Polyisobutylene: fractional precipitation from binary solvent induced by non-solvent addition
1981; Elsevier BV; Volume: 22; Issue: 4 Linguagem: Inglês
10.1016/0032-3861(81)90160-9
ISSN1873-2291
AutoresMartin‐Pierre Sauviat, J. P. Cohen‐Addad,
Tópico(s)Advanced Physical and Chemical Molecular Interactions
ResumoLarge fractions of polyisobutylene chains may be obtained from precipitation induced by acetone added to solutions of polymer in a binary mixture (chloroform and dichloromethane). Fractions were characterized by weight average molecular weights, M̄w, and average radii of gyration, R̄2G, obtained from light-scattering measurements performed on a good solvent (cyclohexane); the product M̄w × R̄2G was found to vary according to the formula: Mw × R2G = 1.33 × Mmw with m = 2.22; while the intrinsic viscosity of fractions was found to vary as: [keta;] = 1.11x10-4 × Mmw with n = 0.76. Considering that m = 2v + 1 and n = 3v − 1, where v is the critical exponent associated with the description of properties of polymer chain solutions; values of v derived from m and n were found to be 0·61 or 0·58, respectively; the theoretical value is known to be 0·588. Polydispersity indices, l, were obtained from g.p.c. measurements: 1.1 < l < 1.3.
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