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The complex strain-optical ratio and the complex Young's modulus of a polyarylate with a low molecular anisotropy, PAr1, were measured around the glass-to-rubber transition zone. The polyarylate was synthesized from 2,2′-dicarboxy biphenyl and 4,4′-dioxydiphenyl-2,2′-propane. The data were analysed with a modified stress-optical rule: The Young's modulus and the complex strain-optical ratio were separated into two component functions (denoted by G and R) for which the ordinary stress-optical rule held well individually. A comparison of the component functions was made with a conventional amorphous polyarylate (UP) and bisphenol A polycarbonate (PC). The limiting modulus of the R component at high frequencies for PAr1 was about two times higher than that for UP and PC. This result suggested that PAr1 had a highly flexible main-chain structure. This high flexibility was in accord with a zigzag structure of 2,2′-dicarboxy biphenyl unit of the main chain. The stress-optical coefficient for the R component of PAr1 was 9.0 × 10 −10 Pa −1 , and approximately five times smaller than that for UP. Conversely, the intrinsic birefringence for PAr1 was estimated to be 2.5 times smaller than that for PC. This result indicates that reducing stiffness of main chain with flexible junctions and also optical anisotropy are effective in decreasing C R . The stress-optical coefficient for the G component of PAr1 was 3.1 × 10 −11 Pa −1 . This value agreed well with that for the polymers containing phenyl rings in their repeating unit.

Published data of dynamic birefringence and viscoelasticity of amorphous polymers were compared with the molecular expression of stress proposed by Gao and Weiner. The theory states that the stress is composed of contributions from the chain orientation (orientation term), the monomer orientation around the chain axis (rotation term), and the fluctuation of the local stress tensor (fluctuation term); the birefringence is composed of only two terms corresponding to the first two of the stress. The experimental data indicate that in the glassy zone and the high-frequency region of the glass-to-rubber transition zone the stress is attributable to the rotation and the fluctuation terms and the degrees of contribution vary with polymer species. For polymers with flat units (like polycarbonate), the fluctuation term is negligible and the relaxation spectrum in the glassy zone is low. For polymers with thin axisymmetric units (like polyisobutylene) or bulky irregular units (like poly(2-vinylnaphthalene)), the relaxation spectrum in the glassy zone is enhanced by the fluctuation term. It is also argued that, for polymers with thin axisymmetric units, the relaxation spectrum for the rotation term resembles that of a dilute solution; the role of rotational barrier along the chain is relatively enhanced since the rotational barrier from the surrounding is low because of the symmetry of the unit and because of the high fluctuation of the local stress. Some experiments are proposed to verify the statements

The studies on dynamic birefringence of amorphous polymers are reviewed. The birefringence in oscillatory deformation is related to the viscoelasticity through the stress-optical rule (SOR) in the rubbery and the terminal flow zones. The deviation from the SOR in the glassy and the glass-to-rubber transition zones can be described with a modified SOR, based on the assumption that the stress is a sum of two components associated with respective stress-optical coefficients. Experimental results are reviewed for 14 polymers: polystyrene, poly(α-methyl styrene), poly(2-vinyl naphthalene), polyisobutylene and 10 polymers for engineering plastics. The nature of various parameters is discussed in relation to the molecular structure.

The complex Young's modulus, E*(ω), and the complex strain-optical coefficient, O*(ω), of a polystyrene (PS)/bisphenol A polycarbonate (PC) blend and a graft copolymer were studied in the glass-to-rubber transition zone at frequencies ranging from 1 to 130Hz at various temperatures between 102°C and 182°C. The relaxation behaviors in E*(ω) and O*(ω) of two alloys were compared with each other in relation to the relaxation behaviors of constituents, PS and PC. It was clarified that for the blend in the mechanical spectrum two isolated relaxation peaks are detected at frequencies apart from each other, which means that the consitituents relax independently. For the copolymer two relaxation peaks of constituents were almost merged giving rise to about a single peak which indicates cooperating relaxation of the two components.The optical relaxation spectra, O*(ω), of two alloys showed distinct difference in quality and it also made us predict their compatibility to some extent. For both alloys, the stress-optical coefficient, CR, in the rubbery zone was reduced to 1/4-1/6 of the absolute value of components polymer as a result of compensation of the opposite-signed birefringences of constituent polymers. The photoelastic coefficient, Cd, for two alloys and the component polymers, PS and PC, exhibited a strong correlation with the stress-optical coefficient, CR.

