Carbon‐13 NMR of polyethylenes: Correlation of the crystalline component <i>T</i><sub>1</sub> with structure

Axelson, David E.; Mandelkern, L.; Popli, R.; Mathieu, P.

doi:10.1002/pol.1983.180211109

Cited by 122 publications

(69 citation statements)

References 38 publications

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“…The data were analyzed with a linear least squares procedure similar to that used for analysis of 13C magnetization decay curves. 18,21 Wide-angle x-ray diffraction patterns were registered by a CSS/STOE STADI/ZPL diffractometer using CuK, radiation ( A = 1.5418 A). The profile fit/deconvolution program (WAXS) used in the analysis of the patterns" was derived from a program written for the analysis of spectroscopic data.…”

Section: Methodsmentioning

confidence: 99%

Crystallization of side chains in copolymers of ethylene and 1-alkenes

Russell

McFaddin

Hunter

et al. 1996

J. Polym. Sci. B Polym. Phys.

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The phase structure of random copolymers of ethylene and ethylene‐d4 with 1‐octadecene and other 1‐alkenes has been investigated. CPMAS 13C NMR spectra show that a fraction of the central sections of C16H33 side chains in ethylene‐d4 copolymers are in ordered environments at 298 K. They give rise to resonances from 32.9 ppm to 33.8 ppm, which show that they are in trans conformations; T1C values for this group of resonances range from 1 s to 7 s. The remaining side chains are in an amorphous environment, the internal methylenes having a chemical shift of 30.8 ppm and a T1C close to 0.4 s. A Raman band at 1062 cm−1 in the spectrum of an ethylene‐d4‐1‐octadecene copolymer is consistent with partial crystallization of side chains. Some side‐chain crystallization also occurs in a 1‐tetradecene copolymer. X‐ray diffraction studies suggest that smaller side chains do not crystallize to a significant extent at 298 K. © 1996 John Wiley & Sons, Inc.

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Section: Methodsmentioning

confidence: 99%

Crystallization of side chains in copolymers of ethylene and 1-alkenes

Russell

McFaddin

Hunter

et al. 1996

J. Polym. Sci. B Polym. Phys.

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“…to 4500 sec. 85 These admittedly represent a very large range in the values of a relaxation time. The reason for this unusual result is that the T1 's are shown to be a monotonic function of the crystallite thickness when the interface is characteristic of bulk crystallized polymers.…”

Section: Propertiesmentioning

confidence: 99%

“…The other independent structural variables do not affect T1 . 85 Several of the dynamic mechanical relaxations, characteristic of the polyethylenes, have also been studied. 83 • 86 The polyethylenes as a class display a set of such transitions.…”

Section: Propertiesmentioning

confidence: 99%

The Relation between Structure and Properties of Crystalline Polymers

Mandelkern

1985

Polym J

174

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ABSTRACT:The influence of both structure and crystallization conditions on a variety of properties characteristic of semi-crystalline polymers are discussed. A careful distinction needs to be made between molecular structure and the independent structural variables which describe the crystalline state. This set of independent variables includes the degree of crystallinity; the structure of the non-crystalline regions; the crystallite thickness distribution; the structure and relative amount of interface; the crystallite structure and the supermolecular structure. The dependence of these variables on molecular structure and crystallization conditions are examined in detail as is their influence on properties. By following this procedure the influence of molecular structure on properties is deduced. A variety of thermodynamic, spectral and mechanical properties are analyzed by these methods.KEY Studies of the crystallization behavior of polymers have proceeded sufficiently far so as to enable an analysis to be made of the influence of structure on properties. Two distinctly different types of structure needs to be carefully distinguished. On the one hand there is the concern with the influence of molecular or chain structure. In this case the principle variables are the chain length, for molecular weight fractions, the polydispersity, for whole polymers and the structural regularity of the chain. In addition the structural variables which define the crystalline state also have to be given consideration. We shall be concerned here with how these independent structural variables are influenced by the important elements of molecular structure and by the crystallization conditions. The question then arises as to how these structural variables influence properties. These include thermodynamic, spectroscopic and mechanical properties as well as other macroscopic ones. By following this procedure the influence of molecular structure will be established. Thus, although we shall be considering both kinds of structure they will be carefully delineated.A set of independent structural variables have been identified which either individually or in particular combinations contribute to and control a specific property. The variables which have been thus identified are: the level, or degree, of crystallinity; the structure of the residual non-crystalline region; the crystallite thickness distribution; the structure and relative amount of the interfacial region; the crystallite structure; and the molecular structure. We shall examine each of these structural variables. Emphasis will be given to their meaning, method of determination how they are influenced by molecular structure and crystallization conditions. Then their influence on properties will be considered. The experimental examples to be discussed have been selected predominantly from among the polyethylenes. However, studies with other polymers are sufficiently far advanced to substantiate the generality of the results and conclusions. RESULTS AND DISCUSSIONIt is instruct...

