A321 flight crew reported Captain's sliding cockpit window shattered in cruise. Diverted and landed uneventfully.

Narrative

Just past ZZZ approximately XA:10ZLoud smack like getting hit by a rock on CA's side sliding windowSpiderweb on outer pane on entire windowFelt window and no cracks on the inside; normal temp warmFO expediently referenced Cracked Window QRH Decided all was ok due to no inner cracksWithin about 5 minutes cracks started becoming apparent by feel on top left and right cornersApplied QRH and reduced cabin pressure to 5psi in manual modeTried to get ahold of Maintenance Control to get input about diverting to ZZZ1. But the crew phone could not connect to my ear bud microphone. I could hear him; but he could not hear me. Sent divert possibility to ZZZ1 message or returning to ZZZ2The inside cracking continued to grow and began descent to FL240 As soon as ATC could clear us we went to FL200Advised ATC Inner pane began degrading further and resulted in small particles continually snowing down on CA; side pedestal; flight bag; and down CA shirt around the neck.Descended to 10;000' Proceeded to divert immediately to ZZZ3Rapidly the inside window degraded and entire surface became course and fractured; especially around top corners and center point of patternLanding was uneventfulNo injuriesCause: Unable to communicate with Maintenance Control via crew phone and ACARS is pitiful when trying to get input for decision-making in a timely manner.