Synthesis And Two-Dimentional Self-Assembly Of Amphiphilic Conjugated Polymers Based On Poly(Phenylenebutadiynylene)s

Conjugated polymers(CPs)as a class of organic semiconductors have been widely used in the fabrication of various electronic devices such as organic solar cells,organic field-effect transistors(OFETs),organic light-emitting diodes(OLEDs)because of their surprising chemical and physical properties.Moreover,CPs can also be utilized for the development of the next generation of flexible,stretchable,and highly conductive electronic devices.In order to improve the chemical and physical properties of CPs to fabricate high performance devices,the construction of ordered nano structured CPs including one dimentional(1D),two dimentional(2D)and three dimentional(3D)nanostructures are of great importance.Among the various multidimensional nanostructures,organic 2D nanostructures have drawn much attention due to their merits,such as light-weight,structural control,flexibility and diversity of fabrication approaches.What's more,specific functional organic 2D materials can be prepared by designing the self-assembly precursor.At present,the methods of fabricating ordered 2D nanostructures can be categorized into two main classes:"top-down" method and "bottom-up" method.Self-assembly is a kind of "bottom-up" method which possesses the advantages in facile,highly efficient,and energy-efficient.Thus,exploring the 2D self-assembly behavior of CPs is very significant not only to the chemistry research but also to the materials fabrication.Here,two kinds of amphiphilic CPs with different structures were synthesized,and the two dimentional self-assembly behaviors of them were invesgated.The main content is as follows:1.Amphiphilic CPs based on poly(meta-phenylenebutadiynylene)s(A-m-PPB)was designed and synthesized,which were comprised of a hydrophobic rigid conjugated main chain and a hydrophilic flexible side chain with carboxylic anions.The proton nuclear magnetic resonance(1H NMR),fourier transform infrared spectroscopy(FT-IR)were used to characterize the structure and the degree of polymerization(DP)of m-PPB.The correlation between the morphology of the aggregates and the solvent,the self-assembly time and the DP of the polymer was investigated by transmission electron microscopy(TEM).The results showed that A-m-PPB with the higher DP would self-assemble into supramolecular 2D layers after standing in water for 24 hours at 0.5 mg/mL.TEM images also indicated that most of A-m-PPB aggregated into non-layered structure which were disordered structures proved by X-ray diffraction(XRD)even at the optimal self-assembly conditions.It can be concluded that the preparation of supramolecular 2D layers by the two-dimentional self-assembly of A-m-PPB was inefficient.2.Using the same method as part 1,amphiphilic CPs based on poly(para-phenylenebutadiynylene)s(A-p-PPB)were designed and synthesized.Comparisons with A-m-PPB,A-p-PPB possessed a linear conjugated main chain which was beneficial for self-assembling into supramolecular 2D layers.The structure and DP of the precursor of A-p-PPB(p-PPB)were characterized by 1H-NMR,FT-IR and Raman spectroscopy.TEM was used to characterize the morphology of the A-p-PPB aggregates in different solvent.The results showed that A-p-PPB in water self-assembled into tow dimentional supermolecular nanosheets(2D-SNS)with size ranged from hundred nanometers to several micrometers.The tapping-mode atomic force microscopy(AFM)indicated the thicknesses of 2D-SNS was about 5 nanometers,indicating few-layered 2D-SNS was formed.The results of the high-resolution TEM(HRTEM),selected-area electron diffraction(SAED)and XRD demonstrated that 2D-SNS was formed by the parallel arrangement of A-p-PPB,and the distance between the adjacent two A-p-PPB chains was in line with the typical ?-? stacking distance.On the other hand,A-p-PPB in methanol formed irregular aggregates because of high solubility.However,when toluene was added into the methanol solution of A-p-PPB,multilayered aggregates were obtained.Moreover,non-amphiphilic precursor p-PPB in mixed solvent of chloroform and methanol formed multi-layered aggregates.In addition,amphiphilic oligo(phenylenebutadiynylene)s(A-p-OPB)with the DP of 8 formed disordered aggregates in water.3.A-p-PPB with electron-rich main chain can be utilized to synergistic self-assembly with electron-deficient fullerenes(C60)to fabricate donor-acceptor multicomponent hybrids.Here,we explore the correlation between the kinds of solvent,the weight ratio of A-p-PPB and C60 and the self-assembly morphology.TEM results showed that phase separation emerged regardless of the self-assembly conditions because of the difference of the polarity between A-p-PPB and C60.