Synthesis and characterization of fluorocarbon chain end‐capped poly(carbonate urethane)s as biomaterials: A novel bilayered surface structure

Abstract

Poly(carbonate urethane)s (PCUs) are usually considered as biostable elastomers for long-term implantation. However, their hydrolytic stability is still questionable. The biodegradation appears to be initiated by oxidative and hydrolytic substances released by inflammatory cells. Therefore, the biostability of polyurethane might be improved with control of surface structure to reduce inflammatory response. A new type of PCUs end-capped with perfluoro chains was synthesized to explore a new avenue. A fluorinated alcohol, 2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluoro-1-octanol (PDFOL), was end-capped to the backbones of PCUs by reaction of the --OH in PDFOL with the --NCO end groups in PCU backbones. Contact angle measurement, X-ray photoelectron spectroscopy, atomic force microscopy, and attenuated total reflectance-Fourier transform infrared spectroscopy were used to examine their surface structure and properties. Elemental analysis, gel permeation chromatography, differential scanning calorimetry, and tensile testing were used to assess bulk chemistry and properties. The fluorocarbon end-capped poly (carbonate urethane)s (FPCUs) maintained the high mechanical properties (about 40 MPa tensile strength) and typical microphase separation structure of polyurethane elastomers. Results from surface analyses revealed the presence of a double-layered structure at the surfaces of the FPCUs. The first one was composed of fluorocarbon tails rising up on the uppermost layer and the second one made up of hard-segments. This novel bilayered surface structure could protect the weak carbonate linkages in soft segments, and consequently, may potentially increase the biostability of this kind of polyurethanes.

Fluorocarbon chain end‐capped poly(carbonate urethane)s as biomaterials: Blood compatibility and chemical stability assessments

“…Both the PCU and FPCU‐A materials showed quite similar spectra after air, water, and PBS incubations as shown in Figures 7 and 8. And no absorbance assigned to the fluorocarbon tails was observed in FPCU‐A, which was in well agreement with a previous study 25. The differences between the two materials came from the oxidative treatments.…”

“…Such phenomena have been attributed to the water repelling and low surface free energy properties of fluorocarbon chains 35. Our previous study has shown that the fluorocarbon tails of FPCU‐A could migrate to the surface and formed an extremely hydrophobic surface 25. This unique surface structure must have made some contributions to the low adhesion and less deformation of platelets.…”

“…The fluorocarbon tails were linked with hard segments through urethane linkages. Our previous work demonstrated that the fluorocarbon tails in the FPCU‐A could migrate to the outermost surface and pull the hard segments to the subsurface 25. Therefore a bilayered surface structure self‐organized on the surface, that is, a top fluorocarbon layer and a subsurface region rich in hard segments.…”

“…The fluorocarbon end chains were obtained from the reaction of a fluorinated alcohol [CF 3 (CF 2 ) 6 CH 2 OH, 400 Da] with NCO groups in hard segments during synthesis. The synthesis of the three polyurethanes and determination of the fluorine content of FPCU‐A were described in our previous work 25…”

“…Because polycarbonate urethanes were proved to bemore stable than polyether analogues both in vitro and in vivo ,21–24 the addition of fluorinated endgroups might further improve their biostability. In our previous work, new fluorocarbon (CF 3 (CF 2 ) 6 CH 2 O‐, 399 Da) end‐capped polycarbonate urethanes (FPCUs) were synthesized, and a bilayered surface structure (i.e., top fluorocarbon dominated and subsurface hard segment dominated layers) was confirmed by the investigations of X‐ray photoelectron spectrum and atomic force microscopy 25. In this work, the in vitro chemical stability was investigated by glass wool‐H 2 O 2 /CoCl 2 test10 and phosphate‐buffered saline (PBS, pH = 3.1–3.3) incubation.…”