Search

The hierarchical pathway from homogeneous solution to gel of a large-ring crown ether symmetrically substituted with four first-generation Percec-type dendrons (1) in n-dodecane has been followed by differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), and fluorescence anisotropy methods. The 1/n-dodecane mixture requires a rather low gelation concentration of ∼0.1% (w/v) at room temperature. Mainly on the basis of in situ thermal SAXS measurements, we have found that upon cooling from the homogeneous solutions of 1/n-dodecane the 1 molecule first undergoes a solution self-assembly to form wormlike micelle with the core of crown ether and the shell of alkyl tails, which is “living polymers” containing only one disklike molecule of 1 per cross-sectional repeating unit. The driving force of the assembly can be mainly attributed to the reduction of free energy during microphase separation among the different regions of molecules with distinct chemical properties and the lipophilic−lip...

A kind of novel amphiphilic triblock copolymers containing polyrotaxane (PR) as a central block was synthesized via the ATRP of poly(ethylene glycol) methyl ether methacrylate (PEGMA) initiated with polypseudorotaxanes made from a distal 2-bromopropionyl end-capped Pluronic F127 with a varying amount of β-CDs in the presence of Cu(I)Cl/ N , N , N ′, N ″, N ″-pentamethyldiethylenetriamine (PMDETA) at 25 °C in aqueous medium. The structure of the resulting copolymers was characterized in detail by 1 H NMR, 2D ROESY NMR, GPC, DSC and WAXD analyses. The degree of polymerization of PEGMA oligomers appeared to be adjustable. As a typical sample, F-30β-CD-60 with a molar feeding ratio of Pluronic F127 to β-CD to PEGMA holding 1:30:60 was found to self-assemble into nano-sized aggregates in water. Its critical aggregation concentration was assessed by fluorescence probe technique. The corresponding hydrodynamic radius and radius of gyration were also determined by dynamic and static light scattering measurements. The transmission electron microscopy images further revealed that the sizes of the polymeric micelles of the selected copolymer were in nano-scale and smaller than those of the blank brush-like block copolymer. These nano-sized particles showed great potential to be used as carrier for the controlled release of Amphotericin B (AmB) holding 8.7% drug-loading content and 87% drug-loading efficiency with the cumulative release profile substantially longer than that of the blank brush-like block copolymer.

A basic problem with many promising solid electrolyte materials for battery applications is that crystallization in these materials at room temperature makes ionic mobilities plummet, thus compromising battery function. In the present work, we consider the use of a polymer additive (polyethylene oxide, PEO) to inhibit the crystallization of a promising battery electrolyte material, the organic crystal forming molecule succinonitrile (SN) mixed with a salt (LiClO4). While SN spherulite formation still occurs at low PEO concentrations, the SN spherulites become progressively irregular and smaller with an increasing PEO concentration until a ‘critical’ PEO concentration (20% molar fraction PEO) is reached where SN crystallization is no longer observable by optical microscopy at room temperature. Increasing the PEO concentration further to 70% (molar fraction PEO) leads to a high PEO concentration regime where PEO spherulites become readily apparent by optical microscopy. Additional diffraction and thermodynamic measurements establish the predominantly amorphous nature of our electrolyte–polymer mixtures at intermediate PEO concentrations (20–60% molar fraction PEO) and electrical conductivity measurements confirm that these complex mixtures exhibit the phenomenology of glass-forming liquids. Importantly, the intermediate PEO concentration electrolyte–polymer mixtures retain a relatively high conductivity at room temperature in comparison to the semicrystalline materials that are obtained at low and high PEO concentrations. We have thus demonstrated an effective strategy for creating highly conductive and stable conductive polymer–electrolyte materials at room temperature that are promising for battery applications.

The phase structures and transition behaviors of a series of side-chain liquid crystalline (LC) polymethacrylates based on p-methoxyazobenzene (PMnAzs, n ¼ 6, 8, 10, 12) were studied using differential scanning calorimetry, one- and two-dimensional (1D and 2D) wide-angle X-ray diffraction, and Fourier transform infrared spectroscopic experiments. The LC phase transition of PMnAz follows the sequence of smectic A (SmA)4 nematic (N)4 isotropic (I). For PM10Az and PM12Az, the transition of SmA-to-N is not complete upon heating. In the low-temperature SmA phase, the polymers adopt a fully interdigitated side-chain packing with the smectic layer period almost identical to the side-chain length. For all the four samples, the first-order diffraction of the SmA structure only renders when the temperature approaches the transition of SmA 4 N, with the intensity much lower than that of the second-order diffraction. The absence of the first-order diffraction at low temperatures is ascribed to the possible matching of the electron densities between the center portion of the side-chain sublayer and the main-chain sublayer of the SmA structure. Since only the mesogens from the same main-chain sublayer can stack parallel together, the distribution of the azobenzene domains may cause some sort of density undulation within the smectic layer. Among the samples, PM6Az presents the strongest undulation with some additional orders. We also examined the annealing effect on the H-aggregation of PMnAzs. It is found that isothermal annealing at a temperature slightly higher than the T g of PM8Az and PM10Az can significantly enhance

A series of new monomers of 2,5-bis[(4-tertbutyl-phenyl)-1,3,4-oxadiazole] styrene (M-Ct) and 2,5-bis[(4-alkoxy-phenyl)-1,3,4-oxadiazole]styrene (M−OCm, m is the number of the carbons in the alkoxy groups, m = 8, 10, 12, 14) were synthesized. Conventional radical polymerization of the monomers resulted in a series of new mesogen-jacketed liquid crystalline polymer (MJLCP) containing the 1,3,4-oxadiazole unit. The chemical structures of the monomers were confirmed by elemental analysis, mass spectrometry, 1H NMR, and IR. The molecular characterization of the corresponding polymers of P-Ct and P-OCms was performed with 1H NMR, gel permeation chromatography, and thermogravimetric analysis. Their phase structures and transitions were investigated by differential scanning calorimetry, wide-angle X-ray diffraction, and polarized light microscopy experiments. The P-Ct formed the hexatic columnar nematic (ΦHN) phase that is typical for MJLCPs, wherein the chain molecules were rodlike. The P-OCms exhibited a well-...