Synthesis and property studies of linear and kinked poly(pyreneethynylene)s

A series of fluorescent conjugated polymers, poly(pyreneethynylene)s, have been designed and synthesized to investigate the effect of shape of polymer backbone on physical properties. Polymers with linear and kinked backbone were synthesized using 1,6- and 1,8-disubstituted pyrene. The target copolymers were designed to incorporate various spacer units, such as, alkoxyphenyl, carbazole and fluorene on the polymer backbone. Characterization of the target compounds was achieved by NMR, IR, GPC and MALDI-TOF mass spectrometry. Detailed investigation on their optical, electrochemical and thermal properties revealed significant contribution of the geometry of polymer backbone towards physical properties. Kinked backbone of cisoid-polymers was found to result in lower optical band gap, less negative E_HOMO and higher thermal stability as compared to their linear analogues, most probably due to the coiling of polymer chains. Comparison of the physical properties of the polymers with those of the model compounds suggested similar extent of conjugation through 1,6- and 1,8-position of pyrene.     

Synthesis,characterization, and studies on the solid-state crosslinking of functionalized vinyl cinnamate polymers

Functionalized vinyl cinnamate monomers were synthesized by the reaction between hydroxyethylacrylate (HEA) and substituted cinnamoyl chlorides possessing electron releasing and withdrawing functional groups like chloro, methoxy, and nitro groups at the para position of the aromatic ring. The structures of these monomers were characterized by Fourier transform infrared (FTIR), ¹H-, and ¹³C-NMR spectral techniques. The homopolymers of the synthesized monomers were obtained by the free radical solution polymerization in dimethylformamide (DMF) at 80°C for 12 h using azobisisobutyronitrile (AIBN) as a radical initiator. The sensitivity of these polymers towards light was studied by monitoring the photocrosslinking nature of the polymers by ultraviolet (UV) and FTIR techniques. The effect of the functional groups on the crosslinking efficiency was studied and compared with that of the unsubstituted polymer. The cyclobutane-type addition mechanism involved in the photocrosslinking phenomena was confirmed by the above spectral studies in the functionalized vinyl cinnamate polymers. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 441–448, 1998     

Synthesis and characterization of chiral polyacrylates and their applications as positive tone photoresists

To estimate the effects of diastereomeric copolymers as photoresists, diastereomeric copolymers containing chiral and racemic bornyl methacrylates (BMAs) were synthesized. Both alicyclic BMAs were synthesized from (?)‐borneol and (±)‐borneol, and then copolymerized with t‐butyl methacrylate (t‐BMA), tetrahydro‐pyranyl methacrylate (THPMA), and α‐methacryloxy‐γ‐butyrolactone (MABL). The glass transition temperature of the copolymers was found to increase with an increase in the content of alicyclic bornyl groups in the copolymers. To investigate the effect of both the alicyclic butyrolactone and the bornyl groups on photosensitivity, thermal property, and etching resistance, the synthesized alicyclic copolymers were used to prepare photoresists with photoacid generators. The sensitivity and the contrast of the photoresists were calculated. This investigation demonstrated that the existence of alicyclic butyrolactone and bornyl groups increases the etching resistance of photoresists. It was also found that high stereo hindered bornyl structures disturb and restrict the mobility of the polymer chain, leading to an increase in the thermal stability of the polymers. A real pattern recording of photoresists with PR3 composition was performed; an optimal sensitivity of 20 mJ/cm² and resolution of 1 μm of positive tone photoresists with 1 μm thickness was achieved. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Development of novel processable electron accepting conjugated polymers containing fluoranthene units in the main chain

Considerable interest exists in the development of novel n-type conjugated polymers, since many currently available polymer systems have insufficient electron mobility and/or electron affinity. In this work, a universal synthesis route is presented towards a new class of n-type conjugated polymers, i.e. poly(p-fluoranthene vinylene) (PFV) and its derivatives. This route is illustrated with three examples, i.e. unsubstituted PFV and functionalized hexyl-PFV and dodecyl-PFV. All polymers have been synthesized via the dithiocarbamate precursor route. Solubility was introduced by incorporation of alkyl side chains, which leads to a significantly enhanced purity and processability as compared to unsubstituted PFV. Under the applied electrochemical conditions PFV-type polymers demonstrate typical n-type behavior. Additional CELIV mobility measurements on dodecyl-PFV reveal an excellent electron mobility, μ_e = 1.4 × 10⁻⁴ cm²/Vs. Hence, poly(p-fluoranthene vinylene) and its derivatives are promising n-type materials for organic optoelectronic applications.     

