Functional Polymeric Composite Films Based On Supramolecular Complexes

Layer-by-layer (LbL) assembly is a versatile and efficient method tofabricate composite films, which involves the alternate deposition of speciesapplying electrostatic interactions, hydrogen-bonds, and other complementarychemical interactions. LbL assembly can finely control the thickness,chemical compositions, structures, and functions of composite films. With thedevelopment of spin-and spray-assisted LbL assembly, traditional dippingLbL assembly has been upgraded to an efficient method showing greaterpotential in industrial fields. The research in LbL assembly is promoted by thedevelopment of new molecular interactions driving LbL assembly as well asthe introduction of new building blocks into multilayer films. Supramolecularchemistry guides our understanding of chemistry from covalent bonds tononcovalent binds. Supramolecular complexes refer to sophisticatedmolecular aggregates self-assembled by a minimum of two subunits throughmultilevel noncovalent interactions. Taking supramolecular complexes as thebuilding block of LbL assembly can bring multilayer films with newstructures as well as novel functions. Research in this dissertation focuses onsupramolecular complexes as building blocks to fabricate composite films,which covers the follows:(1) The preparation ofpolyelectrolyte-deoxynucleotide complexes and their LbL assembly withoppositely charged polyanions.(2) The preparation of polyrotaxane coatingswith topologically interlocked supramolecular networks through clickreaction-assisted LbL assembly.(3) The preparation of stimuli-responsivemultilayer films based on photo-heat convertible and humidity-sensitivegraphene-based nanocomposites.In chapter1, a brief introduction about supramolecular complexes arisingfrom the development of supramolecular chemistry was given. Also, unique merits of LbL assembly were summarized. The abundant chemicalcompositions and various driving forces for the formation of supramolecularcomplexes endow them with novel properties. Introducing supramolecularcomplexes into LbL assembled multilayer films is believed to produce newstructures for LbL assembled films and facilitate the integration of functionsin multilayer films.In chapter2, electrostatic interactions between positively chargedpoly(allylamide hydrochloride)(PAH) and negatively chargeddeoxyguanosine monophosphate sodium salt (dGMP) was employed tofabricate supramolecular complexes (denoted as PAH-dGMP complexes).Guanine bases confined in the PAH-dGMP complexes formed G-quartet discsthrough self-complementary hydrogen bonds. Then, G-quartet discs stacked toG-quartet columns through π-π stacking interactions. Therefore, multiplesimple interactions (i.e., electrostatic interactions, H-bonding, and π-πstacking) acted synergistically to produce the final PAH-dGMPsupramolecular complexes. In this work, PAH can stabilize G-quartet columnsand the resultant PAH-dGMP complexes can be LbL assembled withpoly(acrylic acid)(PAA) to prepare PAA/PAH-dGMP films. Our studydemonstrated that the stacked G-quartets existed in aqueous PAH-dGMPcomplexes and LbL-assembled multilayer films. Multilayer films bearingchiral stacks of G-quartets are expected to broaden their applications inanticancer assessing and strengthen their potentials as vectors for smallmolecular therapeutic agents.In chapter3, polyrotaxanes (PRs) bearing azide-decorated cyclodextrin(CD) rings was LbL assembled with various multi-alkyne molecules byCu(I)-catalyzed alkyne-azide cycloaddition. After LbL assembly, CD ringsbelonging to different PRs were chemically crosslinked by multi-alkynemolecules, which somehow restricted their free sliding along the includedpolymer axle by forming topologically interlocked supramolecular networks.This work demonstrates that click-type LbL assembly can provide a simpleand general strategy to bring building blocks with unique architecture into multilayer films.In chapter4, Near-infrared (NIR) light-driven bilayer actuators capableof fast, highly efficient, and reversible bending/unbending motions towardperiodic NIR light irradiation were fabricated by exploiting the photothermalconversion and humidity-sensitive properties of polydopamine-modifiedreduced graphene oxide (PDA-RGO). The bilayer actuator comprised aPDA-RGO layer prepared by a filtration method, and this layer wassubsequently spin-coated with a layer of UV-cured Norland Optical Adhesive(NOA)-63. Given the hydrophilicity of PDA, the PDA-RGO layer can absorbwater to swell and lose water to shrink. The intrinsic NIR absorbance of RGOsheets converted NIR light into thermal energy, which transferred thehumidity-responsive PDA-RGO layer to be NIR light-responsive. Consideringthat the shape of the NOA-63layer remained unchanged under NIR light,periodic NIR light irradiation led to asymmetric shrinkage/expansion of thebilayer, which enabled fast and reversible bending/unbending motions of thebilayer actuator. Ag nanowires (AgNWs) can form a resistive heating networkthat can convert electric power into heat. By attaching the AgNW layer ontoPDA-RGO/NOA-63bilayer film, we got a trilayer, low-operating voltageelectrothermal actuator.