A series of multiblock poly(ether urethane)s comprising poly(ethylene glycol) (PEG), and poly(propylene glycol) (PPG) segments were synthesized. Their aqueous solutions exhibited thermogelling behavior at critical gelation concentrations (CGC) ranging from 8 to 12 wt%. The composition and structural information of the copolymers were studied by GPC and 1H NMR. The critical micellization concentration (CMC) and thermodynamic parameters for micelle formation were determined at different temperatures. The temperature response of the copolymer solutions were studied and found to be associated with the composition of the copolymers. 相似文献
Summary: we have investigated by DSC and FTIR the miscibility and phase behaviour of binary and ternary blends of different ratios of poly(styrene-co-methacrylic acid) containing 15 mol% of methacrylic acid (SMA15) with poly(styrene-co-N,N-dimethylacrylamide) containing 17 mol% of N,N,-dimethylacrylamide (SAD-17) and poly(styrene- co-4-vinylpyridine) containing 15 mol% of 4-vinylpyridine. SMA15 is miscible with both SAD17 and S4VP15 and interacts more strongly with S4VP15 than with SAD17 as evidenced by the positive deviations from linear average line observed with these blends and the appearance of new bands in the 1800–1550 cm−1 region. This behaviour is known as ΔK effect. The FTIR study confirms that though the specific intermolecular interactions that occurred with each pair of the SMA15/S4VP15 and SMA15/SAD17 binary components are of different strength, they still exist in the ternary blend. Even though the three binary polymer pairs are individually miscible, the ternary system of SMA15/S4VP15/SAD17 exhibits only partial miscibility with small loop of immiscibility due to a significant ΔK effect. These results obtained by DSC and FTIR are in a fair agreement with theoretical prediction applying the Painter-Coleman association model. 相似文献
Superhydrophobic films mainly based on poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) polyelectrolyte multilayer have been deposited onto cleaned glass substrate by a layer-by-layer dip coating method. 3 bilayers of the PAH and PAA was directly coated onto the substrate as an underlying layer for subsequent coating. Desired surface roughness on the polyelectrolyte bilayers was created by etching the bilayers in hydrochloric acid solution so as to create the open pore having suitable size at the surface. Then, nanoparticles such as SiO2 and TiO2 of various sizes were deposited onto the etched polyelectrolyte bilayers. Finally, the surfaces were further modified with semifluorinated silane followed by cross-linking at 180 °C for 2 h to obtain desirable surface morphological features. The effect of etching time and addition of nanoparticles on surface morphology was investigated using an atomic force microscope (AFM). Wetting ability of the prepared film was determined by measuring water droplet contact angle using a goniometer. Adhesion between the superhydrophobic films and the substrate was evaluated by using a standard tape test method (D3359). The adhesion was improved by reducing the organic content in the films. 相似文献
Poly(p-phenylene benzobisoxazole)/poly(pyridobisimidazole) block copolymers (PBO-b-PIPD) were prepared by introducing poly(pyridobisimidazole) (PIPD) moieties into the main chains of poly(p-phenylene benzobisoxazole) (PBO) in order to enhance its photostability. PBO and copolymer fibers were directly prepared from the polymerization solutions by dry-jet wet-spinning. Chemical structures and molecular chains arrangement of the block copolymers were characterized by Fourier transform infrared (FTIR) spectroscopy, solid-state 13C-NMR and wide angle X-ray diffraction (WAXD). Thermal stability of the copolymers was investigated by thermogravimetric analysis (TGA) in nitrogen. Thin films of PBO and copolymers were cast from methanesulfonic acid (MSA) solutions. Both the films and fibers were exposed to UV light to determine their photostability. Changes in the chemical structures and surface morphologies of the films were characterized by FTIR spectra and scanning electronic microscopy (SEM), respectively. After UV light exposure, the retention of strength for copolymer fibers is improved compared to PBO fibers. The results revealed that copolymers suffered less photodegradation in comparison with homopolymer. The mechanism for the improved photostability of the copolymers was discussed. 相似文献
Summary: The reaction of hydrazine with ethyl glycolate results in 1,2‐bisglycoylhydrazine, a monomer that was used for the lipase‐catalyzed synthesis of biodegradable poly(ester hydrazide)s. The polymers derived from the hydrazide‐containing monomer and vinyl‐activated adipic, suberic, and sebacic acid, respectively, showed low melting temperatures of 136 to 141 °C and are thermally stable up to 300 °C. The aliphatic poly(ester hydrazide)s (PEHs) are highly crystalline, as proven by polarization microscopy and atomic force microscopy. Further, the PEHs represent the first described biodegradable poly(hydrazide)s. They degrade in the presence of lipase at 37 °C within a few weeks.
The effect of surfactants on the phase transition of poly(N-isopropylacrylamide) (PNIPAM) and poly(N-isopropylacrylamide-co-dimethylaminoethylmethacrylate) (P(NIPAM-co-DMAEMA)) was extensively investigated by a turbidometry. When the concentration of cetyltrimethyl ammoniumchloride (CTAC) increased from 0.01 to 0.32%, the cloud point of PNIPAM increased from 32 to 38.5°C. When the concentration of sodium dodecyl sulfate (SDS) increased from 0.01 to 0.08%, the cloud point increased from 32.5 to 38°C. The cloud points with SDS were higher than the values obtained with CTAC. In addition, SDS suppressed the temperature sensitivity much more effectively than CTAC did. The adsorption of the ionic surfactants (CTAC, SDS) on the polymer chains may account for the increase in the cloud point. On the other hand, Tween 20 had little effect on the cloud point and the temperature sensitivity of the homopolymer, possible because it is nonionic. The effect of surfactants on the phase transition of P(NIPAM-co-DMAEMA) exhibited a trend similar to the effect on the phase transition of PNIPAM. 相似文献