Morphological Studies of Semicrystalline Poly(2,6-dimethylphenylene oxide)

Abstract

A sample of poly(2,6-dimethylphenylene oxide) (PPO) has been crystallized by exposure to 2-butanone (MEK) vapor. This sample has been investigated by wide and small angle x-ray scattering (WAXS and SAXS), differential scanning calorimetry (DSC), and light-scattering techniques. The W AXS and DSC experiments reveal a maximum crystallinity of about 30%. The SAXS, analyzed according to the linear paracrystal model of Hosemann, indicates a high degree of order in the superlattice with an average crystal lamellar thickness of 38 A. Extensive peak broadening occurs in the W AXS curve arising from crystal lattice distortions or defects. These distortions or defects most probably are a consequence of the removal of solvent molecules from the lattice during the drying process. The light-scattering studies show a rodlike morphology apparently made up of fibrous bundles. The exact nature of the structures responsible for the observed light-scattering patterns cannot be conclusively demonstrated.

Thermal and structural properties of poly(vinyl alcohol) doped with hydroxypropyl cellulose

“…A change in the crystalline structure could have resulted from polymer–polymer (PVA and HPC) interactions in the amorphous phase. So, disorder in the crystals was created, reducing the enthalpy of the phase change 33, 34. The observed change in endotherm area may have indicated the existence of polymer–polymer interactions between HPC and PVA molecules.…”

Synthesis and properties of carboxylate poly(2,6-dimethyl-1,4-phenylene oxide) and its ionomer

“…In DSC measurements, the fractional crystallinity of C-PPO was estimated by the quantity W/ = AQf/AH{ (3) where AQf is an observed fusion enthalpy proportional to the area under the DSC endotherm and AH{ is the heat -COOH mol % 2 THETA Figure 7. Wide-angle X-ray scattering (WAXS) curves of -^.…”

Glass transition and melting behavior of poly(oxy-2,6-dimethyl-1,4-phenylene)

“…Annealing and Fusion of Semicrystalline PPO. A look at Figures [6][7][8][9][10] shows that annealing below the major melting peak of the initial semicrystalline sample causes (1) a reduction in rigid amorphous (strain release), (2) a reduction in crystallinity (fusion), and (3) an increase in perfection of the remaining crystals (annealing) indicated by a shift in melting peak (without broadening) (see Table II). Effect 3 is well illustrated by Figures 11 and 12.…”

“…Solution crystallization of PPO was studied,9,20 and the morphology of the resulting crystals has been reported. 10 It is generally accepted that solvent molecules are incorporated into the PPO crystal.7 Removal of the solvent on drying leaves severely distorted and defect crystals.7,10 Melt crystallization, in contrast, has received less attention.8 It was not possible to crystalline PPO melt in the narrow temperature range between Tg and Tm in isothermal experiments of 8-h duration. It is reported, however,8 that nucleating agents such as anthraquinone or 2-mercaptobenzimidazole can cause crystallization with Avrami exponents of 1.6.…”

“…Exposure to solvent vapors, such as 2-butanone, also leads to crystallization. 10 Compared to other phenylene-containing macromolecules such as poly(ethylene terephthalate),21 poly(oxyl,4-phenyleneoxy-l,4-phenylenecarbonyl-l,4-phenylene) (PEEK),22 and poly(thio-1,4-phenylene) (PPS),23 the thermal properties of PPO were less well understood. The present work will show that some of the thermal properties of PPO such as the interplay between rigid amorphous and crystals may be unique.…”