TY - JOUR
T1 - The smallest amphiphiles
T2 - Nanostructure in protic room-temperature ionic liquids with short alkyl groups
AU - Atkin, Rob
AU - Warr, Gregory G.
PY - 2008/4/10
Y1 - 2008/4/10
N2 - Room-temperature ionic liquids (ILs) are low-melting-point organic salts that, until recently, were thought to have homogeneous microstructure. In this work, we investigate nanoscale segregation of short (4) alkyl chain ILs using propylammonium nitrate (PAN) and ethylammonium nitrate (EAN). Structure peaks at q = 0.54 Å-1 for PAN and at q = 0.66 Å-1 for EAN, corresponding to Bragg spacings (D* = 2π/qmax) of 11.6 and 9,7 Å respectively, provide the first experimental evidence of nanoscale heterogeneity for ILs with alkyl chains less than C4. The observation that these ILs are not optically birefringent and the fits obtained suggest a disordered, locally smectic or sponge-like structure. Solvophobic interaction between alkyl groups is the most important factor for the production of nanoscale heterogeneities, but electrostatic and hydrogen bonding attractions between the amine nitrogen and the nitrate anion will also play a role.
AB - Room-temperature ionic liquids (ILs) are low-melting-point organic salts that, until recently, were thought to have homogeneous microstructure. In this work, we investigate nanoscale segregation of short (4) alkyl chain ILs using propylammonium nitrate (PAN) and ethylammonium nitrate (EAN). Structure peaks at q = 0.54 Å-1 for PAN and at q = 0.66 Å-1 for EAN, corresponding to Bragg spacings (D* = 2π/qmax) of 11.6 and 9,7 Å respectively, provide the first experimental evidence of nanoscale heterogeneity for ILs with alkyl chains less than C4. The observation that these ILs are not optically birefringent and the fits obtained suggest a disordered, locally smectic or sponge-like structure. Solvophobic interaction between alkyl groups is the most important factor for the production of nanoscale heterogeneities, but electrostatic and hydrogen bonding attractions between the amine nitrogen and the nitrate anion will also play a role.
UR - http://www.scopus.com/inward/record.url?scp=46949110592&partnerID=8YFLogxK
U2 - 10.1021/jp801190u
DO - 10.1021/jp801190u
M3 - Article
AN - SCOPUS:46949110592
SN - 1520-6106
VL - 112
SP - 4164
EP - 4166
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 14
ER -