Polyamides with a Choice of Structure and Crystal Surface Chemistry. Studies of Chain-Folded Lamellae of Nylons 8 10 and 10 12 and Comparison with the Other 2N 2(N + 1) Nylons 4 6 and 6 8

作者：Nathan A. Jones, E. D. T. Atkins, Matthew J. Hill, Sharon J. Cooper, Lourdes Franco · 发表于：Macromolecules · 年份：1997 · DOI：10.1021/ma961494g · 被引用次数：101 · 研究领域：Polymer crystallization and properties、Synthesis and properties of polymers、Muon and positron interactions and applications

Nylons 8 10 and 10 12 have been synthesized and crystallized as chain-folded lamellae from 1,4-butanediol and the results compared with previous studies on Nylons 4 6 and 6 8. In 2 N 2( N + 1) Nylons, the lengths of the two alkane segments are equal and two different hydrogen-bonded sheet schemes are possible: progressive or alternating shear. At room temperature, Nylons 8 10 and 10 12 adopt the progressive scheme and the adjacent re-entry folds in the crystals must be in the alkane chain segments. In contrast, Nylons 4 6 and 6 8 lamellae, crystallized from the same solvent, exhibit the alternating hydrogen bonding scheme and each adjacent re-entry fold must contain an amide group. The transition in the chemical nature of the lamellar surface, from the amide fold to the alkane fold, occurs in passing from Nylon 6 8 to 8 10. Thus, the progressive hydrogen-bonded sheet/alkane fold structure is energetically more favorable, provided the alkane-folding geometry is sufficiently relaxed; this comes with increasing alkane segment length. For each hydrogen-bonded sheet structure there are still two principal intersheet stacking modes in lamellar crystals: the progressively sheared α-phase or the alternatingly sheared β-phase, both of which have been found in the 8 10 and 10 12 Nylons. The 2 N 2( N + 1) Nylons have the choice of four possible structures. The melting points of solution grown crystals of Nylons 4 6, 6 8, 8 10, and 10 12 decrease with decreasing intrachain amide density....