Polymorphism in syndiotactic polystyrene: a proton NMR relaxation study

Abstract

A marked shortening of T I relaxations in solid aromatic polymers can be attributed to O2 adsorbed on the aromatic rings. This effect, observed as a function of temperature, is modulated by the amount of adsorbed 02, which, in turn, varies according to the molecular packing and crystaUine/amorphous ratio. Within the temperature range 77-400 K, semicrystalline syndiotactic polystyrenes (s-PS) in the a, 8, and y polymorph modifications were studied by pulse lH NMR at 30 MHz. Due to the presence of many relaxation components, 1,2,2-trideuterio-s-PS was synthesized, crystallized, and characterized by X-ray powder diffraction. At low temperature, when both the 0 2 diffusion and the spin-diffusion processes are slow enough, the backbone-deuteriated polymers exhibit multiple T I relaxations: three for a and j3 s-PS and two for y s-PS. These T l components are attributed to crystalline and amorphous phases. From the study of these components as a function of temperature and from direct comparison of TI values in the different phases, the following conclusions were drawn: (i) Clear differentiation was possible between different s-PS polymorphs. (ii) Determination of the crystalline vs amorphous ratio fully consistent with X-ray diffraction data was achieved. (iii) The amorphous component of different semicrystalline s-PS polymorphs could be distinguished.

Polymorphic behavior in syndiotactic polystyrene/clay nanocomposites

“…Syndiotactic polystyrene (sPS) has received considerable attention because of its high melting temperature, fast crystallization rate, low dielectric constant and permeability to gases, and good chemical resistance. Structural studies carried out with X‐ray diffraction,1–6 electron diffraction,7, 8 Raman spectroscopy,9, 10 Fourier transform infrared spectroscopy,11–16 and solid‐state nuclear magnetic resonance spectroscopy17–20 have revealed a complex polymorphic behavior. The various crystalline structures differ with respect to the chain conformation and the chain packing within a unit cell.…”

Vapor sorption in emptied clathrate samples of syndiotactic polystyrene

“…Inclusion compounds (clathrates) fraction (XRD), [4][5][6][7][8][9][10][11][12][13][14][15][16][17] electron diffraction, 18,19 Fouwith inorganic and organic hosts have been widely rier-transform infrared spectroscopy (FTIR), [20][21][22][23][24][25][26][27][28][29][30] studied. Several applications in chemicals separaand solid-state nuclear magnetic resonance, [31][32][33][34] tion, purification of gases and liquids, and catalhave shown a very complex polymorphic behavior ysis, which mainly involve zeolite, have been for this polymer. Using the nomenclature profound.…”

Evaluation by Fourier Transform Infrared Spectroscopy of the different crystalline forms in syndiotactic polystyrene samples

“…[1][2][3] Several which are intermediate to those of the two limstructural studies, essentially by X-ray diffraciting disordered modifications (a and b) and the tion, 4-17 electron diffraction, 18,19 FTIR,[20][21][22][23][24][25][26][27][28][29][30] and two limiting ordered modifications ( aЉ and solid-state NMR [31][32][33][34] have shown a very complex bЉ). 4,6,11,16 In these descriptions, structural disorpolymorphic behavior for this polymer.…”