Infrared spectroscopy has been used to study the evolution of polyurethane foam structure,
providing measures of relative reaction kinetics, hard segment growth, the onset of phase separation,
the formation of order, and the development of final morphology. Changes in free, monodentate, and
bidentate hydrogen-bonded urea groups dominate the organization of the entire ensemble. Hard segments
formed by reaction of 2,6-toluene diisocyanate (2,6-TDI) and by a mixture of 80% 2,4-TDI and 20% 2,6-TDI displayed very different local segmental alignment, a factor crucial in the development of morphology.
Phase separation occurred faster, with fewer and shorter hard segments, in the systems with well-ordered
straight chains. The formation and time evolution of monodentate ureas suggest that phase development
may be incomplete, or trapped, in systems with ill-defined urea structures. A low degree of spatial order
exists in the systems containing these structures.
The morphological development of crystallizable polymer blends has been investigated using optical microscopy and infrared and Raman spectroscopy. Both binary and ternary blends were studied. In each case, a crystallizable polyester, either poly(hexamethylene adipate) (PHMA) or poly(hexamethylene sebacate) (PHMS), is mixed with noncrystallizable polyether, poly(propylene glycol) (PPG). Although they possess similar chemical structures, PHMA and PHMS exhibit very different miscibility behavior. In ternary blends, an acrylate, poly(methyl methacrylate and n-butyl methacrylate) [P(MMAnBMA)], is also incorporated in the mixture. With the high spatial resolution achievable (∼1 µm 2 ), the composition distribution can be carried out using a micro-Raman instrument. Specific Raman features associated with polyesters have been established. For immiscible PPG/PHMA blends, the composition and distribution within PHMA-rich and PHMA-poor phases are characterized. The exact composition in each phase has been obtained by analyzing Raman data obtained. Additionally, on the basis of the measured intensity for conformation-sensitive Raman peaks, the distribution of crystallites within each phase has been characterized. The third relative immobile acrylate component is extremely effective in changing the overall blend morphology.
A B S T R A C TThe amphiphilic additive Pluronic F127 can effectively improve the hydrophilic character of membranes. This article reported the effects of Pluronic F127 additive, Pluronic F127/oxalic acid, and Pluronic F127/polyethylene glycol 4000 blended additives on morphology, separation properties and hydrophilic of poly (ether sulfone) (PES) ultrafiltration membrane. The membrane was made by liquid/solid phase inversion method. The results showed that the Pluronic F127 can improve the water flux and retention of PES ultrafiltration membrane, increase pore size and porosity, and change the cross-section structure. The flux of PES membrane with F127 was lower than that with oxalic acid at the same concentration. As the concentration of F127 increased, the flux increased, the retention showed undulation, and the hydrophilic improved. Compared with only F127, the flux of the membrane with F127 blended additives slightly increased and the effect of F127 is the major in the blending system, and the blended additives changed the hydrophilic of membranes. The blended additives have a greater impact on the performance of F127 membrane. As the blended additives concentration increased, the membrane structure exhibited a skin layer, a porous layer, and a support layer. When blended additives were in high concentration, the morphology changed from finger-like to sponge-like macro-voids structure.
By the water droplet templating method, regular honeycomb pattern polysulfone (PSf) fi lms were prepared in a humid atmosphere. The effects of some factors on characters of regular honeycomb PSf fi lms have been studied, such as, polymer concentration, solvent, the way of vapor intake, the position of the sample in the chamber. The results showed that (1) the average pore sizes of fi lms fi rst ascended with increase in polymer concentration then decreased when further increasing the polymer concentration, thus a maximum average pore size of 11.966 μm was observed at the polymer concentration of 45 g/l; (2) The vertical intake and the central location of the chamber were easy to form stable gaseous environment on the polymer solution surface, which induced to form the ordered honeycomb-structured fi lm; (3) Comparing to CH 2 Cl 2 and THF, CHCl 3 was the best solvent. However, the mixed solvent (CHCl 3 /CH 2 Cl 2) formed better honeycomb structure than single solvent, and the average pore size increased as the CH 2 Cl 2 ratio increased.
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