signed vs unsigned integers

Hi

for a project including communication with an arduino board, we try to "save" bytes in order to send less data as possible.

I wonder how i can turn my lists of signed integers into unsigned integers.
We send consecutive leds state, by list of 100.
The example would be :
2 leds are on = 2 x 255
and i would like to turn it into 11111111 11111111 or 65535

Is there an object which converts into char ?

thanks