998 resultados para Poly(urethane urea)
Resumo:
A series of narrow molecular weight distribution fractions of phenolphthalein polyarylether sulfone(PES-C) had been prepared, The <(M) over bar (w)> of these fractions were determined by conventional light scattering method. The [eta] and the Huggins slope constant k' in DMF, CHCl3 and 1,2-dichloroethane were also determined. The Huggins constants are greater than 0.5 in all of these solvents showing a special solubility behavior. The Mark-Houwink equations of PES-C in these solvents at 25 degrees C are [eta] = 2.79 x 10(-2) <(M) over bar (0.615)(w)> (DMF); [eta] = 3.96 x 10(-2) <(M) over bar (0.58)(w)> (CHCl3); [eta] = 7.40 x 10(-2) <(M) over bar (0.52)(w)> (CH2ClCH2Cl).
Resumo:
Using a recently developed laser light-scattering (LLS) procedure, we accomplished the characterization of a broadly distributed unfractionated phenolphthalein poly(aryl ether ketone) (PEK-C) in CHCl3 at 25 degrees C. The laplace inversion of precisely measured intensity-intensity time correlation function from dynamic LLS leads us first to an estimate of the characteristic line-width distribution G(Gamma) and then to the translational diffusion coefficient distribution G(D). By using a previously established calibration of D (cm(2)/s) = 2.37 X 10(-4)M(-0.57), were able to convert G(D) into a differential weight distribution f(w)(M). The weight-average molecular weight M(w) calculated from f(w)(M) agrees well with that directly measured in static LLS. Our results indicate that both the calibration and LLS procedure used in this study are ready to be applied as a routine method for the characterization of the molecular weight distribution of PEK-C. (C) 1996 John Wiley & Sons, Inc.
Resumo:
The miscibility and crystallization behaviour of the blends of poly(ether ether ketone) (PEEK) with two thermoplastic polyimides (PI), PEI-E and YS-30, prepared by solution blending were studied by the use of small-angle X-ray scattering (SAXS), differential scanning calorimetry (d.s.c.) and polarizing microscopy techniques. The results obtained show that PEEK/YS-30 is miscible, while PEEK/PEI-E is partially miscible only in the composition range with PEI-E content up to 20 wt%. The crystallization behaviour of PEEK in PEEK/PI blends depends on the crystallization condition of the blend sample as well as the chemical structure and the content of the PI added. Our SAXS results indicate that the segregation of PI molecular chains during crystallization of PEEK chains in the blends is interfibrillar for PEEK/PEI-E blends, but interlamellar for PEEK/YS-30 blends. The compatibility and the crystallization behaviour are discussed in terms of charge transfer interaction between PI and PI molecules and between PI and PEEK molecules.
Laser light-scattering study of novel thermoplastics .2. Phenolphthalein poly(ether sulfone) (PES-C)
Resumo:
Five narrowly distributed fractions of phenolphthalein poly(ether sulfone) (PES-C) were studied in CHCl3 by both static and dynamic laser light scattering (LLS) at 25 degrees C. The dynamic LLS showed that the PES-C samples contain some large polymer clusters as in previously studied phenolphthalein poly(ether ketone)(PEK-C). These large clusters can be removed by a 0.1-mu m filter. Our results showed that [R(g)(2)](1/2)(z) = (3.35 +/- 0.13) x 10(-2) M(w)((0.52 +/- 0.03)) and [D] = (2.26 +/- 0.02) x 10(-4)M(w)-((0.54) +/- 0.03)) with [R(g)(2)](1/2)(z), M(w) and [D] being the z-average radius of gyration, the weight-average molecular weight, and the z-average translational diffusion coefficient, respectively. A combination of static and dynamic LLS results enabled us to determine D = (2.45 +/- 0.04) x 10(-4)M-((0.55 +/- 0.05)), where D and M correspond to monodisperse species. Using this scaling relationship, we have successfully converted the translational diffusion coefficient distribution into the molecular weight distribution for each of the five PES-C fractional The weight-average molecular weights obtained from dynamic light scattering have a good agreement with that obtained from static laser light-scattering measurements.
