Influence of PDMS molecular weight on transparency and mechanical properties of soft polysiloxane-urea-elastomers for intraocular lens application. (April 2018)

• Record Type: Journal Article
• Authors: Riehle, Natascha; Thude, Sibylle; Götz, Tobias; Kandelbauer, Andreas; Thanos, Solon; Tovar, Günter E.M.; Lorenz, Günter
• Is Part Of: European polymer journal. Volume 101(2018)
• Page Start: 190
• Page End: 201
• Publication Date: 2018-04
• Subjects: Segmented polyurea-elastomers -- Poly(dimethylsiloxane) -- Ring-chain-equilibration -- Mechanical properties -- Cytocompatibility -- Biomedical application; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; Polymerization; Polymers; Periodicals; Electronic journals; 547.705
• DOI: 10.1016/j.eurpolymj.2018.02.029
• Languages: English
• ISSNs: 0014-3057

Abstract

Graphical abstract: Highlights: Polysiloxane-ureas (PSU) were prepared for the application as biomaterial for IOLs. MWs of amino-terminated PDMS were precisely controlled by APTMDS-concentration. RI equivalent to a young human lens was achieved in a Methyl-Phenyl-PDMS-copolymer. Most PSUs were highly transparent and exhibited suitable mechanical properties. Extracts of a tested PSU-elastomer were not cytotoxic to HaCaT-cells. 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) (H12 MDI) 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 (D4 Me, 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.