Cocrystallization phenomena in piperazine‐based copolyamides as examined by differential scanning calorimetry, wide‐angle X‐ray diffraction, and solid‐state NMR

Abstract

Copolyamides 2.14/piperazine.14 with variable built-in ratios of 1,2-ethylenediamine (1,2-EDA) and piperazine (pip) were synthesized by solution polycondensation. The built-in ratio of both diamine comonomers was determined with solution 13 C NMR analysis. The gradual replacement of 1,2-EDA units by cycloaliphatic pip units in polyamide 2.14 resulted in a progressively decreased melting (T m ) and crystallization temperature of the obtained copolyamides. Apparently, the T m raising effect of the incorporation of rigid cycloaliphatic moieties is overruled by the simultaneous T m reduction caused by a decreasing hydrogen-bond density. Indications for cocrystallization of 2.14 and pip.14 repeating units were obtained by the thermal analysis of copolyamides 2.14/pip.14 and of a blend of both homopolyamides. A preliminary wideangle X-ray diffraction study pointed to the same conclusion. Solid-state NMR spectroscopy was used to investigate the influence of the composition on the percentage of the rigid phase of the copolyamides and delivered additional indications for cocrystallization.

Influence of Hydrogen Bonding on the Conformational Changes, the Brill Transition, and Lamellae Thickening in (Co)polyamides

“…The homopolymers PA2,14 and PApip,14 as well as the copolymers PA2,14-co-pip,14 were synthesized via a polycondensation reaction of 1,12-dodecanedicarbonyl dichloride and varying amounts of 1,2-ethylenediamine and piperazine as described elsewhere. 3 The piperazine-based copolyamides used in this study have a piperazine molar fraction of 0.30, 0.46, 0.54, 0.62, 0.82, and 0.90. These copolymers are referred to as coPA 0.30 through to coPA 0.90.…”

“…However, piperazine can act as a hydrogen bond acceptor. 3,4 Copolyamides of polyamide 2,14 (PA2,14) and piperazine (PApip,14) 3,4 were synthesized from 1,12-dodecanedicarboxylic acid and variable amounts of 1,2-ethylenediamine (1,2-EDA) and piperazine (pip). A range of copolyamides (PA2,14-copip,14) were prepared with varying piperazine content of 30-90 mol % as well as the homopolymers polyamide 2,14 (PA2,14) and polyamide pip, 14 (PApip,14).…”

“…Since piperazine does not contain any amide hydrogens, it is unable to act as a hydrogen bond donor; thus, hydrogen bonding is reduced. However, piperazine can act as a hydrogen bond acceptor. ,

1 Chemical structure of (a) 1,2-ethylenediamine-based and (b) piperazine-based repeat units.

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Cocrystallization in Piperazine-Based Polyamide Copolymers: Small- and Wide-Angle X-ray Diffraction Studies at 30 °C

“…4 The chemical structures of the two corresponding amide units are shown in Figure 1. In contrast to 1,2-EDA-based monomer residues, the piperazine-based residues do not contain any amide hydrogens and thus are not able to act as hydrogen bond donors.…”

Segmented Block Copolymers with Monodisperse Hard Segments: The Influence of H‐Bonding on Various Properties

“…As for the polyurethanes discussed above, non‐hydrogen‐bonding amides can be prepared using the secondary piperazine amine 17. By choosing to utilize piperazine instead of ethylene diamine, the melting temperature was reduced by 100 °C and the amide chain mobility was found to occur at a lower temperature.…”