摘要:

AbstractA new calculation of the vibrational frequencies of poly(ethy1 ethylene) based on the actual molecular geometry was performed. The calculation takes into account new experimental data such far‐infrared spectra and Raman spectra of the stretched polymer, infrared spectra of poly(ethyl ethylene)‐(2,2;d2) (P‐4‐1‐d2) and poly(ethyl ethylene)‐(3,3,4,4;d4) (P‐4‐1‐d4), and Raman spectra of poly(ethyl ethylene)‐(1,3,3;d3) and poly(ethyl ethylene)‐(3,3,4,4;d4). Refinement produced a set of force constants; it is also applicable to

ISSN:0098-1273    

DOI:10.1002/pol.1979.180170101

出版商:John Wiley&Sons, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractThe vibrational analysis of modification I of poly(propyl ethylene), poly(propyl ethylene)‐(2,2;d2), and poly(propyl ethylene)‐(1,2,2;d3) has been performed using the valence force field derived for poly(ethyl ethylene) and the actual molecular geometry. The band assignments are based on infrared polarization and Raman d

ISSN:0098-1273    

DOI:10.1002/pol.1979.180170102

出版商:John Wiley&Sons, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractCarbon‐13 spin‐lattice relaxation times (T1), nuclear Overhauser enhancements (NOE), and resonance linewidths (Δp) have been measured for a series of terephthalic acid polyesters containing ethyl, butyl, hexyl, and isopropyl groups between neighboring terephthalate units. The relaxation parameters of all carbons in the terephthalate groups are independent of the length of the separating alkyl chain. Reduced NOE's are seen for all carbons. The data are interpreted in terms of a log X2distribution of correlation times of constant width, but variable average mobility. The average mobility in the alkyl chain increases with increasing distance from the terephthalate group in a given polymer. For a given position in the chain. mobility increases with increasing chain length. This behavior is consistent with the presence of independently reorienting, highly solvated terephthalate gr

ISSN:0098-1273    

DOI:10.1002/pol.1979.180170103

出版商:John Wiley&Sons, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractThe nucleation and growth of the crystalline core in the row structures of isotactic polystyrene were investigated by transmission electron microscopy. The number of core crystals, nucleated at a specific temperature, depends on the external strain. Their length was found to increase with time if the sample is kept at the straining temperature. If a strained sample is cooled to room temperature and subsequently reheated, no further growth of the core crystals is observed. Obstacles in the path of growth were circumvented by local changes of the growing direction. Melt‐soluble noncrystallizable molecules are rejected by the growing core into the surrounding melt. The observations suggest a growth mechanism of the cores based on the successive self‐induced alignment of molecules at the tip of the growing co

ISSN:0098-1273    

DOI:10.1002/pol.1979.180170104

出版商:John Wiley&Sons, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractRecent experiments have supported the view that polyethylene (PE) single crystals kept in suspension, in a variety of liquids, have different physical properties compared with the same crystals after drying. The present work was undertaken in an attempt to directly measure one of the basic properties of crystals in suspension, namely their percent crystallinity (X). Differential scanning calorimetry was chosen as the primary tool for this investigation. A method has been developed to determine the weight of PE in a suspension of crystals in a nonsolvent. Thus, a determination ofXcan be made. For suspension crystals,Xwas found to be at least 88.5%, some 6% larger than that for the corresponding dried or freeze‐dried material. Implications with regard to the fold‐surface structure are discussed. Differences in degree of crystallinity as a function of drying procedure have also been obser

ISSN:0098-1273    

DOI:10.1002/pol.1979.180170105

出版商:John Wiley&Sons, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractPolytetrafluoroethylene (PTFE) was extruded from a capillary rheometer at temperatures between the first‐order transition at 30°C and the melting point. Both PTFE at 50–300°C and various smectic states of certain low‐molecular benzylidene anilines obey the following relationship between the shear stress τ and the apparent shear rate$ \dot \gamma :{\rm }\tau = K\dot \gamma ^{{1 \mathord{\left/ {\vphantom {1 4}} \right. \kern-\nulldelimiterspace} 4}} $. The apparent viscosities for the two classes of substances are similar even though their molecular weights differ by a factor of about 104. Both have characteristic shear planes which are parallel to the polymer chains in PTFE and normal to the long axes of the benzylidene aniline molecules. The melting process in virgin PTFE begins near 300°C. Above this temperature, the shear stress at constant shear rate increases and the rheological exponent rises from 0.25 toward 0.5 at the final melt

