Multiscale Structural Characterization of Biocompatible Poly(trimethylene carbonate) Photoreticulated Networks

Poly(trimethylene carbonate) (PTMC) polymeric networks are biocompatible materials with potential biomedical applications. By controlling the chemical synthesis, their functional macroscopic properties can be tailored. In this regard, this work presents the coupling of two experimental techniques, dynamic mechanical analysis (DMA) and solid-state nuclear magnetic resonance (NMR), as an innovative, robust, and straightforward approach to fully characterize the inner structure and its relationship with the macroscopic properties of these PTMC materials. The studied photocured networks had an increasing macromer molecular weight M̅n, varying from 3 to 40 kg/mol, which permitted us to assess the variation of thermomechanical properties and the NMR signal decay with this parameter. DMA results showed that the thermomechanical behavior of the PTMC networks depends on the network’s M̅n. Indeed, the elastic modulus E′ and the main α relaxation
temperature Tα decrease with PTMC’s M̅n. Moreover, multiple-quanta solid-state 1H NMR investigations demonstrated that the network’s cross-link density is also linked to this chemical parameter. Interestingly, both techniques showed for the 40 kg/mol PTMC a neat difference of the effect of the chemical cross-links and the physical entanglements on the material’s network structure and thermomechanical behavior. Specifically, two different molecular relaxation domains were highlighted, which are not observed for the rest of the studied materials. By utilizing DMA and solid-state NMR in a complementary and synergetic manner, this work provides a novel and robust approach to determining and better understanding key structure−property relationships, specifically the inner structure and macroscopic properties, of such functional polymers.