Change ionic nav buttons side dynamically

Hello everyone,
I’m creating a side menu and I need to change the side of the nav button dynamically according to some conditions I’m making in the controller. Anyone could help?

Note: Here is the code I’m expecting to change.
buttonSide is a variable in my controller to bind the side with left or right. but it’s not working

    <ion-nav-buttons side="{{buttonSide}}">
      <button class="button button-icon kk button-clear ion-navicon" ng-click="toggle()">