Study On Synthesis, Characterization And Properties Of Novel Main-Chain Ferrocene-Based Polymers

Even though ferrocene-based polymers have been discovered from many decades, the research into ferrocene-based polymers continues apace, due to their incorporation into a wide variety of applications in the modern life. These applications have been based on the properties of the ferrocene-based polymers like the liquid-crystalline properties, the electrochemical properties, the thermal stability and the good solubility.Thermotropic liquid crystals (including liquid crystalline compounds and polymers) are soft materials in which their molecules self-assemble into macroscopically ordered structures with anisotropic properties. In addition, this type of liquid crystals has assumed great importance in many powerful technological applications in different fields like optics, chemistry and biology, which has created new avenues in academic and industrial research. Therefore, there exist many efforts to improve the properties of liquid crystals via developing and synthesizing of novel thermotropic liquid crystalline compounds and polymers.In the past few decades, metallomesogenic polymers have attracted much attention. Among them, ferrocene-based liquid crystalline polymers represent one of the most valuable mesomorphic materials.Several novel main-chain ferrocene-based polymers were synthesized employing the solution polycondensation of1,1’-ferrocenedicarbonyl chloride with different monomers. Two different routes were exploited for the synthesis of the polymers including the solution polycondensation route and the interfacial polycondensation route. Afterwards, the chemical structure of the synthesized main-chain ferrocene-based polymers was elucidated using many techniques involving1H NMR spectra, UV-VIS absorption spectra and the FTIR spectra. In addition, the X-ray diffractograms of the synthesized polymers were measured to determine their crystallinity degree. Following the characterization, the electrochemical properties of the synthesized polymers were studied using the technique of cyclic voltammetry and the effect of many parameters (involving the effect of organic solvents, the effect of scan rate, the effect of the electrolyte’s concentration and the effect of the concentration of the electroactive ferrocene moiety) on the cyclic voltammetric behavior of the synthesized polymers was investigated. The thermal properties of the synthesized polymers were examined employing the TGA and DTGA techniques. Finally, the liquid crystalline properties of the synthesized polymers were explored via the DSC and the POM techniques.(1) Liquid crystalline poly(diethyleneglycol1,1’-ferrocene dicarboxylate)(PDEFD) and poly(bis(4-hydroxyoctoxyphenyl)sulfone1,1’-ferrocene dicarboxylate)(PHOSFD) were synthesized successfully by solution polycondensation reaction of1,1’-ferrocenyl chloride with diethylene glycol and bis(4-hydroxyoctoxyphenyl)sulfone (HOS), respectively. HOS was synthesized from bisphenol S using8-chloro-l-octanol as a reagent in DMF. PDEFD and PHOSFD were characterized via the measurement of their1H NMR spectra, UV-VIS absorption spectra and FTIR spectra. PDEFD and PHOSFD possessed a molecular weight of11587and6155, respectively. The XRD measurements showed that PDEFD and PHOSFD are almost amorphous polymers. The electrochemical behaviors of PDEFD and PHOSFD were investigated and the influence of many parameters, including the solvent, the scan rate and the electrolyte concentration, was studied. The shape of the CV peaks, of both polymers, was affected by the polarity of the solvents. The CV of PDEFD and PHOSFD indicate their coplanar structures that make the polymers tightly contacted with the surface of the electrode. In addition, the peak current values of PDEFD and PHOSFD solutions increased with increasing the scan rate and had a linear relationship with the square root of scan rate. Furthermore, the electrochemical processes of PDEFD and PHOSFD solutions are neither reversible nor totally irreversible. Generally, the electrochemical properties of PHOSFD and PDEFD are similar to each other. Moreover, the measurement of TGA and DTGA of PDEFD and PHOSFD indicated their relative thermal stability. In spite of the presence of two phenyl rings in the polymer backbone of PHOSFD, PDEFD with aliphatic backbone was found to be more thermally stable than PHOSFD and the Tg value of PDEFD were higher than that of PHOSFD. The liquid crystalline properties of the synthesized polymers were examined exploiting the DSC and the POM techniques. Both of the polymers possessed nematic phases during heating and cooling and they exhibited textures with schlieren disclinations. The synthesized polymers possessed high phase duration and the clearing point is above the decomposition temperature of the polymers.