Thermal and mechanical properties of poly(methacrylate) networks with cooligo(lactone) branches

Poly(methacrylate) networks with cooligo(lactone) branches are obtainable b y free radical copolymerization of cooligo(lactone) macromonomers and tri(e thyleneglycol) dimethacrylate (TEGDMA). These cooligo(lactone) macromonomer s were prepared by ring-opening cooligomerization of(S,S)-3,6-dimethyl-1,4- dioxane-2,5-dione (L-lactide) with delta-valerolactone and epsilon-caprolac tone, respectively, initiated by Bisphenol-A-bis(2-hydroxypropyl methacryla te) (BisGMA). Partially biodegradable composites with a potential applicati on as bone implant material have been received by cross-linking copolymeriz ation of the macromonomers in the presence of 45 wt.% hydroxy apatite. Ther mal and mechanical properties of the composites were studied in dependence on the structure of the polymer matrix. Copolymers from certain macromonome rs contain crystalline domains of oligo-L-lactide branches as proved by wid e angle X-ray scattering. The formation of the crystalline domains will be promoted if the oligo-L-lactide branches are linked via the flexible spacer delta-valerolactone to Bis-GMA. The partial crystallinity results in highe r Young's moduli in the temperature range between grass transition and melt ing of the composites. Furthermore it gives rise to a higher compressive st rength and to a decreasing rate of hydrolytic degradation.