@article{RiehleThudeG{\"o}tzetal.2018,
  author    = {Riehle, Natascha and Thude, Sibylle and G{\"o}tz, Tobias and Kandelbauer, Andreas and Thanos, Solon and Tovar, G{\"u}nter and Lorenz, G{\"u}nter},
  title     = {Influence of PDMS molecular weight on transparency and mechanical properties of soft polysiloxane-urea-elastomers for intraocular lens application},
  journal   = {European polymer journal},
  number    = {101},
  issn      = {0014-3057},
  doi       = {10.1016/j.eurpolymj.2018.02.029},
  institution = {Life Sciences},
  pages     = {190 -- 201},
  year      = {2018},
  abstract  = {Soft thermoplastic polysiloxane-urea-elastomers (PSUs) were prepared for the application as a biomaterial to replace the human natural lens after cataract surgery. PSUs were synthesized from amino-terminated polydimethylsiloxanes (PDMS), 4,4′-Methylenebis(cyclohexylisocyanate) (H12MDI) and 1,3-Bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane (APTMDS) by a two-step polyaddition route. Such a material has to be highly transparent and must exhibit a low Young's Modulus and excellent dimensional stability. Polydimethylsiloxanes in the range of 3000-33,000 g·mol-1 were therefore prepared by ring-chain-equilibration of octamethylcyclotetrasiloxane (D4) and APTMDS in order to study the influence of the soft segment molecular weight on the mechanical properties and the transparency of the PSU-elastomers. 2,4,6,8-Tetramethyl-2,4,6,8-tetraphenylcyclotetrasiloxane (D4Me,Ph) was co-polymerized with D4 in order to adjust the refractive index of the polydimethyl-methyl-phenyl-siloxane-copolymers to a value equivalent to a young human natural lens. Very elastic PSUs with Elongation at Break values higher than 700\% were prepared. PSU-elastomers, synthesized from PDMS of molecular weights up to 18,000 g·mol-1, showed transmittance values of over 90\% within the visible spectrum range. The soft segment refractive index was increased through the incorporation of 14 mol \% of methyl-phenyl-siloxane from 1.4011 to 1.4346 (37 °C). Young's Moduli of PSU-elastomers were around 1 MPa and lower at PDMS molecular weights up to 15,000 g·mol-1. 10-cycle hysteresis measurements were applied to evaluate the mechanical stability of the PSUs at repeated stress. Hysteresis values at 100\% strain decreased from 32 to 2\% (10th cycle) with increasing PDMS molecular weight. Furthermore, hysteresis at 5\% strain was only detected in PSU-elastomers with low PDMS molecular weights. Finally, preliminary results of in vitro cytotoxicity tests on a PSU-elastomer showed no toxic effects on HaCaT-cells.},
  language  = {en}
}