(2) Three novel main-chain ferrocene-based liquid-crystalline polyesters poly (N-phenyldiethanolamine1,1’-ferrocene dicarboxylate)(PPFD), poly(α,α’-bis(4-hydroxyphenyl)-1,4-diisopropylbenzene1,1’-ferrocene dicarboxylate)(PHDFD), and poly(methyldiethanol amine1,1’-ferrocene dicarboxylate)(PMFD) were synthesized successfully using the solution polycondensation method of1,1’-ferrocenyl chloride with phenyldiethanolamine (PDE), α,α’-bis(4-hydroxyphenyl)-1,4-diisopropyl benzene (bisphenol-P), and N-methyldiethanolamine (MDE), respectively. The first polymer (PPFD) was synthesized in two different conditions and the properties of the two products (PPFD1and PPFD2) were compared. The structure of the synthesized polymers was characterized by’H NMR spectroscopy. The molecular weight of the polymers was determined via the GPC technique. The GPC results showed that they are mostly oligomers rather than polymers. The polymers were also characterized via the measurement of their FTIR and UV-VIS spectroscopy and the properties were structurally dependent. The XRD results showed that the four synthesized main-chain ferrocene-based polymers are mostly amorphous but have some degree of crystallinity. This amorphous nature was reflected in the polymers’good solubility in many solvents with different polarities. Furthermore, both of the chemical structure and the synthesis conditions affect the crystallinity degree of the polymers. The cyclic voltammetry was employed to study the electrochemical properties of the polymers in CH2Cl2, CHCl3, THF, DMF and DMSO. The shape of the peaks was found to be compact in high polar solvents including DMF and DMSO. The electrochemical behavior of the polymers was investigated in CH2Cl2at different potential scan rates and the results indicated that the electrochemical processes of the synthesized polymers were neither totally irreversible nor perfectly reversible. The influence of the concentration of the electrolyte and the concentration of [Fe] unit was also studied. With increasing the concentration of the electrolyte, the peak-to-peak potential separation decreased in a general trend, which indicates that the reversibility of the electrode process becomes better at high electrolyte concentrations. With increasing the concentration of the [Fe] unit, the peak currents increased generally. All the synthesized polymers possessed nematic phases during heating and cooling and they exhibited textures with schlieren disclinations. The ordered structures were permanently retained in the cooling and the heating scan cycles. (3) Three novel main-chain ferrocene-based polyesters with azobenzene in the side-chain (MFPAS):4-nitrophenylazo-functionalized-PPFD (PPFD-NT),4-carboxyphenylazo-functionalized-PPFD (PPFD-CA), and4-cyanophenylazo-functionalized-PPFD (PPFD-CN) were synthesized successfully using the post-polymerization azo-coupling reaction of PPFD with4-nitroaniline,4-aminobenzoic acid and4-aminobenzonitrile, respectively. The synthesized polymers were characterized by’H NMR spectroscopy. The degrees of functionalization of the MFPAS were determined from the1H NMR analysis and they were found to be66%,34%and54%for PPFD-NT, PPFD-CA and PPFD-CN, respectively. The synthesized polymers were also characterized via the measurement of their FTIR and UV-VIS spectroscopy. The XRD results showed that the three synthesized MFPAS were amorphous. This amorphous nature was reflected in the MFPAS’good solubility in many solvents with different polarities. The MFPAS exhibited trans to cis photoisomerization upon the irradiation of their DMF solutions with UV light. The azobenzene-containing main-chain ferrocene-based polyesters were also found to display bathochromic shifts upon the addition of HCl due to the formation of the azonium ions that make these polymeric species good candidates as pH indicators. The thermal properties of the synthesized polyesters showed that PPFD-CA and PPFD-CN were thermally more stable than PPFD-NT. The Tg of PPFD was found to be lower than those of the MFPAS due to the presence of the azo phenyl group in the MFPAS. All the synthesized polymers possessed nematic phases during heating and cooling and they exhibited textures with schlieren disclinations. The ordered structures were permanently retained in the cooling and the heating scans.