Pyrene‐functional star polymers as fluorescent probes for nitrophenolic compounds

Novel tetra‐armed star‐shaped styrenic copolymers with pyrene side groups [ (S1‐S3)‐Pyr ] were prepared and employed as fluorescence sensing probe for fast and sensitive determination of nitroaromatic compounds. (S1‐S3)‐Pyr depicted characteristic pyrene monomer emission signals as well as broad excimer bands in their fluorescence emission spectra due to close proximity of the pyrene groups on the polymer chains and the ratio of monomer to excimer emission intensities gradually decreased as the pyrene content of the star polymers were increased from S1‐Pyr to S3‐Pyr . The highest quenching efficiency in the presence of 25 equivalent nitroaromatics was observed for 2,4,6‐trinitrophenol/picric acid (99.4%) followed by 2,4‐dinitrophenol (84.2%), 4‐nitrophenol (82.6%), 2,4,6‐trinitrotoluene (44.0%), 2,4‐dinitrotolunene (32.6%), and 4‐nitrotoluene (28.8%). Superior quenching efficiencies of nitrophenolic compounds were ascribed to their strong binding affinity for (S1‐S3)‐Pyr due to the acidity of phenolic hydroxyl units. Besides, quenching ratios of S1‐Pyr , S2‐Pyr , and S3‐Pyr were measured to be very close to each other. Thus, (S1‐S3)‐Pyr are considered to be highly selective and sensitive fluorescence probes for phenolic nitroaromatic compounds. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46310.     

Synthesis and antimicrobial activities of new water‐soluble bis‐quaternary ammonium methacrylate polymers

New methacrylate monomers containing pendant quaternary ammonium moieties based on 1,4‐diazabicyclo‐[2.2.2]‐octane (DABCO) were synthesized. The DABCO group contains either a butyl or a hexyl pendant group comprising the hydrophobic segment of the monomers and one tether group to the methacrylate moiety. The monomers were homopolymerized in water by using 2,2′‐azobis(2‐methylpropionamide) dihydrochloride (V‐50) as an initiator. The monomers and polymers were characterized by elemental analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), FTIR, and ¹³C‐NMR. The antimicrobial activities of the corresponding small molecules (bis‐quaternary ammonium monocarboxylates) and polymers were investigated against Staphylococcus aureus and Escherichia coli. Although the small molecules did not show any antimicrobial activity, the polymers were moderately effective against both Gram‐positive and Gram‐negative bacteria. The minimum inhibitory concentration (MIC) values of the polymers with butyl and hexyl hydrocarbon chains against S. aureus and E. coli were found to be 250 and 62.5 μg/mL, respectively. The minimum bactericidal concentration (MBC) value for the polymer with the butyl group was higher than 1 mg/mL, whereas the MBC value for the polymer with hexyl group was found to be 62.5 μg/mL. Thus, an increase of the alkyl chain length from 4 to 6 significantly increased the antimicrobial activity of the polymer. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 635–642, 2004     

Synthesis of alicyclic polymers and characterization of chemical amplified positive photoresists having the same

