Solution
The number of CompactDAQ (cDAQ) Ethernet Chassis that can be chained together is dependent on the chassis and topology used for the application (as explained here). For the cDAQ-9189 chassis, the maximum hops per line is 15, so you can daisy chain (line topology) up to 15 ethernet 9189 chassis together and synchronized them. This also works for the cDAQ-9185 chassis.
The cDAQ-9183 and cDAQ-9187 do not support daisy chaining, but they can act as the endpoint of the daisy chain.