Water transfers heat better than coolant. The coolant is there to lower the freezing point and raise the boiling point of the liquid and to prevent internal corrosion of the cooling system. Straight coolant would have superior anti-corrosion and a wider operating temperature range but would not remove heat from the engine like you need it to.
It is absolutely NOT going to work properly to run 100% antifreeze in ANY situation. It is too thick, it will not flow properly, and will not properly pick up and transfer heat without water added in the proper mix.