Effect of orientation and crystallization on dielectric and mechanical relaxations in uniaxially stretched poly(ethylene naphthalene 2,6 dicarboxylate)(PEN) films

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.…”

“…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.…”

“…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. an amorphous contribution that do not contribute to the specific heat increment at the glass transition 7 . Such confinement effects in polymer materials generally lead to a change in the dynamics in the amorphous phase, but slower, faster or unchanged confined dynamics have previously been described 29 as a function of the interactions between the rigid confining phase and mobile polymeric phase.…”