The present invention provides a polymer-based piezoelectric composite material from which a piezoelectric film capable of outputting a higher sound pressure and exhibiting excellent flexibility even in a low-temperature environment is obtained in a case of using a piezoelectric speaker, a piezoelectric film formed of the polymer-based piezoelectric composite material, and a piezoelectric speaker and a flexible display which are formed of the piezoelectric film. The polymer-based piezoelectric composite material of the present invention is a polymer-based piezoelectric composite material including a polymer matrix which contains a polymer containing a group represented by Formula (1), and piezoelectric particles.
*-L.sup.1-(CR.sup.1R.sup.2).sub.nCNFormula (1) In Formula (1), L.sup.1 represents a divalent linking group excluding a urethane group. R.sup.1 and R.sup.2 each independently represent a hydrogen atom, an alkyl group, or an aryl group. n represents an integer of 3 or greater. * represents a bonding position with respect to the main chain of a polymer.

The present invention relates to a transition metal complex or oxidation-reduction polymer including a phenyl-pyridine derivative, and an electrochemical biosensor including the same. The transition metal complex according to the present invention can be easily linked to various types of polymers. In addition, the transition metal complex according to one aspect of the present invention is electrochemically and structurally stable. Furthermore, in accordance with a method for preparing the transition metal complex according to one aspect of the present invention, various types of functional groups can be easily linked to a ligand.

In an embodiment, the present disclosure pertains to a method of changing the glass transition temperature of a polymer. In some embodiments, the polymer includes at least one hydrazone-containing compound. In general, the methods of the present disclosure include one or more of the following steps of: (1) applying light to the polymer; and (2) thereby changing the glass transition temperature of the polymer. In another embodiment, the present disclosure pertains to a polymer having a light-adjustable glass transition temperature. In some embodiments, the polymer includes at least one hydrazone-containing compound.