Structure and phase transitions in poly[bis‐(2,2,3,3‐tetrafluoropropoxy) phosphazene]

Abstract

The structure and phase transitions in poly[bis‐(2,2,3,3‐tetrafluoropropoxy)phosphazene] have been studied by differential scanning calorimetry (DSC) and x‐ray diffraction. Two crystalline phases and one mesomorphic phase are found, denoted I, II, and III, respectively. These phases convert reversibly one into the other on heating and cooling. The Phase I–Phase II transition occurs in a temperature range from 5 to 30°C whereas the Phase II mesophase (Phase III) transition proceeds above 80°C. Heats of transitions are measured to be about 29.0 J/g and 3.6 J/g, respectively. Crystalline Phase I is characterized by a monoclinic unit cell with the parameters: α = 24.4 Å, b = 9.96 Å, c = 4.96 Å, γ = 123°. The axes of both chains, traversing the unit cell, are directed along the “c” axis, the main chains having cis‐trans conformation. Phase I is the common crystalline structure for the main chain and side chains. The structure of Phase II is controlled mainly by packing of the side chains. Transition of Phase II into mesomorphic Phase III is accompanied with distortion of packing of the side chains. Only regular packing of the main chains of macromolecules in the plane perpendicular to their axes exists in Phase III. Mesomorphic phase III is stable up to the degradation temperature of the polymer. A significant effect of stress on the Phase II–III transition in oriented samples was found.

Polyphosphazene Elastomers Containing Interdigitated Oligo-p-phenyleneoxy Side Groups: Synthesis, Mechanical Properties, and X-ray Scattering Studies

“…The synthesis of all the polymers followed a similar protocol (Scheme 2). First, poly(dichlorophosphazene) (7) was synthesized by the uncatalyzed thermal ring-opening polymerization of hexachlorocyclotriphosphazene, (NPCl 2 ) 3 , in an evacuated Pyrex tube at 250 °C. After removal of unpolymerized cyclic trimer, the chlorophosphazene polymer (7) was treated with the sodium salt of 2,2,2-trifluoroethanol to replace 75 mol % of the chlorine atoms along the polymer chain.…”

“…7,8 From these data, three main points emerge. First, as the aryloxy side group concentration is increased, both signals begin to lose intensity and broaden, which can be correlated with a loss of crystallinity.…”

Polyphosphazenes and Cyclotriphosphazenes with Propeller-like Tetraphenylethyleneoxy Side Groups: Tuning Mechanical and Optoelectronic Properties

“…As illustrated by their WAXS patterns (Figure a–c), all the polymers yielded two main diffraction peaks centered at q ≈ 0.60 and 1.45 Å –1 , which correspond to an average spacing of 10.4 and 4.33 Å. Similar spacings have been identified as the interchain spacing distance (11.8 Å) and the near cis–trans planar repeat-unit length (4.2 Å) in other polyphosphazenes. , As the TPEO concentration in the polymers was increased, both peaks began to lose intensity and broaden, which suggests a decrease in crystallinity. This is consistent with the DSC analysis.…”

Structural Characterization of Self-Organized Mono- and Multilayers of Partly Fluorinated Polydialkoxyphosphazenes at the Air/Water Interface

“…Partly fluorinated polydialkoxyphosphazenes demonstrate the thermotropic polymorphism, i.e., the 3D low-temperature and intermediate crystalline phases and one mesophase form in the bulk state [5,6]. They transform reversibly one into another on heating and cooling.…”

“…The phase behavior in bulk of poly[bis-(2,2,3,3-tetrafluoropropoxy)phosphazene] (PFP-C3), poly[bis-(2,2,3,3,4,4,5,5-octafluoropentoxy)phosphazene] (PFP-C5) and poly[bis- (2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptoxy)phosphazene] (PFP-C7) was studied in Refs. 5 and 6, which was shown to be determined by an interplay between the packing of macromolecules on the whole and the registering of side groups.…”