DEBONDING ON DEMAND IN PHOTOPOLYMER NETWORKS: AN IRREVERSIBLE APPROACH VIA THERMALLY INDUCED GAS FORMATION AND NETWORK REGULATION

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1 DEBONDING ON DEMAND IN PHOTOPOLYMER NETWORKS: AN IRREVERSIBLE APPROACH VIA THERMALLY INDUCED GAS FORMATION AND NETWORK REGULATION Dipl.-Ing. Christoph Schnöll Institute of Applied Synthetic Chemistry, Technische Universität Wien, Austria

2 Introduction: Photopolymers Fast curing Good adhesive strength High hardness Difunctional monomers: Highly crosslinked Photopolymer non reworkable non degradable difficult separations Strong request for DoD!!! Christoph Schnöll 2

3 Introduction: State-of-the-art DoD concepts Polymer networks with cleavable crosslinkers DoD impulse Δ, hν polymer backbone crosslink cleaved crosslink reversible bonds: hetero Diels-Alder homolytic cleavage: Azo compounds moderate temperatures ~ 90 C reversability colored C=S derivates photopatterning possible possible post-curing via recombination limited penetration of light Ayer, M. A.; Simon, Y. C.; Weder, C., Azo-Containing Polymers with Degradation On-Demand Feature. Macromolecules 2016, 49 (8), Schenzel, A. M.; Klein, C.; Rist, K.; Moszner, N.; Barner-Kowollik, C., Reversing Adhesion: A Triggered Release Self-Reporting Adhesive. Advanced Science 2016, 3 (3) Christoph Schnöll 3

4 Introduction: Novel DoD concept DoD via network regulation and thermally induced gas formation AFCT reagents: defined thermomechanical properties Blocked isocyanates (BICs) as thermolabile crosslinkers: thermally induced gas formation fast & easy seperation Moszner, N.; Rist, K.; Lamparth, I.; Burtscher, P.; Gorsche, C.; Liska, R. Dental materials, comprising thermolabile radically polymerizable compd., having debonding-ondemand properties. WO A1, Christoph Schnöll 4

5 Thermally induced gas formation Blocked isocyanates (BICs) deblocking temperature (T d ) dependent on: Isocyanate 4 model compounds synthesized: Blocking Agent (BA) CO 2 detection using Ba(OH) 2 T d : 113 C 105 C 135 C 45 C Christoph Schnöll 5

6 Thermally induced gas formation Gas formation in thermoplastic polymer matrix Thermomicroscopy T d (TM) / C NAM, 5 mol% BIC, 1 wt% Darocour 1173 BIC1 116 UV curing: nm; 45 mw cm -2 ; 10 min BIC2 BIC3 113 BIC4 start at 100 C; heating rate: 2 C min T start T d(tm) T i T final Christoph Schnöll 6

7 Thermolabile crosslinker BIC-based photopolymerizable crosslinker CO 2 detection using Ba(OH) 2 Homopolymerization and subsequent heat treatment ( 200 C) : No gas formation, due to highly T d(ba) : 117 C crosslinked network! Christoph Schnöll 7

8 DoD in highly crosslinked polymer networks Slight modification of network architecture necessary AFCT Dynamic mechanical thermal analysis (DMTA) UV curing: nm; 20 mw cm -2 ; 20 min 4 photopolymer specimen: polyudma polybic5 poly(udma-co-das)* poly(bic5-co-das)* * 25 mol% DAS temperature program: 20 C C; heating rate: 2 C min Christoph Schnöll 8

9 DoD in highly crosslinked polymer networks Dynstat impact test 8 photopolymer specimens: polyudma polybic5 poly(udma-co-das)* poly(bic5-co-das)* without thermal treatment with thermal treatment (120 C, 20 h) * 25 mol% DAS Christoph Schnöll 9

10 DoD in highly crosslinked polymer networks Proof of concept poly(bic5-co-das)* * 25 mol% DAS DoD 10 min. ~ 150 C UDMA reference no DoD ~ 200 C Christoph Schnöll 10

11 Conclusion various BICs synthesized & analyzed thermolabile crosslinker synthesized combination of BICs and AFCT Good for other applications! Successful DoD Christoph Schnöll 11

12 Acknowledgements Thank you!!! Prof. Robert Liska Dr. Christian Gorsche Institute of Applied Synthetic Chemistry, Technische Universität Wien, Austria Dr. Thomas Koch Institute of Materials Science and Technology Technische Universität Wien, Austria Prof. Norbert Moszner IVOCLAR VIVADENT AG Schaan, Liechtenstein Christian Doppler Research Association Photopolymers in digital and restorative dentistry Christoph Schnöll 12