First off I am a bit confused as to what type of interface you were aiming for. In the subject line you mentioned RS485 and then in the body you bring the MAX232 chip into the discussion which is of course normally used for RS232 interfacing.

If indeed you were aiming for RS232 then you should focus on a part like the MAX3232. Here is a link to the data sheet. This part is able to run properly over a range of power supply from 3.0V to 5.5V.

Michael Karas