A heat transfer system , comprising an electrocaloric material comprising: a copolymer of a monomer mixture comprising: (i) vinylidene fluoride, and (ii) an addition polymerization monomer selected from vinyl chloroformate, vinyl trifluoroacetate, vinyl acetate, vinyl benzoate, 1,1-dichloroethylene, 2-vinyl-1,3-dioxolane, n-vinylformamide, 2-vinylpyridine, 1-vinyl-2-pyrrolidinone, acrylonitrile, 1-cyanovinyl acetate, methacrylamide, acrylamide, methyl methacrylate or a monomer represented by the formula: wherein -R 1 , -R 2 , and -R 3 are each independently -H, -F, or -C(R 4 ) 3 , and R 4 is H or F, and X is selected from OClO 2 , OCN, OCIO, NO 2 , ONO 2 , NCO, NO, ONO, N 3 , OCl, NCS, OF, SCN, CN, P(=O)F 2 , PO, OCF 3 , OCl, C 6 H2(NO 2 ) 3 , NF 2 , P(=O)(OH) 2 , CH=CHC6H2(NO 2 ) 3 , OCHO, OH, COOH, CF 3 , OBr, CF 2 CF 3 , CF(CF 3 ) 2 , C 6 H 3 (NO 2 ) 2 , SiF 3 , P(=O)Cl 2 , PF 2 , GeF3, CH(CF 3 ) 2 , CH=CHC 6 H 3 (NO 2 ) 2 , NHOH, NCl 2 , CHO, SnF 3 , P(=O)Br 2 , S(=O) 2 CH 3 , -O-C(O)-R 5 , -NH-C(O)-R 6 , -C(O)-NHR 6 , cyano, or a heterocyclic group; electrodes disposed on opposite surfaces of the electrocaloric material ; ; a first thermal flow path between the electrocaloric material and a heat sink a second thermal flow path between the electrocaloric material and a heat source ; and an electric power source configured to provide voltage to the electrodes . a copolymer of a monomer mixture comprising: (i) vinylidene fluoride, and (ii) an addition polymerization monomer selected from vinyl chloroformate, vinyl trifluoroacetate, vinyl acetate, vinyl benzoate, 1,1-dichloroethylene, 2-vinyl-1,3-dioxolane, n-vinylformamide, 2-vinylpyridine, 1-vinyl-2-pyrrolidinone, acrylonitrile, 1-cyanovinyl acetate, methacrylamide, acrylamide, methyl methacrylate or a monomer represented by the formula: wherein -R 1 , -R 2 , and -R 3 are each independently -H, -F, or -C(R 4 ) 3 , and R 4 is H or F, and X is selected from OClO 2 , OCN, OCIO, NO 2 , ONO 2 , NCO, NO, ONO, N 3 , OCl, NCS, OF, SCN, CN, P(=O)F 2 , PO, OCF 3 , OCl, C 6 H2(NO 2 ) 3 , NF 2 , P(=O)(OH) 2 , CH=CHC6H2(NO 2 ) 3 , OCHO, OH, COOH, CF 3 , OBr, CF 2 CF 3 , CF(CF 3 ) 2 , C 6 H 3 (NO 2 ) 2 , SiF 3 , P(=O)Cl 2 , PF 2 , GeF3, CH(CF 3 ) 2 , CH=CHC 6 H 3 (NO 2 ) 2 , NHOH, NCl 2 , CHO, SnF 3 , P(=O)Br 2 , S(=O) 2 CH 3 , -O-C(O)-R 5 , -NH-C(O)-R 6 , -C(O)-NHR 6 , cyano, or a heterocyclic group; (i) vinylidene fluoride, and (ii) an addition polymerization monomer selected from vinyl chloroformate, vinyl trifluoroacetate, vinyl acetate, vinyl benzoate, 1,1-dichloroethylene, 2-vinyl-1,3-dioxolane, n-vinylformamide, 2-vinylpyridine, 1-vinyl-2-pyrrolidinone, acrylonitrile, 1-cyanovinyl acetate, methacrylamide, acrylamide, methyl methacrylate or a monomer represented by the formula: wherein -R 1 , -R 2 , and -R 3 are each independently -H, -F, or -C(R 4 ) 3 , and R 4 is H or F, and X is selected from OClO 2 , OCN, OCIO, NO 2 , ONO 2 , NCO, NO, ONO, N 3 , OCl, NCS, OF, SCN, CN, P(=O)F 2 , PO, OCF 3 , OCl, C 6 H2(NO 2 ) 3 , NF 2 , P(=O)(OH) 2 , CH=CHC6H2(NO 2 ) 3 , OCHO, OH, COOH, CF 3 , OBr, CF 2 CF 3 , CF(CF 3 ) 2 , C 6 H 3 (NO 2 ) 2 , SiF 3 , P(=O)Cl 2 , PF 2 , GeF3, CH(CF 3 ) 2 , CH=CHC 6 H 3 (NO 2 ) 2 , NHOH, NCl 2 , CHO, SnF 3 , P(=O)Br 2 , S(=O) 2 CH 3 , -O-C(O)-R 5 , -NH-C(O)-R 6 , -C(O)-NHR 6 , cyano, or a heterocyclic group; electrodes disposed on opposite surfaces of the electrocaloric material ; ; a first thermal flow path between the electrocaloric material and a heat sink a second thermal flow path between the electrocaloric material and a heat source ; and an electric power source configured to provide voltage to the electrodes . <EOS>