Crystal Structure of a Highly Efficient Clarifying Agent for Isotactic Polypropylene

Abstract

Using a combined approach based on X-ray powder diffraction and solid-state NMR spectroscopy, we were able to determine the crystal structure of 1,3,5-tris(2,2-dimethylpropionylamino)benzene, an efficient clarifying agent for isotactic polypropylene. The XPRD data and 1D solid-state NMR experiments allowed to exclude most of the possible primitive orthorhombic space groups with the exception of 11. The structure solution was carried out using real space methods including a close-contact penalty. Four space groups lead to reasonable wRp values below 10%. 13C13C double quantum (DQ) experiments of the labeled carbonyl group were measured with a supercycled symmetry based dipolar recoupling sequence. Taking into account the wRp values after Rietveld refinement as well as simulations of DQ build-up curves based on nine spin systems, the space group P212121 is clearly favored. The largest dipolar coupling within these spin systems was about 60 Hz corresponding to a distance of 5 Å. 1,3,5-Tris(2,2-dimethylpropionylamino)benzene crystallizes in an orthorhombic metric (a = 14.91(5) Å, b = 24.05(8) Å, c = 6.80(2) Å). The molecules are arranged in a pseudohexagonal rod packing with medium-strong hydrogen bonds and π-stacking. The antiferroelectric arrangement of neighbored rods leads to an averaging of the net dipolar moment in the whole crystal.

Controlling the Aspect Ratio of Supramolecular Fibers by Ultrasonication

“…For our investigations, we selected 1,3,5‐Tris(2,2‐dimethylpropionylamino)benzene) (t‐Bu‐BTA), a 1,3,5‐benzenetrisamide derivative (BTA) based on a 1,3,5‐triaminobenzene core and pivalic acid side groups, a carboxylic acid with a tert‐butyl moiety. This BTA is a well investigated supramolecular building block, which crystallizes in bulk in an orthorhombic space group . Under appropriate self‐assembly conditions upon cooling from hot non‐polar solutions, it readily forms rigid supramolecular micro and nanofibers .…”

Polarisation auf der Mesoskala durch geometrische Frustration in kolumnaren supramolekularen Kristallen

“…Diese wurden anschließend mittels Einkristallröntgenbeugung analysiert (kristallographische Details sind in Kapitel 2 der Hintergrundinformationen (SI) enthalten). Alle vier BTAs kristallisieren in hexagonalen Stabpackungen (Abbildung b), was mit früheren Studien für 1 und 2 übereinstimmt. Während 1 , 2 und 4 ähnliche interkolumnare Abstände d cc von 14.1 Å, 14.5 Å und 13.9 Å aufweisen, erhöhen die längeren peripheren Gruppen von 3 d cc auf 17.1 Å. Im Vergleich zu den N‐zentrierten Systemen mit einer Torsionsflexibilität der Amidgruppen mit mittleren Seitenkettentorsionen Φ (C ar C ar C O O) von ungefähr 35.1° ( 2 ) und 23.7° ( 4 ) weisen die C=O‐zentrierten Verbindungen von 1 und 3 eine höhere Torsionsflexibilität mit mittleren Seitenkettentorsionen Φ (C ar C ar C O O) von 39.5° ( 1 ) und 34.6° ( 3 ) auf.…”

A New Class of Ultra‐Efficient Supramolecular Nucleating Agents for Isotactic Polypropylene

“…As demonstrated by this image, this compound features a fi brillar, whisker-like crystals of diameters in the 50-200 nanometer range, indicative of preferential 1-dimensional columnar molecular aggregation. [ 22 ] A similar, a whisker-like needle prepared at higher concentrations was placed onto a compression-molded i -PP fi lm and examined under the polarized light microscope. In…”