UIKit Dynamics only supports rectangle shapes as defined by this protocol.
@protocol UIDynamicItem <NSObject>
@property (nonatomic, readwrite) CGPoint center;
@property (nonatomic, readonly) CGRect bounds;
@property (nonatomic, readwrite) CGAffineTransform transform;
@end
Maybe SpriteKit's SKPhysicsBody
would work for your case. Specifically, by passing a hexagon path to this initializer.
+ (SKPhysicsBody *)bodyWithPolygonFromPath:(CGPathRef)path