Crystal Orientation of Poly(ε-caprolactone) Homopolymers Confined in Cylindrical Nanodomains

Abstract

The crystal orientation of poly(ε-caprolactone) (PCL) homopolymers, spatially confined in cylindrical nanodomains surrounded by polystyrene (PS) matrices, has been investigated as a function of crystallization temperature T c (−60 °C ≤ T c ≤ −40 °C) using two-dimensional small-angle X-ray scattering (2D-SAXS) and wide-angle X-ray diffraction (2D-WAXD). The sample was prepared by microphase separation of an PCL-block-PS copolymer followed by photocleavage at the block junction between PCL and PS blocks. The results were compared with crystal orientation of PCL blocks before photocleavage, i.e., PCL chains with one chain-end tethered at the cylinder interface. The lamellar crystals of PCL homopolymers and PCL blocks were preferentially oriented in cylindrical nanodomains irrespective of T c, i.e., the b axis of crystal unit cells was oriented parallel to the long axis of cylinders. The degree of crystal orientation increased remarkably with increasing T c for PCL homopolymers, whereas it improved slightly for PCL blocks, yielding a large difference in the degree of crystal orientation between two systems at higher T c (≥−45 °C).

Crystallization of polymer chains confined in nanodomains

“…Thus, we could prepare block chains and homopolymers both confined in identical nanospheres, nanocylinders, or nanolamellae (Fig. 9), and examined the substantial difference in crystallization behavior and crystal orientation between them as a function of nanodomain shape, size, or crystallization temperature [74][75][76][77][78]. …”

Eine genügt: Beeinflussung von Polymereigenschaften mittels einer einzelnen Chromophoreinheit

“…Nojima et al verwendeten ein photoschaltbares Diblockcopolymer, um die Kristallisation und Kristallorientierung von Poly(e-caprolacton) (PCL) in eingeschränkter Geometrie zu untersuchen. [15] Sie synthetisierten ein PCL-b-PS-Blockcopolymer mit einer photospaltbaren ONB-Verknüpfungsstelle und nutzten Scherkräfte, um die Vorzugsorientierung von PCL-Nanozylindern einzustellen. Die PCLKristallorientierung wurde anschließend in Abhängigkeit von der Kristallisationstemperatur (T C ) für die unbestrahlte und die bestrahlte Probe (d. h. für das intakte bzw.…”

Molecular composition distribution of polycarbonate/polystyrene blends in cylindrical nanopores

“…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.…”

“…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.…”