Resumo:
C-13 and H-1 relaxation times were measured as a function of temperature in two magnetic fields for dilute solutions of phenolphthalein poly(ether sulfone) (PES-C) in deuterated chloroform. The spin-lattice relaxation times were interpreted in terms of segmental motion characterized by the sharp cutoff model of Jones and Stockmayer (J. S. model). The phenyl group rotation is treated as a stochastic diffusion by the J. S. model. The restricted butterfly motion of the phenyl group attached to the cardo ring in PES-C is mentioned but is not discussed in detail in this work. Correlation times for the segmental motion are in the picosecond range which indicates the high flexibility of PES-C chains. The correlation time for the phenyl group internal rotation is similar to that of the segmental motion. The temperature dependence of these motions is weak. The apparent activation energy of the motions considered is less than 10 kJ/mol. The simulating results for PES are also reasonable considering the differences in structure compared with PES-C. The correlation times and the apparent activation energy obtained using the J. S. model for the main chain motion of PES-C are the same as those obtained using the damped orientational diffusion model and the conformational jump model.
Resumo:
The miscibility and phase behavior of polysulfone (PSF) and poly(hydroxyether of bisphenol A) (phenoxy) with a series of copoly(ether ether ketone) (COPEEK), a random copolymer of poly(ether ether ketone) (PEEK), and phenolphthalein poly(ether ether ketone) (PEK-C) was studied using differential scanning calorimetry. A COPEEK copolymer containing 6 mol % ether ether ketone (EEK) repeat units is miscible with PSF, whereas copolymers containing 12 mol % EEK and more are not. COPEEK copolymers containing 6 and 12 mol % EEK are completely miscible with phenoxy, but those containing 24 mol % EEK and more are immiscible with phenoxy. Moreover, a copolymer containing 17 mol % EEK is partially miscible with phenoxy; the blends show two transitions in the midcomposition region and single transitions at either extreme. Two T(g)s were observed for the 50/50 blend of phenoxy with the copolymer containing 17 mol % EEK, whereas a single composition-dependent T-g appeared for all the other compositions. An FTIR study revealed that there exist hydrogen-bonding interactions between phenoxy and the copolymers. The strengths of the hydrogen-bonding interactions in the blends of the COPEEK copolymers containing 6 and 12 mol % EEK are the same as that in the phenoxy/PEK-C blend. However, for the blends of copolymers containing 17, 24, and 28 mol % EEK, the hydrogen-bonding interactions become increasingly unfavorable and the self-association of the hydroxyl groups of phenoxy is preferable as the content of EEK units in the copolymer increases. The observed miscibility was interpreted qualitatively in terms of the mean-field approach. (C) 1996 John Wiley & Sons, Inc.
Resumo:
Five different molecular weight phenolphthalein poly(aryl ether ketone) (PEK-C) fractions in CHCl3 were studied by static and dynamic laser light scattering(LLS). The dynamic LLS revealed that the PEK-C samples contain some large polymer clusters. These large clusters can be removed by filtering the solution with a 0.1-mu m filter. We found that the persistence length of PEK-C in CHCl3 at 25 degrees C is similar to 2 nm and the Flory characteristic ratio, C-infinity is similar to 25. Our results showed that [R(g)(2)](1/2)(z) = (3.50+/-0.20) x 10(-2)M(w)(0.54+/-0.01) and [D] = (2.37+/-0.05) x 10(-4)M(w)(-0.55+/-0.01), with [R(g)(2)](1/2)(z), M(w), and [D] being the z-average radius of gyration, the weight-average molecular weight, and the z-average translational diffusion coefficient, respectively. A combination of static and dynamic LLS results enabled us to determine D = (2.20+/-0.10) x 10(-4)M(-0.555+/-0.015), where D and M correspond to monodisperse species. Using this calibration between D and M,we have determined molecular weight distributions of five PEK-C fractions from their corresponding translational diffusion coefficient distribution.
Resumo:
Structures of poly(ether ether ketone ketone)-poly(ether biphenyl ether ketone ketone) copolymers were studied by using small angle X-ray scattering and the one-dimensional electron density correlation function method. The results revealed that structures of the aggregated state of the copolymers depend closely on the biphenyl content (n(b)). When n(b) = 0.35, invariant Q, long period L, average thickness of crystal lamellae (d) over bar, electron density difference eta(c) - eta(a) and degree of crystallinity W-c,W-x assume minimum values.