Details

Autor(en) / Beteiligte

• Krishnamoorti, Ramanan
• Graessley, William W.
• Zirkel, Achim
• Richter, Dieter
• Hadjichristidis, Nikos
• Fetters, Lewis J.
• Lohse, David J.

Titel

Melt-state polymer chain dimensions as a function of temperature

Ist Teil von

• Journal of polymer science. Part B, Polymer physics, 2002-08, Vol.40 (16), p.1768-1776

Ort / Verlag

New York: Wiley Subscription Services, Inc., A Wiley Company

Erscheinungsjahr

2002

Link zum Volltext

Quelle

Wiley Online Library Journals Frontfile Complete

Beschreibungen/Notizen

• The unperturbed chain dimensions (〈R2〉o/M) of cis/trans‐1,4‐polyisoprene, a near‐atactic poly(methyl methacrylate), and atactic polyolefins were measured as a function of temperature in the melt state via small‐angle neutron scattering (SANS). The polyolefinic materials were derived from polydienes or polystyrene via hydrogenation or deuteration and represent structures not encountered commercially. The parent polymers were prepared via lithium‐based anionic polymerizations in cyclohexane with, in some cases, a polymer microstructure modifier present. The polyolefins retained the near‐monodisperse molecular weight distributions exhibited by the precursor materials. The melt SANS‐based chain dimension data allowed the evaluation of the temperature coefficients [dln 〈R2〉o/dT(κ)] for these polymers. The evaluated polymers obeyed the packing length (p)‐based expressions of the plateau modulus, G oN = kT/n 2tp3 (MPa), and the entanglement molecular weight, Me = ρNan 2tp3 (g mol−1), where nt denotes the number (∼21) of entanglement strands in a cube with the dimensions of the reptation tube diameter (dt) and ρ is the chain density. The product n 2tp3 is the displaced volume (Ve) of an entanglement that is also expressible as pd 2t or kT/G oN. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1768–1776, 2002