Synthesis, characterization and photoconductive properties of optically active methacrylic polymers bearing side-chain 9-phenylcarbazole moieties

The synthesis of two novel optically active monomers containing 9-phenylcarbazole moieties, such as (S)-(+)-2-methacryloyloxy-N-[4-(9-carbazolyl)phenyl]succinimide [(S)-(+)-MCPS] and (S)-(+)-3-methacryloyloxy-N-[4-(9-carbazolyl)phenyl]pyrrolidine [(S)-(+)-MCPP], is described. Each monomer has been radically homopolymerized to afford the corresponding optically active polymeric derivatives, which have been fully characterized. Their spectroscopic, thermal and photoconductive properties were compared to those of the new achiral homopolymer poly[N-(2-methacryloyloxyethyl)-N-[4-(9-carbazolyl)phenyl]ethylamine] {poly[MCPE]}, devised as an optically inactive macromolecular model compound, as well as to analogue polymeric derivatives containing side-chain optically active carbazolyl moieties. The chiroptical properties of the chiral polymers are quantitatively higher than in the corresponding monomers. Owing to the substantially stereoirregular structure of the main chain, this suggests that the overall optical activity is mainly due to conformational dissymmetry of the macromolecules. Spectroscopic evidence suggests the presence in all polymeric derivatives of dipole-dipole interactions between the 9-phenylcarbazolyl chromophores, occurring as a consequence of their anchorage to the polymer backbone, which favours their aggregation and justifies their high decomposition temperatures.     

Optically active 2,4-dimethylglutarate azoaromatic esters of known relative configuration as models of dyads present in the related methacrylic polymeric derivatives

Novel chiral dimeric models of isotactic (meso) and syndiotactic (dl) dyads of optically active methacrylic polymers containing in the side-chain the pyrrolidinyl group of one single configuration linked through the nitrogen atom to the azobenzene chromophore, have been synthesized by functionalization of 2,4-dimethylglutaric acids with known streoisomeric composition.Their characterization afforded the possibility to investigate the relationship between the chiroptical and spectroscopic properties displayed by the dimeric model compounds and those of the related homopolymeric derivatives with known main chain stereoregularity.In particular, the optical rotation values and circular dichroism spectra of the models allow to establish the contribution of main chain microtacticity to the overall optical activity of the polymeric derivative.     

Hydrophobic methacrylic copolymers containing azobenzene moieties

The functionalization of polymer materials to produce hydrophobic surfaces is an important goal for a number of applications, especially those associated with self-cleaning and anti-adherent surfaces. Azopolymers are known for photoisomerization property that can lead to photoinduced anisotropy, photomechanical effect and surface modification with surface-relief gratings. In this study, we combine the low surface energy property of perfluoroalkyl methacrylates with the photoinduced characteristics of azopolymers, by fabricating cast films of copolymers of 2,2,2 trifluorethyl methacrylate (TFEMA) or 2,2,3,3,4,4,5,5 octafluoropentyl methacrylate (OFPMA) and 4′-[N-ethyl-N-(2methacryloxy-ethyl)]amine-4-nitro-azobenzene (DR13MA). The intended structures of the copolymers synthesized using radicalar polymerization was confirmed with Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR). The polymers had much higher thermal stability than conventional azopolymers, and formed hydrophobic surfaces with a water contact angle of ca. 96°. These hydrophobic azopolymers were amenable to the formation of surface-relief gratings at room temperature resulting from an all-photonic mass transport process, which opens the way for a number of new applications to be designed.     

Optically active photochromic methacrylic polymers with controlled average molecular weight and defined end-groups by atom transfer radical polymerization

We report a new approach based on atom transfer radical polymerization (ATRP) to produce optically active polymers containing azoaromatic moieties in the side chain with controlled average molecular weights, that can be used to investigate the conformational origin of chirality in this class of synthetic materials. The ATRP technique has been successfully applied to the synthesis of a series of optically active photochromic homopolymers poly[(S)-3-methacryloyloxy-1-(4-azobenzene)pyrrolidine] {poly[(S)-MAP]}, containing a chiral group of one prevailing configuration interposed between the methacrylic moiety and the photochromic azoaromatic chromophore. By just changing the duration of the polymerization process, macromolecules having distinct average chain lengths with low polydispersity values and well defined end-groups have been obtained.Optical activity and thermal properties of the resulting polymeric derivatives result to depend on their average molecular weight. In particular, a dependence of optical rotation and circular dichroism on chain-length has been evidenced.     

