摘要:

Solution characterization of four samples of high molecular weight linear polystyrene (HMWLPS) in the molecular weight range of 1.61 × 106to 9.71 × 106in methyl ethyl ketone (MEK) at 25°C. was assessed from light scattering (LS), viscosity, and small-angle x-ray scattering (SAXS) under five different entrance-slit (E) /counter-slit (Z) combinations of 20/50, 30/75, 60/150, 100/250, and 150/375 μ, using the Kratky camera. The molecular weights and radii of gyration (<S2>1/2) obtained from SAXS under various slit combinations were then compared to the values obtained from LS. Further, the calculated values of<S2>1/2based on the theoretical relationship between size, entrance-slit and counter slit openings were compared to he experimental values of <S2>1/2of each sample. Thus establishing the upper limits of size for a given E/Z combination.

ISSN:0022-2348    

DOI:10.1080/00222348708248055

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Blends of poly(1-octadecene-co-maleic anhydride) and eicosane prepared from solution and the melt have been studied by differential scanning calorimetry, dynamic mechanical analysis and wide-angle x-ray scattering. The melting point and heat of fusion associated with the side chains of the copolymer increased with increasing eicosane content for blends prepared from the melt. It is hypothesized that this behavior results from the cocrystallization of eicosane with the paraffin-like side chains of the copolymer. The Tgof the copolymer was decreased by the addition of eicosane, and the Tmof eicosane was observed to decrease at high concentrations of the copolymer for blends prepared by both mechanisms. The possible contribution of both crystal morphology and thermodynamics to this melting point depression is discussed.

ISSN:0022-2348    

DOI:10.1080/00222348708248056

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Three grades of polyethylene differing mainly in their molecular weight were irradiation and peroxide crosslinked. Their gel content, degree of swelling, melting temperature, degree of crystallinity, and tensile properties were determined. The irradiation and peroxide crosslinking of the same polymers makes it possible to properly compare the effects of the two crosslinking methods. Upon irradiation the competition between crosslinking and chain scission reactions determines the level of the critical dose required to form the first gel and the magnitude of maximum attainable gel content. Crosslinking causes trapping of entanglements which then contribute to the effective network density determined by solvent swelling. crystalline polyethylene enhances the degree of crystallinity and crystal perfection while subsequent crystallization from the melt is hindered by the presence of crosslinks. The homogeneity of the crosslinked network, or distribution of crosslinks, depends on the crosslinking method. Irradiation crosslinking is essentially a selective process taking place mainly in amorphous regions. The resulting structural changes by the two crosslinking methods significantly affect the polymers' tensile behavior.

ISSN:0022-2348    

DOI:10.1080/00222348708248057

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The structure and structural transformations of the water/ POE-1000 eutectic system were studied in the interval -100° to 0°C by means of light microscopy. It was established that microphase separation and eutectic crystallization takes place, resulting in the formation (along cracks initially present in the sample) of rows (bands) of crystals of the polymer-rich component, surrounded by zones of water. A spinodal mechanism is suggested for the liquid-liquid phase separation of the water/POE-1000 eutectic system when it is supercooled with a temperature gradient and then heated. A good correlation was found between the temperatures of the phase transformations (melting and crystallization) as determined by light microscopy, x-ray, and calorimetrie analyses.

ISSN:0022-2348    

DOI:10.1080/00222348708248058

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Interaction of cationic and amphoteric polyelectrolytes on the basis of vinylethynylpiperidol derivatives with polyacids, transition metal ions, surfactants, drugs, and dyes has been investigated. The influence of ionic strength of the solution and organic solvent additions on the behavior of the poly-electrolyte complexes is discussed. Study of such systems can be useful for understanding the important role of metal ions in living organisms, the nature of protein-lipid interactions, the mechanism of protein denaturation, etc.

ISSN:0022-2348    

DOI:10.1080/00222348708248059

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The electrical conductivity of coordinated polychelates derived from bissemicarbazone and bisthiosemicarbazone of 5. 5′-methylene-bis-salicylaldehyde with Cu(II), Co(II), Ni(II), and Mn(II) metal ions was measured at various temperatures. The results for polychelates of both ligands showed that the conductivity varied as Cu(Il) > Ni(II) > Co(II) > Mn(II) polychelate, and that the activation energy, E, increased from Cu(II) through Ni(II) and Mn(II) to Co(II) polychelates. Hall effect and Seebeck effect studies of Cu(II) polychelates revealed that they are found as p-type semiconductors and that the mechanism of transport is of the hopping type.

ISSN:0022-2348    

DOI:10.1080/00222348708248060

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The influence of crosslinking and copolymerization on the glass transition temperature, Tg, of a range of diepoxide-diamine network polymers is examined. It is established that existing theories relating Tgto the level of crosslinking are inexact above a crosslink concentration of approximately 0.5 mole dm−3. To account for this deviation, the thermodynamic treatment of the glass transition is modified to take into consideration a non-Gaussian spatial distribution of chain segments and the steric restrictions upon movement of segments in the vicinity of junctions. The resulting equation-involving two empirical parameters, and the number of rotatable bonds between junctions—is shown to adequately explain data for the diglycidylethers of bisphenol A and butanediol, crosslinked with benzidine/aniline and 1,8-oc-tanediamine/n-butylamine mixtures. The behavior of networks prepared from α, ω-alkyldiamines containing from 2 to 36 methylene units can be predicted provided it is assumed that

ISSN:0022-2348    

DOI:10.1080/00222348708248061

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor