Abstract Blends of poly(pyridinium ethyl methacrylate perchloride) and poly[oligo(oxyethylene) methacrylate-co-acrylamide] were prepared, and the ionic conductivity and mobility of the blends were investigated. Results indicate that both the transference of perchlorate anion and the dissociation of the polymeric salt in the comblike polyether obey the thermoactivation mechanism, and that the perchlorate anion in the blends is free. 相似文献
Summary: Nanometer scale morphological order of macroscopically amorphous polyesters, obtained from the melt at moderate cooling rates, was observed in the past. The effect of such order on mechanical properties of a PET/PEN blend, evaluated by AFM nanoindentations, is reported in this study. Results show that nanoindentations conducted at relatively high load, with penetration depths of the order of 100 nm, confirm the information obtained from mechanical tests at micrometer scale, i.e., microhardness. On the other hand, true nanometer scale indentations (<40 nm) are seen to discriminate between the mechanical properties of the nanophases formed during solidification.
Statistical distribution of elastic moduli observed after 60 nanoindentations performed at 1 µN on each sample solidified at the cooling rates reported in the legend. 相似文献
The oriented crystallization of poly(vinylidene fluoride) (PVDF) in stretched films of a PVDF/nylon 11 blend was investigated. At low crystallization temperature the c‐axis of the PVDF α‐form was oriented to the orientation axis of the nylon 11 matrix, but c‐axis orientation gradually changed to a‐axis orientation upon increasing the crystallization temperature. Under all crystallization conditions studied, considerable amounts of PVDF in its β‐form with c‐axis orientation were produced as well.
Phase morphology of a stretched film of PVDF/nylon 11 blend observed with confocal laser scanning microscopy. 相似文献
Stereocomplex (SC) crystallization has been an effective way to improve the physical performances of stereoregular polymers. However, the competition between homo and SC crystallizations can lead to more complicated crystallization kinetics and polymorphic crystalline structure in stereocomplexable polymers, which influences the physical properties of obtained materials. Herein, we select the medium-molecular-weight (MMW) poly(L-lactic acid)/poly(D-lactic acid) (PLLA/PDLA) asymmetric blends with different PDLA fractions (fD=0.01–0.5) as the model system and investigate the effects of fD and crystallization temperature (Tc) on the crystallization kinetics and polymorphic crystalline structure. We observe the fractionated (i.e., multistep) crystallization kinetics and the formation of peculiar β-form homocrystals (HCs) in the asymmetric blends under quiescent conditions, which are strongly influenced by both fD and Tc. Precisely, crystallization of β-form HCs is favorable in the MMW PLLA/PDLA blends with high fD (≥0.2) at a low Tc (80–100 °C). It is proposed that the formation of metastable β-form HCs is attributed to the conformational matching between β-form HCs and SCs, and the stronger constrain effects of precedingly-formed SCs in the early stage of crystallization. Such effects can also cause the multistep crystallization kinetics of MMW PLLA/PDLA asymmetric blends in the heating process.
Stereocomplex-type polylactide (SC-PLA) consisting of alternatively arranged poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) chains has gained a good reputation as a sustainable engineering plastic with outstanding heat resistance and durability,however its practical applications have been considerably hindered by the weak SC crystallizability.Current methods used to enhance the SC crystallizability are generally achieved at the expense of the precious bio-renewability and/or bio-degradability of PLAs.Herein,we demonstrate a feasible method to address these challenges by incorporating small amounts of poly(D,L-lactide) (PDLLA) into linear high-molecular-weight PLLA/PDLA blends.The results show that the incorporation of the atactic PDLLA leads to a significant enhancement in the SC crystallizability because its good miscibility with the isotactic PLAs makes it possible to greatly improve the chain mixing between PLLA and PDLA as an effective compatibilizer.Meanwhile,the melt stability (i.e.,the stability of PLLA/PDLA chain assemblies upon melting) could also be improved substantially.Very intriguingly,SC crystallites are predominantly formed with increasing content and molecular weight of PDLLA.More notably,exclusive SC crystallization can be obtained in the racemic blends with 20 wt％ PDLLA having weight-average molecular weight of above 1 ×10s g/mol,where the chain mixing level and intermolecular interactions between the PLA enantiomers could be strikingly enhanced.Overall,our work could not only open a promising horizon for the development of all SC-PLA-based engineering plastic with exceptional SC crystallizability but also give a fundamental insight into the crucial role of PDLLA in improving the SC crystallizability of PLLA/PDLA blends. 相似文献
Abstract Poly(oxyethylene)s functionalized with quaternary phosphonium end groups were obtained by converting terminal hydroxyl end groups into phosphoniurn ion groups in the polymer-analogous reactions with phosphines and hydrogmu chloride. The products were characterized by: IR, UV. H NMR spectroscopy, thin-layer chromatography. 相似文献
