Structural Changes in Thermally Induced Phase Transitions of Uniaxially Oriented δ_e Form of Syndiotactic Polystyrene Investigated by Temperature-Dependent Measurements of X-ray Fiber Diagrams and Polarized Infrared Spectra

Abstract

The empty δ (δ e ) form of uniaxially oriented syndiotactic polystyrene (sPS) was obtained by extracting the solvent molecules from the δ form of the sPS-solvent complex in acetone and methanol. The X-ray fiber diagrams of the δ e form of different solvents like chloroform, toluene, and benzene were found to be appreciably different from each other, probably reflecting the difference in the cavity size after solvent evaporation. Temperature dependence of the X-ray fiber diagram has been measured successfully starting from the uniaxially oriented δ e form at various temperatures for the first time. It has been found that the δ e form transforms to the intermediate form transiently before transforming into the γ form. Temperature-dependent polarized FTIR spectra were measured also for the uniaxially oriented δ e sample derived from the sPS and chloroform complex. The infrared band intensity characteristic of the T 2 G 2 conformation was found to change drastically in the course of transition from the δ e to the intermediate phase and to the γ phase. On the basis of the X-ray diffraction profile and infrared spectra, the intermediate form is speculated to take the structure of disordered chain packing probably due to the empty cavities present in the original δ e form. Thermal data showing an endotherm followed by an exotherm during the transition can be interpreted reasonably using such order-to-disorder-to-order transitions among the δ e , intermediate, and γ forms.

Microporous-crystalline microfibers by eco-friendly guests: An efficient tool for sorption of volatile organic pollutants

“…These features are typical of the disordered microporous crystalline phase [15] and definitely different from the so-called helical mesomorphic phase (as obtained by thermal treatments of δ form of s-PS), which instead presents two broad reflections at 2θ ≈10° and 19.5° [12,45].…”

“…In addition to these microporous polymer materials, the formation of microporouscrystalline forms (often referred as nanoporous crystalline forms in the literature), presenting a density lower than the corresponding amorphous phase, have been also discovered for two industrially relevant polymers: syndiotactic polystyrene (s-PS) [10][11][12][13][14][15][16][17] and poly(2,6-dimethyl-1,4-phenylene)oxide (PPO) [18][19][20][21].…”

“…a density definitely smaller than that one of the amorphous phase (1.05 g cm -3 ). Two different modifications have been described for the δ form: a monoclinic M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT 3 one with two cavities per unit cell [10][11][12][13] (Fig. 1A, A') and a triclinic one with only one bigger cavity per unit cell (Fig.…”

Factors controlling the structure of syndiotactic polystyrene upon the guest exchange and guest extraction processes

“…The extraction of guest molecules from the δ co-crystal and ε co-crystal by suitable methods lead to the formation of nanoporous δ (δ e ) [14,41,42], and ε (ε e ) forms [15,43], respectively. The helical structure is perfectly retained along with the cavities or channels after the guest extraction.…”

Induced vibrational circular dichroism and polymorphism of syndiotactic polystyrene

“…[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.…”