Investigation Of The Structure And Thermal Response Behavior Of Thermo-responsive Block Copolymer Films

Thermo-responsive polymers are attracting more and more attention because of their special properties.They can be used in the fields of smart textiles,medical treatment and industrial applications.In this dissertation,the thermo-responsive properties and transition behaviors of polymers with different structures have been studied,which laid a solid foundation for the further applications of thermo-responsive polymers.In this dissertation,two kinds of monomers with thermo-responsive properties:2-?2-methoxyethoxy?ethyl 2-methyacrylate?MEO₂MA?and polyethylene glycol methyl ether Acrylate(OEGMA₃₀₀)were chosen to synthesize random P(MEO₂MA-co-OEGMA₃₀₀)and block PMEO₂MA-b-POEGMA₃₀₀ copolymers.Their transition behavior were studied systematically in solution and thin films.To further study the influence of the chain structure to the transition behaviors,the structure and transition behavior of a star-shaped thermo-responsive?poly?methoxy diethylene glycol acrylate?-block-polystyrene?₃ film were also studied.The main research results obtained are as following:?1?MEO₂MA and OEGMA₃₀₀ were used to synthesis a random copolymer P(MEO₂MA-co-OEGMA₃₀₀)by atom transfer radical polymerization?ATRP?.The P(MEO₂MA-co-OEGMA₃₀₀)obtained was first characterized by ¹H-NMR and GPC to confirm its structure and molecular weight.Afterwards,the transition behavior of P(MEO₂MA-co-OEGMA₃₀₀)in aqueous solution were investigated by UV-Vis spectroscopy.P(MEO₂MA-co-OEGMA₃₀₀)only presented one low critical solution temperature?LCST?.The value of LCST shifted towards lower temperature when the solution concentration increased.By applying white light interferometry,the transition of P(MEO₂MA-co-OEGMA₃₀₀)films was obtained.When the temperature gradually increased,the film showed a prominent shrinkage when the temperature reached its LCST.?2?Di-block copolymer PMEO₂MA-b-POEGMA₃₀₀ was prepared by ATRP in two steps.First of all,the POEGMA₃₀₀-Br was synthesized from OEGMA₃₀₀.Afterwards POEGMA₃₀₀-Br was used as initiator and MEO₂MA was added to synthesize the block copolymer PMEO₂MA-b-POEGMA₃₀₀.The structure and molecular weight of PMEO₂MA-b-POEGMA₃₀₀ was measured by ¹H-NMR and GPC.The transition behaviors of PMEO₂MA-b-POEGMA₃₀₀ in aqueous solution were studied by UV-Vis spectroscopy and small angle X-ray scattering.The results showed that the film was spin-coated after no obvious structure,uniform film,PMEO₂MA and POEGMA₃₀₀blocks are randomly distributed.The film did not show obvious ordered structure after absorbing water,but the film near the substrate had more water content than the film close to the water vapor environment.PMEO₂MA-b-POEGMA₃₀₀ possessed two LCSTs.It can self-assemble into micellar structure upon heating.The transition behaviors of PMEO₂MA-b-POEGMA₃₀₀ films were investigated by white light interferometry.Unlike P(MEO₂MA-co-OEGMA₃₀₀)only showed one prominent shrinkage upon heating,PMEO₂MA-b-POEGMA₃₀₀ film showed a linear collapse when the temperature increased.?3?The structure and transition behavior of star-shaped?PMDEGA-b-PS?₃ thin films were investigated by white light interferometry and in-situ neutron reflectivity.Due to the star-shaped chain structure,the swelling and transition were significantly slower than PS-b-PMDEGA-b-PS with linear structure.After mounting in vapor atmosphere,the formerly homogeneous film presented a tri-layer structure.The layer close to the hydrophilic Si substrate and humid air possessed larger amount of water,which can be attributed to the attraction of water by the substrate and surrounding air.Upon application of external temperature stimuli?rapid increase of temperature above LCST?,it was found that the film thickness experienced three period:shrinkage,remained unchanged and then expanded.But the final thickness was significantly lower than the initial value.In this process,the water content of the film also goes through three stages.