Polymorphism in alternating polyketones studied by x‐ray diffraction and calorimetry

Abstract

Differential scanning calorimetry and high temperature x‐ray diffraction were used to study the perfectly alternating copolymer of ethene and carbon monoxide (polyketone; POKC2). It was found that oriented POK‐C2 fibers show a crystalline phase transition at a temperature between 110–125°C with a 10% change in crystalline density. At this temperature, the crystal structure reported recently (POK‐α) is transformed to a crystal structure that was reported in the past for room temperature imperfectly alternating polyketone. The latter structure will be designated as POK‐β. The influence of chain defects on the crystal structure was studied by synthesizing terpolymers (POK‐C2/C3), in which small amounts of propylene‐CO units are incorporated into the polymer backbone. The resulting terpolymers differ from the copolymer by the presence of methyl groups randomly distributed along the polyketone backbone chain. Evidence is presented that indicates that the methyl groups are built into the crystal lattice as defects. With more than 5 mole‐% propene the terpolymer fibers crystallize exclusively in the β‐modification. Below this level the α/β ratio (at room temperature) increases with decreasing amounts of propene. Both as‐synthesized and as‐spun POK‐C2 were found to consist of both POK‐α and POK‐β; the α/β ratio depends on the method of preparation. Because the drawn POK‐C2 fibers studied here consist exclusively of POK‐α, the process of spinning and drawing leads to the transformation of unoriented β‐rich material into oriented POK‐α. © 1995 John Wiley & Sons, Inc.

Terpolymerization of propene and ethene with carbon monoxide catalyzed by [PdCl2(dppf)] in HCOOH–H2O as a solvent [dppf=1,1′-bis(diphenylphosphino)ferrocene]

“…The IR spectra show typical stretching absorptions of CO groups at 1695 cm −1 and of -CH 2 − groups at 2915 cm −1 . Table 1 shows some selected 1 H NMR e 13 C NMR signals and the assignments are in good agreement with the values reported in literature [34,35]. The LVN of a dilute polyketone solution was determined by using the Huggins relationship between the viscosity number and the polymer concentration by extrapolation to zero concentration [36].…”

“…This is because the ECO copolymer is a highly crystalline material with high melting point (T m ), whereas the terpolymers have lower melting points, making them more easily processable [13][14][15][16][17][18][19]. As matter of fact, the first commercialized PK, was the propene (P)-ethene-CO (PECO) terpolymer (trade name CARILON ® by Shell [20] and KETONEX ® by BP [21]).…”

Stretching calorimetry and X‐ray characterization of deformational behavior of new high molecular weight propene‐carbon monoxide alternating co‐ and terpolymers

“…2. From the comparison of the observed and the literature data for perfectly alternating ethene-CO (E-CO) copolymers, it can be concluded that the chains of EPEC 2 terpolymer crystallize in the distorted lattice close to the b-form of ethene-CO which is characteristic for copolymers with a low content of P-CO units [14][15][16] . The released specimen shows almost the same wide angle X-ray pattern in accordance with the earlier described irreversible mechanical behavior of the semicrystalline EPEC 2 sample.…”

Optically Active Polyketones

“…The crystal structure of poly(ethene-alt-CO) in well-oriented fibers (a-structure) was determined by wide-angle X-ray scattering methods [64]. Klop et al showed that the a-form was dominant in the perfectly alternating copolymer at room temperature and that the phase transition from a to b was observed at 110-125 C [66]. The very dense packing is a result of the arrangement of the dipoles in the crystal lattice, giving rise to strong lateral forces between the polymer chains.…”