Study On Preparation And Properties Of Isosorbide-Based Copolycarbonates

Due to the excellent properties including high impact strength,heat resistance,good transparency and durability,polycarbonate（PC）has become one of the most widely used engineering plastics.Bisphenol-A（BPA）is the crucial monomer for the preparation of PC,which can affect the health of human due to its chronic toxicity.Isosorbide（ISB）is considered as the perfect candidate to replace BPA due to its attractive rigidity,non-toxicity,and chirality.However,the industrial application of poly（isosorbide carbonate）（PIC）still is one of challenges due to its high brittleness and poor processability.In order to improve mechanical properties of PIC,copolymerization with isosorbide and functional diols was studied by non-phosgene melt transesterification in this research.By using diphenyl carbonate（DPC）as carbon source,two series of ISB-based copolycarbonates were prepared by introducing two flexible monomers,oligo（ethylene glycols）（OEG）and polydimethylsiloxane（PDMS）,into PIC.The main research contents and results are as follows:（1）Oligoethylene glycol（OEG）is a flexible chain because the intramolecular rotation of carbon-oxygen bond is much easier than carbon-carbon bond and cyclic structure.In this study,a series of ISB-based copolycarbonates containing OEG（POICs）were successfully prepared under the optimum reaction conditions by using ionic liquid[Bmim][CH₃CHOHCOO]as catalyst,and the weight average molecular weight（M_w）was up to 146200 g/mol.In addition,a series of ISB-based copolycarbonates containing aliphatic diols were also prepared as comparative study（PAICs）.The composition and structure of POICs and PAICs were characterized by nuclear magnetic resonance（NMR）and fourier transform infrared（FT-IR）instrument and the results showed that POICs were successfully prepared and the reactivity of OEG was better than that of aliphatic diols.Differential scanning calorimetry（DSC）and thermogravimetric analysis（TGA）were used to investigate the thermal properties of the copolycarbonates and the results indicated that the glass transition temperature of POICs was in the range of 72 to 105°C.Furthermore,POICs possessed excellent thermal stability,which was fully satisfied for general applications in the plastic industry.The mechanical properties of copolycarbonates were measured by dynamic mechanical analysis and universal testing machine,and the results revealed that the introduction of OEG greatly improved the flexibility of PIC.The elongation at break was up to 160%,which was seven times higher than PIC（18%）.Simultaneously,the tensile strength of the copolycarbonates（80 MPa）was 1.25-fold higher than that of commercial BPA-PC（63 MPa）.（2）The large bond angle and long bond length of Si-O-Si group in PDMS give it high flexibility and good processing flow performance.In this research,a series of ISB-based copolycarbonates with different molar ratios of ISB/PDMS（PHIC）were successfully prepared employing the[Bmim][CH₃CHOHCOO]ionic liquid catalyst,and the M_w of PHIC reached up to 134300 g/mol.The composition and structure of PHIC were characterized by NMR spectroscopy.The results showed that the silicon content in PHIC reached the maximum value（17.2%）when the molar ratio of ISB and PDMS is 82/18.The melt mass-flow rate（MFR）of PHIC was also analyzed by melt flow indexer and the results showed that with the increase of silicon content,the MFR values of copolycarbonates increased gradually,which were much higher than that of PIC.It indicated that the processing flow performance of ISB-based copolycarbonate was improved significantly.The research results of this paper can provide basic data and theoretical basis for the industrial application of ISB-based PC,which possesses important scientific significance and application value.