Synthesis,characterization And Flame Retardant Application Of Diblock Copolymers Containing Titanium Hybrid POSS Motif

Organometallic hybrid polymers,which combined the advantages of metals and polymers,were widely used in many fields.Constructing metal hybrid organic polymers by introducing metal elements into polyhedral oligomeric silsesquioxane(POSS)has become an important method to improve performance.9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(DOPO)and its derivatives were often used as high-efficiency flame retardants in flame retardancy.The monomer containing DOPO and the monomer containing metal hybrid POSS were copolymerized to form a new type of polymer,which is expected to modify epoxy resin(EP).Based on the advantages of both POSS hybridized with titanium and DOPO,this work proposed a method of combining reversible addition fracture chain transfer(RAFT)polymerization and aldoamine condensation reaction(or Schiff base reaction)to prepare the diblock copolymer with side-linked titanium hybrid POSS motif,which was applied it to modify EP,so that the flame retardant performance,mechanical performance and thermal performance of EP composites can be improved.The specific research content is as follows:(1)Synthesis and characterization of diblock copolymers containing titanium hybrid POSS motif in the side chain:4-formylphenyl methacrylate(HAMA)was regarded as the monomer,4-cyano-4-dithiobenzoic acid estervaleric acid(CPAD)was used as the chain transfer agent,azobisisobutyronitrile(AIBN)acted as the chain initiator,and the macromolecular chain transfer agent PHAMA-CTA with a degree of polymerization(m)of 30 was obtained by RAFT polymerization.Then titanium hybrid aminopropyl polyhedral oligomeric silsesquioxane(NH2-POSS-Ti)and aminopropyl polyhedral oligomeric silsesquioxane(NH2-POSS)were further added,the diblock copolymers Poly(Ti-POSS-HAMA30-b-HEPOMA15)and Poly(Ti-POSS-HAMA30-bHEPOMA30)and Poly(Ti-POSS-HAMA30-b-HEPOMA120),and Poly(POSS-HAMA30b-HEPOMA30)were obtained by the Schiff base reaction of the amino group and the aldehyde group of Poly(HAMAm-b-HEPOMAn),which are abbreviated as PolyTil,PolyTi2,PolyTi3 and PolyC(Control sample).Finally,the chemical structure and thermal properties of the polymer are characterized by analysis methods such as 1H NMR,31P NMR,FITR,TGA,and Differential Scanning Calorimetry(DSC).(2)Modification of epoxy resin with PolyTi,a diblock copolymer containing titanium hybrid POSS motif in the side chain:5 wt%of PolyTi1,PolyTi2,PolyTi3 were respectively incorporated to EP used as flame retardants to prepare EP/PolyTil,EP/PolyTi2 and EP/PolyTi3 composites.Thermogravimetric analysis(TGA),limiting oxygen index(LOI),vertical combustion tester(UL-94),dynamic mechanical thermal analyzer(DMA),scanning electron microscope(SEM),Raman spectroscopy(Raman),three-point bending testing were used to study the thermal properties,flame retardant properties and mechanical properties of EP composites,and further explore the influence of different block ratios in block copolymers.The results show that when the block ratio of Ti-POSS-HAMA and HEPOMA was close to 1:1,EP/PolyTi2 showed relatively higher LOI value,residual chars content,better carbon layer structure and greater bending strength and elastic modulus,which confirmed that the diblock copolymer PolyTi2 with the best effect on improving the performance of EP.(3)The investigation of the influence of the addition amount of the diblock copolymer polyTi2:1 wt%,3 wt%,5 wt%and 7 wt%of PolyTi2 was respectively introduced to EP to prepare four EP composites and their properties were studied in detail.Studies have shown that with the increase of PolyTi2 addition,the comprehensive performance of EP composites gradually improves.However,when the addition of PolyTi2 exceeded 5 wt%,the mechanical properties began to decrease for the worse compatibility between EP and PolyTi2.At the same time,compared with EP/PolyC,EP/PolyTi shows better enhancement effect on improving the overall performance of the composites.In summary,this thesis focuses on metal hybrid POSS block copolymers,which provides a certain reference value for the development of organic-inorganic hybrid materials and the development of modifying EP,and has positive significance for the further expansion and deepening of research on functional materials in the future.