The effects of the annealing on the properties of PET/PC block copolymers, obtained by reactive blending in the presence of different catalysts and for different mixing times, have been studied. The annealing, performed in conditions that promote the crystallization, has been used to better understand the role of block length in determining the phase behaviour. The copolymers characterized by blocks with molecular weight larger than 8000 are able to reorganize towards more ordered domains. This rearrangement maintains the phase separation, as two crystalline phases are present before and after annealing, due to the immiscibility of long blocks. In copolymers characterized by blocks with molecular weight equal to about 2500, that is the higher limit for the miscibility in the amorphous state in PET/PC block copolymers studied in this work, the rearrangement of the chains during annealing causes a phase separation leading to two crystalline phases. Only in the copolymers with molecular weight of blocks lower than 1500, the very short block length hinders the crystallization: therefore, only in this case a phase separation does not take place after annealing. 相似文献
An automated procedure for correcting the interference due to mixing the reagents in the determination of ATP by a bioluminescent
technique is described. The measurements were performed by an in-house interfaced PC photometer. An automated procedure based
on a robust regression method and outliers detection was applied to exclude the time of the mixing of the reagents from the
global time of reaction. In fact the mixing of the reagents is responsible of the poor analytical precision (RSD%>25) and
low sensitivity (limit of detection≈2×10-8 mol/l). By this procedure, the precision (RSD%<7) and sensitivity (limit of detection≈8×10-10 mol/l) were improved. The method was applied to the determination of ATP in marine sediments and good recovery within 90–108%
was obtained. For non-polluted samples the measurement can be carried out by direct comparison with standard solutions. The
standard addition procedure is recommended for polluted samples.
Received: 25 April 1996/Revised: 28 June 1996/Accepted: 3 July 1996 相似文献
Surface modification of enzymes for a potential use in therapy was obtained with a new type of tailor-made copolymers ofNacryloylmorpholine andN-acryloxysuccinimide. The first monomer was designed to confer solubility on the polymer, whereas the second was used to give
it reactivity toward protein amino groups. The reactivity of polymers of different composition towards amino acid derivatives
and model proteins, such as catalase and ribonuclease-A, is described. Water soluble and catalytically active enzyme derivatives
were obained using copolymers prepared with a mixture of N-acryloxysuccinimide andn-acryloylmorpholine in a 1:99 molar ratio. At increasing molar ratio (3:97, 10:90) extensive crosslinking between polymer
and enzymes takes place, yielding insoluble adducts. 相似文献
Some aliphatic and partially aromatic polyamides have been prepared from hexamethylene diamine and the following dicarboxylic acids: deca-, octa-, hexa-methylenedicarboxylic, p-carboxymethylphenoxyacetic, p-carboxyethylphenoxyacetic, p-phenylenedipropionic, p-phenylenediacetic, p-carboxymethoxyphenoxyacetic, β(p-carboxymethyl)phenylpropionic.The dynamic-mechanical properties at 110 Hz have been measured between ?140° and about 200. Three relaxation processes α β and γ have been found: only the main transition α appreciably depends on chemical structure.The influences of the length of repeating unit and of in-chain substitution on melting points, crystallinity and the dynamic-mechanical α transition have been investigated. The results have been discussed in terms of chain flexibility, chain packing and intermolecular forces. 相似文献
Ethyl (S)-3-hydroxy-3-phenylpropionate (S)-2 was obtained by the asymmetric reduction of ethyl 3-phenyl-3-oxopropionate 1 with the yeast Saccharomyces cerevisiae (ATCC 9080). The kinetic resolution of racemic ethyl 2-acetoxy-3-phenyl-propionate rac-3 with the same microorganism, gave after hydrolysis ethyl (R)- and (S)-3-hydroxy-3-phenylpropionates (R)-2 and (S)-2 which were converted by a straightforward series of reactions to the enantiomers of 3-amino-3-phenyl-propionic acids (S)-6 and (R)-6. The asymmetric reduction and hydrolytic kinetic resolution were also tested with several other whole cell systems under a variety of conditions. 相似文献
A simple software, to be used as an aid in the identification of non-tryptic peptides based on low resolution (3D-ion trap) tandem (MS/MS) and sequential (MS3) mass spectrometry data, is presented. 相似文献
This contribution presents an optofluidic droplet router which is able to route and steer microdroplets using optically induced forces created solely by the bulk photovoltaic effect on a nonlinear substrate. The combination of microfluidic tools with the properties of a photorefractive crystal allows for the generation of dielectrophoretic forces that can be either repulsive, leading to virtual barriers, or attractive, creating virtual rails. The sign of these forces is solely determined by the electrical properties of the liquid medium under investigation. Moreover, the induced structures on the bottom of the microfluidic channel are optically reconfigurable, so that the same device can easily be adopted for different purposes. Appropriate droplet‐generating devices are fabricated by UV illumination of SU‐8 and polydimethylsiloxane replica molding of the master structures. The bottom of the channels is formed by an iron‐doped lithium niobate crystal, whose internal electric fields are induced by structured illumination patterns and exert dielectrophoretic forces on droplets in the microfluidic section.