Dynamic birefringence of poly(methyl methacrylate)

Read, B. E.

doi:10.1002/polc.5070160405

Cited by 21 publications

(15 citation statements)

References 13 publications

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“…The contribution of the ester group to the optical anisotropy of a statistical segment depends on the orientation of the -COO-plane with respect to the axis of the segment. Calculations of the optical anisotropy by Tsvetkov et al [11] and Read [17] based upon the additivity of bond polarizabilities show that the values of the optical anisotropy differ for different positions of the -COOplane. In the case of a fixed trans-position where the -COO-plane is perpendicular to the axis of the segment the optical anisotropy of a monomer unit is negative.…”

Section: Hindered Side Group Rotation and Associationsmentioning

confidence: 99%

Orientational birefringence of uniaxially compressed PMMA networks in the unswollen state

Kock

Rehage

1985

Colloid & Polymer Sci

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Swollen PMMA networks show significant deviations from the theory of rubber elasticity. The unusual mechanical, optical and swelling properties have been explained by the existence of associations, well known for PMMA solutions.Unswollen PMMA networks show stress optical properties which are very similar to the networks swollen in carbon tetrachloride which is known as a strong complexing solvent. This indicates that associations exist in the bulk material. Swelling in carbon tetrachloride does not change the content of associations, only the glass transition temperature is reduced.Increasing the amount of crosslinking agent proves that the stress optical coefficient depends on the crosslinking density. This is contrary to the theoretical predictions. An explanation given by the effect of short network chains is not satisfactory. However, the consideration of a crosslinking chain instead of a crosslinking point gives a sufficient explanation. An oriented crosslinking chain gives a positive contribution to the total optical anisotropy while a PMMA chain shows a change from negative values (hindered rotation) to positive values (free rotation).

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Section: Hindered Side Group Rotation and Associationsmentioning

confidence: 99%

Orientational birefringence of uniaxially compressed PMMA networks in the unswollen state

Kock

Rehage

1985

Colloid & Polymer Sci

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“…2 Dynamic measurements on polymers far above and well below the glass transition temperature have been interpreted in terms of a C that is independent of stress and test frequency. [14][15][16][17][18][19][20][21][22] In rubbers, a direct proportionality between stress and birefringence implies that both have the same physical originsorientation of the segments comprising the polymer chains. 2,3,23 Four departures from the stress optical law are known: (i) When the orientation of the bond vectors (responsible for the intrinsic birefringence) is no longer proportional to the orientation of the chain end-to-end vector (responsible for the mechanical stress).…”

Section: Introductionmentioning

confidence: 99%

“…(ii) Behavior in the softening zone of the viscoelastic spectrum ostensibly violates the stress optical law; however, the stress optical coefficient obtained from dynamic mechanical experiments in this regime can be decomposed into a glassy and rubbery component, both conforming to eq 1. [14][15][16][17][18][19][20][21][22] (iii) While the intrinsic birefringence is proportional to the stress, the form birefringence, arising from spatial variations of the dielectric constant, is not. Significant for phase-separated blends and semicrystalline polymers, 2,24 the form birefringence is negligible in homogeneous materials.…”

Section: Introductionmentioning

confidence: 99%

“…Due to its random cis and trans copolymer structure, the material is incapable of crystallizing; this avoids a complication in the natural rubber experiments of Saunders. 9 Deformations were carried out 100 deg above the glass transition temperature, so that any interference from a "glassy" stress optical coefficient [14][15][16][17][18][19][20][21][22]30 is also avoided.…”

Section: Introductionmentioning

confidence: 99%

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Birefringence of Rubber during Creep and Recovery

Mott

Roland

1996

Macromolecules

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Measurements of creep and recovery of lightly cross-linked polybutadiene, carried out in both shear and compression geometries, reveal two deviations from the stress optical law: the birefringence increases during the constant stress creep, and the birefringence is not zero during the stress-free recovery. Most interestingly, the sign of the birefringence during recovery was found to be opposite to that during creep. This implies that the chain segments have a net orientation opposite to the macroscopic deformation.

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“…If all positions of the side group have the same probability, the calculated optical anisotropy of the monomer unit is positive ("free rotating" side group). If the side group is in a perpendicular position to the main chain (~ = z/2) Aam is negative [6,7]. The actual mean position of the side group and consequently Aam are functions of the temperature.…”

Section: Introductionmentioning

confidence: 99%

Photoelasticity and structure of PMMA networks

Kock

Rehage

1984

Colloid & Polymer Sci

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Abstract:The optical anisotropy Aa (a = polarizability) of uniaxial deformed swollen and unswollen PMMA networks depends on the temperature. This is not in agreement with the Kuhn-Griin-theory. The temperature dependence and the negative values even above the glass transition temperature 7[2 can be explained by the existence of associations which cause a hindrance of the ester side group mobility. The swelling of the network in the optical isotropic solvent carbon tetrachloride does not degrade the associations and therefore not change the network structure; only Tg decreases. The situation is more complicated if optical anisotropic solvents are used. Polar aliphatic and aromatic solvents degrade the associations to some extend and the birefringence is shifted to more positive values. An additional change is caused by specific polymer solvent interactions. Aromatic solvents form complexes with the ester side group and the aliphatic solvent chloroform completely degrades the associations, which can be explained by the formation of hydrogen bonds. Sign and magnitude of the optical anisotropy allow statements on the orientation of the solvent molecules with respect to the polymer chain or the ester side group.

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Dynamic birefringence of poly(methyl methacrylate)

Cited by 21 publications

References 13 publications

Orientational birefringence of uniaxially compressed PMMA networks in the unswollen state

Orientational birefringence of uniaxially compressed PMMA networks in the unswollen state

Birefringence of Rubber during Creep and Recovery

Photoelasticity and structure of PMMA networks

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