Biocompatible and biodegradable polymers are provided herein as compositions, methods, and systems for making the compositions. These polymers can be adjustably stable and used in medical applications as adhesives and sealants, and in non-medical applications. Radical polymerization protocols, and two-step cationic and radical polymerization protocols, are provided for the creation of stable, polydisulfide polymers, which can be done in aqueous solution and at ambient and in vivo temperatures ranging, for example, from 0° C. to 37° C. The compositions are biocompatible and can be used as fast curing, biocompatible and biodegradable adhesives and sealants suitable for use in the consumer, industrial, military and medical arts, namely as a functional biomaterial, sustainable plastic, surgical superglue, bone adhesive, pressure-sensitive adhesive, structural adhesive, and other relevant sustainable materials with closed-loop recycling.