Polymer Crystallization on the Surface of Water or Aqueous Salt Solution

Abstract

The crystallization of two semicrystalline and water-insoluble polymers with ester moieties, namely poly(e-caprolactone) (PCL) and isotactic poly(methyl methacrylate) (i-PMMA), was studied on the water surface using Langmuir trough measurements and Brewster angle microscopy. Additionally, Langmuir-Blodgett films were prepared and examined by atomic force microscopy. It was demonstrated that PCL forms distinct single crystals on the water surface with polymer chain orientation perpendicular to the water surface. i-PMMA behaved differently and crystallized upon compression on the water surface in a homogeneous layer with polymer chain orientation parallel to the water surface. In contrast, poly(ethylene oxide) (PEO) is a water-soluble polyether and its crystallization at the air/liquid interface could only be studied when the water subphase was replaced with aqueous salt solutions containing kosmotropic salts according to the Hofmeister series.

Controlling Nucleation in Quasi-Two-Dimensional Langmuir Poly(l-lactide) Films through Variation of the Rate of Compression

“…Therefore, exact positional order in condensed phases is difficult to achieve and for certain polymeric systems probably not possible at all. There are, however, a few systems where crystallization in Langmuir polymer films was observed. − All these systems have hydrophilic moieties that serve as anchors to the water surface, and therefore the polymer chains have reduced internal flexibility, which seems to support crystallization at the air/water interface. PLA can also anchor to the water surface via ester groups and has already been investigated as Langmuir films using optically pure PLLA , or equimolar mixtures of PLLA and PDLA, which are prone to form stereocomplexes. − Helical structures have been observed in both systems, but it is not clear whether they form already in the spreading solution or whether the helix formation is induced at later stages through the lateral pressure applied through the barriers.…”

Influence of Tacticity on the Structure Formation of Poly(methacrylic acid) in Langmuir/Langmuir–Blodgett and Thin Films

“…This indicates that the structure of it ‐PMAA Langmuir films is significantly smaller than that of many other Langmuir polymer films (LPF). [ 14,39,40 ] Some bright spots can be seen in epifluorescence images, suggesting microparticle formation incorporated with dye molecules ( Figure b,c). At high surface compression, the number of bright spots (microparticles) increases as well as some dark lines appear (Figure 2d).…”

“…The latter approach provides less entanglements and more mobility to the polymer chains, which facilitates increased crystallization rates. Upon compression on the water surface of a Langmuir trough it-PMMA crystallizes in a matter of hours [13,14] while other techniques generally take weeks. [15,16] It also allows crystallizing polymers in monolayers that help to reveal molecularlevel information as, for example, double helices by atomic force microscopy (AFM) in Langmuir-Blodgett (LB) films.…”

Formation of Surface Wrinkles in Collapsed Langmuir Films of a Polyhedral Oligomeric Silsesquioxane Containing Diblock Copolymer

“…Prior to this, the phase behavior of the Langmuir film upon compression and expansion will thoroughly be characterized by surface pressure versus mean molecular area (π– mmA ) isotherm measurements and BAM. Langmuir–Blodgett (LB) films will also be prepared at different compression states to reveal the film morphology by atomic force microscopy (AFM) and the molecular ordering by grazing incidence wide-angle X-ray scattering (GI-WAXS) …”