Morphology and structure of micro-fibrillar crystal of nylon 10 10

The nanoscale and microscale fibrillar crystals of nylon 10 10 were obtained by atomizing the very dilute formic acid solution. The length-diameter ratio of these fibrillar crystals increases as the concentration of the atomizing solution increases. Electron diffraction (ED) analysis showed that the hydrogen-bonded sheet in these solution-grown fibrillar crystals was imperfect and had a lower order. Both electron diffraction and characteristic morphology show that melt-crystallized fibrillar crystals always possess perfect packing order and stable structure. A rather perfect ED pattern of the triclinic form of nylon 10 10 along the [001] zone was obtained by tilting the specimen 41 degrees along the elongated direction of the crystal. Fibrillar crystals from bulk have a great tendency to aggregate with parallel packing to form crystal clusters, which look like shish kebabs in morphology. Spherulite is observed occasionally in the domains with very rich sample. (C) 2001 Elsevier Science Ltd. All rights reserved.

Isotope effect in proton-transfer and association-dissociation reactions for butylamine by ultrasonic relaxation methods

Ultrasonic absorption coefficients were measured for butylamine in heavy water (D2O) in the frequency range from 0.8 to 220 MHz and at concentrations from 0.0278 to 2.5170 mol dm(-3) at 25 degrees C; two kinds of relaxation processes were observed. One was found in relatively dilute solutions (up to 0.5 mol dm(-3)), which was attributed to the hydrolysis of butylamine. In order to compare the results, absorption measurements were also carried out in light water (H2O). The rate and thermodynamic parameters were determined from the concentration dependence of the relaxation frequency and the maximum absorption per wavelength. The isotope effects on the diffusion-controlled reaction were estimated and the stability of the intermediate of the hydrolysis was considered while comparing it with the results for propylamine in H2O and D2O. Another relaxation process was observed at concentrations greater than 1 mol dm(-3) in D2O. In order to examine the solution characteristics, proton NMR measurements for butylamine were also carried out in D2O. The chemical shifts for the gamma- and delta-proton in butylamine molecule indicate the existence of an aggregate. From profiles of the concentration dependence of the relaxation frequency and the maximum absorption per wavelength of sound absorption, the source of the relaxation was attributed to an association-dissociation reaction, perhaps, associated with a hydrophobic interaction. The aggregation number, the forward and reverse rate constants and the standard volume change of the reaction were determined. It was concluded from a comparison with the results in H2O that the hydrophobic interaction of butylamine in D2O is stronger than that in H2O. Also, the isotope effect on this reaction was interpreted in terms of the solvent structure.

Enzymatic degradation of poly(epsilon-caprolactone)/poly(DL-lactide) blends in phosphate buffer solution

Blend films of poly(epsilon-caprolactone) (PCL) and poly(DL-lactide) (PDLLA) with 0.5 weight fraction of PCL were prepared by means of solution casting and their degradation behavior was studied in phosphate buffer solution containing Pseudomonas (PS) lipase. Enzymatic degradation of the blend films occurred continuously within the first 6 days and finally stopped when the film weight loss reached 50%, showing that only PCL in the blends degraded under the action of PS lipase in the buffer solution. These results indicate the selectivity of PS lipase on the promotion of degradation for PCL and PDLLA. The thermal properties and morphology of the blend films were investigated by differential scanning calorimetry, wide-angle X-ray diffraction and scanning electron microscopy (SEM). The morphology resulting from aggregate structures of PCL in the blends was destroyed in the enzymatic degradation process, as observed by SEM. These results confirm again the enzymatic degradation of PCL in the blends in the presence of PS lipase. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.

Compatibilization of blends of polystyrene and zinc salt of sulfonated polystyrene by poly(styrene-b-4-vinylpyridine) diblock copolymer

The compatibilizing effect and mechanism of poly(styrene-b-4-vinylpyridine) diblock copolymer, P(S-b-4VPy), on the immiscible blend of polystyrene (PS)/zinc salt of sulphonated polystyrene (Zn-SPS) were studied. SEM results show that the domains of the dispersed phase in the blend become finer. DSC experiments reveal that the difference between the two T-g's corresponding to the phases in the blends becomes larger on addition of P(S-b-4VPy), mainly resulting from dissolving of the poly(4-vinylpyridine (P4VPy) block in the Zn-SPS phase. FTIR analysis shows that compatibility of P4VPy and Zn-SPS arises from the stoichiometric coordination of the zinc ions of Zn-SPS and pyridine nitrogens of P4VPy. SAXS analysis indicates the effect of the P(S-b-4VPy) content on the structure of the compatibilized blends. When the content of the block copolymer is lower than 4.1 wt%, the number of ion pairs in an aggregate in the Zn-SPS becomes smaller, and aggregates in ionomer in the blend become less organized with increasing P(S-b-4VPy). When the P(S-b-4VPy) content in the blend is up to 7.4 wt%, a fraction of P(S-b-4VPy) form a separate domain in the blend. (C) 1999 Elsevier Science Ltd. All rights reserved.