To investigate the effects of cyclic structures of polymers on the physical properties of photoresist, a series of copolymers consisting of various comonomers selected from 3,6‐endo,oxo‐1,2,3,6‐tetrahydrophthalic anhydride (THPA), bornyl methacrylate (BMA), methacrylic acid (MA), t‐butyl methacrylate (t‐BMA), and 2‐norborene (NB) was synthesized. The molecular weight, glass transition temperature, and the components of the synthesized copolymers were estimated. Photoresists consisting of the synthesized polymers and photoacid generator were prepared. The dependence of the molecular structures on the developers was investigated. The exposure characteristic curves of the photoresists were studied. The existence of the alicyclic comonomers was clearly found to increase the plasma resistance of the photoresist. The sensitivity, contrast, and exposed real image of the prepared photoresists were all investigated. The results obtained suggest that the alicyclic polymers synthesized in this investigation could be used as positive tone photoresists. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1505–1514, 2005     

Amino‐functional electrospun nanofibrous membrane for detecting nitroaromatic compounds

A novel amino‐functionalized polystyrene copolymer (PS‐NH₂) was designed and synthesized with styrene and 4‐vinylbenzyl amine. Additionally, an amino modified glass (G‐NH₂) was obtained as a carrier. (PS‐NH₂/pyrene)/G‐NH₂ fluorescent nanofibrous membrane [named (PS‐NH₂/pyrene)/G‐NH₂] was designed and prepared via electrospinning technique to detect representative saturated nitroaromatic (NAC) explosive vapor. The (PS‐NH₂/pyrene)/G‐NH₂ showed highly fluorescence stability in ambient condition and further displayed a high quenching efficiency of 70.9% toward trinitrotoluene (TNT) vapor (～10 ppb) with an exposure time of 150 s at room temperature. The abundance of amino groups could effectively adsorb NACs and the binding of electron‐deficient NACs to the amino groups on the (PS‐NH₂/pyrene)/G‐NH₂ surface led to the formation of charge‐transfer complexes. The quenching constant (K_SV) to TNT was obtained to be 1.07 × 10¹¹ mL/g in gaseous phase with a limit of detection up to 2.76 × 10^?13g/mL. Importantly, the (PS‐NH₂/pyrene)/G‐NH₂ showed notable selectivity toward TNT and 2,4‐dinitrotoluene vapors. Straightforwardly, the colorimetric sensing performance can be visualized by naked eye with a color change for detecting of different vapor phase NACs explosives. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46708     

Synthesis of complex architectures of comb block copolymers

The synthesis of comb block copolymers by ring opening metathesis polymerization (ROMP), ring opening polymerization (ROP), and atom transfer radical polymerization (ATRP) is described. Block copolymers were synthesized by the ROMP of oxanorbornene and norbornene monomers followed by hydrogenation of the olefins along the backbone. One block of these diblock copolymers possessed initiators either for the ROP of (3S)-cis-3,6-dimethyl-1,4-dioxane-2,5-dione or the ATRP of butyl acrylate. The synthesis and characterization of comb polymers with arms composed of poly(lactic acid) and poly(butyl acrylate) are described. These polymers had well-defined peaks in the size exclusion chromatography spectra which indicated that no homopolymers were synthesized. A comb block copolymer with polymeric arms of poly(styrene-b-vinylpyridine) is described. Vinylpyridine was polymerized from a comb polymer with poly(styrene) arms by ATRP at high dilution of the comb polymer.     

Synthesis of disubstituted amine-functionalized diene-based polymers

Diene-based polymers with two amine groups within each repeat unit were successfully synthesized by bulk and solution free radical polymerization techniques. All polymers have exclusive 1,4-microstructure. The number average molecular weights of the materials obtained were in the range of 30–52 × 10³ g/mol using 2,2′-azobisisobutyronitrile (AIBN), t-butyl peracetate (t-BPA), or t-butyl hydroperoxide (t-BHP) as the initiators. The highest molecular weight achieved was 72 × 10³ g/mol when t-butyl peroxide (t-BPO) was used as the initiator. Quantitative quaternization was achieved yielding hydrophilic water soluble polymers. Prior to quaternization, the polymers are hydrophobic and dissolve in most organic solvents.     

