The effect of trans-stilbene unit in the compensation of birefringence of poly(methyl methacrylate) in the random copolymerization method and anisotropic molecule dopant method
2010
We investigated the effects of trans-stilbene unit in compensating birefringence in the random copolymerization method
and the anisotropic molecule dopant method. In the random copolymerization method, trans-stilbene methacrylate
(TSMA) containing the trans-stilbene unit in the side chain was polymerized with methyl methacrylate (MMA) in
solution polymerization to compensate the photoelastic birefringence and the orientational birefringence of poly(methyl
methacrylate) (PMMA). In the anisotropic molecule dopant method, trans-stilbene was added to PMMA. In the both
methods, the photoelastic birefringence and the orientational birefringence shifted from the negative side to the positive
side with an increase in the concentration of trans-stilbene unit. 0.8 mol% of TSMA almost eliminated the photoelastic
birefringence. Also, we demonstrated that poly(MMA/TSMA) exhibited no orientational birefringence with 1.9 mol% of
TSMA. 2.0 mol% of trans-stilbene almost eliminated the photoelastic birefringence of PMMA. Similarly, we
demonstrated compensating orientational birefringence with 2.0 mol% of trans-stilbene. Based on the results, the effects
of trans-stilbene unit in compensation of orientational birefringence are almost the same in the two methods. However,
in compensation of photoelastic birefringence, the trans-stilbene unit had 2.5 times higher effect in the random
copolymerization method than that in the anisotropic molecule dopant method. Photoelastic birefringence is caused in
elastic deformation below T g , in which the side chains are mainly orientated while the polymer main chains are scarcely
orientated. Therefore, we concluded that addition of trans-stilbene unit to the side chain enhanced the effect for
compensating photoelastic birefringence.
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