@article{Gonzalez:2018:10.1021/acs.macromol.8b00178,
author = {Gonzalez, Lopez C and Colby, R and Cabral, JP},
doi = {10.1021/acs.macromol.8b00178},
journal = {Macromolecules},
pages = {3165--3175},
title = {Electrostatic and hydrophobic interactions in NaCMC aqueous solutions: effect of degree of substitution},
url = {http://dx.doi.org/10.1021/acs.macromol.8b00178},
volume = {51},
year = {2018}
}

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TY  - JOUR
AB  - The rheology of water soluble polyelectrolytesat intermediate and high concentrations is controlled byentanglements,  hydrophobic  and  electrostatic  interac-tions, whose influence is difficult to isolate. We investi-gate the rheology of semidilute solutions of sodium car-boxymethyl cellulose (NaCMC) with molecular weightMw'2.5×105g/mol  and  varying  degree  of  substi-tution (D.S.) as a function of polymer concentration invarious solvent media: salt-free water (long ranged elec-trostatic  interactions),  0.5M  aqueous  NaCl  (screenedelectrostatics) and 0.5M aqueous NaOH (screened elec-trostatics, diminished hydrophobic interactions) in or-der to selectively probe the different interactions. De-creasing D.S. is found to decrease solubility and inducepartial  aggregation  and  eventual  gelation.  In  salt-freeand 0.5M NaCl solution, NaCMC with D.S.'1.2 ex-hibits hydrophilic polyelectrolyte and neutral polymerin good solvent behaviour respectively. Decreasing D.S.to'0.7-0.8  leads  to  hydrophobic  behaviour  in  bothsolvents, becoming weak gels at high concentrations. In0.5M NaOH (pH = 13.5) the viscosities of samples withdifferent  D.S.  become  identical  when  plotted  againstthe  overlap  parameter,  which  we  interpret  as  result-ing  from  the  solubilisation  of  unsubstituted  celluloseblocks. Small angle neutron scattering (SANS) data in-dicate  that  the  polymer  conformation  is  not  stronglyaffected by hydrophobic interactions. By varying D.S.,ionic  strength  and  pH,  we  demonstrate  the  tuning  ofNaCMC-solvent interactions, controlling separately the electrostatic  and  hydrophobic  effects  on  the  solutionrheology.
AU  - Gonzalez,Lopez C
AU  - Colby,R
AU  - Cabral,JP
DO  - 10.1021/acs.macromol.8b00178
EP  - 3175
PY  - 2018///
SN  - 0024-9297
SP  - 3165
TI  - Electrostatic and hydrophobic interactions in NaCMC aqueous solutions: effect of degree of substitution
T2  - Macromolecules
UR  - http://dx.doi.org/10.1021/acs.macromol.8b00178
UR  - http://hdl.handle.net/10044/1/58673
VL  - 51
ER  - 

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