Design Rules for Binary Bisamide Gelators: toward Gels with Tailor-Made Structures and Properties

This study intends to develop design rules for binary mixture of gelators that govern their assembly behavior and subsequently explore the impact of their supramolecular assembly patterns on the gels’ rheological properties. To achieve these goals, nBA gelators with odd and even parities [n-methylene spacers between the amide groups (n = 5–10) and 17 carbons at each end] were blended at different ratios. Such bisamides with simple structures were selected to study because their different spacer lengths offer the possibility to have matching or non-matching hydrogen bonds. The results show that the assembly behavior of binary mixtures of bisamide gelators is the same in the solid and gel states. Binary mixtures of gelators, which only differ two methylene moieties in the spacer length, form compounds and co-assemble into fibers and sheets observed for (5BA)1(7BA)1 and (6BA)1(8BA)1 mixtures, respectively. Binary gelator mixtures of the same parity and a larger spacer length difference still lead to mixing for the odd parity couple (5BA)1(9BA)1), but to partial phase separation for the even parity mixture (6BA)1(10BA)1. Binary mixtures of gelators of different parities gave complete phase separation in the solid state, and self-sorted gels consisting of discrete fibers and sheets in the gels of (5BA)3(6BA)1 and (5BA)3(10BA)1. The even–even binary gels (20 wt %) consisting of co-assembled sheets show higher G′ than odd–odd binary gels (20 wt %) consisting of co-assembled fibers. In general, the self-sorting of odd and even molecules into the separate primary structures results in a dramatic decrease of G′ compared to the co-assembled gels (20 wt %), except for (5BA)1(9BA)1 gel (20 wt %). It might be due to larger woven spheres in (5BA)1(9BA)1 gel (20 wt %), which probably have a less entangled gel network.

. Phase behavior of 5BA10BA gelators: (a) the second heating traces for various mixing ratios 5BA and 10BA and DSC N (T) fits on the experimental traces (the traces and fits were shifted vertically for clarity) and (b) XRD patterns of (5BA) 3 (10BA) 1 in comparison to single 5BA and 10BA gelators and binary (5BA) 1 (10BA) 1 which also shows two DSC peaks and two distinct first-order reflections (curves were normalized to the highest intensity), the insets magnify high-angle (20°-25° (2ϴ)) and low-angle (0°-10° (2ϴ)) regions.Table S1.Fit parameters and statistical coefficient of the DSC N (T) function fitted to the experimental DSC trace of molecularly mixed binary 5BA7BA at different ratios [a] .ΔC p,m,1 (W.g -1 .K -1 ) NA Second peak ΔH 2 (J.g -1 ) 126.18±0.04 104.52±0.23 116.64±0.29 131.82±0.12 120.[a] The samples (6 mg) were heated at 10 (K min -1 ) after calibration at the onset for the given weight and rate, in the case of (5BA) 1 (7BA) 1, only one fitting peak is required due to the peak overlap (the error margins are from the nonlinear fitting), ΔC p,m doesn't converge (Not available=NA) due to purely mathematical artefact, if the peaks are sufficiently apart with sufficient baseline tail on each side, the cumulative ΔC p,m can be reliably determined via the DSC N (T) function for binary systems.
Table S2.Fit parameters and statistical coefficient of the DSC N (T) function fitted to the experimental DSC trace of 6mg of molecularly mixed binary 5BA9BA at different ratios [a] .
First peak ΔH 1 (J.g -1 ) [a] The samples (6 mg) were heated at 10 (K min -1 ) after calibration at the onset for the given weight and rate, in the case of (5BA) 1 (9BA) 1, only one fitting peak is required due to the peak overlap (the error margins are from the nonlinear fitting), ΔC p,m does not converge (Not available=NA) due to purely mathematical artefact, if the peaks are sufficiently apart with sufficient baseline tail on each side, the cumulative ΔC p,m can be reliably determined via the DSC N (T) function for binary systems.
Table S3.Fit parameters and statistical coefficient of the DSC N (T) function fitted to the experimental DSC trace of 6mg of molecularly mixed binary 6BA8BA at different ratios [a] .[a] The samples (6 mg) were heated at 10 (K min -1 ) after calibration at the onset for the given weight and rate, in the case of (6BA) 1 (8BA) 1, only one fitting peak is required due to the peak overlap (the error margins are from the nonlinear fitting), ΔC p,m does not converge (Not available=NA) due to purely mathematical artefact, if the peaks are sufficiently apart with sufficient baseline tail on each side, the cumulative ΔC p,m can be reliably determined via the DSC N (T) function for binary systems.
Table S4.Fit parameters and statistical coefficient of the DSC N (T) function fitted to the experimental DSC trace of 6mg of molecularly mixed binary 6BA10BA at different ratios [a] .[a] The samples (6 mg) were heated at 10 (K min -1 ) after calibration at the onset for the given weight and rate, in the case of (6BA) 1 (10BA) 1, only one fitting peak is required due to the peak overlap (the error margins are from the nonlinear fitting), ΔC p,m does not converge (Not available=NA) due to purely mathematical artefact, if the peaks are sufficiently apart with sufficient baseline tail on each side, the cumulative ΔC p,m can be reliably determined via the DSC N (T) function for binary systems.
Table S5.Fit parameters and statistical coefficient of the DSC N (T) function fitted to the experimental DSC trace of 6mg of molecularly mixed binary 5BA6BA at different ratios [a] .
First peak ΔH 1 (J.g -1 ) [a] The samples (6 mg) were heated at 10 (K min -1 ) after calibration at the onset for the given weight and rate, in the case of (5BA) 3 (6BA) 1, only one fitting peak is required due to the peak overlap (the error margins are from the nonlinear fitting), ΔC p,m does not converge (Not available=NA) due to purely mathematical artefact, if the peaks are sufficiently apart with sufficient baseline tail on each side, the cumulative ΔC p,m can be reliably determined via the DSC N (T) function for binary systems.
Table S6.Fit parameters and statistical coefficient of the DSC N (T) function fitted to the experimental DSC trace of 6mg of molecularly mixed binary 5BA10BA at different ratios [a] .

First peak
ΔH 1 (J.g -1 ) [a] The samples (6 mg) were heated at 10 (K min -1 ) after calibration at the onset for the given weight and rate, in the case of (5BA) 3 (10BA) 1, only one fitting peak is required due to the peak overlap (the error margins are from the nonlinear fitting), ΔC p,m does not converge (Not available=NA) due to purely mathematical artefact, if the peaks are sufficiently apart with sufficient baseline tail on each side, the cumulative ΔC p,m can be reliably determined via the DSC N (T) function for binary systems.