This depends on whether your channel is registered, and if so which IRC network youre on. If the channel is not registered, its gone when everyone parts it and its modes are cleared. If youre on an IRC network that provides channel services thru registration, ask the chan services help chan on that network, since each one has a different method for chan services. Your other option is to run your own bot from a 24/7 connection to keep the chan open and the modes controlled by the bot.
