Conclusions
Metropolis Monte Carlo simulations showed that the number of gauche
bonds is effectively zero for TC hydrocarbon chains at a temperature of
30°. This means that, at that temperature, TC molecules are fully
extended and effectively rigid.
Using the experimental q-value for the Bragg peak, a tilted angle of 27°
was obtained, which seems to be in essential agreement with one of the
local free energy minimum, the predicted value of 33° from the paper
Peyronel et al. (in review) The disagreement between 27° and 33° is,
perhaps, not surprising when one considers the crudity of the model.
This result, however, justifies the concept of “locked-in” states and
supports the results obtained using the MMC method in which the TC and
BL chains are rigidly extended.
Similar conclusions can be said for the BL molecule, except that for BL,
the tilt angle obtained using the MMC and the experimental value was
~40°. 40° was not one of the computed local minimum.
This also is not surprising because of the effects of electrostatic
interactions dealt with by Peyronel et al. (in review). There we
compared the strengths of the repulsive electrostatic interactions and
the attractive dispersion energies and concluded that it was not
possible within the context of the hydrocarbon chain “lock-in” model
to easily deduce a unique tilt angle. In the case of BL, MMC computation
would be necessary, but that is not the purpose of this paper.
The theory of chain tilting reported by Peyonel et al. (in review) could
also apply to other symmetric monolayer systems in which this phenomenon
can be observed. Chain tilting alone, however, should not be applied to
systems which contain asymmetric layering or bilayers, in which twists
(gauche bonds) may be more appropriate to explain these and other kinds
of phenomena.
These results should help food scientists simulate and predict, by using
these techniques, the average length of a bilayer of possible
oleogelators.
Acknowledgements: This project was supported by the Utah
Agricultural Experiment Station, Utah State University and approved as
paper number 9645. Authors would like to thank Utah State University,
the University of Guelph, St. Francis Xavier University. DAP likes to
acknowledge NSERC of Canada (grant # R0178050).
Conflict of interest: Authors declare no conflict of interest.
Authors contribution: Dr. Silvana Martini, Dr. David Pink, and
Dr. Fernanda Peyronel conceived the idea and provided insight into the
project. Dr. Silvana Martini and Dr. Pink provided funding and wrote
parts of the manuscript. Mr. Joseph Cooney designed, coded, and tested
the simulation, gathered and presented data, and wrote the manuscript.
All authors reviewed the manuscript before submission.