Synthesis of optically active methacrylic oligomeric models and polymers bearing the side-chain azo-aromatic moiety and dependence of their chiroptical properties on the polymerization degree

Three oligomeric models (dimer, trimer and tetramer) of optically active methacrylic polymers containing in the side-chain the pyrrolidinyl group of one single configuration linked through the nitrogen atom to the azobenzene chromophore and the related homopolymers in a wide range of average polymerization degree and different molecular weight distributions, were synthesized. Their characterization afforded the possibility to investigate the dependence of the properties on the average molecular weight of polymeric derivatives. In particular, the investigation of optical rotation and chiroptical properties by circular dichroism allowed to confirm the conformational origin of chirality in this class of materials as well as to correlate the optical activity to the molecular weight.     

Relevant chiroptical and thermal properties in optically active methacrylic copolymers containing carbazole and azoaromatic chromophores in the side-chain

Novel optically active methacrylic copolymers, bearing carbazole and azoaromatic moieties linked to the main chain with a rigid (S)-hydroxysuccinimide residue of one prevailing absolute configuration, have been prepared and characterized with the aim to establish the effects of the chiral group and of the dipolar interactions between the two side-chain chromophores on their properties.In particular, the observed chiroptical properties suggest the presence of ordered chiral conformations at least for chain segments of the macromolecules. Spectroscopic, thermal and chiroptical characterizations of these copolymers demonstrate the occurrence of significant electronic interactions between carbazole chromophores and azobenzene moieties. These interactions are related to the unusual partially alternating structure of the investigated copolymers and the relevant chiroptical and thermal properties. In fact, the polymeric derivates show high glass transition temperatures and good thermal stability, thus opening the way to a variety of potential applications based on photoconductive and optoelectronic properties.     

Optically active fluoro-substituted polyaniline prepared in organic media: The synthesis, chiroptical properties, and comparison with optically active non-substituted polyaniline

Optically active polyaniline (PANI) bearing an electron-withdrawing fluorine substituent, poly(2-fluoroaniline) (F-PANI), was synthesized in organic solvents by using (+)- or (−)-camphorsulfonic acid (CSA) as a chiral dopant, in which 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) was used as an electron acceptor. Formations of the optically active (chiral) F-PANI/(+)- or (−)-CSA, the dedoped F-PANI, and the redoped F-PANI/CSA were confirmed by the FT-IR, UV/vis/near-IR, and/or circular dichroism (CD) spectroscopy. The CD spectra of the chiral F-PANIs/(+)- and (−)-CSA were investigated in various organic solvents and compared with those of non-substituted PANI/(+)- or (−)-CSA. The F-PANI/(+)-CSA and PANI/(+)-CSA interestingly indicated almost mirror-imaged CD spectra in the visible region, although CD absorptions of the F-PANI/CSA were slightly blue shifted compared with those of PANI/CSA. The chiral F-PANI/CSA was unexpectedly confirmed to remain the initial chiral conformation during reversible dedoping/redoping cycles in solution state. The chiroptical properties of F-PANI/(+)-CSA in organic solvents were found to be affected by the solvent, probably due to the solvent effect to the polymer backbone, and the helical conformation was drastically reversed by change of the solvent. Furthermore, the conformation of F-PANI/CSA in m-cresol can be significantly changed when the F-PANI/CSA was dissolved in cosolvent of m-cresol and DMSO at various volume ratios, in which the sign inversions of CD absorption bands were caused when the ratio of DMSO in the m-cresol/DMSO cosolvent exceeded 10%. On the other hand, in the case with PANI/(+)-CSA, the similar sign inversions of CD absorption bands were not observed under the similar conditions, and then the helical conformation of chiral F-PANI/CSA was supposed to be rather flexible compared with that of chiral PANI/CSA, presumably due to relatively weak interaction among F-PANI backbone, CSA, and m-cresol.     