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“…In particular, chain diffusion of segments between amorphous and crystalline regions will occur, which can be observed by NMR [69] since the different conformational environments lead to different isotropic chemical shifts observed under magic-angle spinning. In addition to cross-peaks in 2D exchange NMR spectra at high temperatures, the diffusive rather than exponential 13 C T 1 relaxation [69,78] with its strong crystallite-thickness dependence [78] are strong indications that this chain-diffusion process indeed occurs.…”

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confidence: 98%

Polymer ultradrawability: the crucial role of α-relaxation chain mobility in the crystallites

1999

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An explanation of the varying (ultra)drawability of semicrystalline polymers is proposed, based on NMR evidence of αc‐relaxation‐associated helical jumps and chain diffusion through the crystallites of polyethylene and several similarly “αc‐mobile” polymers; these include isotactic polypropylene, poly(ethylene oxide), poly(oxymethylene), poly(tetrafluoroethylene), poly(vinyl alcohol), and several others. The chain motions provide a mechanism by which hot drawing of these polymers can extend an initially formed fiber morphology by an order of magnitude to draw ratios > 30, without melting. A second class of polymers, including nylons, poly(ethylene terephthalate), syndiotactic polypropylene, isotactic polystyrene, and isotactic poly(1‐butene) (form I) lack a crystalline α‐relaxation and the associated chain mobility. Therefore, these polymers are “crystal fixed” and drawability is limited to draw ratios < 14, arising mostly from break‐up of crystalline lamellae and deformation of the amorphous regions. On this basis, we can explain which polymers are drawable to high draw ratios, given a sufficiently low level of entanglement. The motion through the crystallites is thermally activated and the applied stress only biases the direction of the jumps; this explains the crucial role of temperature and rate in tensile drawing and solid‐state extrusion processes. The behavior of the crystal‐fixed, poorly drawable polymers strongly suggests that melting, straight chain pull‐out, and sliding on crystal planes are not significantly operative during ultradrawing, and that weak intermolecular forces are not a sufficient condition for ultradeformation. Various stages of drawing are distinguished and other models of ultradrawability are discussed critically.

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Carbon‐13 NMR of polyethylenes: Correlation of the crystalline component T₁ with structure

Cited by 122 publications

References 38 publications

Crystallization of side chains in copolymers of ethylene and 1-alkenes

Crystallization of side chains in copolymers of ethylene and 1-alkenes

The Relation between Structure and Properties of Crystalline Polymers

Polymer ultradrawability: the crucial role of α-relaxation chain mobility in the crystallites

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Carbon‐13 NMR of polyethylenes: Correlation of the crystalline component T1 with structure

Cited by 122 publications

References 38 publications

Crystallization of side chains in copolymers of ethylene and 1-alkenes

Crystallization of side chains in copolymers of ethylene and 1-alkenes

The Relation between Structure and Properties of Crystalline Polymers

Polymer ultradrawability: the crucial role of α-relaxation chain mobility in the crystallites

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Carbon‐13 NMR of polyethylenes: Correlation of the crystalline component T₁ with structure