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S. Baudis:
"Additive Manufactured Polymer-based Biomaterials";
Vortrag: Advanced Functional Polymers for Medicine 2019, Aalto, Finland (eingeladen); 05.06.2019 - 07.06.2019; in: "Advanced Functional Polymers for Medicine 2019", (2019), S. 12.

Introduction
Additive manufacturing technologies, esp. based on li¬tho¬graphy (L-AMTs), open the pos¬sibility to pro¬vide pa¬tient-spe¬ci¬fic im¬plants with fea¬ture re-so¬lu¬tions down to the sub-micron range.1,2 Vinyl esters (VE, incl. vinyl carbonates) have been established as bio¬com¬patible pre¬cursor for photo¬polymers,3 which are the ba¬sis for L-AMTs. Esp. in combination with thiols (thiol-ene chemistry) VEs attain reactivities to¬wards photopolymerization comparable with those of acry¬lates, the benchmark materials for L-AMTs, how¬ever, VEs have an about two orders of ma-gni¬tu¬des lower toxicity.4 Moreover, VEs have ve-ry favorable degradation products. Low molecular weight polyvinyl alcohol and carbon acids can be excreted easily and residual monomers hydrolyze to ace¬tic aldehyde.5
Owing their characteristic polymer architecture, pho¬to¬polymers have a very low toughness in general. How¬ever, by application of toughness enhancers, high molecular weight co-monomers as well as chain trans¬fer agents, toughness can be increased to values en¬abling the fixation of the implants by screws.6
Experimental Methods
Synthesis of VEs is either accomplished by lipase (CAL-B) ca¬talyzed trans¬esteri¬fication reactions of desired building blocks (e.g., po¬ly¬ca-pro¬lactone te¬le¬che¬lics, PCL)4 with di¬vi¬nyl adi¬pate or by con¬den¬sa¬tion re¬ac¬tion with vi¬nyl chlo¬ro¬for-mate.6
Besides clas¬si¬cal me¬cha¬nical cha¬rac¬te¬ri¬za¬tion of cu¬red spe¬ci¬mens, RT-NIR-photo¬rheology was em¬ployed to in¬ve¬sti¬ga¬te the pho¬to¬po¬ly¬meri¬zation cha¬rac¬teri¬stics of for¬mu¬lations with dif¬ferent mo-no¬mers and ad¬ditives.7
For ad¬di¬tive ma¬nu¬fac¬tu¬ring a di¬gital light pro¬ces-sing (DLP) L-AMT system with upside-down set-up and an InVision® WUXGA 1080p light engine with 460 nm LED was used (Figure 1).8
Results and Discussion
The facile synthesis VEs enables the generation of a tool¬box system (Figure 2) containing a variety of com¬po¬nents for the formulation of materials with different properties.

Figure 2. Vinyl ester (VE) based monomers: divinyl adipate (1), x-armed PCL-VE (2), gycitol based VE (3), ethylene glycol based VE (4), urethane based VE (5).3-6
An appropriate combination of base monomers (VEs and thiols), additives to adjust the toughness and degradation characteristics, and e.g. hydroxyapatite for bone regeneration, enable the manufacturing of patient specific implants by L-AMT.

Additive manufacturing technologies, patient-specific implants, Vinyl esters, biocompatible precursor for photopolymers, lower toxicity