Optically active copolymers of N-(oxazolinyl)phenylmaleimides with methyl methacrylate: Synthesis and chiral recognition ability

The free radical copolymerization of three N-phenylmaleimides bearing a chiral oxazoline residue at ortho-position of the phenyl group (OPMI) with methyl methacrylate (MMA) was carried out in tetrahydrofuran by varying the molar ratio of the comonomers. The monomer reactivity ratios and Alfrey-Price Q-e values were determined. The data revealed that the monomer OPMI has a distinct tendency to cross-propagate and MMA is inclined to block formation. Meanwhile, the MMA co-units affected significantly the chiroptical property of resulted copolymers besides endowing them with a moderate film-forming ability. Poly(OPMI-co-MMA)s coated on macroporous silica were used as a high-performance liquid chromatography chiral selector, and the optical resolution performance was briefly evaluated toward some racemic compounds including amino- and hydroxy-acids as well as 1,1′-bi-2-naphthol. The observation indicated that the column combining MeOPMI/MMA copolymers with higher chiral component exhibits an extent of enantioselectivity in both normal and reversed-phase modes.     

Optically active tyrosine‐containing poly(N‐propargylamides): Synthesis,helical conformation,and infrared emissivity study

Novel optically active and racemic poly(N‐propargylamides) bearing tyrosine pendants (LPT, DPT, and RPT) were synthesized and characterized. The polymers possessed moderate molecular weights and were thoroughly soluble in common organic solvents. The secondary structure of these three polymers in chloroform was studied and the results indicated that LPT and DPT could adopt helical structures with predominantly one‐handed screw sense according to their intense Cotton effect and large specific rotation values, while RPT adopted random coiled polymer chain. The amide groups could form amide‐amide hydrogen bonds to engender the twist of dihedral angle and the strong steric repulsion of phenol groups might have the opposite effect on the helix. The helical structure of the optically active polymers were conclusively constructed and stabilized by the optimization of intra‐ and intermolecular hydrogen bonding and steric repulsion of the side chains. Moreover, the infrared emissivity values of LPT and DPT at 30 °C were 0.682 and 0.671, which were much lower than RPT. LPT and DPT also showed superior heat resistance due to their unique helical conformation. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44824.     

Alternating phenylenevinylene copolymers with dithienbenzothiadiazole moieties: Synthesis,photophysical, and photovoltaic properties

Two new soluble alternating phenylenevinylene copolymers S and L which contained dithienbenzothiadiazole moieties were synthesized by Heck coupling. The repeating unit of L was longer than that of S and contained two additional phenylene rings and two cyano‐vinylene bonds. Both copolymers were stable up to about 350°C and afforded char yield of 52–66% at 800°C in N₂. Their absorption spectra were broad and extended up to about 600 nm with a longer wavelength maximum at 447–502 nm and optical band gap of ～ 2.0 eV. These copolymers emitted yellow light in solution with PL maximum at 551–580 nm and orange‐red light in thin film with PL maximum at 588–661 nm. The emission maximum of L was considerably red‐shifted relative to S . Photovoltaic cells based on S (or L ) as donor and [6,6]‐phenyl C61‐butyric acid methyl ester as acceptor were investigated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and properties of vinylic copolymers with fluorescent moieties as optical brighteners for liquid crystals

The synthesis and characterization of new side‐group copolymers of styrene or methylmethacrylate with fluorescent 1,8‐naphthalimide derivatives are described. Basic photophysical characteristics of produced low molar and polymeric fluorescent brighteners are reported. The utility of the brighteners in liquid crystalline displays of the guest‐host type is discussed on the basis of their spectral properties and their effect on the behavior of nematic liquid crystal ZLI 1840 (Merck, Darmstadt, Germany) at phase transition. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 151–157, 1999     

Synthesis and characterization of main‐chain,second‐order,nonlinear optical polyurethanes with isolation moieties and zigzag structures

In this study, two main‐chain second‐order nonlinear optical (NLO) polyurethanes were successfully prepared with indole‐based chromophores. The introduced phenyl isolation group and the continuous zigzag polymer backbone were found to be helpful for effectively decreasing the intermolecular dipole–dipole interactions and enhancing the NLO properties of the resulting polymers. The studied polymers exhibited good optical transparency, high thermal stability, and excellent NLO effects; this indicated that the nonlinearity–stability trade‐off and nonlinearity–transparency trade‐off could be alleviated by this newly designed polymer system. Poly{4‐anilinocarbonyl[N‐ethoxyl‐5‐phenyl‐3‐azo(2′‐oxyethylene‐4′‐nitrobenzene)indole]carbonylimino} with a zigzag backbone showed a large second harmonic generation coefficient (d₃₃) value of 88.4 pm/V. However, poly{5‐naphthyliminocarbonyl[N‐ethoxyl‐5‐phenyl‐3‐azo(2′‐oxyethylene‐4′‐nitrobenzene)indole]carbonylimino} (PUAZN) with a continuous zigzag structure exhibited a higher d₃₃ value of 116.2 pm/V, which was attributed to the unique rigid and zigzag linkage of 1,5‐naphthalene as the isolation spacer. The enhanced NLO efficiency and relatively longer term temporal stability made PUAZN as a promising candidate for practical applications in photonic devices. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42974.     