Investigation on thermotropic liquid crystalline and photocrosslinkable polyarylidene arylphosphate esters containing cyclohexanone units

Two series of novel liquid crystalline-cum-photocrosslinkable divanillylidene cyclohexanone containing polymers have been synthesized from 2,6-bis[m-hydroxyalkyloxy(vanillylidene)]cyclohexanone [m=6, 8, 10] with different arylphosphorodichloridates (naphthyl, biphenyl) by solution polycondensation method at ambient temperature. Their chemical structures were confirmed by FT-IR, ¹H, ¹³C and ³¹P NMR spectroscopy. The intrinsic viscosity values were measured to find out molecular weight of the synthesized polymers. The mesogenic properties and phase behaviors were investigated with differential scanning calorimetry and hot stage optical polarized microscopy. The experimental results demonstrated that the mesogenic transition and isotropization temperature gradually decreases with increase in even number of methylene spacer of the polymer chain. All the polymers showed anisotropic behavior under hot stage optical polarized microscope (HOPM). The thermal behaviors of the polymers were studied by thermogravimetric analysis and stable between 292 and 330 °C. The photocrosslinking of the polymers was investigated in thin film by UV light/UV spectroscopy and the cyclobutane ring formation via 2π-2π cycloaddition reactions of the divanillylidene exo-cyclic double bond of the polymer backbone. The pendant naphthyloxy containing polymers show faster crosslinking than the pendant biphenyloxy containing polymers.     

Investigation of liquid crystalline and photocrosslinkable poly[4‐x‐phenyl‐4′‐(m‐methacryloyloxyalkyloxy)cinnamate]s

Three series of liquid‐crystalline‐cum‐photocrosslinkable polymers were synthesized from 4‐x‐phenyl‐4′‐(m‐methacryloyloxyalkyloxy)cinnamates (x = ? H, ? OCH₃ and ? CN; m = 6, 8 and 10) by free radical solution polymerization using azobisisobutyronitrile as an initiator in tetrahydrofuran at 60 °C. All the monomers and polymers were characterized using intrinsic viscosity, and FTIR, ¹H NMR and ¹³C NMR spectroscopy. The liquid crystalline behavior of these polymers was examined using a hot stage optical polarizing microscope. All the polymers exhibited liquid crystalline behavior. The hexamethylene spacer‐containing polymers exhibited grainy textures; in contrast, the octamethylene and decamethylene spacer‐containing polymers showed nematic textures. Differential scanning calorimetry data confirmed the liquid crystalline property of the polymers. Thermogravimetric analysis revealed that all the polymers were stable between 236 and 344 °C in nitrogen atmosphere and underwent degradation thereafter. As the methylene chain length increases in the polymer side‐chain, the thermal stability and char yield of the polymers decrease. The photocrosslinking property of the polymers was investigated using the technique of exposing the polymer solution to UV light and using UV spectroscopy. The crosslinking reaction proceeds via 2π–2π cycloaddition reactions of the ? CH?CH? of the pendant cinnamate ester. The polymers containing electron‐releasing substituents (? OCH₃) showed faster crosslinking than the unsubstituted polymers and those containing electron‐withdrawing substituents (? CN). Copyright © 2007 Society of Chemical Industry     

Synthesis and characterization of novel monomers and polymers containing chiral (−)-menthyl groups

To investigate the steric effects of chiral menthyl groups on the induction of cholesteric liquid crystals and the sensitivity of the photoisomerizable azobenzene derivatives, a series of chiral monomers and a photoisomerizable chiral azobenzene derivative with various spacers end-capped with (−)-menthyl group were synthesized. The structures of the novel chiral compounds synthesized in this investigation were identified using ¹³C NMR, FTIR, and elemental analysis. The phase transition temperatures of the chiral compounds were investigated using X-ray diffraction, differential scanning calorimetry, and polarizing optical microscopy. The thermogravimetric characteristics, the glass-transition temperatures (T_g) and the weight-average molecular weights (M_w) of the homopolymers were also evaluated. Polymers containing chiral menthyl groups with a biphenyl segment were found to reveal high thermal resistance. However, the existence of the steric hindered menthyl group disturbed the arrangement of chiral monomers leading to the disappearance of liquid crystal phases. The specific optical rotation of the synthesized monomers and polymers were also evaluated. The effect of the synthesized chiral compounds, monomers and photoisomerizable azobenzene derivative on the induction of the cholesteric liquid crystal films was investigated. The morphological network structure of the polymer matrix inside a liquid crystal cell was studied using a scanning electron microscope (SEM). The phototuning ability of the AzoM on the cholesteric liquid crystals was also established.     

