Chemical Modification Of Poly(Propylene Carbonate) By Diepoxied,Epoxide POSS And Epoxide Nano-silica

Poly（propylene carbonate）（PPC）derived from alternating copolymerization of carbon dioxide and propylene oxide exhibits a series of excellent properties including biodegradability,biocompatibility,transparency and oxygen barrier.So PPC have promising applications in the fields of medical materials,agricultural plastic films and packaging materials.However,PPC has low thermal stability and poor mechanical properties,which limits its large-scale application.In order to broaden its application,PPC need to be modified.In this paper,DGEBA,NNDE,G-POSS,O-POSS and RNS-E are chosen as the third monomer to be copolymerized with CO₂ and PO usiing SalenCo/PPNCI binary catalysts.The structure and properties of the prepared PPC materials were determined by Fourier-transform infrared spectroscopy（FT-IR）,1H-nuclear magnetic resonance（1H NMR）,gel permeation chromatography（GPC）,differential scanning calorimeter（DSC）,thermal gravimetric analysis（TGA）,dynamic mechanical analyzer（DMA）and scanning electron microscopy（SEM）measurements.The main results are listed as follows.1.The new polymers were successfully synthesized by polymerization of CO₂,PO and DGEBA or NNDE using homogeneous SalenCo/PPNCl binary catalysts.The yields of the polymer were improved due to the introduction of the third monomers.With increasing the content of the third monomers,the gel in the polymer materials was improved.The third monomers have no remarkable effect on the Mn of the soluble part of the prepared product and improve the T_g and the decomposition temperature.When the addition of DGEBA or NNDE was no more than 0.6 mol%relative to PO,the polymers exhibit dramatically enhanced thermal stability and mechanical properties.Moreover,when NNDE was introduced into the polymerization system,the product exhibited some color.2.A series of the new polymers were successfully synthesized by polymerization of CO₂,PO and G-POSS using homogeneous SalenCo/PPNCl binary catalysts.The addition of G-POSS did not have remarkable impact on the glass transition temperature,thermal stability and Mn.But the introduction of G-POSS increased the hydrophobic property.The addition of G-POSS improved the storage modulus of PPC and the resistance to deformation of the PPC-DGEBA was improved.3.A one-step strategy was used to synthesize thermally and mechanically reinforced pseudo-interpenetrating PPC networks by polymerization of CO₂,PO and O-POSS.The results show that introduction of O-POSS can remarkably increase the catalyst activity and alter the properties of PPC.increasing the amount of O-POSS leads to the improvement of the T_g,the decomposition temperature and storage modulus of PPC.However,when the amount is more than 1 wt%,the T_g of the PPC-O-POSS were obviously decreased.4.PPC/SiO₂ nanocomposites were synthesized via in situ polymerization.When the addition of RNS-E was less than 2 wt%,the yields were improved.However,further increasing the content of RNS-E result in decreasing the yield of the product.Moreover,the introduction of RNS-E lead to the decrease of Mn.Morphological observation shows that RNS-E is uniformly dispersed in PPC matrix and has good compatibility with PPC.To some extent,the addition of RNS-E results to improving the thermal stability and mechanical properties of PPC.With increasing the content of RNS-E,the thermal stability was increased gradually.When the content of RNS-E was 3wt%,the Tmax of PPC-RNS-E-5 was 278.5 ℃increased by 64.7 ℃ compared with neat PPC 213.8 ℃.The addition of RNS-E did not have remarkable impact on the T_g of the PPC-RNS-E,but the addition of RNS-E caused the decrease of Mn of the PPC-RNS-E material.The addition of RNS-E improved the storage modulus of PPC.The resistance to deformation of the PPC-RNS-E was improved.