Thermal Transitions of ε Crystalline Phases of Syndiotactic Polystyrene

Abstract

Thermal transitions of the three crystalline phases (γ, δ, and ε) of syndiotactic polystyrene (s-PS), presenting s(2/1)2 helices, have been compared by X-ray diffraction, differential scanning calorimetry (DSC), and dynamic-mechanical analyses. These analyses have been conducted on crystalline (δ and ε) films, obtained by similar solvent sorption and desorption procedures, starting from a same γ-form film. The Fourier transform Infrared (FTIR) spectra of the three films have also been compared. The obtained results indicate that the recently discovered ε-phase, as the already known δ-phase, is transformed in γ-phase by heating above 100 °C. However, the ε → γ transition occurs directly without the formation, for intermediate temperatures, of a helical mesomorphic phase, as instead observed for the δ → γ transition. DSC studies and FTIR measurements also suggest that the crystalline packing of the ε-form could be rather similar to that one of the γ-form.

Induced vibrational circular dichroism and polymorphism of syndiotactic polystyrene

“…Moreover, subsequent treatments with chloroform and acetonitrile on g form samples induce phase transition toward the e nanoporous crystalline phase. [33][34][35] FTIR and VCD spectra of g (A, B) and e (C, D) form films, as obtained from the sPS/(2)-(R)-carvone and s-PS/(1)-(S)-carvone cocrystalline films of Figure 2B, are shown in Figure 3.…”

“…In particular, the spectral ranges 1000-880 cm 21 (A) and 630-590 cm 21 (B) (particularly suitable to distinguish between sPS polymorphic crystalline phases with s(2/1)2 helical conformation) 34 of films obtained from sPS/R-carvone cocrystals are shown in Figure 4. The VCD spectra of Figure 3B are strictly similar to those of films as obtained by guest extraction from the corresponding cocrystalline phases, and reported in Ref.…”

“…[11][12][13][14] Polymer films, which are able to detect, amplify, and memorize the chirality of several volatile organic molecules have been recently reported. [11][12][13][14] These chiral sensing films are based on syndiotactic polystyrene (s-PS), a stereoregular polymer, [15][16][17][18][19][20][21][22] with a very complex polymorphic behavior, [19][20][21][22] which involves two crystalline phases (a 23,24 and b 25,26 ) with transplanar chains and three crystalline phases (g, [27][28][29] d, [30][31][32] and e [33][34][35] ), as well as many different cocrystalline phases with low-molecular-mass guest molecules, [36][37][38][39][40][41][42][43] with s(2/1)2 helices. Recently, the origin of this chiral sensitivity has been elucidated by Infrared Reflection Absorption Spectroscopy (IRRAS), Vibrational Circular Dichroism (VCD), and X-ray diffraction measurements.…”

Characterization of toluene and 2-methylnaphthalene transport separated by syndiotactic polystyrene having various crystalline forms

“…1-3 and b (orthorhombic, unit cell a ¼ 0.881 nm, b ¼ 2.828 nm, c ¼ 0.551 nm) 4,5 forms assume an all-trans sequence, whereas the g (uncertain monoclinic suggested, unit cell a ¼ 1. [13][14][15] forms assume a trans-trans-gauchegauche (ttgg) sequence. The all-trans conformation is thermally stabilized with a melting temperature as high as 270 1C.…”

Absorption Kinetics of Phenol into Different Size Nanopores Present in Syndiotactic Polystyrene and Poly (p-methylstyrene)

“…It has been reported that there are five crystalline modifications. The [4][5][6][7][8] and [9,10] forms consist of a planar zigzag chain with period of 5.1 Å, whereas the [11][12][13], [14][15][16][17], and [18][19][20] forms adopt a helical structure with a trans-trans-gauche-gauche (ttgg) conformation, having a period of 7.7 Å. The crystal with an all-trans conformation is a thermally stabilized form induced above about 180 °C and its high melting temperature around 270 °C is expected to be useful as an engineering plastic.…”