Fabrication And Properties Of Self-assembly Aggregates Formed By Multiblock Amphiphilic Copolymers

In view of the extensive application of amphipathic multiblock copolymers in real life,such as it can be used for nano materials,drug carrier,biochemical separation and other aspects,a series of different amphipathic multiblock copolymers were designed in this paper.A series of(mPEO-nPPO)k amphipathic multiblock copolymers with different block numbers and proportion of EO/PO were synthesized via anion ring-opening living polymerization of propylene oxide(PO)and ethylene oxide(EO),using ethylene glycol as the initiator.The molecular structures were con?rmed by FT-IR,1H NMR and GPC.The self-assembly properties of multiblock copolymers in aqueous solution were studied by the automatic tensiometer,fluorescence spectroscopy(pyrene was used as the probe)and ultraviolet visible spectrophotometer(UV-vis)spectra,and the effects of the block number and EO/PO ratio on the self-assembly behavior were investigated.The critical micelle concentration of multiblock copolymer aqueous solution became larger gradually as the increase of the blocks number and EO content;For multiblock copolymers,it need to go through a process of folding and rearrangement for self-assembly to form micelle aggregates,and differences on block numbers and the EO/PO ratio will have an impact on the formation of micellar aggregates.In addition,n-butanol which was used as the cosurfactant,together with multiblock copolymers,hexamethylene and water were used to build the microemulsion system,and through mapping the ternary phase diagram,the influences of block numbers,the EO/PO ratio,n-butyl alcohol content and temperature on the formation of microemulsion were investigated more intuitively.With the increase of the blocks and the decrease of the EO/PO ratio,the area of microemulsion became smaller.Besides,the increase of temperatureis not conducive to the formation of microemulsion.The influence of different proportion of cosurfactant to different system was different,and it need to choose the better addition according to different systems.All in all,studies on the behavior of multiblock copolymers in the aqueous solution have demonstrated that the block number and EO/PO ratio are all the important influencing factors.The rheological properties of the several kinds of multiblock copolymers were determined by the advanced rheometer and the influences of block numbers and the EO/PO ratio on the rheological properties was studied.On the whole,the rheological properties of multiblock copolymers were similar to the general block oligomers,which showed that the rheology type of multiblock copolymers belong to the pseudoplastic fluid and have a larger linear viscoelastic region;Beyond that,the increase of the block number can enlarge the range of its linear viscoelastic region,but the increase of the EO/PO ratio can improve the elasticity of copolymer in terms of viscosity relatively.In a word,differences of the block number and EO/PO ratio can make obvious differences between the rheological properties of different copolymers.A series of multiblock polyurethane with different crosslinking degree was synthesized via the crosslinking reaction between E540 and TDI which was used as the cross-linking agent,and also series of polyurethane aqueous solution with different concentration have been configurated.The rheological properties of the series of multiblock polyurethane and its aqueous solution were determined by the advanced rheometer.The results showed that the viscosity and linear viscoelastic region of multiblock polyurethane all increased with the increase of the crosslinking degree.The forming structures of amphiphilic multiblock polyurethane in aqueous solution were extremely complex,of which the stability and the ability to resist external interference all became stronger with the increase of the concentration of polyurethane aqueous solution,and besides the structure of polyurethane aqueous solution with a higher concentration was relatively easy to recover after the external disturbance.When the system temperature gradually rises,there would be some complicated changes in the internal structure of polyurethane aqueous solution,which showed that temperature cancause larger influences on the structure.In conclusion,the crosslinking degree,concentration,temperature and other factors all can generate obvious influences on the rheological properties of polyurethane.