The present invention provides a polymer which has a small change in relative permittivity before and after exposure to a high-temperature and high-humidity environment, and is capable of forming a film having few wrinkles; a composition; a piezoelectric composite material; a piezoelectric film; and a piezoelectric element. The polymer of an embodiment of the present invention is a polymer including a repeating unit represented by Formula (A) and a repeating unit represented by Formula (B), in which a content of the repeating unit represented by Formula (A) is 60% by mole or more with respect to all repeating units of the polymer, a content of the repeating unit represented by Formula (B) is 1% to 40% by mole with respect to all repeating units of the polymer, and the polymer includes no repeating unit represented by Formula (C), or in a case where the polymer includes the repeating unit represented by Formula (C), a content of the repeating unit represented by Formula (C) is 5% by mole or less with respect to all repeating units of the polymer.

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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.

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.