Distinct alignment of benzene derivatives in stretched polystyrene and polybutylacrylate gels: Specific polymer–solute interactions

Abstract

We have measured the alignment of a range of benzene derivatives in cross-linked polystyrene and poly(butyl acrylate) using a small number of residual dipolar couplings and simple geometric considerations. For apolar solutes in polystyrene and protic solutes in poly(butyl acrylate), the preferred molecular orientation does not coincide with the longest molecular axis (steric aligment). This behavior may be explained by specific π-π and hydrogen bonding interactions between solute and polymer, respectively, the latter being confirmed by molecular dynamics simulations.

Orientation and conformation of two [6]carbohelicenes in stretched polystyrene and a thermoresponsive polyaspartate

“…The least preferred orientation is the one with “flat” part, that is, the inner four rings approximately perpendicular to the field axis (green axis), where steric obstruction with the polymer chains along the stretching axis is maximal. As required for C 2 ‐symmetric molecules, the remaining principal axis of A (red axis) coincides with the symmetry axis.…”

“…As required for C 2 -symmetric molecules, [14,21] the remaining principal axis of A (red axis) coincides with the symmetry axis. For 2, we aimed at the determination of the preferred conformation of the para-methoxyphenyl substituent relative to the helicene.…”

“…7,7′‐Dimethyl‐[6]carbohelicene ( 1 ) and 7,7′‐di( p ‐methoxyphenyl)‐[6]carbohelicene ( 2 ) were synthesized as previously described . PS/CDCl 3 gels were prepared as described in Niklas et al. The copolymer (poly(benzyl) 0.5 (phenethyl) 0.5 ‐L‐aspartate) was generously donated by Dr. Mira Schwab (group Prof. Dr. Christina Thiele, TU Darmstadt), and samples were prepared according to the instructions .…”

“…During our ongoing research addressing the microscopic mechanism of molecular alignment, we recently became interested in the alignment of helical molecules, for which we anticipated likewise high enantiodifferentiation. [6]Carbohelicenes present ideal candidates because they (a) are synthetically readily available, (b) do not racemize at ambient temperature, and (c) have a C 2 symmetry axis and hence give rather simple NMR spectra.…”

Resonance and structural assignment in (car)borane clusters using 11B residual quadrupolar couplings

“…Due to the C 2v symmetry the alignment tensor contains only two unknowns so that the Q factor determined from four 11 B RQCs should become large for all except the correct assignment. 25 Taking into account the sign information received from the 1 H, 11 B-HMQC, the Q factors for the six possibilities to assign the green, red and blue 11 B triplets to B 1 /B 4 , B 7 /B 9 and B 8 /B 10 are displayed in Fig. 4 (black bars).…”