The present invention provides peptoid polymers and salts thereof that comprise hydrophobic and polar peptoid monomers and are capable of reducing or inhibiting the formation of ice crystals at sub 0° C. temperatures. Also provided are peptoid-peptide hybrids and salts thereof comprising the peptoid polymers provided herein. The peptoid polymers, peptoid-peptide hybrids, and salts thereof provided herein are useful for making cryoprotectant solutions. The peptoid polymers, peptoid-peptide hybrids, salts thereof, and cryoprotectant solutions provided herein are useful for making antifreeze solutions, frozen food products, and cosmetic care products. Also provided herein are methods for preserving a tissue, an organ, a cell, or a biological macromolecule using the compositions described herein.