A polymer with a backbone having at least one structural unit represented by formula (I): ##STR00001## Wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, and R.sub.5 independently denote one of a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, or a substituted or unsubstituted alkenyl group, and n preferably denotes an integer from 1 to 10.