Chain-folded lamellar crystals of aliphatic polyamides. Investigation of nylons 4 8, 4 10, 4 12, 6 10, 6 12, 6 18 and 8 12

Structure and morphology of nylon 2 4 lamellar crystals: Comparison with polypeptides and relationship with other nylons

“…The chemical synthesis and detailed chemical characterization has already been reported by Wang, Shao, and Yu. 18 Unlike many other aliphatic polyamides, [1][2][3][4][5][6]19,20 nylon 2 4 will not thermally crystallize from polyols, such as 1,4-butanediol, and alternative crystallization methods need to be used. The polymer was crystallized from a 0.1% w/v solution in phenol at Computer-generated space-filling models of: (a) the nylon 2 4 apolar chain; (b) the nylon 3 polar chain.…”

“…Across the range, from nylons with long alkane segments, 12 12 and 6 18 for example, to nylons 4 4 and 2 6, we find similarities and also subtle and important differences in both crystal structure and behavior on heating. [1][2][3][4][5][6] The length of the alkane segments affects the melting behavior 7 and can influence the type and nature of the adjacent reentry folds; below a certain length, the alkane segments alone are not able to achieve stereochemically unstrained folds, and amide units need to be incorporated within the folds. 3 We now consider nylon 2 4, which has only two methylene units in both the diamine and diacid alkane segments, as shown in Figure 1(a).…”

Polymorphism of poly(nonamethyleneoxamide) crystal

“…Above behavior of the molecular chain packing is often observed for other nylon below the Brill transition. On heating, the crystalline phase transition, the so-called Brill transition, is observed in aliphatic nylons [4,5,19,20]. The Brill transitions of various nylons have been extensively studied [21][22][23].…”

“…The crystal structures for aliphatic nylons have been widely investigated [1][2][3][4][5]. Generally, the  form appears in the crystals of even-even nylons [1,6].…”

Amorphous and crystalline phase interaction during the Brill transition in nylon 66

“…At the transition point the two diffraction maxima are replaced by one with a spacing of 0.42 nm [6][7][8]. Over the years since its discovery, the Brill transition has been studied for various types of even-even and odd-even polyamides [9][10][11][12][13] and for different crystallization conditions [10]. In a recent study on the Brill transition in transcrystalline nylon 66 we pointed out that the explanation for the effect of the crystalline structure on this first order transition must be based on the existence of reciprocal interactions between the crystalline and amorphous phases [14], which corresponded to the finding that structural changes within the crystalline domains in the lamellae (as in the Brill transition) are accompanied by changes in the packing of the amorphous chain segments outside the lamellae [15].…”