditions. During the heating process, the α-like forms of the solution-crystallized samples for nylons 8 11, 10 11, and 12 11 transform into the high-temperature hexagonal phases prior to melting, while those of nylons 4 11 and 6 11 did not show such transformations before melting. Variable-temperature Fourier transform infrared spectroscopy was applied to investigate the crystalline transition phenomena and illustrate their essential features in the molecular level. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2048–2060, 2005

Hyperbranched polymethacrylates were prepared by means of oxyanionic vinyl polymerization of commercially available monomers, including hydroxyethyl methacrylate (HEMA) and poly(ethylene glycol) methacrylate (PEG-MA). Hyperbranched polymethacrylates with high molecular weight were obtained with the complex of potassium hydride and 18-crown-6 as the initiator. The effect of 18-crown-6 is very important, and only oligomer can be obtained in the polymerization without 18-crown-6. The molecular structure of the hyperbranched polymers was confirmed with ¹H NMR and ¹³C NMR spectra. The ratio of initiator to monomer significantly affects the architecture of the resultant polymers. When the ratio of initiator to monomer equals 1 in the oxyanionic vinyl polymerization of HEMA, the degree of branching of the resulting polymer was calculated to be around 0.49. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3502–3509, 2005

Cooperation of mother and daughter vesicles, which are self-assembled from an ill-defined hyperbranched copolymer, leads to fission of the daughter membrane in a cytomimetic process (see picture; red: mother vesicle, green: daughter vesicle). This is the first example of giant polymer vesicles (5–200 μm) being used as model membranes.

Die Zusammenarbeit von Mutter- und Tochtervesikel, die durch Selbstorganisation eines schlecht definierten hyperverzweigten Copolymers entstehen, führt in einem cytomimetischen Prozess zur Teilung der Tochtermembran (siehe Bild; rot: Muttervesikel, grün: Tochtervesikel). Bei dieser Untersuchung fungierten riesige Polymervesikel (5–200 μm) zum ersten Mal als Modellmembranen.

Abstract

The macroscopic molecular self-assembly of an amphiphilic hyperbranched copolymer in acetone generated multiwalled tubes millimeters in diameter and centimeters in length. The thickness of the tube walls approaches 400 nanometers, and the walls have an inhomogeneous lamella structure that alternates between ordered hydrophilic domains and amorphous, partly irregular hydrophilic domains.

Summary: The one step synthesis of a series of branched azobenzene side-chain liquid-crystalline copolymers by the self-condensing vinyl copolymerization (SCVCP) of a methyl acrylic AB* inimer, 2-(2-bromoisobutyryloxy)ethyl methacrylate (BIEM), with the monomer 6-(4-methoxy-azobenzene-4′-oxy)hexyl methacrylate (M), by atom transfer radical polymerization (ATRP) in the presence of CuBr/N,N,N′,N′,N″-pentamethyldiethylenetriamine as a catalyst system, and in chlorobenzene solvent, is reported. The degree of branching (DB), and the molecular weights and polydispersities of the resultant polymers were determined by NMR spectroscopy and size exclusion chromatography, respectively. The phase behaviors of the branched copolymers were characterized by differential scanning calorimetry (DSC) and thermal polarized optical microscopy (POM). The degree of branching of the branched copolymers could be controlled by the comonomer ratio in the feed and influenced their liquid-crystal properties. Liquid-crystal properties were not exhibited when the comonomer ratio was low. Comonomer ratios greater than 8 gave polymers with a lower number of branches, which exhibited both a smectic and a nematic phase.

An ill-defined hyperbranched multiarm copolymer (see picture) with a high hydrophilic fraction (>60 %) self-assembles in water to form giant polymer vesicles (branched polymersomes). The size of the branched polymersomes can be easily controlled by adjusting the hydrophilic fraction of the copolymer, with the average diameter of the larger branched polymersomes exceeding 100 μm.

Ein hochverzweigtes, vielarmiges, schlecht definiertes Copolymer (siehe Bild) mit einem hohen hydrophilen Anteil (>60 %) lagert sich in Wasser zu riesigen Polymervesikeln zusammen (verzweigte Polymersome). Die Größe der verzweigten Polymersome kann leicht durch Anpassen des hydrophilen Anteils gesteuert werden. Der durchschnittliche Durchmesser der größeren verzweigten Polymersome beträgt mehr als 100 μm.