title: Phase behavior of cationic hydroxyethyl cellulose-sodium dodecyl sulfate mixtures: effects of molecular weight and ethylene oxide side chain length of polymers.
abstract: Novel cationic hydroxyethyl cellulose (HEC) polymers with different molecular weights (1.1 x 10(5) to 1.7 x 10(6) g/mol) and ethylene oxide (EO) side chain lengths (1.5-2.9 EO units) were mixed with sodium dodecyl sulfate (SDS) in aqueous solutions. The phase diagrams of cationic HEC-SDS complexes were determined in the dilute polymer concentration regime (< 0.5 wt %) with gradual addition of SDS molecules. The viscosity and structures of the complexes during the phase evolution were studied using rheometry and dynamic light scattering. The gradual addition of SDS first induced interchain associations with the bound SDS aggregates serving as cross-linkers to form an open network structure, producing a very broad size distribution and high viscosities of the complex solutions, and then condensed the network and induced a structure reorganization, resulting in globular aggregates with narrow size distributions. The growth of these globular aggregates in size eventually led to macroscopic sedimentation near charge neutralization. Further addition of SDS randomly broke the sedimentary aggregates into small particles and SDS micelles with low solution viscosities. The effects of molecular weight and EO side chain length of polymers on the phase boundary, viscosity, and structure of cationic HEC-SDS complexes were discussed.
authors.affiliation: Department of Chemistry, College of Staten Island, The City University of New York, 2800 Victory Boulevard, 10314, USA. zhoush@mail.csi.cuny.edu
authors.forename: Shuiqin
authors.initials: S
authors.lastname: Zhou
authors.forename: Chang
authors.initials: C
authors.lastname: Xu
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
authors.forename: Patricia
authors.initials: P
authors.lastname: Golas
authors.forename: James
authors.initials: J
authors.lastname: Batteas
authors.forename: Lowell
authors.initials: L
authors.lastname: Kreeger
mesh_terms: D002412:Cations / Q000737:chemistry; D002482:Cellulose / Q000031:analogs & derivatives* / Q000737:chemistry; D005027:Ethylene Oxide / Q000737:chemistry*; D008956:Models, Chemical; D008970:Molecular Weight; D044367:Phase Transition; D011108:Polymers / Q000737:chemistry*; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry
chemical_list: D002412:Cations; D011108:Polymers; D012996:Solutions; D012967:Sodium Dodecyl Sulfate; D002482:Cellulose; C002283:hydroxyethylcellulose; D005027:Ethylene Oxide