later on vs after

later on is not an adjective while after is an adjective.

Word	Noun	Adjective	Verb	Adverb
later on	No	No	No	Yes
after	No	Yes	No	Yes

As adverbs, later on and after are synonyms defined as:

Other synonyms of later on include afterward, afterwards, later, subsequently.

later on (adjective)	after (adjective)
	located farther aft

later on (adverb)	after (adverb)
happening at a time subsequent to a reference time	behind or in the rear
	happening at a time subsequent to a reference time