The birefringence of polyisobutylene

Abstract

The variation of stress and birefringence occurring during the relaxation of elongated samples of polyisobutylene at constant length was observed at temperatures between −40° and +50°C. It is found that stress and birefringence relax in the same way throughout this region, and that the quantity (stress/birefringence × temperature) is a constant. This indicates that this material behaves in a manner consistent with the kinetic theories of elasticity and birefringence for an ideal rubber, and that the statistical segment size is fairly independent of temperature in this range. A value of 3.5 × 10−24 cm.3 is obtained for the difference between the principal polarizabilities of the statistical segment.

Short-Range Order in Deformed Polymer Networks

“…Observations on are not few which suggest the presence of certain short-range orders in other polymer networks also. [16][17][18][19][20][21] Many of them could be likewise explained, at least qualitatively.…”

“…We now turn to our main problem. For our models, the packing entropy eq 2 is given by (16) where we have setM -1 ~ ~M + 1. The equilibrium value of p (= p* + q) is obtained from eq 5, which now reads…”

Strain birefringence studies on poly(vinyl acetate) networks

“…For example, over the total range of stereochemical structure, the molar Kerr constant , K can change by more than three orders of magnitude and even change ~i g n .~,~ Other optical properties used to characterize chain molecules are the stressoptical coefficient C and the related optical configuration parameter Aa. [5][6][7][8][9][10][11] Some studies of these quantities have been carried out, on a variety of long-chain molecules. In the case of symmetric chains, the agreement between experiment and the results of rotational-isomeric-state theory have not been very good; in asymmetric chains, including the vinyl type, very little has been done.…”

Optical Birefringence of Polyisobutylene during Creep and Recovery

“…The value of the stress optical coefficient, C ) 1.45 GPa -1 , compares well with previous measurements. [21][22][23] An inter- Figure 1. Schematic of the apparatus used to simultaneously measure birefringence, stress, and strain during creep and recovery.…”