Free volume study of poly(chlorotrifluoroethylene) using positron annihilation spectroscopy as a microanalytical tool

Ramachandra, P.; Ramani, R.; Ravichandran, T. S. G.; Ramgopal, G.; Gopal, S.; Ranganathaiah, C.; Murthy, N. Sanjeeva

doi:10.1016/0032-3861(96)88467-9

Cited by 25 publications

(11 citation statements)

References 18 publications

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“…(44) and Figure 11 reveal that the volume fraction of immobile voids (free-volume clusters) in a stress-free medium ⌳(0) is about 6 -8%. These values coincide with measurements of the free-volume fraction in poly-(vinyl acetate) 36 and poly(chlorotrifluoroethylene) 37 obtained by positron-annihilation lifetime spectroscopy.…”

Section: Comparison With Experimental Datasupporting

confidence: 76%

Stress-induced densification of glassy polymers in the subyield region

Drozdov¹

1999

J. Appl. Polym. Sci.

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Constitutive equations are derived for the viscoelastic response of amorphous glassy polymers in the region of subyield deformations. The model treats an amorphous polymer as a composite material consisting of an ensemble of flow units, immobile holes, and clusters of interstitial free volume moving through a network of long chains to and from voids. Changes in macropressure lead to an increase in the equilibrium concentration of interstitial free volume that, in turn, induces diffusion of free-volume elements from holes. The mass flow results in dissolution of voids that is observed as time-dependent densification of a glassy polymer. It is demonstrated that the model correctly predicts stress relaxation and a decrease in the specific volume observed in uniaxial tensile and compressive tests on polycarbonate at room temperature.

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Section: Comparison With Experimental Datasupporting

confidence: 76%

Stress-induced densification of glassy polymers in the subyield region

Drozdov¹

1999

J. Appl. Polym. Sci.

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“…Sharp crystalline peaks can be interpreted as due to pseudohexagonal packing of the helical chains with varying degrees of lateral and chain axis disorder. 42 The grafting of PSSA-PTMSPMA from P(VDF-co-CTFE) backbones alters the resulting molecular structure and physical network, leading to a decrease in the crystalline peaks at 18.2 o and 26.6 o (Figure 4(b)). It may be explained by the fact that the randomness of the amorphous phase in graft copolymer is enhanced by introducing grafting side chains, which gives rise to a perturbation of longranged spacing between the chains.…”

Section: Resultsmentioning

confidence: 97%

Nanocomposite proton conducting membranes based on amphiphilic PVDF graft copolymer

et al. 2010

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A novel comb-like amphiphilic graft copolymer of poly(vinylidene fluoride-co-chlorotrifluoroethylene)-graft-poly(4-styrene sulfonic acid-co-trimethoxysilyl propyl methacrylate), i.e. P(VDF-co-CTFE)-g-P(SSA-co-TMSPMA) was synthesized using an atom transfer radical polymerization (ATRP) technique. Successful synthesis and a microphase-separated structure of the copolymer were confirmed by proton nuclear magnetic resonance ( 1 H NMR), FTIR spectroscopy and transmission electron microscopy (TEM). This graft copolymer was combined with tetraethoxysilane (TEOS) under acidic conditions to produce organic-inorganic nanocomposite membranes through an in-situ sol-gel reaction between TEOS and PTMSPMA, as characterized by X-ray diffraction (XRD) and TEM. Upon the introduction of silica, the proton conductivity and water uptake of the membranes decreased slightly but the thermal and mechanical properties of the membranes were enhanced significantly. Various morphologies of the nanocomposite membranes were obtained after controlling the TEOS concentration, which were correlated with the thermal, mechanical and transport properties.

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“…Some crystalline peaks at diffraction angles of 18.5°, 20.4°and etc. were observed in the pristine P(VDF-co-CTFE) due to pseudohexagonal packing of the helical chains with varying degrees of lateral and chain axis disorder [19]. The grafting of POEM from the P(VDF-co-CTFE) backbone resulted in change of the molecular structure and physical network of pristine polymer, which leads to a dramatic decrease in the polymer crytallinity.…”

Section: Resultsmentioning

confidence: 98%