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Membrane Technology and Applications

Correlation of separation factor versus permeability for polymeric membranes

Different polymers can be combined into a single material in many ways, which can lead to a wide range of phase behaviors that directly influence the associated physical properties and ultimate applications. Four factors control polymer-polymer phase behavior: choice of monomers, molecular architecture, composition, and molecular size. Current theories and experiments that deal with the equilibrium thermodynamics and non-equilibrium dynamics of polymer mixtures are described in terms of these experimentally accessible parameters. Two representative molecular architectures, binary linear homopolymer mixtures and diblock copolymers, exhibiting macrophase separation and microphase segregation, respectively, are examined in some detail. Although these model systems are fairly well understood, a myriad of mixing scenarios, with both existing and unrealized materials applications, remain unexplored at a fundamental level.

https://science.sciencemag.org/content/sci/251/4996/898.full.pdf

Polymer-polymer phase behavior.

Direct polymerization of sulfonated poly(arylene ether sulfone) random (statistical) copolymers: candidates for new proton exchange membranes

Energy-efficient polymeric gas separation membranes for a sustainable future: A review

Polymer-polymer miscibility

Melt blends of poly(butylene terephthalate) (PBT) and the polyhydroxyether of bisphenol A (phenoxy) exhibit excellent transparency above the melting point of PBT as well as for the quenched molded specimens. Dynamic mechanical and calorimetric characterization revealed single and sharp glass transitions intermediate between those for the individual constituents. Increasing phenoxy content in the blends depressed the crystallization rate of PBT due to dilution and viscosity (Tg increase) effects. The apparent miscibility is believed due to the potential specific interactions between phenoxy pendant hydroxyl (proton donor) and the ester carbonyl of PBT (proton acceptor). Heat of fusion results surprisingly show an increase in the degree of PBT crystallinity as the phenoxy content of the blend is increased. No explanation is offered at this point for this unexpected behavior.

Miscible blends of poly(butylene terephthalate) and the polyhydroxyether of bisphenol A

A series of polysulfone/poly(dimethylsiloxane) (AB)n block copolymers have been synthesized over a wide composition range by varying the molecular weights of the polysulfone and poly(dimethylsiloxane) blocks. The properties vary from a rigid material at high polysulfone content (>65% polysulfone) to an elastomeric material at high poly(dimethylsiloxane) content (>65% poly(dimethylsiloxane)).



A simple extension of MAXWELL's analysis of heterogeneous systems is shown to be applicable to the prediction of permeability data and a similar treatment of KERNER's analysis can be used for predicting modulus data. Analysis of both the permeability data and modulus data predict a similar phase inversion composition for this two-phase block copolymer.



Different properties can be obtained with a given block copolymer composition by casting films from different solvents or by swelling the films in a non-solvent which preferentially swells one phase only. The tendency of poly(dimethylsiloxane) to crystallize at low temperature is dependent upon the flexibility of the block copolymer, which can be influenced by the method of film preparation.



Eine Reihe von Polysulfon-Polydimethylsiloxan-(AB)n-Blockcopolymeren wurde uber eine breite Zusammensetzungsweite durch Variation des Molekulargewichtes der Polysulfon- und Polydimethylsiloxan-Blocke dargestellt. Die Eigenschaften dieser Polymeren reichen von einem harten Stoff bei hohem Polysulfongehalt (>65% Polysulfon) bis zu einem elastischen Stoff bei hohem Gehalt an Polydimethylsiloxan (>65% Polydimethylsiloxan).



Es wird gezeigt, das eine einfache Erweiterung der MAXWELL-Analyse von heterogenen Systemen genugt, um Permeabilitatsdaten vorherzusagen. Eine ahnliche Handhabung der KERNER-Analyse kann angewandt werden, um die Moduli vorherzusagen. Die Analyse der Permeabilitats-Ergebnisse und der Moduli-Ergebnisse zeigt das Auftreten der Phasenumkehrung bei ahnlicher Zusammensetzung dieser Zweiphasen-Blockcopolymeren an.



Von einem gegebenen Blockcopolymeren konnen verschiedene physikalische Eigenschaften erhalten werden, wenn Polymerfilme aus verschiedenen Losungsmitteln hergestellt werden, oder wenn der Polymerfilm mit einem Losungsmittel fur nur eine Phase des Polymeren angequollen wird. Die Neigung der Polydime-thylsiloxan-Komponente zu kristallisieren, hiingt von der Flexibilitiit des Copoly-meren ab. Die Flexibilitiit kann bei der Herstellung des Filmes eingestellt werden.

Physical property characteristics of polysulfone/poly‐(dimethylsiloxane) block copolymers

Melt mixtures of a polyarylate based on bisphenol A and tere/isophthalates were made with poly(ethylene terephthalate), several cyclohexane dimethanol-based polyesters, polycarbonate, and the poly(hydroxy ether) of bisphenol A. The phase behavior was determined using classical methods. With minimum time and temperature exposure, polyarylate exhibits phase separation with poly(ethylene terephthalate) (PET) at >30 wt % PET. With moderate time and temperature exposure, adequate ester exchange occurs with polyarylate/PET blends to yield single-phase behavior. The activation energy of the ester-exchange reaction was determined to be 37.0 kcal/mole.

Under minimum time and temperature exposure conditions, miscibility of polyarylate with three different cyclohexane dimethanol-based polyesters was observed. A polyarylate-polycarbonate 50:50 mixture was shown to be phase separated under minimum mixing conditions but capable of exchange reactions to yield single-phase behavior with proper time and temperature exposure. Likewise, a 70:30 polyarylate-poly(hydroxy ether of bisphenol A) blend was phase separated as mixed, but with further elevated temperature exposure, a cross-linked single-phase system resulted.

The density versus composition of the polyarylate-PET blends was linear with the phase-separated systems but exhibited a slight densification with the miscible systems produced by higher temperature exposure. The glass transition of the miscible polyarylate-polyester blends exhibited a significant deviation (lower) than predicted by a linear or Fox equation prediction. This was attributed to the low value of ΔCp (specific heat difference between the glass and rubber states) of polyarylate as noted by the Couchman equation to be a major factor in the Tg versus composition relationship. The optical characteristics of the blends paralleled the observed phase behavior as single-phase blends were all transparent (in the amorphous state) whereas phase-separated blends were translucent to opaque. These results clearly demonstrate the importance of ester-exchange or transesterification reactions in the phase behavior of blends of polymers capable of these reactions.

Phase behavior of polyarylate blends

Described herein are molding compositions comprising a blend of (a) a polyarylate derived from a dihydric phenol and a mixture of isophthalic acid and terephthalic acid, of which more than about 65 mole percent is terephthalic acid, (b) a polyarylate derived from a dihydric phenol and a mixture of terephthalic acid and isophthalic acid, of which more than about 70 mole percent is isophthalic acid, and (c) at least one thermoplastic polymer compatible therewith An article molded from these compositions has a good balance of mechanical properties and improved environmental stress crack resistance

Lloyd Mahlon Robeson

Papers

Polymer-polymer miscibility

Miscible blends of poly(butylene terephthalate) and the polyhydroxyether of bisphenol A

Physical property characteristics of polysulfone/poly‐(dimethylsiloxane) block copolymers

Phase behavior of polyarylate blends

Polyarylate containing blends