Uniaxially stretched poly(ethylene naphthalene 2,6-dicarboxylate) films studied by broadband dielectric spectroscopy

Tie molecules, morphology and confinement effects in semi – crystalline poly(ethylene naphthalene-2,6-dicarboxylate) (PEN)

“…The relaxation phenomena in amorphous and semi-crystalline PEN have been previously investigated by means of dynamic mechanical analysis (DMA) and dielectric relaxation spectroscopy (DRS) [4][5][6][7] . Three relaxation processes: ,  * and  have been observed in order of increasing temperatures: -The -relaxation can be observed at around -20°C for a frequency of 1 kHz.…”

“…This process was assigned to the out of plane motions of the naphthalene cycle by Bellomo et al 36 and more precisely to the motions within nano-scale aggregates of naphthalene rings motions 4,6,7,37,38 . In the frequency/temperature region of the * process, the contribution of motions within liquid-crystalline nanodomains are also reported after crystallization from the molten state 42 which can complicate the exact attribution of the * process.…”

“…Therefore, this paper will deal mainly with the study of α-process in PEN as a function of crystallization conditions. Previous works have shown that -relaxation of PEN classically shifts to higher temperatures as the result of the confinement of the amorphous phase by the crystalline phase [4][5][6][7] . In addition to the development of the semi-crystalline morphology, a structuration of the amorphous phase is likely to occur with the formation of a rigid amorphous phase, i.e.…”

“…The molecular mobility in semi-crystalline polymers has been studied by several authors using a large number of systems and spectroscopic methods [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] . However, there are still few works analyzing simultaneously in details their molecular and nano structure in relation with their dynamics [9][10][11][12] .…”

“…Obviously, this trend is attributed to the slowing down of the molecular mobility in the amorphous phase that is constrained by the presence of the crystalline phase. The confinement effect is due to the participation of the chains within the crystals and can also result in the formation of a rigid amorphous fraction (RAF) 6,7,[19][20][21] . Cheng and Wunderlich 20 previously showed that the glass transition of semi-crystalline PEN increases and an increasing RAF is developed with decreasing crystallization temperatures.…”