that are used in producing fixation devices for bone fracture surgery, was reinforced by octadecylamine (ODA)-modified nanodiamonds. Long hydrophobic chains of ODA were transplant to nanodiamonds surface in order to increase the affinity of nanodiamonds towards the polymer matrix and improve the dispersion of the nanofiller, while at the same time decreased unpleasant nanoparticle–nanoparticle attractive interactions by exchange nanodiamonds polar functional groups prone to hydrogen bonding and other types of stronger interactions with alkyl chains, which can only interact via weak van der Waals forces186. Successful covalent binding of ODA to nanodiamond was established by detection of newly produced amide bonds in FTIR and NMR and indirectly by AFM. In contrast to pristine ND, the resulting nanodiamond–ODA material is hydrophobic, resulting in good miscibility with hydrophobic polymers and solvents. TEM images of PLLA– nanodiamond –ODA films show single nanodiamonds – ODA particles and loosely bonded nanodiamonds –ODA agglomerates dispersed in the matrix. Good dispersion translates into high mechanical properties: PLLA–ND–ODA composites carrying upto 10 wt.% ND–ODA shows upto 2 times higher Young’s modulus and up to 8 times higher hardness when compared to neat PLLA, measured using nanoindentation187. As expected, unmodified nanodiamonds reinforced PLLA to a lesser extent. The bulk compression modulus of a PLLA– nanodiamonds –ODA composite consist 10 wt.% nanodiamonds was increased the ODA by 22%, and a 316% increase in fracture energy was observed at the same time. It is theorize that ND–ODA-induced crazing, as confirmed by light and TEM microscopy, which is responsible for the large increase in strain to failure and fracture energy. It is essential to mention that ND can behave as multifunctional nanofiller.
Beyond mechanical reinforcement, nanodiamonds –ODA have blue fluorescent when illuminated with UV radiation, and assist biomineralization, giving additional advantages in bone surgery and tissue engineering188. In a similar biodegradable system, poly-L-(lactide-co-?-caprolactone) or poly(LLA-co-CL), a copolymer, in which ?-caprolactone lower the glass transition temperature and increases the elongation at break of L-lactic acid, the reinforcing effects of three different NDs involving milled acid-purified oxygen terminated nanodiamonds, nanodiamonds with grafted polylactide (ND– PLA), and benzoquinone functionalized nanodiamonds (ND–BQ) were