Electrical conductivity and thermal properties of poly(m‐aminophenyl acetic acid) and its copolymers with aniline

Poly(m‐aminophenyl acetic acid) was synthesized under different conditions from the respective monomer, using ammonium persulfate as oxidizing agent in both the presence and the absence of CuCl₂ in HCl(aq). Moreover, the copolymers between aniline and m‐aminophenyl acetic acid were prepared at several feed mol ratios (f₁) of aniline. Copper was introduced by the Batch method in the homo‐ and copolymers of different compositions. The polymers were characterized by FTIR and UV‐vis spectroscopy, elemental analysis, thermal analysis, and electrical conductivity. The thermal stability and the content of copper increased as the content of aniline was increased in the copolymers. Moreover, the copolymers showed a high thermal stability; at 400°C a weight loss < 10% was observed. The electrical conductivity was increased with a higher content of aniline in the copolymers, achieving semiconduction values. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1484–1492, 2003     

Studies on water-swellable elastomers. II. Thermal properties and crystalline behavior of amphiphilic graft copolymers with poly(ethylene glycol) side chains

The thermal properties and crystalline structure of the amphiphilic graft copolymers CR-g-PEG600, CR-g-PEG2000, and CR-g-PEG6000 using chloroprene rubber (CR) as the hydrophobic backbone and poly (ethylene glycol) (PEG) with different molecular weights as the hydrophilic side chains were studied by DSC and WAXD. The results showed that a distinct phase-separated structure existed in CR-g-PEGs because of the incompatibility between the backbone segments and the side-chain segments. For all the polymers studied, T_m2, which is the melting point of PEG crystalline domains in CR-g-PEG, decreased compared to that of the corresponding pure PEG and varied little with PEG content. For CR-g-PEG600 and CR-g-PEG2000, T_m1, which is the melting point of the CR crystalline domains, increased with increasing PEG content when the PEG content was not high enough, and at constant PEG content, the longer were the PEG side chains the higher was the T_m1. The crystallite size L_o11 of CR in CR-g-PEGs increased compared to that of the pure CR and decreased with increasing PEG content. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 2441–2447, 1997     

Conjugated copolymers of cyanosubstituted poly(p‐phenylene vinylene) with phenylene ethynylene and thienylene vinylene moieties: Synthesis,optical, and electrochemical properties

Three alternating conjugated copolymers of cyanosubstituted poly(p‐phenylene vinylene) (CN–PPV) with phenylene ethynylene and thienylene vinylene moieties, P1, P2, and P3, were synthesized via cross‐coupling polycondensation with Pd(PPh₃)₂Cl₂ as a catalyst. Their structures were confirmed by ¹H‐NMR, IR spectroscopy, elemental analysis, and gel permeation chromatography, and the thermal, photophysical, and electrochemical properties of the copolymers were also investigated. The incorporation of a triple bond into the CN–PPV backbone led to higher reduction potentials, which corresponded to lower lowest unoccupied molecular orbital energy levels. The three copolymers possessed broader absorption spectra, especially copolymer P3 with its polymerization units containing two thiophene rings, which showed the broadest absorption spectrum, from 300 to 710 nm. Their high electron affinities, broad absorptions, and relatively higher oxidation potentials make the copolymers potentially good electron‐acceptor material for use in photovoltaic devices. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis of a novel difunctional NLO azo‐dye chromophore and characterizations of crosslinkable copolymers with stable electrooptic properties

The synthesis and the nonlinear optical (NLO) properties of crosslinkable copolymers based on a novel NLO azo‐dye chromophore bearing two functions: one used the free‐radical copolymerization, that is, the methacrylate group, and the other one used for the crosslinking process, that is, the carboxylic acid function, are described. Copolymerization of this new monomer with glycidyl methacrylate leads to novel soluble crosslinkable NLO copolymers bearing free epoxy and carboxylic groups. The poling process, before crosslinking, is achieved at a temperature (T_p) close to the glass transition temperature, T_g (<70°C), of the copolymers. At this temperature, no reaction takes place between epoxy and carboxylic acid functions. In fact, crosslinking begins to start at a higher temperature, T_c (T_c ≫ T_p ≈ T_g). After the optimization of the poling and crosslinking processes, the NLO crosslinked polymer with 30 mol % of the chromophore exhibits a T_g of 157°C and a high quadratic susceptibility (d₃₃) of 30 pm/V at 1320 nm. This coefficient is stable at 85°C for several weeks. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 974–982, 1999     