ISSN:0098-1273    

DOI:10.1002/pol.1979.180170106

出版商:John Wiley&Sons, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractThe far‐infrared spectra of polystyrene methacrylic acid/(PSMA) ionomers have been investigated as a function of cation and ion‐site concentration to obtain spectroscopic evidence of domain formation. A far‐infrared band, due to the vibration of a higher‐order cluster, is found at 170 cm−1in Na+‐form PSMA. This band, which is observed in addition to the known cation‐motion bands, is assigned to the vibrations of aggregates involving many cations and anionic sites close together, and the results are discussed in light of ion aggre

ISSN:0098-1273    

DOI:10.1002/pol.1979.180170107

出版商:John Wiley&Sons, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractHeat capacities of poly(vinylidene fluoride) (PVF2) and polytetrafluoroethylene (PTFE) have been measured between 5 and 100°K with an accuracy of (1–5)% by adiabatic calorimetry. Calculations based on contributions from known optical lines and the Tarasov continuum model are in good agreement with experimental results down to 30°K for PVF2and 10°K for PTFE, and yield characteristic temperatures θ1and θ3which are consistent with previous values determined from high‐temperature (100—350°K) data. At lower temperature the measured heat capacity is significantly higher [(30–100)%] than the model prediction, and can be satisfactorily accounted for by the introduction of localized vibrators at a concentration of about 1% as compared to acoustical oscillators and at a characteristic temperature of about 20°K. Using established data on polyethylene for comparison, the principle of additivity for heat capacities is found to be valid down to at least 20°K, convering the region (<60°K) where interchain vibrations contribute significantly to the heat capacity. Possible reasons for this unexpected behavi

ISSN:0098-1273    

DOI:10.1002/pol.1979.180170108

出版商:John Wiley&Sons, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractThe charge decay of polymer electrets in the presence of solvent vapor is analyzed. In order to account for this phenomenon, several hypotheses are considered and tested experimentally. It is shown that the penetration of the solvent is responsible for the observed charge decay, and that it is the rate limiting factor. Moreover, the phenomenon is not due to the screening of the injected charges, but to the motion of these charges, which are liberated by the penetration of the solvent. Finally, the possible applications of this phenomenon in investigations on both the microscopic and macroscopic scale are outlined.

ISSN:0098-1273    

DOI:10.1002/pol.1979.180170109

出版商:John Wiley&Sons, Inc.    

年代:1979

数据来源: WILEY

摘要:

AbstractElectron microscopy and x‐ray diffraction data have been obtained on nylon 6 which has been crystallized from solutions in 1,6‐hexanediol and 1,2,6‐hexanetriol. Lamellar single crystals and spherulites of the γ form are obtained by crystallization from 1,2,6‐hexanetriol. The morphology of the single crystals is different from that obtained from glycerine solutions. The spherulites of the γ form are composed of larger lamellae. Sheaflike crystals of the α form are obtained from both solvents. α‐form and γ‐form crystals both grow from 1,2,6‐hexanetriol at appropriate crystallization temperatures. α‐form crystals alone are obtained from 1,6‐hexanediol solution at every crystallization temperature. The long periods measured by small‐angle x‐ray diffraction for the solution‐grown crystals are in the range 56 to 66 Å. The melting behavior of the solution‐grown crystals is examined and discussed. Effects of solvent on growth of the two crystalline form

ISSN:0098-1273    

DOI:10.1002/pol.1979.180170110

出版商:John Wiley&Sons, Inc.    

年代:1979

数据来源: WILEY