Use of surface-modifying macromolecules to enhance the biostability of segmented polyurethanes

Abstract

Polyurethanes are widely used as biomaterials for medical implants because of their excellent mechanical properties and moderate biocompatibility. However, the demand for more bioresistant and biocompatible polyurethanes to meet the needs of long-term implant devices still remains an important issue. Since most biological interactions with materials occur at the interface, a significant number of studies for improving the biocompatibility of polyurethanes have concentrated on surface modification. It is well known that additives used in polymeric materials as processing aids, mold releasing agents, antioxidants, etc., migrate to the surface and change the surface properties of the material. Under certain conditions polymeric additives may also migrate toward surfaces. This study describes two fluorine-containing, surface-modifying macromolecules (SMMs) that have been evaluated for their ability to inhibit polyurethane degradation. These materials actively migrate to the upper surface of a material film when they are mixed with a base polymeric materia. Contact angle measurements for the mixture of SMM with base polyurethane indicate that the surface becomes more hydrophobic after adding the SMMs, while X-ray photoelectron spectroscopy analysis shows an enrichment of fluorine on the polymer surfaces. Differential scanning calorimetry thermograms indicate that the micro-structure, as defined by the thermal transitions of the base polymer, are not altered by the addition of SMMs. Enzyme-induced biodegradation tests exhibit a significant reduction of polyurethane degradation in the presence of these surface-resident materials. The results indicate that the SMMs have the potential to resist hydrolytic degradation mediated by lysosomal enzymes while generating a surface chemistry on the native elastomer which is similar in nature to that of a fluoropolymer, e.g., Teflon.

Application of surface modifying macromolecules in polyethersulfone membranes: Influence on PES surface chemistry and physical properties

“…They were then washed with HPLC-grade 1,1,2-trichloro-trifluoroethane (TCTFE, supplied by BDH, Toronto, ON, Canada) (2 ϫ 1 minute rinses) to remove traces of silicone contamination. 27 Each sample then was rinsed with distilled water and put in an aluminum dish, covered with a non-lint tissue, and dried under vacuum at room temperature for 24 h to remove all traces of solvent. The samples then were placed inside a sterile plastic pouch and sent for analysis.…”

Preparation, characterization, and properties of fluorinated polyurethanes

“…Kajiyama and coworkers24 synthesized fluorinated PUs by using various fluorinated diols and studied their surface properties. Taylor and coworkers34, 35 mixed fluorine‐containing PUs with base PUs to improve the surface properties, biocompatibility, and biostability of the base PUs.…”

Surface modifying oligomers used to functionalize polymeric surfaces: Consideration of blood contact applications

“…The presence of terminal fluorinated chains in the PU confers to the final polymer a set of desirable properties such as enhanced thermal and environmental stability, water and oil repellency, low coefficient of friction, good chemical resistance, and generally good blood compatibility with low denaturing of coagulation proteins . Most commonly reported in the literature, fluorinated segments are incorporated into PUs via fluorinated polyester or polyether diols as soft segments, using fluorinated diisocyanates or fluorinated chain extenders as hard segment components,or via end‐capping active functionalized fluorinated segments . Although showing promising blood compatible behavior, some reported disadvantages of classical linear FPU structures have included limited control over the surface's hydrophobicity associated with the restricted surface migration of the fluorinated hard segments, the loss of some mechanical properties associated with a decrease in the molecular weight, particularly reported for long‐term biomedical applications …”