Shell Structure of Natural Rubber Particles: Evidence of Chemical Stratification by Electrokinetics and Cryo-TEM
(2013) In Langmuir 29(47). p.14655-14665- Abstract
- The interfacial structure of natural rubber (NR) colloids is investigated by means of cryogenic transmission electron microscopy (cryo-TEM) and electrokinetics over a broad range of KNO3 electrolyte concentrations (4-300 mM) and pH values (1-8). The asymptotic plateau value reached by NR electrophoretic mobility (mu) in the thin double layer limit supports the presence of a soft (ion- and water-permeable) polyelectrolytic type of layer located at the periphery of the NR particles. This property is confirmed by the analysis of the electron density profile obtained from cryo-TEM that evidences a similar to 2-4 nm thick corona surrounding the NR polyisoprene core. The dependence of mu on pH and salt concentration is further marked by a... (More)
- The interfacial structure of natural rubber (NR) colloids is investigated by means of cryogenic transmission electron microscopy (cryo-TEM) and electrokinetics over a broad range of KNO3 electrolyte concentrations (4-300 mM) and pH values (1-8). The asymptotic plateau value reached by NR electrophoretic mobility (mu) in the thin double layer limit supports the presence of a soft (ion- and water-permeable) polyelectrolytic type of layer located at the periphery of the NR particles. This property is confirmed by the analysis of the electron density profile obtained from cryo-TEM that evidences a similar to 2-4 nm thick corona surrounding the NR polyisoprene core. The dependence of mu on pH and salt concentration is further marked by a dramatic decrease of the point of zero electrophoretic mobility (PZM) from 3.6 to 0.8 with increasing electrolyte concentration in the range 4-300 mM. Using a recent theory for electrohydrodynamics of soft multilayered particles, this "anomalous" dependence of the PZM on electrolyte concentration is shown to be consistent with a radial organization of anionic and cationic groups across the peripheral NR structure. The NR electrokinetic response in the pH range 1-8 is indeed found to be equivalent to that of particles surrounded by a positively charged similar to 3.5 nm thick layer (mean dissociation pK similar to 4.2) supporting a thin and negatively charged outermost layer (0.6 nm in thickness, pK similar to 0.7). Altogether, the strong dependence of the PZM on electrolyte concentration suggests that the electrostatic properties of the outer peripheral region of the NR shell are mediated by lipidic residues protruding from a shell containing a significant amount of protein-like charges. This proposed NR shell interfacial structure questions previously reported NR representations according to which the shell consists of either a fully mixed lipid protein layer, or a layer of phospholipids residing exclusively beneath an outer proteic film. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/4273417
- author
- Rochette, Christophe N. ; Crassous, Jerome LU ; Drechsler, Markus ; Gaboriaud, Fabien ; Eloy, Marie ; de Gaudemaris, Benoit and Duval, Jerome F. L.
- organization
- publishing date
- 2013
- type
- Contribution to journal
- publication status
- published
- subject
- in
- Langmuir
- volume
- 29
- issue
- 47
- pages
- 14655 - 14665
- publisher
- The American Chemical Society (ACS)
- external identifiers
-
- wos:000327360500039
- scopus:84888616269
- pmid:24152085
- ISSN
- 0743-7463
- DOI
- 10.1021/la4036858
- language
- English
- LU publication?
- yes
- id
- d3c3214f-4e80-4fd0-a599-ab7121de3b52 (old id 4273417)
- date added to LUP
- 2016-04-01 10:17:20
- date last changed
- 2022-04-27 20:33:42
@article{d3c3214f-4e80-4fd0-a599-ab7121de3b52,
abstract = {{The interfacial structure of natural rubber (NR) colloids is investigated by means of cryogenic transmission electron microscopy (cryo-TEM) and electrokinetics over a broad range of KNO3 electrolyte concentrations (4-300 mM) and pH values (1-8). The asymptotic plateau value reached by NR electrophoretic mobility (mu) in the thin double layer limit supports the presence of a soft (ion- and water-permeable) polyelectrolytic type of layer located at the periphery of the NR particles. This property is confirmed by the analysis of the electron density profile obtained from cryo-TEM that evidences a similar to 2-4 nm thick corona surrounding the NR polyisoprene core. The dependence of mu on pH and salt concentration is further marked by a dramatic decrease of the point of zero electrophoretic mobility (PZM) from 3.6 to 0.8 with increasing electrolyte concentration in the range 4-300 mM. Using a recent theory for electrohydrodynamics of soft multilayered particles, this "anomalous" dependence of the PZM on electrolyte concentration is shown to be consistent with a radial organization of anionic and cationic groups across the peripheral NR structure. The NR electrokinetic response in the pH range 1-8 is indeed found to be equivalent to that of particles surrounded by a positively charged similar to 3.5 nm thick layer (mean dissociation pK similar to 4.2) supporting a thin and negatively charged outermost layer (0.6 nm in thickness, pK similar to 0.7). Altogether, the strong dependence of the PZM on electrolyte concentration suggests that the electrostatic properties of the outer peripheral region of the NR shell are mediated by lipidic residues protruding from a shell containing a significant amount of protein-like charges. This proposed NR shell interfacial structure questions previously reported NR representations according to which the shell consists of either a fully mixed lipid protein layer, or a layer of phospholipids residing exclusively beneath an outer proteic film.}},
author = {{Rochette, Christophe N. and Crassous, Jerome and Drechsler, Markus and Gaboriaud, Fabien and Eloy, Marie and de Gaudemaris, Benoit and Duval, Jerome F. L.}},
issn = {{0743-7463}},
language = {{eng}},
number = {{47}},
pages = {{14655--14665}},
publisher = {{The American Chemical Society (ACS)}},
series = {{Langmuir}},
title = {{Shell Structure of Natural Rubber Particles: Evidence of Chemical Stratification by Electrokinetics and Cryo-TEM}},
url = {{http://dx.doi.org/10.1021/la4036858}},
doi = {{10.1021/la4036858}},
volume = {{29}},
year = {{2013}},
}