Optical and electrochemical properties and sensing application for iron(II) and mercury(II) ions of polyfluorenes with imidazole in the main chain

Polyfluorenes bearing imidazole and triphenylamine moieties in the main chain were synthesized. The imidazole/triphenylamine molar ratios in the polymer backbone were 100/0 (PFIM100), 50/50 (PFIM50) and 25/75 (PFIM25). Cyclic voltammetry revealed reversible oxidation only for polymers containing triphenylamine moieties (PFIM50 and PFIM25) and irreversible reduction for all polymers. Optical properties of the polymers were investigated using UV‐visible and photoluminescence spectroscopies in solution. The sensing properties of PFIM100 were investigated. The polymer showed recognition towards two analytes, Fe²⁺ and Hg²⁺. PFIM100 exhibited selective fluorescence ‘turn‐off’ response to Fe²⁺ cations. Interaction of PFIM100 with I^? anions produced a non‐emissive complex. The PFIM100/I^? complex exhibited excellent ‘turn‐on’ sensing properties for detection of Hg²⁺. © 2019 Society of Chemical Industry     

A series of novel high-temperature-resistant multiwall carbon nanotubes dispersants: Polyphenylene sulfones with pyrene groups in main chain

A series of polyphenylene sulfones were synthesized with pyrene groups in the main chain. Using a traditional Suzuki coupling reaction followed by a reduction, the pyrene-containing monomer was synthesized as the diphenol. A series of copolymers were synthesized using this new monomer, a biphenyldiphenol, and 4,4′-difluorodiphenylsulfone. These polymers were characterized using ¹HNMR and FTIR spectroscopy. The introduction of rigid pyrene groups provided these new polymers with good thermal stability and mechanical strength. In this work, these polymers are shown to functionalize and disperse multiwall carbon nanotubes (MWCNTs). The associations of our copolymers to the MWCNTs appear to operate through pi stacking interactions between the pyrene group and the sidewalls of the MWCNTs, referred to in this article as f-MWCNTs. The dispersibility of f-MWCNTs in solvents and polymer matrixes was systematically studied by preparation of f-MWCNTs/polyphenylene sulfone (PPSU) composites with various f-MWCNTs content. Improvements in the dispersability of f-MWCNTs in PPSU resin result in enhancement of the mechanical and thermal properties of f-MWCNTs/PPSU composites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48379.     

Adsorption and selective recognition of 17?-estradiol by molecularly imprinted polymers

The 17?-estradiol-imprinted polymers using non-covalent approach with methacrylic acid as the functional monomer was prepared and characterized. The effect of porogenic solvents on the adsorption capacity and thermal stability of the molecularly imprinted polymers (MIPs) were examined. Scanning electron microscopic images showed that the synthesized MIPs were bulk porous materials. The surface areas of MIPs increased from 151?C188 to 239?C292?m²?g^-1 when templates were removed by methanol using Soxhlet extraction. In addition, the MIPs prepared in chloroform had a higher adsorption capacity towards 17?-estradiol (1,212???g?g^-1) than that in acetonitrile (769???g?g^-1), indicating that less polar porogenic solvent is suitable for synthesis of non-covalent MIPs. FTIR showed that the carbonyl group is the major functional group in MIPs to form monomer-template complex via H-bond. In addition, only a slight decrease (< 5?%) in adsorption capacity of the MIPs was observed when incubated at 80?°C for 5?h. Analysis of the capacity factor values (??_imp??) for MIPs indicated that the rebinding ability from selective recognition sites of MIPs decreased in the order 17?-estradiol?>?testosterone?>?benzo[a]pyrene?>?progesterone?>?phenol, and the ??_imp?? values decreased from 2.68 to 0.63, indicating the excellent selectivity of MIPs among closely related compounds. Results obtained in this study clearly indicate that the imprinted polymer is specific for recognizing 17?-estradiol. The excellent selectivity and high adsorption capacity of 17?-estradiol-imprinted polymers open the door to develop MIPs for effective separation and adsorption of estrogenic compounds.     

