Studies On Properties Of Bismaleimide-based And Ferrocene-based Polymers

Functional polymers are one of most important research branches in materials science.Shape memory polymers(SMPs)are able to recover to their original shape from a temporary shape under various external stimuli.This kind of smart materials have great potential to be applied in the fields of aerospace,biomedicine,flexible electronics,etc.The self-assembly behavior of amphiphilic block copolymers in solvents enables one to achieve aggregations in various morphologies,such as sphere,rod,vesicle and composite micelle,which promotes the application of amphiphilic block copolymers in the areas of drug release,seperation,electronics,catalyst,etc.In recent years,the macroscopic shape memory property and the microscopic self-assembly behaivor have attracted increasing interests from researchers.Based on this background,bismaleimide-based polymers with triple-shape memory behavior and ferrocene-based polymers with living crystallization-driven self-assembly behaviour were sysytematically studied in this thesis.Meanwhile,the alignment behavior of the self-assembled rod-like nanostructures on SMP substrates was also characterized.The synthesis methods,property characterizations and functional verifications of the two polymers in different scales were discussed in detail.The achieved results are desired not only to further improve the understanding between structures and functions of the materials,but also provide reference significance for the development and applications of functional polymers.A series of covalent crosslinking thermosetting polymers with triple shape memory effects were synthesized sucessfully via introducing bisphenol-A cyanate ester(BACE)to bismaleimide(BMI)networks.Due to the complex covalent crosslinking structures,such BMI based triple-shape memory polymers(TSMPs)present broad glass transition temperature ranges,which is a crucial preconditi on for the triple-shape memory behavior.Results demonstrated that BMI based TSMPs showed excellent thermal stabilities and mechanical properties.Moreover,triple shape memory behavior was achieved successfully by choosing two switching temperatures to fix two separate shapes independently.Upon heating,both the programmed shapes could recover to their former shape separately.This paper provides fundamental attempts for the further development of thermosetting triple shape memory polymers.Combining the superior comprehensive properties with the smart triple shape memory behavior,such materials present great potential to be applied as smart materials and structures,especially for aerospace areas.Solution self-assembly of a linear ABA triblock copolymer with two terminal crystallizable poly(ferrocenyldimethylsilane)(PFS)core-forming “A” blocks and a central poly(dimethylsiloxane)(PDMS)corona-forming “B” block has been investigated.The low dispersity(D = 1.05)copolymer,PFS26-b-PDMS584-b-PFS26(block ratio 1.0 : 22.5 : 1.0),was prepared through a combination of living anionic polymerization and end-to-end coupling.The block ratio and dispersity were established by a combination of matrix-assisted laser desorption/ionization time of flight(MALDI-TOF)mass spectrometry,1H nuclear magnetic resonance(NMR),and gel permeation chromatography(GPC).Individual 1D fiber-like micelles with looped PDMS coronas were formed in mixed solvents of hexane and decane.Low length-dispersity fiber-like micelles of controlled length were prepared from short seed micelles of PFS26-b-PDMS584-b-PFS26 derived from sonication using the seeded growth method termed living crystallization-driven self-assembly.In addition,seeded growth of blends of both PFS26-b-PDMS584-b-PFS26 and PFS26 homopolymer and of PFS26-b-PDMS584-b-PFS26 and the analogous diblock copolymer PFS26-b-PDMS292 were also explored.Large aggregates with fiber-like protrusions were formed by adding the blends of PFS26-b-PDMS584-b-PFS26 and PFS26 to the cylindrical PFS26-b-PDMS584-b-PFS26 seeds.In contrast,surprisingly,seeded growth of blends of PFS26-b-PDMS584-b-PFS26 and PFS26-b-PDMS292 or the individual components using seeds of either PFS26-b-PDMS584-b-PFS26 or PFS26-b-PDMS292 showed that growth is only detected in the case of matching of the seed and multiblock copolymer chemistries.A series of PFS-b-PDMS block copolymers with different block ratios were synthesized by living anionic ring open polymerization.The chemical structures were sytematically charactized by MALDI-TOF mass spectrometry,1H NMR,and GPC.The thermal properties of the fabricated block copolymers were studied by thermogravimetric analysis(TGA)and differential scanning calorimeter(DSC).Results showed that the length of PDMS block has an effect on the thermal stability and the thermal transiton temperatures of the materials.But the thermal decomposition temperatures of all the samples were above 300 ? and the melting transition temperatures of PFS block were above 120 ?,which are higher than the operating temperature of the shape memory polymers.Highly monodisperse cylindrical block copolymer micelles with the length around 1 ?m were formed by living crystallization-driven self-assembly.The size and the morphology of the micelles were characterized.We further investigated the alignment behaivor of the self-assembled PFS-b-PDMS micelles under the influences of the shape memory behavior.The alignment status before and after the deformation of the shape memory behavior were observed by atomic force microscope(AFM)and polarized optical microscope(POM).We found that the micelles were aligned along the stretched direction of the SMP substrate,which enables the composite sample to present obvious birefringent phenomenon,providing the stretched samples with anisotropic property.