Environmentally friendly biopolyols have been produced with crude glycerol as the sole feedstock using a one-pot thermochemical conversion process without the addition of extra catalysts and reagents. Structural features of these biopolyols were characterized by rheology analysis. Rigid polyurethane (PU) foams were obtained from these crude glycerol-based biopolyols and the foaming mechanism of the process was explored. Investigations revealed that partial carbonyl groups hydrogen-bonded with N-H were replaced by aromatic rings after the introduction of branched fatty acid ester chains in the "urea rich" phase, and that distinct microphases had formed in the foams. Studies showed that branched fatty acid ester chains in the biopolyols played an important role in reducing the degree of microphase separation
Electrostatic interactions
play a significant role in regulating
biological systems and have received increasing attention due to their
usefulness in designing advanced stimulus-responsive materials. Polypeptoids
are highly tunable N-substituted peptidomimetic polymers that lack
backbone hydrogen bonding and chirality. Therefore, polypeptoids are
suitable systems to study the effect of noncovalent interactions of
substituents without complications of backbone intramolecular and
intermolecular hydrogen bonding. In this study, all-atom molecular
dynamics (MD) simulations were performed on micelles formed by a series
of sequence-defined ionic polypeptoid block copolymers consisting
of a hydrophobic segment and a hydrophilic segment in an aqueous solution.
By combining the results from MD simulations and experimental small-angle
neutron scattering data, further insights were gained into the internal
structure of the formed polypeptoid micelles, which is not always
directly accessible from experiments. In addition, information was
gained into the physics of the noncovalent interactions responsible
for the self-assembly of weakly charged polypeptoids in an aqueous
solution. While the aggregation number is governed by electrostatic
repulsion of the negatively charged carboxylate (COO
–
) substituents on the polypeptoid chain within the micelle, MD simulations
indicate that the position of the charge on singly charged chains
mediates the shape of the micelle through the charge–dipole
interactions between the COO
–
substituent and the
surrounding water. Therefore, the polypeptoid micelles formed from
the single-charged series offer the possibility for tailorable micelle
shapes. In contrast, the polypeptoid micelles formed from the triple-charged
series are characterized by more pronounced electrostatic repulsion
that competes with more significant charge–sodium interactions,
making it difficult to predict the shape of the micelles. This work
has helped further develop design principles for the shape and structure
of self-assembled micelles by controlling the position of charged
moieties on the backbone of polypeptoid block copolymers.
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