split up vs dissociate

split up is a noun but dissociate is not a noun.

Word	Noun	Adjective	Verb	Adverb
split up	Yes	No	Yes	No
dissociate	No	No	Yes	No

As verbs, dissociate is a hyponym of split up; that is, dissociate is a word with a more specific, narrower meaning than split up:

split up (noun)	dissociate (noun)
an increase in the number of outstanding shares of a corporation without changing the shareholders' equity

split up (verb)	dissociate (verb)
become separated into pieces or fragments	to undergo a reversible or temporary breakdown of a molecule into simpler molecules or atoms
get a divorce; formally terminate a marriage	regard as unconnected
discontinue an association or relation; go different ways	part; cease or break association with
separate into parts or portions