摘要:

AbstractThe isothermal adsorption of high‐and low‐molecular‐weight poly(γ‐benzyl‐L‐glutamate) (PBLG) onto (100) alkali‐halide surfaces has been studied with the intent of developing a model for the adsorption process. Data from both the solution and adsorbed phases were correlated in this study. The α‐helical conformation was maintained in solution and on the substrate for all molecular weights investigated. Fourier‐transform infrared spectroscopy proved to be a sensitive technique for conformational analysis of adsorbed PBLG films as thin as 200 Å. High‐molecular‐weight PBLG was adsorbed as an interwoven fibrous mat, homogeneously covering the entire substrate surface. This morphology was independent of the substrate. Adsorption of low‐molecular‐weight PBLG took on a lamellar morphology, often exhibiting epitaxial orientation in the substrate 〈100〉 directions. Quasielastic laser light scattering studies showed that low‐molecular‐weight PBLG had a much higher degree of aggregation in nonpolar solvents than did high‐molecular‐weight PBLG. The proposed adsorption model is essentially a modification of one suggested by Silberberg. It involves segmental adsorption of aggregates, as opposed to single macromolecules of PBLG. The unadsorbed segments of the aggregates form a concentrated interfacial region directly above the substrate. Further interaction and association of PBLG may occur in this region, thus reducing the epitaxial ordering influence of the substrate. Consequently, polymers which do not interact strongly in the concentrated interfacial region, such as polyethylene, are expected to be ad

ISSN:0098-1273    

DOI:10.1002/pol.1978.180161101

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractWith a glass apparatus which is capable of measuring the thickness of adsorbed polymer layers with as accuracy of 0.5 nm, determinations on adsorbed polystyrene layers in contact with extremely dilute solutions (ca. 10−7g/ml) in toluene were performed. Thermodynamic equilibrium was proved to exist between the adsorbed polymer layer and bulk solution. The thicknesses found suggest that a fluid mechanical effect is operative, as has recently been calculated. It was shown that in the very dilute region the thickness of the adsorbed layer is initially a linearly increasing function of concentration, and that regions of (very low) concentrations exist over which a first plateau arises, where the layer is as thin as might be expected from isolated, adsorbed coil analysis. A second much higher plateau arises at concentrations in excess of 10−5g/ml, which is the plateau usually descri

ISSN:0098-1273    

DOI:10.1002/pol.1978.180161102

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractIt is shown that the first‐order perturbation coefficientC1of the cubed viscosity‐radius expansion factor α η3of nondraining flexible chains with excluded volume may be evaluated without great labor and with sufficient accuracy by solving numerically the Kirkwood–Riseman‐type integral equations with a digital computer. The value 1.18 forC1,robtained for ring chains is in good agreement with the corresponding value of Norisuye and Fujita, while the value 1.14 forC1,lobtained for linear chains is appreciably smaller than the corresponding value 1.29 of Fujita et al. despite the fact that the starting equations are the same. However, it is shown that the calculated value ofC1,lof Fujita et al. is incorrect. Thus, the present result thatC1,l

ISSN:0098-1273    

DOI:10.1002/pol.1978.180161103

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractSeveral primary amines have been examined as selective degradative etchants for the investigation of poly(ethylene terephthalate) (PET) morphology. The objective is to remove less ordered regions, leaving crystals intact. The amines include 40% and 20% aqueous methylamine, 70%–40% aqueous ethylamine and pure and 40% aqueous n‐propylamine. Weight‐loss and x‐ray diffraction data show that certain concentration of aqueous amine solution simultaneously degrade and crystallize PET. This observation indicates the hazard of using some of these amine reagents to characterize PET morphology since the crystalline structure found after etching is likely to be a result of solvent‐induced crystallization during degradation. Data for 40% aqueous methylamine used at room temperature shows that crystallization does not occur during etching, and in light of earlier research indicates the favorable nature of this reagent as a selective degradative medium for PET. Application of this reagent disclosed that in oriented PET fibers chemical stress cracking occurs, causing the degradative reagent to lose its se

