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.
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ABSTRACT: Complexation behaviour of cellulose derivative/surfactant mixtures in aqueous solution was investigated by nonlinear enhanced Rayleigh scattering (NERS). The NERS spectra of polymer solutions, including second-order scattering, third-order scattering, frequency doubling scattering and triplet frequency scattering were created using by spectrofluorometer. The results indicated that NERS intensity of cellulose derivative/surfactant systems changes differently with continuing addition of surfactant due to the complexation between cellulose derivative and surfactant. The critical micelle concentration of cellulose derivatives/surfactants system is easy to obtain. The change of NERS intensity reveals the complexation behaviour of cellulose derivative/surfactant and the aggregation state of polymer chains in evidence. Therefore, NERS had been successfully developed to study complexation behaviour of cellulose derivative/surfactant mixtures in solution. KeywordsCellulose derivative–Nonlinear enhanced Rayleigh scattering–Complexation behaviour–Surfactant–Micelle–AggregationColloid and Polymer Science 05/2011; 289(7):767-774. DOI:10.1007/s00396-011-2390-3 · 2.41 Impact Factor
Conference Paper: Geometry And Temperature Extensions To The Gummel-poon ModelCustom Integrated Circuits Conference, 1992., Proceedings of the IEEE 1992; 06/1992
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ABSTRACT: Turbidity, small-angle neutron scattering (SANS), rheology, and dynamic light scattering measurements have been carried out on aqueous semidilute anionic hydroxyethylcellulose (HEC(−)) and its uncharged analogue (HEC(0)) in the presence of an anionic surfactant (SDS) or a cationic surfactant (CTAB or Gemini(+)). Weak interactions between HEC(−) and the like-charged SDS is observed, whereas prominent electrostatic attractions between the polyelectrolyte and the oppositely charged surfactants drive the association behavior for these systems. Turbidity experiments and SANS measurements on aqueous semidilute solutions of the HEC(−) with a cationic surfactant (CTAB or Gemini(+)) reveal the formation of large polymer–surfactant association complexes as the surfactant concentration increases. The dynamic light scattering measurements also disclose pronounced interactions between HEC(−) and the oppositely charged surfactants and the formation of association complexes. The relaxation process is bimodal, and the slow mode becomes very dominant in mixtures of HEC(−)/CTAB and HEC(−)/Gemini(+). The SANS results at high q values suggest that the polymer chains are locally stretched. The q dependence of the reduced intensity from light scattering measurements on semidilute solutions of HEC(0) and HEC(−) indicate the formation of compact structures.Colloids and Surfaces A Physicochemical and Engineering Aspects 04/2006; 279(1-3):40-49. DOI:10.1016/j.colsurfa.2005.12.031 · 2.35 Impact Factor