A solid state NMR study on crystalline forms of nylon 6

Abstract

SynopsisHigh-resolution 13C-NMR spectra were studied for two different crystalline structures of nylon 6 in the solid state by the crass polarization/magic angle spinning (CP/MAS) method. Two crystalline structures, a-form and y-form, gave different chemical shifts for methylene carbons. The results showed that the hydrogen bonds between intermolecular chains are stronger in the y-form than in the a-form. This strongly supports the results of the X-ray study of nylon 6 by Malta et al. Our results also showed that intramolecular delocalization of positive charges occurs in the y-form through hyperconjugation in which the dihedral angle between the I bond and neighboring a bonds is 3 0 ' while no such effect can be expected in the a-form in which the angle is 0".

The effect of zinc oxide addition on the compatibilization efficiency of maleic anhydride grafted high‐density polyethylene compatibilizer for high‐density polyethylene/polyamide 6 blends

“…Slow cooling and high crystallization temperatures leads to the preponderance of the a-form. 39,40 It was hoped that WAXS spectra would be able to be used to quantify the amount of each crystalline structure for nylon in the blends; unfortunately, as shown in Figure 9, the polyethylene110 and 200 reflections interfere with the 2 g reflections, and the subsequent error in peak deconvolution was too large.…”

Structure and Dynamic Mechanical Properties of Melt Intercalated Polyamide 6—Montmorillonite Nanocomposites

“…In general, conditions that enhance chain mobility, such as high crystallisation temperatures or slow rates of cooling, favour the formation of the a-phase whereas conditions that inhibit chain mobility, such as rapid cooling or the addition of fillers, favour the formation of the g-phase. [28][29][30] Thus, given the large polymer-filler interfacial area created in a PLSN, resulting in significant polymer-filler interactions, it is perhaps no surprise that the incorporation of OMMTs into PA6 has been shown to strongly promote the formation of the g-phase. [15,19,31 -35] It has been proposed [32] that interactions between PA6 chain segments and the surface of a silicate lamella impose conformational changes that inhibit the formation of hydrogen-bonded sheets, thus promoting the formation of gphase at the polymer-lamella interface.…”

Comparison of Polyamide‐6 Nanocomposites Based on Pristine and Organic Montmorillonite Obtained via Anionic Ring‐Opening Polymerization

“…The band at about 3 300 cm À1 is hydrogen-bonded N-H stretching vibration. [33,35] As we can see that there is a similar trend for N-H stretching with increasing temperature: the band shifts to high frequency, the intensity of band decreases and the width of the band becomes broad. It is well known that the breadth of the band is mainly a reflection of the distribution of hydrogenbonded groups -the broader the band, the more disordered the sample.…”