Magic angle carbon‐13 NMR study of solid poly(ethylene naphthalene‐2,6‐dicarboxylate)

Abstract

Amorphous (1) and semicrystalline (2) samples of poly(ethylene naphthalene‐2,6‐dicarboxylate) (PEN) have been investigated by cross‐polarization/magic angle spinning (CP/MAS) 13C NMR at 26°C (1 and 2), 100°C (1) and 120°C (2) in order to study the phase structure and the local motion of polymer chain segments at temperatures below and close to Tg (120°C). The lineshape of the ethylene unit 13C signal in sample 2 is consistent with the presence of two components which were assigned to trans and gauche conformations. The first component arises mainly from the crystalline regions and the second one from the amorphous part. Cross‐polarization curves were traced by changing the contact time between carbon and proton reservoirs. TCH (cross relaxation time) and proton T1p (spin‐lattice relaxation time in the rotating frame) values were obtained as best fit parameters by fitting calculated curves to the experimental data. All 13C NMR data are consistent with the presence of highly rigid ethylene units in both semicrystalline and amorphous samples within the temperature range (T) investigated. This result is in disagreement with the 1H NMR wide line spectra which showed a noticeable narrowing of the linewidth with increasing temperature in the same range, hence indicating a great mobility of the chain segments. To account for this discrepancy a qualitative model based on the existence of two distinct dynamic regions, one where motion is highly restricted and the other one where large reorientations of ethylene group torsional angles take place, is suggested. The NMR results led to the conclusion that three structural phases are present in PEN: crystalline, very rigid amorphous, and very mobile amorphous. © 1995 John Wiley & Sons, Inc.

Conformation of spacers in smectic poly(ester imide)s

“…Figure 3 represents the 13 C NMR CP/MAS at 30.5 ppm has to be attributed to a disordered ''dd''-arrangement of the spacer segments. The obspectra of PEI 1 (n Å 12,16,and 22) in the smectic-crystalline phase at 20ЊC. All spectra exhibit served line shape and the concluded spacer conformation differ from those found by Cheng et al 11 the signal of the g-carbons at about 26.5 ppm.…”

“…The crystal lamellae themselves contain a number of smectic layers. In contrast, the PEI 2 (n Å 12, 16,22) and PEI 3 (n Å 12,20) form monotropic smectic LC phases, which undergo a transition into the smectic-crystalline state upon further cooling. Rapid quenching of the isotropic phase or the LC melt below the glasstransition temperature freezes the smectic LC phase.…”

“…polymers. 22,23 These oscillations have been explained by a coherent energy transfer and Ernst et al 24 derived an equation which describes the…”

Poli(Etileno Naftalato) - PEN: uma revisão do seu histórico e as principais tendências de sua aplicação mundial

“…A inclusão do grupo naftaleno na cadeia polimérica do PEN, comparado com os anéis benzênicos do PET, aumenta a rigidez da cadeia, o que resulta em maior temperatura de transição vítrea (115°C -125°C para o PEN e 65°C -80°C para o PET) e maior temperatura de fusão cristalina (260°C -270°C para o PEN e 240°C -255°C para o PET), tão bem como variação em outras propriedades, incluindo o módulo de elasticidade em tração (35% mais elevado para o PEN), o módulo de elasticidade em flexão (50% mais elevado para o PEN), e as resistências à tração e à fluência [1,[12][13][14]17,[19][20][21][22][23]37] . Vários estudos recentes revelam que o PEN apresenta outras características de desempenho muito favorável em relação ao PET: uma melhor barreira ao oxigênio, ao dióxido de carbono e ao vapor de água (as permeabilidades ao oxigênio e ao dióxido de carbono do PEN são aproximadamente 5 vezes menores que a do PET, e a capacidade de barreira ao vapor de água do PEN é 3,5 vezes superior ao PET); melhor resistência química; melhor barreira aos raios ultravioleta; ciclos de moldagem mais curtos; maior temperatura de distorção térmica (120°C para o PEN contra 70°C para o PET), [20,[26][27][28] .…”

TSDC study of relaxations in drawn semi-crystalline polyesters containing a rigid amorphous fraction

“…Dielectric properties of different PET have been reviewed by several workers [4,51 with generally a focus on the glass transition which is influenced by the presence of a crystalline phase even if the degree of crystallinity is low for these polyesters (= 30%) [5, 61. A three phases model has been proposed to explain the results obtained on the most studied semi-crystalline polyesters as PET [7], PBT [8] and PEN [9]. It consists in crystalline, amorphous and intermedate rigid amorphous fractions [7, lo].…”