Drawing and orientation development of aromatic polyesters containing terphenyl units in the main chain aliphatic side chains

Bruggeman, Albert; Buijs, J.A.H.M.

doi:10.1016/s0032-3861(96)00393-x

Cited by 7 publications

(12 citation statements)

References 20 publications

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“…[61][62][63][64][65][66][67] Frequently two or more methods to obtain the orientation are combined. 53,[68][69][70][71] The shape and width of the distribution function can be described by higher moments of the orientation distribution. 72 This is especially necessary for LC polymers with more complex organization.…”

Section: Resultsmentioning

confidence: 99%

Magnetic Field Orientation of Liquid Crystalline Epoxy Thermosets

Benicewicz¹,

Smith²,

Earls³

et al. 1998

Macromolecules

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The effect of magnetic fields on the orientation and properties of 4,4'-bis(2,3-epoxypropoxy)-alpha-methylstilbene cured with sulfanilamide has been studied. This epoxy system is initially isotropic and forms a smectic A phase upon curing. A magnetic field was applied during the cure reaction, resulting in alignment of the molecules along the direction of the applied field. Measurement of the orientation parameter of the fully cured material by wide-angle X-ray scattering (WAXS) showed that orientation improved with an increase in field strength. The orientation parameters of the smectic layer normals calculated from the inner reflection of the WAXS pattern attained a maximum level of approximately 0.8 at a field strength of approximately 12 T. The orientation parameters calculated from the outer reflection of the WAXS pattern were considerably lower, possibly due to the presence of amorphous regions associated with domain boundaries or the loss of molecular alignment within the smectic layers due to topological restrictions of the cross-linking sites. Orientation resulted in an anisotropic linear thermal expansion coefficient after curing, although the overall volumetric expansion was constant. The elastic tensile modulus increased with the square of the orientation parameter, attaining a maximum value of 8.1 GPa, compared to 3.1 GPa for the unoriented material. The change in modulus with orientation could be fit with a simple model for the modulus of anisotropic materials.

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Section: Resultsmentioning

confidence: 99%

Magnetic Field Orientation of Liquid Crystalline Epoxy Thermosets

Benicewicz¹,

Smith²,

Earls³

et al. 1998

Macromolecules

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“…Moreover, this effect of side chains on molecular orientation seems to persist at a larger-scale orientation of crystalline domains, probed with WAXD. 19 Finally, this work demonstrates that Raman microscopy provides more accurate information on orientation than the classical Raman spectroscopy, 11 due to the significantly better conditions of alignment and focusing and hence better measurements in different polarization geometries.…”

Section: Discussionmentioning

confidence: 75%

“…30 Indeed, this model compares well both qualitatively and quantitatively with the obtained P 2 data, and thus it can represent to a good approximation the orientation of rigid rods in a viscous matrix, suggesting that elongation (rather than shear) may be the dominant mechanism of orientation during the drawing deformation. 11,19 However, as already pointed out in ref 11, its detailed evaluation is not truly meaningful, since it is based on principles of continuum mechanics and does not contain molecular parameters; thus it does not provide hints on the molecular origins of the orientation mechanism.…”

Section: Resultsmentioning

confidence: 99%

“…Uniaxially oriented films were obtained by drawing the films in an oven at a temperature of about 270 °C for PES1.3/C 6 and 200 °C for PES1.3/ C12; this was recently confirmed by WAXS measurements. 19 The temperature was controlled by passing preheated dry nitrogen gas through the oven. The standard drawing speed was 2 cm/min, and the specimen length and width before drawing were 5 and 1 cm, respectively.…”

Section: Methodsmentioning

confidence: 99%

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Molecular Orientation of Hairy-Rod Polyesters: Effects of Side Chain Length

Andrikopoulos¹,

Vlassopoulos²,

Voyiatzis³

et al. 1998

Macromolecules

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Polarized laser Raman microscopy was employed in order to investigate the effects of side chain length on the orientability of uniaxially drawn films of a model hairy-rod polymer, as a function of draw ratio; an aromatic polyester containing terphenyl units in the main chain and aliphatic side chains (hexyl and dodecyl units) was used in the experiments. The second and fourth moments of the segment orientation distribution function, P 2 and P 4, respectively, determined from the analysis of the Raman spectra, indicate that the polyester with longer (dodecyl) side chains clearly exhibits higher molecular orientation compared to the one with shorter (hexyl) side chains, for the same draw ratio. Complementary FTIR measurements provide detailed information on the segmental orientation and confirm the effects of side chain length in inducing orientation; the latter result strongly suggests that the longer aliphatic side chains are oriented toward the polyesteric main chain, much more effectively than the shorter ones, apparently due to their higher flexibility. Raman measurements at high wavenumbers corresponding to the CH2 and CH3 stretching modes of the aliphatic side chains corroborate this suggestion. Further evidence comes from independent measurements of optical anisotropy of p-phenylene oligomers bearing hexyl and dodecyl side chains. The implications to the processing of hairy polymers are evident.

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“…Background correction was done by subtracting the constant intensity level at high azimuthal angle. In the literature, the minimum intensity has generally been taken as the background value . In order to obtain an estimate of 〈cos 2 ϕ 110 〉, experimental data points were fitted using Peak Fit software.…”

Section: Methodsmentioning

confidence: 99%

Determination of intrinsic birefringence values of polycaprolactone filaments

Krishnanand

Deopura

Gupta

2012

Polymer International

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Intrinsic birefringences of polycaprolactone filaments are determined using the approach suggested by Samuels. First, intrinsic lateral moduli are determined from the values of crystallinity and sonic moduli of unoriented filaments. These values are found to be 3.473 GPa and 0.071 GPa, respectively, for crystalline and amorphous regions. The crystallinity, sonic moduli and crystalline orientation function of drawn and heat set filaments are used to evaluate amorphous orientation functions. Finally, Stein and Norris's equation along with birefringence data is used to obtain intrinsic birefringence values of crystalline and amorphous regions and these values are found to be 0.079 ± 0.002 for crystalline regions and 0.066 ± 0.008 for amorphous regions. Copyright © 2012 Society of Chemical Industry

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Drawing and orientation development of aromatic polyesters containing terphenyl units in the main chain aliphatic side chains

Cited by 7 publications

References 20 publications

Magnetic Field Orientation of Liquid Crystalline Epoxy Thermosets

Magnetic Field Orientation of Liquid Crystalline Epoxy Thermosets

Molecular Orientation of Hairy-Rod Polyesters: Effects of Side Chain Length

Determination of intrinsic birefringence values of polycaprolactone filaments

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