Provided is preparation of poly through alternating copolymerization of carbon dioxide and epoxide. The electrode structures described herein may include one or more protective layers. The cap also includes an internal compartment for storing a liquid or other material in a sealed manner. A frame is disposed in engagement with the input cam lobe, and is pivotally and slidably coupled to the guide member. The distal portion and the proximal portion are freely rotatable relative to each other.