Open reduction internal fixation (ORIF) metal plates and screws remain the established standard-of-care for complex fracture fixation. They however have drawbacks such as limited customization, soft-tissue adhesions and a lack of degradation. Bone cements and composites are being developed as alternative fixation techniques in order to overcome these issues. One such composite is a strong, stiff and shapeable hydroxyapatite-containing material consisting of 1,3,5-triazine-2,4,6-trione (TATO) monomers which cures through high energy visible (HEV) light induced thiol-ene coupling (TEC) chemistry. Previous human cadaver and in vivo studies have shown that patches of this composite provide sufficient fixation for healing bone fractures; however, the composite lacks degradability. To promote degradation through hydrolysis, new allyl-functionalized isosorbide-based polycarbonates have been added into the composite formulation and their impact has been evaluated. Three polycarbonates with allyl functionalities, located at termini (aPC1 and aPC2) or in the backbone (aPC3), were synthesized. Composites containing 1, 3 and 5 wt% of aPCs 1-3 were formulated and evaluated with regards to mechanical properties, water absorption, hydrolytic degradation and cytotoxicity. Allyl-functionalized polycaprolactone (aPCL) was synthesized and used as a comparison. When integrated into the composite, aPC3 significantly impacted the material’s properties, with the 5wt% aPC3 formulation showing a significant increase in degradation of 469 %, relative to the formulation not containing any aPCs after 8 weeks’ immersion in PBS, along with a modest decrease in modulus of 28 % to 4.01 (0.3) GPa. Osteosyntheses combining the aPC3 3 and 5 wt% formulations with screws on synthetic bones with ostectomies matched or outperformed the ones made with previously studied neat composite with regards to bending stiffness and strength in 4-point monotonic bending before and after immersion in PBS. The favorable mechanical properties, increased degradation, and non-toxic characteristics of the materials present aPC3 as a promising additive for the TATO composite formulations. This combination resulted in stiff composites with long-term degradation suitable for bone fracture repair.