ISSN:0098-1273    

DOI:10.1002/pol.1978.180161104

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractHigh‐pressure CO2sorption data in semicrystalline poly(ethylene terephthalate) (PET) are presented for temperatures ranging from 25 to 115°C. The results are described by Henry's law above the glass‐transition temperature of PET, while a dual‐mode sorption model comprised of a Henry's law and a Langmuir isotherm applies in the glassy state. The disappearance of the Langmuir capacity of the polymer aboveTgpresumably results from the elimination of regions of localized lower density which are frozen into the glass upon quenching from the rubbery state. Exposure of PET to a high CO2pressure produced a systematic variation in the apparent sorption equilibria. Correlation of the Langmuir capacity of PET with the dilatometric parameters of the polymer provides a useful framework for understanding the origin of the Langmuir sorption mode and for interpreting annealing and conditioning effects in glassy po

ISSN:0098-1273    

DOI:10.1002/pol.1978.180161105

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractThermally stimulated current (TSC) has been observed in extended‐chain crystals of polyethylene above room temperature. The TSC spectra exhibit two current peaks of opposite polarity. The peaks were separated into separate components by curve fitting. The position of the negative peak, which appears at 123°C, is independent of charging conditions. The positive current increases after γ irradiation or aging of the samp

ISSN:0098-1273    

DOI:10.1002/pol.1978.180161106

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractAnalysis of ESR spectra of mechanoradicals from poly(methyl methacrylate) reveals that after mechanical degradation invacuoat 77°K, the sample contains two types of primary radicalsCH2C(CH3)(COOCH3) (I) and CH2C(CH3)(COOCH3)CH2(II) produced by the breaking of the polymer chain, and secondary radicals CH2C(CH3)(COOCH3)CHC(CH3)(COOCH3)CH2 (III). With increasing temperature, radical I remains stable while II reacts with methylene hydrogen of the polymer chain giving rise to the secondary radical III, which decays and finally disappears as the temperature rises. After admission of oxygen at 113°K, the polymer radicals react with oxygen with formation of polymer peroxy radicals ROO. and diamagnetic dimers. With increasing temperature the latter dissociate again to the original polymer peroxy radicals which gradually decay, if the temperature is increased further. The present results are compared with earlier ones obtained on poly(ethylene glyc

ISSN:0098-1273    

DOI:10.1002/pol.1978.180161107

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractThe crystalline elastic modulus of poly(cis1,4‐isoprene) has been measured by x rays and calculated by molecular mechanics. The experimental modulus isE= (2.3 ± 0.3) × 109Nm−2. The calculated modulus isE= (8.8 ± 0.1) × 109Nm−2for chains inS+cisS−Tconformation andE= (6.1 ± 0.1) × 109Nm−2for chains inS+cisS+Tconformation. The modulus calculated for a statistical structure including both conformation isE= (6.7 ± 0.1) × 109Nm−2. The experimental modulus is thought to be a lower limit because of partial crystallinity of the sample. The chief mechanism of deformation is rotation around single bonds adjacent

ISSN:0098-1273    

DOI:10.1002/pol.1978.180161108

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractThe crystal structure of the β form of poly(ethylene oxybenzoate) was analyzed by x‐ray diffraction. Four nearly extended molecular chains pass through a unit cell with parametersa= 8.19 Å,b= 11.07 Å,c(fiber axis) = 19.05 Å, β = 114.8°, and the space groupP21/n‐C 2h5. The structural difference between the α and β forms is mainly due to the internal rotation angles for the virtual bondand the CH2CH2 bond. They are essentially intransconfirmation in the β form, while the α form contains cisandgauche(

ISSN:0098-1273    

DOI:10.1002/pol.1978.180161109

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY

摘要:

AbstractHigh‐resolution electron microscopy studies have been carried out on four glassy polymers examined in previous small‐angle x‐ray scattering (SAXS) investigations. The polymers include polycarbonate, poly(ethylene terephthalate), poly(vinyl chloride), and polystyrene. For all four polymers, both bright field and dark‐field observations indicate the general absence of microstructural features of a size down to the resolution limit of the electron microscope. Only “pepper and salt” features on a scale ca. 5 Å are seen as characteristic of the structures. These features reflect simple interferences as the resolution limit is approached, and are seen for single crystal and oxide glasses as well as for the polymers. The present results, taken together with structural information from light scattering, SAXS, and small‐angle neutron scattering, indicate that glassy polymers should be regarded as having rendom structures. The combined results are inconsistent with heterogeneous microstructures having regions of locally high order present in large vo

ISSN:0098-1273    

DOI:10.1002/pol.1978.180161110

出版商:John Wiley&Sons, Inc.    

年代:1978

数据来源: WILEY