Encapsulation by interfacial polycondensation. I. The capsule production and a model for wall growth

Janssen, Ljj Jos; Nijenhuis, K. te

doi:10.1016/0376-7388(92)87053-z

Cited by 116 publications

(85 citation statements)

References 8 publications

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“…The formation of bubble-like voids with equivalent asymmetric size distributions has been documented for other IP processes producing polyamide [44] and polyester [45] films that are, however, orders of magnitude thicker than MPD-TMC thin films. Nonetheless, the film characterized in [44] showed properties typical of polyamide films such as a relatively smoother surface on the aqueous side.…”

Section: The Internal Morphology Of Fully Aromatic Polyamide Thin Filmsmentioning

confidence: 99%

3D visualization of the internal nanostructure of polyamide thin films in RO membranes

Pacheco

Sougrat

Reinhard

et al. 2016

Journal of Membrane Science

165

123

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The front and back surfaces of fully aromatic polyamide thin films isolated from reverse osmosis (RO) membranes were characterized by TEM, SEM and AFM. The front surfaces were relatively rough showing polyamide protuberances of different sizes and shapes; the back surfaces were all consistently smoother with very similar granular textures formed by polyamide nodules of 20-50 nm. Occasional pore openings of approximately the same size as the nodules were observed on the back surfaces.Because traditional microscopic imaging techniques provide limited information about the internal morphology of the thin films, TEM tomography was used to create detailed 3D visualizations that allowed the examination of any section of the thin film volume. These tomograms confirmed the existence of numerous voids within the thin films and revealed structural characteristics that support the water permeance difference between brackish water (BWRO) and seawater (SWRO) RO membranes.Consistent with a higher water permeance, the thin film of the BWRO membrane ESPA3 contained relatively more voids and thinner sections of polyamide than the SWRO membrane SWC3. According to the tomograms, most voids originate near the back surface and many extend all the way to the front surface shaping the polyamide protuberances. Although it is possible for the internal voids to be connected to the outside through the pore openings on the back surface, it was verified that some of these voids comprise nanobubbles that are completely encapsulated by polyamide. TEM tomography is a powerful technique for investigating the internal nanostructure of polyamide thin films. A comprehensive knowledge of the nanostructural distribution of voids and polyamide sections within the thin film may lead to a better understanding of mass transport and rejection mechanisms in RO membranes.3

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Section: The Internal Morphology Of Fully Aromatic Polyamide Thin Filmsmentioning

confidence: 99%

3D visualization of the internal nanostructure of polyamide thin films in RO membranes

Pacheco

Sougrat

Reinhard

et al. 2016

Journal of Membrane Science

165

123

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“…According to Janssen and Nijenhuis [10], the polycondensation rate constant was in between 10 4 and 10 6 m 3 /kmol s for TDC and DETA system. A typical value for the diffusivity of a molecule such as HMDA through a swollen polymer would lie in the range 10 −11 to 10 −15 m 2 /s [9,12].…”

Section: Estimation Of Kinetic Parameters From Datamentioning

confidence: 99%

“…Experimental evidence [3,5,6,11,[18][19][20][21] points to a strong influence of the conditions employed in the preparation on the nature and properties of the film that forms. However, most of the models [7][8][9][10][11][14][15][16][17] focus on the kinetics and the variation of film thickness with time, and do not attempt to predict quantitatively the polymer properties as a function of process parameters. Properties such as molecular weight, polydispersity and crystallinity affect important characteristics of the polymer [20][21][22] such as mechanical properties, viscosity, ease of processing, permeability.…”

Section: Introductionmentioning

confidence: 99%

“…Second order reaction at the interface No 6 Karode et al [12] (i) Mass transfer of both monomers from bulk to interface; (ii) diffusion of diamine through polymer film (i) Detailed kinetics, reaction in a zone; (ii) phase separation by spinodal decomposition MW and PD 7 Karode et al [13] (i) Mass transfer of both monomers from bulk to interface; (ii) diffusion of diamine through polymer film (i) Detailed kinetics, reaction in a zone; (ii) phase separation by nucleation and spinodal decomposition MW and PD the already-formed film and organic phase) and the entire polymer formed is assumed to form the film [10,11,14]. In the second, the reaction is assumed to occur in a reaction zone which lies on the organic side of the interface mentioned above, and the polymer formed is excluded from the reaction zone as it forms; the reaction zone gets pushed into the organic phase as the film grows [12,13,15,17].…”

Section: Introductionmentioning

confidence: 99%

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Interfacial polycondensation—Modeling of kinetics and film properties

Dhumal

Wagh

Suresh

2008

Journal of Membrane Science

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“…Perhaps the most common method of producing microcapsules is via interfacial step-growth polymerization, whereby a monomer in the continuous phase of an emulsion reacts with a second monomer in the dispersed phase. [13][14][15][16] The polymer forms at the interface. As the polymerization reaction proceeds, the reaction rate decreases.…”

Section: Introductionmentioning

confidence: 99%

Preparation of Aqueous Core/Polymer Shell Microcapsules by Internal Phase Separation

et al. 2004

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Aqueous core/polymer shell microcapsules with mononuclear and polynuclear core morphologies have been formed by internal phase separation from water-in-oil emulsions. The water-in-oil emulsions were prepared with the shell polymer dissolved in the aqueous phase by adding a low boiling point cosolvent. Subsequent removal of this cosolvent (by evaporation) leads to phase separation of the polymer and, if the spreading conditions are correct, formation of a polymer shell encapsulating the aqueous core. Poly(tetrahydrofuran) (PTHF) shell/aqueous core microcapsules, with a single (mononuclear) core, have been prepared, but the low Tg (−84 °C) of PTHF makes characterization of the particles more difficult. Poly(methyl methacrylate) and poly(isobutyl methacrylate) have higher Tg values (105 and 55 °C, respectively) and can be dissolved in water at sufficiently high acetone concentrations, but evaporation of the acetone from the emulsion droplets in these cases mostly resulted in polynuclear capsules, that is, having cores with many very small water droplets contained within the polymer matrix. Microcapsules with fewer, larger aqueous droplets in the core could be produced by reducing the rate of evaporation of the acetone. A possible mechanism for the formation of these polynuclear cores is suggested. These microcapsules were prepared dispersed in an oil-continuous phase. They could, however, be successfully transferred to a water-continuous phase, using a simple centrifugation technique. In this way, microcapsules with aqueous cores, dispersed in an aqueous medium, could be made. It would appear that a real challenge with the water-core systems, compared to the previous oil-core systems, is to obtain the correct order of magnitude of the three interfacial tensions, between the polymer, the aqueous phase, and the continuous oil phase; these control the spreading conditions necessary to produce shells rather than "acorns".

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Encapsulation by interfacial polycondensation. I. The capsule production and a model for wall growth

Cited by 116 publications

References 8 publications

3D visualization of the internal nanostructure of polyamide thin films in RO membranes

3D visualization of the internal nanostructure of polyamide thin films in RO membranes

Interfacial polycondensation—Modeling of kinetics and film properties

Preparation of Aqueous Core/Polymer Shell Microcapsules by Internal Phase Separation

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