Confinement Effects on Crystallization and Curie Transitions of Poly(vinylidene fluoride-co-trifluoroethylene)

Abstract

International audienceNanoscale patterning of piezoelectric and ferroelectric polymers, such as polyvinylidene fluoride (PVdF) and its copolymers with trifluoroethylene (PVdF-TrFE), is increasingly important in organic electronics, memory, and sensing. The nanoscale processing of polymers can lead to materials behavior that is strikingly different from the bulk because of confinement effects. Here we report the effects of confinement of PVdF-TrFE melt-wetted in porous templates of varying pore diameter. PVdF-TrFE is particularly interesting because it possesses a solid-state Curie transition, where both ferro and nonferroelectric phases crystallize into a paraelectric phase. Using modulated differential scanning calorimetry (MDSC), X-ray diffraction (XRD), and broadband dielectric spectroscopy (BDS), we demonstrate that confined PVdF-TrFE crystallizes into an oriented ferroelectric beta phase. Both melting and crystallization temperatures decrease with decreasing pore diameter, and the Curie temperature is weakly affected. Results imply that nanoconfinement enhances the formation and orientation of the ferroelectric beta phase and could potentially enhance ferroelectricty and piezoelectricity in nanoscale PVdF-TrFE features

Molecular composition distribution of polycarbonate/polystyrene blends in cylindrical nanopores

“…32 Figure 4 shows the DSC curves of the PC/PS blends in 300-, 65-and 35-nm diameter nanorods in bulk film, in pure PC and pure PS, for reference. A thermogram of an empty AAO template was featureless, 17 whereas the T g 's of pure PC and pure PS were 150.7 and 105.1 1C, respectively. On the PC/PS bulk film curve (Figure 4d), the transition at 149.0 1C corresponds to the T g of the PC-rich phase, and the transition at 106.5 1C is the contribution of the PS-rich phase.…”

“…1 Attention has been focused on structure formation processes such as chain dynamics, 2-5 crystallization [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] and phase separation [20][21][22][23][24][25][26][27][28] under the influence of the two-dimensional confinement imposed by cylinder geometry and interfacial interactions with pore walls. Owing to the special shape of nanocylinders with high aspect ratios (length to diameter), the fabricated nanomaterials have unusual mechanical, chemical, optical and electronic properties, as well as specific surface properties.…”

“…1 For amorphous polystyrene (PS) confined in cylindrical alumina nanopores, an unexpected enhancement of flow and a reduction in intermolecular entanglement have been observed, leading to higher mobility of polymer in the confined geometry than that of unconfined chains. 2 In the case of semicrystalline polymers under nanocylindrical geometry, the polymers exhibit novel orientation, [5][6][7][8][9][10][11][12][13][14][15][16][17] polymorphism 18 and segmental dynamic behavior. 5,17 The crystals that form in nanorods at low supercooling show perpendicular orientation; that is, the c-axes of the polymer crystals that develop in cylindrical nanopores preferentially orient perpendicular to the long axis of the nanopore.…”

“…2 In the case of semicrystalline polymers under nanocylindrical geometry, the polymers exhibit novel orientation, [5][6][7][8][9][10][11][12][13][14][15][16][17] polymorphism 18 and segmental dynamic behavior. 5,17 The crystals that form in nanorods at low supercooling show perpendicular orientation; that is, the c-axes of the polymer crystals that develop in cylindrical nanopores preferentially orient perpendicular to the long axis of the nanopore. [5][6][7][8][9][10][11][12][13][14][15][16][17] The crystallinities [8][9][10] and melting temperatures 10,17 of nanorods are reduced compared with those of bulk polymer, owing to the spatial confinement of the nanopores.…”

“…5,17 The crystals that form in nanorods at low supercooling show perpendicular orientation; that is, the c-axes of the polymer crystals that develop in cylindrical nanopores preferentially orient perpendicular to the long axis of the nanopore. [5][6][7][8][9][10][11][12][13][14][15][16][17] The crystallinities [8][9][10] and melting temperatures 10,17 of nanorods are reduced compared with those of bulk polymer, owing to the spatial confinement of the nanopores. Strong deviation from the normal relaxation behavior of poly(vinylidene fluoride) was observed inside nanopores.…”