Preparation Of Functionalized Boron Nitride Nanosheets And Their Polymeric Composites

Owing to its unique structure and excellent properties,hexagonal boron nitride nanosheets,a two-dimensional nanomaterial,show great application potential in different fields such as polymeric composites.However,because of their surface inertness and strong tendency of aggregation,it is difficult to functionalize boron nitride nanosheets,greatly hindering their applications.In this paper,the liquid-phase exfoliation method is used to obtain solvent-exfoliated boron nitride nanosheets(BNNSs)further treatment.The boron nitride nanosheets functionalized with various groups of phenyl,benzylthio,cumyloxy,and hydroxy groups were prepared by reduction reaction at low temperature.Polymer(polyvinyl alcohol as a polymer matrix)composites filled with hydroxyl functionalized boron nitride nanosheets were fabricated.We studied the dispersion and microstructures of hydroxyl functionalized boron nitride nanosheets in the polymer matrix and their effects on the macroscopic physical properties of the composites.The specific content includes the following aspects:1.BNNSs were reduced in a lithium/ammonia system and functionalized with sulfide—phenyl sulfide and disulfide—dibenzyl disulfide,respectively,to obtain phenyl-functionalized boron nitride nanosheets and benzylthio-functionalized boron nitride nanosheets.The fourier transform infrared spectrometer(FTIR),thermogravimetric analysis(TGA),X-Ray diffraction(XRD),transmission electron microscope(TEM)and ultraviolet visible(UV-vis)absorption spectroscopy were used to characterize the functionalized boron nitride nanosheets.And the structure and dispersibility of functionalized boron nitride nanosheets were studied.2.BNNSs were reduced in the lithium/ammonia system at low temperature.Oxygen radicals were generated by adding dicumyl peroxide into the system to realize the functionalization of BNNSs,and hence cumyloxy-functionalized boron nitride nanosheets were obtained.FTIR and TGA were used to characterize the grafting and grafting ratio of cumyloxy grafted BNNSs.XRD and TEM were used to characterize the crystal structure,degree of exfoliation and structural integrity of cumyloxy-functionalized boron nitride nanosheets.And UV-vis absorption spectroscopy was used to characterize dispersion and solubility of cumyloxy-functionalized boron nitride nanosheets in chloroform.3.BNNSs were negatively charged in a lithium/ammonia system at low temperature,High-purity oxygen was introduced into the system to react with the negatively charged BNNSs,and then treated with water to prepare hydroxyl functionalized boron nitride nanosheets(OH-BNNSs).Polyvinyl alcohol(PVA)matrix composite filled with OH-BNNSs was fabricated by solution casting method.FTIR,TGA,XRD,TEM and UV-vis absorption spectra were used to characterize the structure,exfoliation and dispersibility of hydroxyl functionalized boron nitride nanosheets.Scanning electron microscope(SEM)was used to characterize the dispersion of OH-BNNSs in PVA.TGA was used to characterize the thermal stability of the composites.And the composites were subjected to tensile testing to investigate the effect of OH-BNNSs on the static mechanical properties of the composites.