Molecular Motion in Polycarbonate and Modified Polycarbonates

Steger, Theodore R.; Schaefer, Jacob; Stejskal, E. O.; McKay, Robert A.

doi:10.1021/ma60077a019

Cited by 71 publications

(26 citation statements)

References 5 publications

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“…PC is well known for its extensive segmental or local molecular mobility in the glassy state. The types of motions that occur in concert deep within the glassy state include librations and rotations of the isopropylidene methyls,24–28 π flips of the phenyl rings,26, 29–32 and cis–trans isomerizations of the carbonate moieties 24, 33–36. The first two of these groups are hydrogenous and therefore dominate 〈 u 2 〉 because of the large incoherent scattering cross section.…”

Section: Discussionmentioning

confidence: 99%

Dynamics of thin polymer films: Recent insights from incoherent neutron scattering

Soles

Douglas

2004

J Polym Sci B Polym Phys

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Incoherent neutron scattering is presented as a powerful tool for interpreting changes in molecular dynamics as a function of film thickness for a range of polymers. Motions on approximately nanosecond and faster timescales are quantified in terms of a mean-square atomic displacement (͗u 2 ͘) from the Debye-Waller factor. Thin-film confinement generally leads to a reduction of ͗u 2 ͘ in comparison with the bulk material, and this effect becomes especially pronounced when the film thickness approaches the unperturbed dimensions of the macromolecule. Generally, there is a suppression (never an enhancement) of ͗u 2 ͘ at temperatures T above the bulk calorimetric glass-transition temperature (T g ). Below T g , the reduction in the magnitude of ͗u 2 ͘ depends on the polymer and the length scales being probed. Polymers with extensive segmental or local mobility in the glass are particularly susceptible to reductions of ͗u 2 ͘ with confinement, especially at the Q vectors probing these longer length scales, whereas materials lacking these sub-T g motions are relatively insensitive. Moreover, a reduced ͗u 2 ͘ value correlates with reduced mobility at long time and spatial scales, as measured by diffusion in these thin polymer films. Finally, this reduced thin-film mobility is not reliably predicted by thermodynamic assessments of an apparent T g , as measured by discontinuities or kinks in the T dependence of the thermal expansion, specific volume, index of refraction, specific heat, and so forth. These measurements illustrate that ͗u 2 ͘ is a powerful and predictive tool for understanding dynamic changes in thin polymer films.

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Section: Discussionmentioning

confidence: 99%

Dynamics of thin polymer films: Recent insights from incoherent neutron scattering

Soles

Douglas

2004

J Polym Sci B Polym Phys

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“…Thus, the ability to obtain a CP spectrum and to measure T l p~ of the swollen samples suggests that at least a small residual component of the static dipolar interaction remains. 27 In addition, CP also may occur via a reduced dipolar broadening by molecular motion. 27 The highest T l p~ values for the 0, m, p aromatic peak indicate that maximum mobility of the phenyl group is found in the gel state, whereby this effect is most dominant for the 1% cross-linked polystyrene.…”

Section: Solid-state Nmr Investigations T L P~ Valuesmentioning

confidence: 99%

“…27 In addition, CP also may occur via a reduced dipolar broadening by molecular motion. 27 The highest T l p~ values for the 0, m, p aromatic peak indicate that maximum mobility of the phenyl group is found in the gel state, whereby this effect is most dominant for the 1% cross-linked polystyrene. T~,,H is controlled by these slow phenylgroup motions for which the kilohertz frequency motional regime is sensitive.…”

Section: Solid-state Nmr Investigations T L P~ Valuesmentioning

confidence: 99%

Investigation of the Diffusion Process in Cross-Linked Polystyrenes by Means of NMR Imaging and Solid-State NMR Spectroscopy

Ilg¹,

Pfleiderer²,

Albert³

et al. 1994

Macromolecules

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The diffusion process of a solvent (dioxane) in samples of different cross-linked polystyrenes can be monitored by combined NMR imaging and solid-state NMR techniques. NMR imaging data reveal a strong dependence of the diffusion behavior upon the cross-link density: in the case of lowest cross-linking ( l % ) , a case I1 diffusion process takes place, whereas in the case of highest cross-linking (5%), Fickian diffusion occurs. The 2.5 % cross-linked polystyrene shows intermediate behavior. Solid-state NMR relaxation parameters indicate great differences between the unswollen and the swollen state. Whereas the relaxation data obtained in the unswollen state are almost independent of the degree of cross-linking, great differences are observed between the 1 % and 5 % cross-linked polymers in the swollen state, with both the highest overall mobility and, in particular, a high mobility of the phenyl group in the case of the 1 % cross-linked material. This behavior can be directly related to the different types of diffusion, suggesting that the strong interaction of the highly mobile phenyl groups with the dioxane in the low cross-linked material favors case I1 diffusion.In the 5% cross-linked materials, with a lower overall mobility and no predominant high phenyl group motion, Fickian diffusion occurs. Increased cross-linking corresponds to increasing Tl,c and TIC values, thus indicating reduced mobility.

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“…The Young's modulus, which reflects the material characteristics, also dictates the morphological phase character (Figure 4(b)). The impact strength and fracture behavior of PC and PC/ABS blends have been extensively researched 38–43 . The unique fracture behavior of the PC polymer, including the notch sensitivity and phase change from ductile to brittle, affects the impact strength (Figure 4(c)) and fracture surface characteristics of the PC/ABS blends, as depicted in Figure 5.…”

Section: Resultsmentioning

confidence: 99%

“…Additionally, when the interchain steric interactions are sufficiently rapid to induce plastic flow, an energy distribution may occur rather than stress concentration, crack initiation, and brittle failure, when an external impact energy is applied. As the thickness increases, the boundary condition changes from a plane stress system to a plane strain system, and the bulk constraints hinder lateral contraction, leading to a transition from the ductile to brittle phase 38–42 . The addition of the ABS polymer, with PBD inducing toughness and preventing crack growth, significantly enhances the impact strength of the blends.…”

Section: Resultsmentioning

confidence: 99%

Effects of blend composition on the morphologies and physical properties of polycarbonate/acrylonitrile‐butadiene‐styrene blends

Seo

Jeon

Han

2020

J of Applied Polymer Sci

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The morphologies and physical properties of twin‐screw‐extruded polycarbonate/acrylonitrile‐butadiene‐styrene (PC/ABS) blends with various blend ratios are studied. The needle‐like co‐continuous phase in PC‐rich blends changes to the sea‐island phase for blend ratios of more than 50 wt% ABS. While pure PC exhibits an almost‐Newtonian flow behavior, PC/ABS blends exhibit the interesting rheological transition. The viscosities of the ABS‐rich blends at low shear rates are almost equal to those of the pure ABS polymer. The yield stress for the PC/ABS blend ratio of 3:7 is the highest in composition. At the frequency of 10 rad/s, the PC‐rich blends exhibit highly viscous properties, whereas the ABS‐rich blends present highly elastic properties as the temperature increases. Moreover, the ABS polymer in the PC/ABS polymer blend induces significant change at the fracture surface of PC, transitioning from brittle to ductile nature.

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Molecular Motion in Polycarbonate and Modified Polycarbonates

Cited by 71 publications

References 5 publications

Dynamics of thin polymer films: Recent insights from incoherent neutron scattering

Dynamics of thin polymer films: Recent insights from incoherent neutron scattering

Investigation of the Diffusion Process in Cross-Linked Polystyrenes by Means of NMR Imaging and Solid-State NMR Spectroscopy

Effects of blend composition on the morphologies and physical properties of polycarbonate/acrylonitrile‐butadiene‐styrene blends

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