Organic-inorganic Hybrid Polymers Containing Polyhedral Oligomeric Silsesquioxanes: Morphologies,Shape Memory And Self-Healing Properties

To meet the growing demand of the properties of polymer materials for modern society,polymer materials tend to be intelligentized and composite.Nowdays,shape memory and self-healing polymers which have enormous applications potentiality in various important fields,as new intelligent materials,attract pepole’s attentions.However,single organic shape memory and self-healing polymers have some drawbacks such as the weak thermal,mechanical properties,weak shape recovery force and poor dimensional stability,which restrict their widespread applications.Therefore,the researchers usually used the inorganic fillers to reinforce them to obtain organic-inorganic hybrid shape memory and self-healing polymers with well comprehensive properties.The organic-inorganic hybrid shape memory and self-healing polymers simultaneous own the advantages of the organic polymers and inorganic fillers so that they are one of the focuses of the current investigative points.Polyhedral oligomeric silsesquioxane(POSS)are a class of interesting building blocks to access organic-inorganic hybrid polymers.POSS can be introduced to organic polymers via various chemical methods due to the particularity of structure.The incorporation of POSS into polymers can result in improved properties of materials such as thermal properties and mechanical strength.What’s more,the organic-inorganic hybrid polymers containing POSS are expected new functionality due to the strong POSS-POSS interaction.In this thesis,various types of POSS had been synthesized.A variety of organicinorganic hybrid polymers containing POSS were prepared by stepwise polymerization,reversible addition-fragmentation chain transfer(RAFT)polymerization,acyclic diene metathesis(ADMET)polymerization and ring-opening metathesis polymerization(ROMP).The morphologies,thermal,machnical,shape memory and self-healing properties of the organic-inorganic hybrid polymers containing POSS were investigated and the effects of the incoparation of POSS were discussed.Moreover,the relationship of structure and properties of organic-inorganic hybrid polymers containing POSS was illustrated systematically.The main research contents are as follows:(1)A novel POSS diol was successfully synthesized and used as a chain extender to obtain the linear organic-inorganic polyurethanes via stepwise polymerization.In the organic-inorganic polyurethanes,the spherical POSS microdomains with the size of 10 ～ 20 nm were formed via POSS-POSS interactions.Compared to plain polyurethane,the organicinorganic polyurethanes displayed increased thermal and mechanical properties.More importantly,the organic-inorganic polyurethanes displayed good shape memory properties,which was attributable to the increasing of the physically-crosslinking densities.(2)A novel POSS monomer containing double bond was synthesized via ADMET reaction,and then by using it as chain transfer agent and cyclooctene as monomer,the linear organic-inorganic polycyclooctenes were synthesized via ROMP.After the reduction of double bond of polycyclooctenes by using p-Toluenesulfonyl hydrazide,the linear organicinorganic polyethylenes were obtained.In the organic-inorganic polyethylenes,the POSS microdomains with the size of 10 ～ 40 nm were formed via POSS-POSS interactions.The existence of POSS macrodomains reduced the crystallization capacity and crystallinity of the organic-inorganic polyethylenes and dramatically changed the tensile behavior of the organic-inorganic polyethylenes.Due to the formation of physical crosslinking networks building by the POSS macrodomains,the obtained linear polyethylenes own the caparbale shape memory abilities than the crosslinked polyethylenes.(3)By using the 5-acetylaminopentyl acrylate(AA)and 3-acryloxypropylheptaphenyl POSS as the monomers,the novel organic-inorganic ABA triblock copolymers were synthesized via sequential RAFT polymerization,in which the A block was [P(POSS)] and B block was poly(acrylate amide)(PAA).The triblock copolymers were microphaseseparated,so that the dynamic exchange of hydrogen bonds was preserved and the triblock copolymers remained self-healing properties at room temperature.The plain PAA was just a viscous liquid without practical application value.However,the organic-inorganic triblock copolymers containing POSS displayed the nature of elastic solids with moderate mechanical strength,which make it suitable candidate for self-healing material.(4)The organic-inorganic polycyclooctadiene copolymers with POSS in the main chains and 2-ureido-4[1H]-pyrimidinone(UPy)as the side groups were synthesized via ROMP by using the poly(POSS)which containg double bond as macromolecular chain transfer agent and 4-(2-hydroxyethyl)-10-oxa-4-azatricyclo [5.2.1.02,6]dec-8-ene-3,5-dione-2-ureido-4[1H]-pyrimidinone(UPy-OBN)/1,5-cyclooctadiene as monomers.The poly(POSS)was synthesized via ADMET polymerization of difunctional POSS.The organic-inorganic polycyclooctadiene copolymers were microphase-separated in which the POSS microdomains with the size of 20 ～ 30 nm were uniform dispersed.The organicinorganic polycyclooctadiene copolymers simultaneously owned shape memory and selfhealing properties.Owing to the POSS-POSS interactions and the quadrupolar hydrogen bond interaction,the organic-inorganic polycyclooctadiene copolymers were physically crosslinked so that the copolymers displayed improved shape memory properties.It is the dynamic exchange of intermolecular quadruple hydrogen bonds of Upy moiety that endowed the organic-inorganic polycyclooctadiene copolymers with self-healing properties.The mechanical properties of the healed samples can be recovered 100% of the original sample.Moreover,the organic-inorganic polycyclooctadiene copolymers displayed the solid plasticity at room temperature due to the dynamic exchange of intermolecular quadruple hydrogen bonds.The solid plasticity imparted the reprograming ability of original shape of the organic-inorganic polycyclooctadiene copolymers.(5)The organic-inorganic linear poly(urea urethanes)(PUUs)with POSS and hindered urea bonds in the main chains were synthesized via stepwise polymerization by using the difunctional POSS and hindered diamine as chain extenders.The organic-inorganic PUUs were microphase-separated and in which the POSS microdomains with the size of 10 ～ 20 nm were uniform dispersed.The organic-inorganic PUUs displayed improved thermomechanical properties compared to the plain PUUs.Moreover,the organic-inorganic PUUs simultaneously owned shape memory and self-healing properties.The shape memory properties were due to the formation of physical cross-linking networks building by POSS macrodomains and the networks were stable even when the samples were heated to 200 °C.The self-healing properties were attribute to the dynamic exchange of hindered urea bonds and the introduction of POSS wouldn’t destroy the exchange reaction.In addition,the inclusion of hindered urea bonds provided the organic-inorganic PUUs with the solid-state plasticity at room temperature.(6)A new difunctional POSS was successfully synthesized.By using this kind of POSS monomer,the organic-inorganic linear poly(hydroxyl urethanes)(PHUs)were synthesized with POSS cages in the main chains via stepwise polymerization.The POSS microdomains were formed in the organic-inorganic PHUs.Due to the formation of physically cross-linked networks of the organic-inorganic PHUs,they were capable of displaying the thermomechanical and shape memory properties similar to thermosetting PHUs.In the meantime,the organic-inorganic PHUs can be reprocessed at elevated temperature,after two times of reprocessing,the mechainal properties of the samples still preserved about 90%of the as-synthesized samples.The reprocessing properties resulted from the transcarbamoylation reaction of hydroxy and urethane bond other than the disintegration of POSS nanodomains at elevated temperature.The introduction of POSS cages slightly slowed down the transcarbamoylation reaction and did not significantly decrease the reprocess properties of the organic-inorganic PHUs.The reprocessing properties can be utilized to program the original shapes of the organic-inorganic PHUs.