PMMA brush-containing two-solution bone cement: preparation, characterization, and influence of composition on cement properties

Two-solution bone cement consisting of poly (methyl methacrylate) (PMMA) brushes in methyl methacrylate has been developed as an alternative to the traditional two-solution (TSBC) and powder-liquid cements. It was hypothesized that the substitution of brushes, for the entire pre-polymer phase of the cement, would permit a decrease in solution viscosity at higher polymer fractions, and allow for physical entanglements with the cement matrix. Consequently, improved cement exothermal and mechanical properties could be expected with brush addition. PMMA brushes were grafted on the surface of cross-linked PMMA nanospheres following a multi-stage synthetic strategy. Brushes exhibiting optimal molecular weight for preparation of TSBC were used for characterization of cement viscosity, flexural and compressive mechanical properties, exothermal properties and residual monomer content. Interactions between grafts and free polymer formed during free radical polymerization of the cement were evaluated based on molecular weight measurements of the cement matrix and brushes. Brush-containing cements exhibited lower viscosity at significantly higher polymer fractions in comparison to TSBC. Cements with PMMA brushes had significantly lower polymerization temperatures and residual monomer content. Measurements of molecular weight revealed the existence of a dry brush regime when using the brush compositions selected in this study, which led to a reduction in the mechanical properties of some of the compositions tested. The optimal cement viscosity and maintenance of other important cement properties achieved with addition of PMMA brushes is expected to expand the use of the two-solution cements in a range of applications.