Entanglement Density at the Interface between Two Immiscible Polymers

Oslanec, Robert; Brown, Hugh R.

doi:10.1021/ma021044q

Cited by 14 publications

(12 citation statements)

References 25 publications

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“…The strength of the interphase depends on the physical entanglement of chains crossing the interface. A minimum of one entanglement is required for good stress transfer, and at least eight may be required to achieve the cohesive strength of theconstituent polymers. − The number of entanglements can be estimated by comparing the thickness of the interphase with the radius of gyration R g,e , corresponding to the entanglement molecular weight M e . Taking an average value of 3 nm for R g,e , the number of entanglements across the interphase, estimated as d I / R g,e , is on the order of only 2−4 for polymer pairs with interphase thickness less than 11 nm.…”

Section: Resultsmentioning

confidence: 99%

Polymer Interphase Materials by Forced Assembly

et al. 2005

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The interphase between two immiscible glassy polymers was probed using nanolayer films with tens to thousands of alternating layers of two polymers. Various combinations of poly(methyl methacrylate), polycarbonate, and a series of styrene-acrylonitrile copolymers were brought together by forced assembly. Continuous nanolayers with thickness on the size scale of the interphase were observed directly using atomic force microscopy. Interphase thickness was extracted from the layer thickness dependence of oxygen permeability. The interphase thickness showed the predicted dependence on the interaction parameter and correlated with interphase strength as measured with the T-peel test. Interphase specific volume, as determined by density, exhibited both positive and negative deviations from constituent additivity. The deviations correlated with the change in free volume hole size from positron annihilation lifetime spectroscopy but did not correlate directly with the parameter. The origin of the deviations was found in the nature of chain packing in the interphase, as evidenced by nonadditivity in entanglement molecular weight. The volumetric effects accounted for the glass transition behavior of the interphase material.

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Section: Resultsmentioning

confidence: 99%

Polymer Interphase Materials by Forced Assembly

et al. 2005

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“…The strength of the interphase depends on physical entanglement of chains crossing the interface. A minimum of one entanglement is required for good stress transfer, and at least eight may be required for maximum strength. − The number of entanglements can be estimated by comparing the thickness of the interphase with the radius of gyration R g,e of the entanglement molecular weight M e . Assuming that PETG has roughly the same molecular dimensions as polycarbonate, R g,e = 0.457 with M e = 1500 g mol -1 .…”

Section: Resultsmentioning

confidence: 99%

Interphase Materials by Forced Assembly of Glassy Polymers

et al. 2004

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When two immiscible polymers are brought into intimate contact, highly localized mixing of polymer chains creates an "interphase" region. We have fabricated materials that are entirely interphase by forced assembly of two immiscible polymers. Assemblies of thousands of alternating layers of two polymers, with individual layer thickness on the nanometer size scale of the interphase, were created by layer multiplying coextrusion. The properties of the interphase materials were probed with conventional tools of polymer analysis. In this study, the effect of interaction strength was examined with assemblies that combined an amorphous polyester with a series of styrene-acrylonitrile copolymers that varied in acrylonitrile content from 0 to 30 wt %. Continuous, uniform layers were directly observed using atomic force microscopy. Interphase thickness was extracted from the layer thickness dependence of oxygen permeability. The interphase thickness showed the predicted dependency on the parameter and correlated with interphase strength as measured with the T-peel test. Unexpectedly, volumetric properties of the interphase deviated from additive predictions. Correspondence between the decrease in specific volume from macroscopic density and the decrease in free volume hole size from positron annihilation lifetime spectroscopy suggested that densification of the interphase occurred primarily by a decrease in free volume hole size rather than by a decrease in the number of free volume holes. The volume change did not directly correlate with the parameter. At present, the origin of the volume change is not clear.

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“…Experimental studies [3] suggested that chain entanglements in the surface vicinity should play a major role in the reinforcement and it can be explained by the presence of trapped entanglements near the interface. Theoretical studies in the past qualitatively suggested that the density of entanglements should decrease in the vicinity of a wall [8,9] because of the average decrease in chain dimensions established earlier by simulation [10,11]. On the experimental side the validity of this assumption was recently questioned for free standing films [7], but direct evidence of this phenomenon near a repulsive wall is still lacking, and it could not be related to mechanical properties.…”

Section: Introductionmentioning

confidence: 99%