MALDI-TOF characterization of highly cross-linked, degradable polymer networks

Multifunctional anhydride monomers were synthesized and photopolymerized to form highly cross-linked, degradable networks. The networks were synthesiz ed from monomers and oligomers of dimethacrylated sebacic acid of varying m olecular weight, as well as under varying reaction conditions. The cross-li nked polymers were subsequently degraded in phosphate buffered saline, and the degradation products, sebacic acid and poly(methacrylic acid), were iso lated. Matrix-assisted laser desorption/ionization time-of-flight mass spec trometry (MALDI-TOF MS) was used to characterize the absolute molecular wei ght distribution of the Linear poly(methacrylic acid) degradation product, especially as a function of the network evolution (i.e., double-bond conver sion), rate of initiation, and monomer size, MALDI-TOF results, supported b y H-1 NMR, showed that the distribution of kinetic chain lengths was relati vely narrow, with average lengths shorter than calculated from experimental ly measured rate data, indicating the influence of diffusion-controlled kin etics as well as chain transfer. Furthermore, the average kinetic chain len gth shifted to lower values with increasing initiation fate and double-bond conversion. Since multifunctional monomer polymerizations are extremely co mplex and notoriously difficult to characterize due to the insoluble nature of the resulting cross-linked polymer structure, this work demonstrates, f or the first time, how these degradable monomers can provide further insigh t and characterization of multifunctional monomer polymerizations.