Unicode

Hello, can somebody explain me why the following program does not work?
Which pages of Unicode are implemented?
the u22xx and 2Axx are math symbols and extensions
Thanks
Heberto Ghezzo
Montreal

 plot(1)
 text(1.0,1.2,"a \u2A8A b \u222C c \u5222 d", cex=2)
 text(1.0,1.1," \u222C ", cex=2)
 text(1.0,1.0,"b \u222C c", cex=2)
 text(1.2,1.0,"c \u5222 d", cex=2)
 text(0.8,0.9,"a \u2A8A b", cex=2)