(4) Four novel main-chain ferrocene-based polymers, including poly(3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-tetraoxospiro-[5.5]-undecane1,1’-ferrocene dicarboxylate)(PSPUFD), poly(diisopropanolamine1,1’-ferrocene dicarboxylate)(PDAFD), poly(diethyl bis(hydroxymethyl)malonate1,1’-ferrocene dicarboxylate)(PDMFD), and poly(2,2-bis(hydroxymethyl) propionic acid1,1’-ferrocene dicarboxylate)(PHPFD), were successfully synthesized with aliphatic units. PSPUFD and PDAFD were synthesized using the solution polycondensation reaction of1,1’-ferrocenedicarbonyl chloride with3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-tetraoxospiro-[5.5]-undecane (SPU) and diisopropanol amine (DA), respectively. PSPUFD and PDAFD were found to possess molecular weights of4107and 1338, respectively. To increase the molecular weight, the polymers PDMFD and PHPFD were synthesized via the interfacial polycondensation reaction of1,1’-ferrocenedicarbonyl chloride with diethyl bis(hydroxymethyl) malonate (DM) and2,2-bis(hydroxymethyl)propionic acid (HP), respectively. PDMFD and PHPFD were found to possess molecular weights of4456and6916, respectively. The structure of the synthesized polymers was elucidated by many techniques such as1H NMR, UV-VIS and the FTIR spectroscopy. The X-ray diffractograms of the synthesized polymers indicate the amorphous nature of these polymers, which was reflected in their good solubility in many solvents. The electrochemical properties of the synthesized polymers were investigated employing the cyclic voltammetry technique. In addition, the effect of the organic solvents, the scan rate, the electrolyte concentration and the effect of [Fe] concentration on the redox behavior of the synthesized polymers were examined. The electrochemical redox processes of the synthesized polymers were found neither reversible nor totally irreversible. The thermal properties of the synthesized polymers were studied via the TGA and DTGA techniques and the results indicated their relative thermal stability. The investigation of the liquid crystalline properties with the POM technique revealed that the synthesized polymers exhibited nematic phases with schlieren desclination during the heating and the cooling processes with high phase duration.(5) Four novel main-chain ferrocene-based polymers, including poly(o-Cresolphthalein1,1’-ferrocene dicarboxylate)(PCPFD), poly(Cresol Red1,1’-ferrocene dicarboxylate)(PCRFD), poly(2,4-quinolinediol1,1’-ferrocene dicarboxylate)(PQDFD), and poly(Sudan Orange G1,1’-ferrocene dicarboxylate)(PSOFD), were successfully synthesized with aromatic units. The first two polymers PCPFD and PCRFD were synthesized via the solution polycondensation reaction of1,1’-ferrocenedicarbonyl chloride with o-Cresolphthalein (CP) and Cresol Red (CR), respectively. PCPFD and PCRFD possessed low molecular weights of2398and1727, respectively. To obtain the other polymers with higher molecular weight, PQDFD and PSOFD were synthesized employing the interfacial polycondensation reaction of1,1’-ferrocenedicarbonyl chloride with2,4-quinolinediol (QD) and Sudan Orange G (SO), respectively. The molecular weights of PQDFD and PSOFD were determined to be8379and21576, respectively. The chemical structure was elucidated via the measurement of1H NMR spectra, UV-VIS absorption spectra and the FTIR spectra for the synthesized polymers. The X-ray diffractograms of indicate the amorphous nature of the synthesized polymers, which is reflected in their good solubility in many solvents. The electrochemical properties of the synthesized polymers were examined using the cyclic voltammetry technique. In addition, the effect of the organic solvents, the scan rate, the electrolyte concentration and the effect of [Fe] concentration on the redox behavior of the synthesized polymers were investigated. The electrochemical redox processes of the synthesized polymers were found neither reversible nor totally irreversible. The thermal properties of the synthesized polymers were studied using the TGA and DTGA techniques and the results indicated their relative thermal stability. The POM technique indicated that the synthesized polymers exhibited nematic phases during the heating and the cooling processes with high phase duration.