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Http Www Theses Fr, 1991
Des polymeres hydrosolubles a faibles teneurs en groupements hydrophobes (0. 75 a 3% mol. ) ont e... more Des polymeres hydrosolubles a faibles teneurs en groupements hydrophobes (0. 75 a 3% mol. ) ont ete synthetises par copolymerisation radicalaire de l'acrylamide et du n-ethylphenylacrylamide. Une etude du mecanisme de polymerisation indique que la distribution des sequences hydrophobes dans le copolymere depend du mode de synthese: polymerisations micellaires (en presence de tensio-actif), heterogene ou en melange de solvant. Seule la polymerisation micellaire conduit a des copolymeres presentant de fortes interactions hydrophobes. Les proprietes rheologiques des copolymeres ont ete etudiees en regime semi-dilue en fonction de la concentration en copolymere, la vitesse de cisaillement, la teneur en groupements hydrophobes et en tensio-actif. Les copolymeres prepares par voie micellaire ont un pouvoir epaississant superieur a celui d'homopolymeres de meme masse moleculaire (2. 10#6). Sous l'action de contraintes de cisaillement, il y a dissociation reversible des liaisons interchaines. L'addition de tensio-actif permet de regler les interactions hydrophobes et donc la viscosite des solutions. L'influence de l'histoire de l'echantillon a ete examinee en detail. La formation de microdomaines hydrophobes a ete suivie par une technique de fluorescence et les resultats obtenus confirment les donnees rheologiques
Macromolecules, 1993
Hydrophobically modified water-soluble polymers have been prepared by radial copolymerization of ... more Hydrophobically modified water-soluble polymers have been prepared by radial copolymerization of acrylamide and ethylphenylacrylamide as the hydrophobic comonomer. Three methods of synthesis in aqueous media have been investigated (i) a 'micellar" process in which the presence of a surfactant ensures the solubilization of the hydrophobic monomer; (ii) a 'homogeneous" process wherein a miscible cosolvent is used; (iii) a "heterogeneous" process, without additive to solubilize the insoluble monomer. The properties of the copolymers in dilute and semidilute aqueous solutions strongly depend on the conditions of the synthesis. Copolymers prepared by the homogeneous and heterogeneous processes behave like homopolyacrylamide; i.e., hydrophobic interactions do not occur significantly. Copolymers obtained by micellar copolymerization exhibit improved thickening properties due to intermolecular hydrophobic associations. These differences can be directly related to the copolymer microstructure, i.e., to a random or blocky distribution of the hydrophobic units. The blockmess of the copolymer can be adjusted by varying the [hydrophobel/[micellel ratio at a constant hydrophobe level. Thus, it is possible to control the association degree and therefore the rheological properties. Fluorescence studies, using pyrene as a probe, reveal the formation of hydrophobic microdomains which corroborate the rheological results.
Berichte der Bunsengesellschaft für physikalische Chemie, 1996
Dioctadecyldimethylammonium chloride (DODMAC) dispersions containing high concentrations of CaC12... more Dioctadecyldimethylammonium chloride (DODMAC) dispersions containing high concentrations of CaC12 were stabilised using cationic polyelectrolytes with terminal hydrophobic anchors. The cationic polyelectrolytes were based on quarternised poly(viny1-2-pyridine). The stability of the dispersions was dependent on the molecular weight of the polymer and the length of the hydrocarbon anchor. The amount of polyelectrolyte required to stabilise the dispersions was dependent on the type of polymer used and the concentration of salt in the dispersion. Some of the polymers were also capable of stabilising dispersions that were heated above the LB-L, phase transition temperature of the DODMAC vesicles. The polyelectrolytes that stabilised the dispersions most successfully in this study had molecular weights of about 1OooO-20000 and hydrocarbon anchors containing 16 carbon atoms.
Http Www Theses Fr, 1991
Des polymeres hydrosolubles a faibles teneurs en groupements hydrophobes (0. 75 a 3% mol. ) ont e... more Des polymeres hydrosolubles a faibles teneurs en groupements hydrophobes (0. 75 a 3% mol. ) ont ete synthetises par copolymerisation radicalaire de l'acrylamide et du n-ethylphenylacrylamide. Une etude du mecanisme de polymerisation indique que la distribution des sequences hydrophobes dans le copolymere depend du mode de synthese: polymerisations micellaires (en presence de tensio-actif), heterogene ou en melange de solvant. Seule la polymerisation micellaire conduit a des copolymeres presentant de fortes interactions hydrophobes. Les proprietes rheologiques des copolymeres ont ete etudiees en regime semi-dilue en fonction de la concentration en copolymere, la vitesse de cisaillement, la teneur en groupements hydrophobes et en tensio-actif. Les copolymeres prepares par voie micellaire ont un pouvoir epaississant superieur a celui d'homopolymeres de meme masse moleculaire (2. 10#6). Sous l'action de contraintes de cisaillement, il y a dissociation reversible des liaisons interchaines. L'addition de tensio-actif permet de regler les interactions hydrophobes et donc la viscosite des solutions. L'influence de l'histoire de l'echantillon a ete examinee en detail. La formation de microdomaines hydrophobes a ete suivie par une technique de fluorescence et les resultats obtenus confirment les donnees rheologiques
Macromolecules, 1993
Hydrophobically modified water-soluble polymers have been prepared by radial copolymerization of ... more Hydrophobically modified water-soluble polymers have been prepared by radial copolymerization of acrylamide and ethylphenylacrylamide as the hydrophobic comonomer. Three methods of synthesis in aqueous media have been investigated (i) a 'micellar" process in which the presence of a surfactant ensures the solubilization of the hydrophobic monomer; (ii) a 'homogeneous" process wherein a miscible cosolvent is used; (iii) a "heterogeneous" process, without additive to solubilize the insoluble monomer. The properties of the copolymers in dilute and semidilute aqueous solutions strongly depend on the conditions of the synthesis. Copolymers prepared by the homogeneous and heterogeneous processes behave like homopolyacrylamide; i.e., hydrophobic interactions do not occur significantly. Copolymers obtained by micellar copolymerization exhibit improved thickening properties due to intermolecular hydrophobic associations. These differences can be directly related to the copolymer microstructure, i.e., to a random or blocky distribution of the hydrophobic units. The blockmess of the copolymer can be adjusted by varying the [hydrophobel/[micellel ratio at a constant hydrophobe level. Thus, it is possible to control the association degree and therefore the rheological properties. Fluorescence studies, using pyrene as a probe, reveal the formation of hydrophobic microdomains which corroborate the rheological results.
Berichte der Bunsengesellschaft für physikalische Chemie, 1996
Dioctadecyldimethylammonium chloride (DODMAC) dispersions containing high concentrations of CaC12... more Dioctadecyldimethylammonium chloride (DODMAC) dispersions containing high concentrations of CaC12 were stabilised using cationic polyelectrolytes with terminal hydrophobic anchors. The cationic polyelectrolytes were based on quarternised poly(viny1-2-pyridine). The stability of the dispersions was dependent on the molecular weight of the polymer and the length of the hydrocarbon anchor. The amount of polyelectrolyte required to stabilise the dispersions was dependent on the type of polymer used and the concentration of salt in the dispersion. Some of the polymers were also capable of stabilising dispersions that were heated above the LB-L, phase transition temperature of the DODMAC vesicles. The polyelectrolytes that stabilised the dispersions most successfully in this study had molecular weights of about 1OooO-20000 and hydrocarbon anchors containing 16 carbon atoms.