Cocontinuous blends from polyethylene and polyethylene oxide (PE/PEO) were prepared using non-functional LDPE and maleic anhydride functional PE-g-MA with different molecular weight PEO, and porous films were produced from them blends by solvent extraction of the continuous PEO phase.  The phase inversion composition, estimated as the center of the range of compositions that could result in cocontinuous porous polymers, was best predicted by a droplet packing model, assuming deformable spheres when viscosity ratio was near one and hard spheres when viscosity ratio was far from one.  Increasing molecular weight increased viscosity, which tended to broaden the range of porous compositions for non-reactive blends.  However, increased molecular weight narrowed the range of porosity in reactive blends due to the formation of interfacial copolymers which resisted coalescence into a continuous phase.  Reactive blending with PE-g-MA and PEO produced smaller pores due to formation of PE-g-PEO graft copolymers at the blend interface.  In both reactive and nonreactive blends, higher molecular weight PEO slowed the rate of coarsening during annealing.  Additionally, reactive blends suppressed coarsening after 10 minutes of annealing.  Estimating the graft density of copolymers at the interface by XPS of laminated samples, it was found that the coarsening ceased once the PE-g-PEO graft density reached 4-5 copolymer chains per pRg2 of the relevant PEO.  This suggests that coarsening was halted once the interfacial copolymers were densified into a slightly elongated brush, and the elastic drive to restore the chains to a random walk prevented further reduction in interfacial area.

Controlling porosity and pore size in cocontinuous blends via interfacial reaction and molecular weight

248th National Meeting (2014)

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