Application of a kinetic gelation simulation to the characterization of in situ cross-linking biomaterials.

Multifunctional monomers that are polymerized in situ to form highly cross-linked biomaterials have been an area of recent interest for medical applications. From a biomaterial application standpoint, the relationship between the reaction conditions, polymer structure, and final physical properties is important, particularly for in situ formed materials, as they must have optimum network properties immediately after Formation. However, multifunctional monomer reaction mechanisms are complicated by mobility restrictions on the reacting species, cyclization of pendant groups, unequal reactivity of functional groups, and structural heterogeneities. Also, experimental characterization of these complexities is difficult and limited by the insolubility of the resulting cross-linked structure. Thus, in this contribution, a kinetic gelation simulation was used to understand and characterize the evolution of in situ forming, three-dimensional polymer structures. Specifically, the reaction of tetrafunctional monomers (i.e. divinyl monomers) to form high strength networks with degradable cross-links was modeled. This work focuses on using a lattice-based model to characterize network properties important for biomaterial applications and compare them with an experimental system (i.e. cross-linked polyanhydrides) where appropriate. Simulated results for pendant group reactivity, kinetic chain lengths, and radical concentrations (trapped and free) are presented herein.