Novel optically active poly(amide‐imide)s with tetrahydropyrimidinone and tetrahydro‐2‐thioxopyrimidine moieties by microwave‐assisted polycondensation

Rapid and highly efficient synthesis of novel poly(amide‐imide)s (PAIs) were achieved under microwave irradiation by using a domestic microwave oven from the polycondensation reactions of 4,4′‐carbonyl‐bis(phthaloyl‐L ‐alanine) diacid chloride [N,N′‐(4,4′‐carbonyldiphthaloyl)] bisalanine diacid chloride (1) with six different derivatives of tetrahydropyrimidinone and tetrahydro‐2‐thioxopyrimidine compounds (2a–2f) in the presence of a small amount of a nonpolar organic medium that acts as a primary microwave absorber. Suitable organic media was o‐cresol. The polycondensation proceeded rapidly and was almost completed within 10 min, giving a series of PAIs with inherent viscosities of about 0.25–0.45 dL/g. The resulting PAIs were obtained in high yield and are optically active and thermally stable. All of the above compounds were fully characterized by means of Fourier transform infrared spectroscopy, elemental analyses, inherent viscosity (η_inh), solubility test, and specific rotation. Thermal properties of the PAIs were investigated using thermogravimetric analysis. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2416–2421, 2001     

Development of poly(lactic acid) films with propolis as a source of active compounds: Biodegradability,physical, and functional properties

Active films (AFs) using poly(lactic acid) (PLA) as a polymeric matrix containing various propolis concentrations (5, 8.5, and 13%) as the active agent (AA) were developed using a casting method. The purpose was to determine the effects of the incorporation of AA on the physical properties of the films and to evaluate the antioxidant and antimicrobial activities. Tensile strength and elastic modulus of the AFs decreased relative to the control (PLA without AA). Introducing the active substances from propolis into the PLA also affected its thermal properties (glass transition). Adding AAs to the polymer generated more opacity with a green-yellowish color compared to the control. In addition, AFs exhibited reduced water vapor permeability as the AA concentration increased. Biodegradation assay showed that the AFs degraded faster than the control. AFs exhibited antioxidant activity, which was measured as the ability to scavenge free radicals (2,2-diphenyl-1-picrylhydrazyl and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate)), due to the presence of bioactive compounds (phenolics). Antimicrobial activity was evaluated against Escherichia coli and showed a reduction over 4-log cycles. Therefore, incorporation of propolis is a useful strategy for the development of active packaging with antioxidant and antimicrobial effects, which increase the shelf life of food products. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47090.     

Synthesis and characterization of poly(ε‐caprolactone)‐b‐poly(ethylene glycol)‐b‐poly(ε‐caprolactone) triblock copolymers with dibutylmagnesium as catalyst

Two series of poly(ε‐caprolactone)‐b‐poly(ethylene glycol)‐b‐poly(ε‐caprolactone) triblock copolymers were prepared by the ring opening polymerization of ε‐caprolactone in the presence of poly(ethylene glycol) and dibutylmagnesium in 1,4‐dioxane solution at 70°C. The triblock structure and molecular weight of the copolymers were analyzed and confirmed by ¹H NMR, ¹³C NMR, FTIR, and gel permeation chromatography. The crystallization and thermal properties of the copolymers were investigated by wide‐angle X‐ray diffraction (WAXD) and differential scanning calorimetry (DSC). The results illustrated that the crystallization and melting behaviors of the copolymers were depended on the copolymer composition and the relative length of each block in copolymers. Crystallization exothermal peaks (T_c) and melting endothermic peaks (T_m) of PEG block were significantly influenced by the relative length of PCL blocks, due to the hindrance of the lateral PCL blocks. With increasing of the length of PCL blocks, the diffraction and the melting peak of PEG block disappeared gradually in the WAXD patterns and DSC curves, respectively. In contrast, the crystallization of PCL blocks was not suppressed by the middle PEG block. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009