Hew-Der Wu

The interaction behavior of polymer electrolytes composed of poly(vinyl pyrrolidone) and lithium perchlorate (LiClO4)

Abstract The interaction behavior of polymer electrolytes composed of poly(vinyl pyrrolidone) (PVP) and lithium perchlorate (LiClO4) has been investigated in detail by solid-state NMR and FTIR spectroscopies. It is found that the N-atom of the PVP polymer is able to donate its lone pair electrons toward the C O group, which results in a higher basicity of the C O group. The complex bond of Li+⋯C O is comparted into two types: the tight primary complex bond of Li+⋯C O; and the secondary complex where Li+ loosely complexed with several C O groups simultaneously. The secondary complex is dominant when the [Li:O] ratio is greater than 0.281. The ClO4− anion is free in the diluted PVP/LiClO4 electrolyte. When the LiClO4 concentration is increased, the ClO4− anion will interact with both N quasi-cation and/or Li+ cation. Solvated Li+ and “free” ClO4− ions are more favorable in diluted electrolyte; whereas neutral solvation-shared ion pair formation increases the incremental addition the LiClO4.

Novel determination of the crystallinity of syndiotactic polystyrene using FTIR spectrum

The crystallinity and crystallization behavior of syndiotactic polystyrene (s-PS) a- and b-crystals have been thoroughly examined using the Fourier Transform Infrared (FTIR). It is shown that absorptivity ratio of respective absorbances of “a-crystal/amorphous, aa” and “bcrystal/amorphous, ab” can be quantitatively determined using FTIR spectra ranging from 865 to 820 cm 21 . Results from curve fitting show that both absorptivity ratios of aa and ab are 0.178 ^ 0.005 and 0.272 ^ 0.005 for a- and b-crystal absorbances, respectively. The crystallization rate and crystallinity of a-crystal calculated from the absorptivity ratios are higher than that of b-crystal crystallized at 2408C for the same isothermal duration in thin film sample. The formation of b-crystal is thermodynamically more favorable while of a-crystal is kinetically more favorable from FTIR spectra. q 2001 Elsevier Science Ltd. All rights reserved.

Compatibilization and elastomer toughening of polyamide-6 (PA6)/poly(phenylene ether) (PPE) blends

In the elastomer-modified (polyamide-6/poly(phenylene ether) (PA6/PPE) = 50/50 blends, poly(styrene-co-maleic anhydride) (SMA) was demonstrated to be an efficient reactive compatibilizer. The G1651 elastomer was shown to be an effective impact modifier to result in superior toughness and heat-deflection temperature (HDT) than is the 1901X elastomer for the SMA-compatibilized blends because G1651 particles exclusively reside within the dispersed PPE phase but 1901X particles tend to distribute in the PA6 matrix and/or along the interface. The apparent average diameter of the dispersed PPE phase is insignificantly dependent on the elastomer content in the G1651-modified blend, whereas it increases with increase of the elastomer content in the 1901X-modified blend. Moreover, there exists a critical elastomer content, 15 phr, for the ductile-brittle transition of the G1651-modified SMA-modified PA6/PPE blends.

The solid state 13C NMR studies of intermolecular hydrogen bonding formation in a blend of phenolic resin and poly(hydroxyl ether) of bisphenol A

Full Paper: The formation of intermolecular hydrogen bonds in blends of novolac type phenolic and poly(hydroxyl ether) of bisphenol A was investigated by studying its Tg behavior, excess volume, and solid state 13 C NMR spectra. The Tg and parameters of solid state 13 C NMR, such as the TCH and spin-lattice relaxation time in the rotating frame T Hq, indicate that the London dispersion force (entropically favored) significantly affects the intermolecular hydrogen bonding of the blend. The phenoxy chain forces opening of the intra-association of phenolic and thus creates more free OHs. This strong entropic effect reduces the total hydrogen bonding of the system, especially when one of the polymer is the minor component. This also results in the reduction of Tg and free volume expansion, reflecting in the increase of crosspolarization (C1H) time and molecular mobility within the phenolic/phenoxy blend.

Thermal Property and Hydrogen Bonding in Blends of Poly(vinylphenol) and Poly(hydroxylether of Bisphenol A)

The thermal property and hydrogen bonding in polymer blends of poly(vinylphenol) (PVPh) and poly(hydroxylether of bisphenol A) (phenoxy) were investigated by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and solid-state nuclear magnetic resonance (NMR). This PVPh/phenoxy blend shows single composition-dependent glass transition temperature over the entire compositions, indicating that the hydrogen bonding exists between the hydroxyl of PVPh and hydroxyl of phenoxy. The negative Tg deviation of the PVPh/phenoxy blend indicates the strong intermolecular hydrogen-bonding interaction. The inter-association constant for the PVPh/phenoxy blend is significantly higher than self-association constants of PVPh and phenoxy, revealing that the tendency toward hydrogen bonding between PVPh and phenoxy is more favorable than the intra-hydrogen bonding of the PVPh and phenoxy in the blend.