The structure of copolymer crystals formed from dilute solution and in bulk

Domszy, R. C.; Alamo, Rufina G.; Mathieu, P.; Mandelkern, L.

doi:10.1002/pol.1984.180221003

Cited by 31 publications

(12 citation statements)

References 41 publications

(9 reference statements)

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“…This interpretation of the increase of the fold-surface free energy is in agreement with former studies of the crystallization behavior of random copolymers [57e61]. It has been suggested that surface energies generally increase with co-unit content, since a larger number of chain segments must participate on the growth of a single crystal of a given size, as compared with the corresponding homopolymer [60], ultimately leading to enhanced covalent coupling of the amorphous phase to the crystals by the increased number of chain segments traversing the phase boundary.…”

Section: Resultssupporting

confidence: 81%

Tailoring the rigid amorphous fraction of isotactic polybutene-1 by ethylene chain defects

Lorenzo

Androsch

Stolte

2014

Polymer

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Section: Resultssupporting

confidence: 81%

Tailoring the rigid amorphous fraction of isotactic polybutene-1 by ethylene chain defects

Lorenzo

Androsch

Stolte

2014

Polymer

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“…Similar results have been obtained with hydrogenated polybutadienes crystallized from dilute solution as well as for isotactic polystyrene and isotactic polypropylene. 88 Although initially surprising, these results are self-consistent. For a quenched high molecular weight linear polyethylene the average crystallite thickness is about half that of the long period.…”

Section: Resultsmentioning

confidence: 70%

Influence of molecular weight on the melting and phase structure of random copolymers of ethylene

Alamo¹,

Chan²,

Mandelkern³

et al. 1992

Macromolecules

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108

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The melting temperatures and phase structures of a series of hydrogenated polybutadienes with fixed co-unit content (2.3 mol % branch points) and varying molecular weights have been studied. These copolymers represent molecular weight and composition fractions of randomly ethyl-branched ethylene copolymers. Also studied were a set of random ethylene-hexene copolymers with a lower co-unit content. The observed melting temperatures, after a variety of crystallization procedures, were found to decrease with increasing molecular weight for both copolymer types. This unusual result could be attributed to the decreasing crystallite thickness in the chain direction with molecular weight. At the higher molecular weights, M = 4.6 X 10®, the crystallite thickness is reduced to about 30 A. Associated with the crystallite is a relatively large disordered overlayer. Although small-angle X-ray measurements and thin-section transmission electron microscopy give results that are in quantitative agreement for the crystallite thickness, the Raman LAM measurement give significantly higher values in the low-size range. The conventional extrapolative method of plotting the observed melting temperature against the crystallization temperature, in order to obtain the equilibrium melting temperature, failed for the random copolymers at low levels of crystallinity. A straight line resulted that paralleled the 45°line. Therefore, extrapolation to the equilibrium melting temperature could not be accomplished. Although the extrapolation could be made for higher levels of crystallinity, this procedure was arbitrary and lead to unreasonable values for the equilibrium melting temperature.

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“…4, compared to those determined from the enthalpy of melting. As usual for ethylene copolymers 16,17) the values from X-ray determination are higher than the DSC ones.…”

Section: Thermal Properties and Crystallinitymentioning

confidence: 64%

Synthesis and characterization of copolymers of ethylene and 1-octadecene using the rac-Et(Ind)2ZrCl2/MAO catalyst system

Quijada¹,

Narváez²,

Rojas³

et al. 1999

Macromol. Chem. Phys.

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SUMMARY: The copolymerization of ethylene and 1-octadecene using a bridged metallocene was studied in order to observe the effect of the comonomer on the catalytic activity. A noticeable increase in activity is seen as the concentration of 1-octadecene in the reaction medium increases. 13C NMR analysis shows 6.4 mol-% incorporation of comonomer at the highest 1-octadecene concentration in the feed used here. The molecular weight of the copolymers shows a drastic decrease that may be attributed to chain termination by transfer or b-elimination of the comonomer. As to the molecular weight distribution, it remains within a narrow range, as expected with metallocene catalysts. The melting temperature and the enthalpy of melting of the copolymers show a decrease with increasing comonomer content. As usual for ethylene copolymers, the X-ray crystallinities are higher than those determined from the enthalpy of melting.

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The structure of copolymer crystals formed from dilute solution and in bulk

Cited by 31 publications

References 41 publications

Tailoring the rigid amorphous fraction of isotactic polybutene-1 by ethylene chain defects

Tailoring the rigid amorphous fraction of isotactic polybutene-1 by ethylene chain defects

Influence of molecular weight on the melting and phase structure of random copolymers of ethylene

Synthesis and characterization of copolymers of ethylene and 1-octadecene using the rac-Et(Ind)2ZrCl2/MAO catalyst system

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