Synthesis of random copolymers of styrene and arylamino substituted styrenes and their sensitivities towards nitroaromatics

Random copolymers of styrene and substituted styrenes bearing arylamino substituents as fluorophore units have been obtained. Their photophysical properties have been investigated by measuring absorption and emission spectra as in solutions as solid-state. All copolymers proved to possess absolute quantum yields up to 0.39 in solution and up to 0.05 in solid-state, depending on their fluorophore substituents. Fluorescence studies have shown that these copolymers show a highly sensitive response towards a diversity of nitroaromatic compounds, both in solutions and in a vapor phase. The detection limits for these compounds towards model nitroaromatic explosives in dichloromethane solution proved to be in the range from 10⁻⁶ to 10⁻⁷ mol/L. The fluorescent materials prepared by electrospinning of synthesized copolymers have been evaluated as sensor materials for detecting nitrobenzene vapor for our hand-made sniffer with detection limits of 0.5 ppm during 100-s exposure to the vapor.     

Relationship between electron sensitivity and chemical structures of polymers as electron beam resist. VII: Electron sensitivity of vinyl polymers containing pendant 1,3-dioxolan groups

Vinyl polymers containing pendant acetal groups were synthesized using (2,2-dimethyl-l,3-dioxolan-4-yl)methyl acrylate (DMA) and (2,2-dimethyl-l,3-dioxo-lan-4-yl)methyl methacrylate (DMM), and were evaluated as negative electron beam (EB) resists. It was found that the EB sensitivity of polymers containing acetal groups in the side chain was higher than that of polymers containing acetal groups in the main chain. A high sensitivity of 3.6 × 10^?8 C/cm² was observed. Copolymers of DMA or DMM with styrene were also synthesized in order to improve the durability for dry etching process. It was found that the copolymers had an excellent dry etching durability and were adaptable to EB lithography.     

Synthesis of polystyrene end-capped with pyrene via reversible addition-fragmentation chain transfer polymerization

A novel benzodithioate compound with a pyrene structure in the R group, pyrenylmethyl benzodithioate (PMB) was synthesized. Using PMB as the chain transfer agent (CTA), the RAFT polymerizations of styrene with AIBN as an initiator were carried out in different reaction conditions. The results indicated that PMB was an effective CTA for the RAFT polymerizations of styrene with the “living”/controlled characteristics. The structures of the obtained polymers were characterized by ¹H NMR. The results showed that majority of the polymer chains contained the pyrene moiety in the chain end. The enhanced fluorescence property in CHCl₃ solution was observed. The chain-extension experiments of the obtained polystyrene (PS) with the monomers of styrene and methyl acrylate were successfully carried out.     

Novel thermotropic liquid crystalline polyphosphonates

Main chain liquid crystalline polyphosphonates containing semi-flexible phenylester mesogen with even number of methylene spacers (2-10) have been synthesized. The monomers and polymers were characterized by IR, ¹H, ¹³C and ³¹P NMR spectroscopy. The spectral details are in accordance with the structures. All the polymers were exhibited liquid crystalline property in the Hot stage optical polarized microscope (HOPM). DSC thermal analysis confirms the mesophase formation for all the polymers. The grain size of the liquid crystalline mesophase is increasing with increasing methylene chain. T_g, T_m and T_i of the polymers decreased with increase in spacer length. The T_g of these phosphorus-containing polymers is much lower than that of non-phosphorus polymers containing triad ester mesogens. Energy minimized structures for the molecules which mimic the polymer chain suggests that the reduction in T_g may be due to entanglement raised by incorporation of phosphorus heterogeneity.