Building tribranch polymers

Hi All,

I want to Build a Polymer with a trifunctional core, and 3 arms. Specifically, a trimethyol propane ethoxylate:

TMP-EO.png

My feeble attempts have so far been defeated by Materials Studio, who insists (inter alia) that:

No.png

Can someone please show me the correct way to construct such as tri-branch chain ?

TIA,

Mat