Chain-fragment diffusion in liquid and glassy polymer blends

Hellmann, E. H.; Hellmann, G. P.; Rennie, A. R.

doi:10.1021/ma00013a013

Cited by 10 publications

(3 citation statements)

References 7 publications

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“…Many techniques have been developed to measure the diffusion coefficients of small or large molecules in polymer melts or solutions. For example, pulsed field gradient‐nuclear magnetic resonance (PFG‐NMR) spectroscopy,22 X‐ray microanalysis in scanning electron microscopy,23 neutron scattering,24, 25 neutron reflection,26 neutron spin echo,27 forward recoil spectrometry,28 Fourier transform infrared spectroscopy,29 and transmission electron microscopy30 have been used. All these techniques require the samples to be either chemically labeled or spectroscopically differentiated.…”

Section: Introductionmentioning

confidence: 99%

Polymer–polymer mutual diffusion via rheology of coextruded multilayers

Zhao

Macosko

2007

AIChE Journal

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in Wiley InterScience (www.interscience.wiley.com).The mutual diffusion coefficient of a pair of polyethylenes using coextruded multilayers has been measured. Two polyethylenes with different molecular weight were coextruded in 32 alternating layers in about 45 s of contact time. When the multilayer sample was remelted in a parallel plate rheometer, its apparent viscosity increased due to interdiffusion. By following the kinetics of the apparent viscosity increase, the mutual diffusion coefficient was measured. The theory of Kramer et al. (Polymer. 1984; 25:473-480) was used to describe the mutual diffusion coefficient as a function of the chain mobility parameter, molecular weight, and concentration. The finite element method was used to solve the nonlinear interdiffusion problem to give a concentration profile in these multilayers. By fitting the apparent viscosity of the sample vs. time, the chain mobility parameter was found to be 4.5 Â 10 11 m/N s, and the range of the mutual diffusion coefficient for these two PE's was 10 À12 -10 À14 m 2 /s at 2008C (depending on concentration). This is an easy and rapid method to measure the mutual diffusion coefficient for miscible polymers with different melt viscosities.

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Section: Introductionmentioning

confidence: 99%

Polymer–polymer mutual diffusion via rheology of coextruded multilayers

Zhao

Macosko

2007

AIChE Journal

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“…The CFD-SANS method referred to in ( 3 ) is discussed in the second part. 13 The principles of the methods are considered in the next section. Results are discussed in the fourth section.…”

Section: Tmpc T = 202°cmentioning

confidence: 99%

“…Diagrams as in Figure 13 were used to determine the very slow diffusion in polymer glasses by the CFD-SANS technique mentioned in the Introduction (point 3 ) .8 *9,13 The method is elaborately described in ref. 13. A difficulty is that both the chains and the fragments of the PC(TxAl-,) copolymers are polydisperse.…”

Section: Sansmentioning

confidence: 99%

Chain fragmentation under liquid‐state and solid‐state conditions

Hellmann

Kuhn

Hellmann

et al. 1992

J Polym Sci B Polym Phys

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SYNOPSISThermally activated fragmentation of copolycarbonates PC (T,A,-.) of bisphenol A (unit CA) and the heat-sensitive diol 1,1,2,2-tetraethyl-l,2-di-(p-hydroxy )phenylethane (unit CT) was studied in the bulk, i.e., in the pure copolymers and in their blends with the polycarbonates of bisphenol A (PCA) or tetramethyl bisphenol A (TMPC) . Fragmentation proceeds via dissociation followed by disproportionation at the central C -C bond of the unit CT. The reaction has rates that are convenient to study near the glass transition temperature. The "chemical" time constants T for the entire reaction and T~ for the disproportionation step compete with the "physical" time constants 6, for segmental motion and 6, for fragment diffusion. A cage effect is observed below T~ = 6,, and effects of delayed matrix response below T = 6, and 7 = 6,. Owing to the two latter effects, parameters such as the glass transition temperature and the structure factor of concentration fluctuations do not respond primarily to the fragmentation, but rather to subsequent relaxation and diffusion processes in the polymer matrix. Keywords: degradation, thermal, of copolycarbonates and their blends glassy polymers, thermal chain fragmentation in liquid and solid states copolycarbonates, pure and in blends, chain fragmentation in RR R"A diphenylethane unit as shown, with four ethyl substituents, was used in this study. The unit was incorporated into polycarbonate chains, at different mole fractions x:has been studied The time constant 7 1 responds sensitively t o intramolecular strain built up by the substituents about the central C -C bond. 7 1 responds also t o polar and mesomeric effects, so that investigation of the thermal stability of these ethanes has helped in understanding the strength of C -C Another feature of this reaction has attracted less CA CT attention. It results in clean irreversible fragmentation. The radicals react, given the necessary vicinal T h e polycarbonates P C ( T,A1-,) are nearly ideal copolycondensates, with several CT units per chain. The synthesis and particularly t h e thermal fragmentation as measured by gel permeation chromatography ( GPC ) are described in detail in ref. 3.

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Neutron Scattering in Analysis of Polymers and Rubbers

Bucknall

2000

Encyclopedia of Analytical Chemistry

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The neutron is in many ways an ideal probe for the investigation of the structure and dynamics of materials. Elastically scattered neutrons can be used to determine the structure of the sample from the atomic to macromolecular length scales, whilst dynamic information describing the vibration, rotation and translation of these molecules is obtained from inelastically scattered neutrons. The use of isotopic substitution provides an easy route to highlighting whole or parts of a molecule in the neutron scattering experiment. Isotopic labeling has been extensively used in polymer studies owing to the large difference between hydrogen and deuterium. The combined use of neutrons often with isotopic labeling schemes has provided a wealth of detailed information about polymer materials, which could not be derived so easily by other methods.

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Chain-fragment diffusion in liquid and glassy polymer blends

Cited by 10 publications

References 7 publications

Polymer–polymer mutual diffusion via rheology of coextruded multilayers

Polymer–polymer mutual diffusion via rheology of coextruded multilayers

Chain fragmentation under liquid‐state and solid‐state conditions

Neutron Scattering in Analysis of Polymers and Rubbers

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