The dynamic Young's modulus, E * , and birefringence of bisphenol A polycarbonate were measured over the glassy to rubbery plateau zone. Measurements were performed over the frequency range of 1 to 130 Hz at various temperatures between 148 and 170°C. A modified stress-optical rule was applied in characteristic analysis of the glassy and glass transition regions. It was earlier proposed to replace the stress-optical rule which, generally, was valid only at relatively low frequencies corresponding to rubbery plateau and rubbery flow regions. E * could be separated into two component functions, E * R and E * R . The stress-optical coefficients, C R and C G , associated with the respective components were 5.0 × 10 −9 and 3.5 × 10 −11 Pa −1 . In constructing master curves of E * R and E * G with the method of reduced variables, an unlike temperature dependence was found. This result could account for the breakdown of the time-temperature superposition principle for E * reported by several investigators.

The complex Young’s modulus, E*(ω), and the complex strain‐optical coefficient, O*(ω), of poly(α‐methyl styrene), PMS, and Bisphenol A polycarbonate, PC, were measured over the frequency range of 1–130 Hz around the glass‐to‐rubber transition point. The real part of O*(ω), O’, of PMS is negative over the entire temperature range considered and the imaginary part, O‘, changes its sign from negative to positive with decreasing temperature. Both O’ and O‘ of PC are positive over the entire temperature range used. These results are qualitatively different from those for polystyrene. The data were analyzed with a modified stress‐optical rule and the complex modulus was separated into two components (denoted by R and G). The G component, which is located in the glassy zone, is related to the high glass modulus, and the shapes of the G components of PMS, PC, and PS are very similar to each other. The R component, located at the long time end of the glass‐to‐rubber transition zone of PC, is quite different from t...

The stress relaxation and simultaneous birefringence variation were measured for bisphenol A polycarbonate over the glassy to the rubbery plateau regions. The measurements were performed at various temperatures of 142–156 °C over the time range of 0.4 to 2000 s. Results of relaxation measurements were consistent with those of dynamic measurements with respect to the birefringence as well as the stress in the framework of linear viscoelasticity. A modified stress‐optical rule was applied to the results of relaxation measurements. This rule was earlier proposed to replace the stress‐optical rule which was suitable only in the rubbery and the terminal flow regions. The relaxation modulus, E(t), was separated into two component functions, ER(t) and EG(t). In constructing master curves of ER(t) and EG(t) with the method of reduced variables, their shift factors were found to have different temperature dependence. This result can account for the break down of time‐temperature superposition principle for E(t) reported by several investigators. The present modified stress‐optical rule was more convenient in several ways compared with the similar modifications proposed earlier by Priss et al. and Read.The stress relaxation and simultaneous birefringence variation were measured for bisphenol A polycarbonate over the glassy to the rubbery plateau regions. The measurements were performed at various temperatures of 142–156 °C over the time range of 0.4 to 2000 s. Results of relaxation measurements were consistent with those of dynamic measurements with respect to the birefringence as well as the stress in the framework of linear viscoelasticity. A modified stress‐optical rule was applied to the results of relaxation measurements. This rule was earlier proposed to replace the stress‐optical rule which was suitable only in the rubbery and the terminal flow regions. The relaxation modulus, E(t), was separated into two component functions, ER(t) and EG(t). In constructing master curves of ER(t) and EG(t) with the method of reduced variables, their shift factors were found to have different temperature dependence. This result can account for the break down of time‐temperature superposition principle for E(t) re...

Complex Young’s modulus, E*(ω), and complex strain‐optical coefficient, O*(ω), of Poly (2‐vinylnaphthalene) (P2VN) were studied in the glass‐to‐rubber transition zone at frequencies ranging from 1 to 130 Hz at various temperatures between 145 and 200 °C. In comparing the master curves of E*(ω) and O*(ω), we apply the modified stress‐optical rule to deliberate the glass transition modulus attributable to different relaxation mechanisms. The characteristics of master curves are also compared with those of polystyrene (PS), poly (a‐methylstyrene) (PMS), and polycarbonate (PC) in view of their chemical structures. The stress‐optical coefficient, CR, determined in the rubbery zone, is −8.3×10−9 Pa1, which is 1.6 times larger than that of PS. The large negative value may be due to the large optical anisotropy of naphthyl side group. In the glassy zone, the relative rate of decrease of E‘(ω) with ω is lower compared with the other polymers. This behavior is believed to be attributed to β relaxation of large naph...