Can defrosting chicken make it slimy?
Chicken naturally contains a lot of water, it also absorbs some more from the cleaning process (up to 8% reportedly). Some manufacturers also "tumble" the raw chicken with brine to increase flavour and, of course, weight and thus profit.

The freezing process will damage cells in the meat as the water expands, so when the chicken is defrosted some of this water/protein mixture will escape from these ruptured cells. When cooking you may see this as a white gunge forming in the pan.

It can feel quite slimy once defrosted, but this is just the raw "juices" coming out. I buy chicken in bulk and vacuum seal/freeze it into portion sizes. Good quality meat and drying the chicken before freezing can help. Flash freezing is preferred, but this is not practical at home. 

I believe food safety is OT here, but it should not be an issue as long as you follow all the recommended guidelines for storage temperature and times.