Amphiphilic Hyperbranched Poly(ether Amine)s Hybrid Two-dimensional Nanosheets And Its Functional Materials

Two-dimensional(2D)nanosheets,with atomic-scale thickness,almost all of the atoms are exposed on the surface,which provid an extremely high specific surface area,in conjunction with special physical,chemical,and electronic properties.To date,a broad range of 2D nanomaterials with sheet-like structure have been prepared and evaluated in different applications.Two critical issues play key roles in 2D nanosheetsbased practical applications for their outstanding physical and chemical characteristics when they are truly 2D:(1)synthesis of regular nanosheets with controlled size,thickness and shape is qualified and necessary to form 2D nanosheets-based materials;(2)interfacial compatibility and distribution between nanosheet and polymer matrix plays a preponderant role in modulating properties of materials,where inorganic 2D nanosheet sheathed in or decorated by a polymeric material.The main aims of this thesis are to solve these two critical issues by using the multi-functional amphiphilic hyperbranched poly(ether amine)s(h PEAs).Based on polyhedral oligomeric silsesquioxane(POSS)and light-sensitive thioxanthone(TX)capped h PEAs,ultrathin single-layered 2D hybrid nanosheets(HNS)with several nanometer in thickness have been successfully fabricated at first via self-assemble strategy.Then we fabricted hybrid membrane with high ordered lamellar structure based on ultrathin h PEA-nanosheets for molecular filtration via bottom-up strategy.Meanwhile,with temperature-responsive polymer brushes introduced on surface of h PEA-nanosheets via photo-polymerization in situ,smart regulation of the substance permeability through based membrane was achieved by virtue of the temperature tunable lamellar spaces to separate multiple molecules of different sizes.Additionally,large-scale,defect-free and high yield graphene nanosheets(GNs)was exfoliated in aqueous phase via top-down strategy by attaching electro-rich π-conjugates to an amphiphilic h PEA,resulting in multi-functional h PEA@G nanosheets that can be used to fabricate a programmable 2D ordered patterns.Taking advantage of this multiresponsive dynamic wrinkling/ordered pattering,the globally 2D ordered surface patterns would be achieved with diverse morphologies and size features on demand.The contents of each part are listed as follows:(1)A bottom-up strategy to fabricate hybrid membranes with ordered lamellar structure that can be used in water purifying and molecular sieving was performed based on ultrathin h PEA-nanosheet(HNS)prepared by the living crystallization-driven self-assembly of h PEA capped POSS.The structure is comprised of h PEA as out-layer and POSS aggregation as inner plane.It can effectively enhance the compatibility between polymer chains and the inorganic POSS moieties based on the uniformed 2D HNS that fabricated with POSS covalent bonded h PEAs.The h PEA layers recognize and restrict desired molecules while POSS used as subtracts.Thousands layers of HNS were formed in a film as thin as 22 μm,which means that thousands of nano-spaces need to pass through in one filtration,231 times longer than that of the thickness of the membrane.The as-prepared lamellar hybrid membranes showed high selective separation of molecules with different size or charges.It also has the ability to efficiently,effectively,and economically(known as 3E)purify products from the mixture with its precursors.This bottom-up strategy based on hybrid nanosheets synthesized through the living self-assembly provides scientific,engineering,and practical process benefits in lamellar hybrid membrane applications.(2)A nano-gating membrane with regulation of substance permeability was achieved by direct-stacking of temperature responsive 2D nanosheets(HNS-P).The HNS-P was formed by covalently bounding poly(N-isoproplacrylamide)(PNIPAM)brush onto the surface of HNS via photo-polymerization in situ for the existing of photo-sensitive thioxanthone(TX)moieties on h PEA.The membranes have negative response coefficients with a gating ratio of as high as 8.5.By virtue of the mass ratio of NIPAM/HNS and polymerization time,a library thickness of HNS with PNIPAM brushes can be achieved.Consequently,the gating membranes could realize gradual small/medium/large molecule separation by both simple step-wise tuning of the temperature and precise the thickness of building block of HNS-P.This study provides insight view and universal platform toward the design of smart gating membranes.It showed promise for applications in fluid transport systems,microfluidic chip systems,and molecular separation devices.(3)Apart from the bottom-up strategy for fabricating functional 2D nanosheets,top-down approach can be adopted to form hybrid 2D nansheets as well.We designed and synthesized a series of super dispersant of anthracene containing amphiphilic h PEA(h PEA-AN).Then it can be used to exfoliate graphene in aqueous phase to obtain graphene nanosheets(GNs).The resulting h PEA-AN can interact strongly with both the GNs and the water molecules.The concentration of the resulting h PEA-AN@G nanosheets is as high as 3.5 mg/m L,which is much higher than those obtained with normal aromatic surfactants or high-shear exfoliated GNs dispersion(< 0.1 mg/m L).Moreover,the total interaction energy(VT)is VT,max = 4.2 me V/nm2 calculated according to the classical Derjaguin-Landau-Verwey-Overbeek(DLVO)theory,as high as 16,800 e V for a 2 μm × 2 μm GNs flake.This suggested the high stability of the GNs aqueous dispersion.The as-prepared GNs dispersion can be re-dispersed well in quiet a few organic solvents including N,N-dimethylformamide(DMF),1,4-dioxane,acetone and ethanol for more than three months.The superior performance and convenient synthesis make the polymer dispersant very promising for production GNs in large-scale both in aqueous and organic solution.The molecular design strategy can generally provide a platform to develop other dispersants for producing and processing GNs solution via introducing other π-conjugates,especially for aqueous system.(4)Based on multi-functional h PEA-AN@G nanosheets,a simple and robust method to realize light-induced programmable 2D ordered patterns was presented.Upon the primary procedure of 365 nm UV light,2D ordered pattern was developed for a continuous gradient mechanical instability caused by photodimerization of AN.Triggered by moisture,2D ordered patterns evolved to oriented patterns perpendicular to boundary.After alternating 254 nm or NIR light exposure,the wrinkled patterns then turned back to its ordered morphology and definitely eliminated.Consequently,taking advantage of the multi-responsive dynamic wrinkling/ordered pattering,we can program surface patterns with UV-triggered gradient modulus in generation,moistureinduced osmotic pressure in evolution,and NIR-driven stress-dissipation in extinction on demand and manipulate the resulted surface properties as desired.This programmable dynamic 2D patterns give a promising application in multi-functional and erasable memory devices or advanced anti-counterfeiting.It is not only substantially enlarge the capacity and density of information storage,but also effectively avoiding the easy replication and clone of static anti-counterfeiting.