Chelate polymers. III. New polyazomethines of 5,5′‐methylene‐bissalicylaldehyde with siloxane diamines and their divalent metal complexes

Novel polymeric azomethines of 5,5′‐methylene‐bissalicylaldehyde with two siloxane diamines {H₂N(CH₂)₃(CH₃)₂SiO[(CH₃)₂SiO]_mSi(CH₃)₂(CH₂)₃NH₂, where m = 0 or 6.5} were obtained. Their structures were confirmed by elemental and spectral [IR, ultraviolet–visible (UV–vis), and ¹H NMR] analysis. The obtained polyazomethines were converted into the chelates of some divalent metals (copper, cobalt, and nickel). The resulting complexes were characterized by electronic and IR spectral measurements, elemental analysis, and thermal studies. From IR and UV–vis studies, the phenolic oxygen and imine nitrogen of the ligand were found to be the coordination sites. The thermogravimetric data indicated that the chelates were less stable than the corresponding ligands and that the thermostability depended on the siloxane segment length and the nature of the metal. Both the macromolecular ligands and the parts of the resultant chelates were soluble in common organic solvents, such as CHCl₃, CH₂Cl₂, dimethylformamide, and dimethyl sulfoxide. The surface compositions of the ligands and some chelates were examined by X‐ray photoelectron spectroscopy. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3169–3179, 2003     

Ru(II)(tpy)2‐functionalized hydrogels: Synthesis,reversible responsiveness,and coupling with the belousov‐zhabotinsky reaction

This work aims at developing an approach to Ru(II)(Tpy)₂‐functionalized hydrogels and exploring the coupling of the hydrogels with the Belousov‐Zhabotinsky (BZ) reaction. Based on free radical polymerization, two synthetic routes are developed. The first one is the direct gelation by copolymerization of acrylamide as hydrophilic component and Ru(II)(Tpy)₂ as the functional group. The second one is carried out through a combined approach. A terpyridine‐containing hydrogel is first prepared and then post‐functionalized by coordination between Ru(III)(Tpy)Cl₃ and terpyridine groups in the hydrogel network. Utilizing the synthetic hydrogels, the reversible redox responsiveness, the coupling with the BZ reaction, the occurrence and the self‐oscillating properties of the BZ reaction in the hydrogel networks are studied. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2214–2222     

Electro‐active Polymer Actuator Based on Sulfonated Polyimide with Highly Conductive Silver Electrodes Via Self‐metallization

We report here a facile synthesis of high performance electro‐active polymer actuator based on a sulfonated polyimide with well‐defined silver electrodes via self‐metallization. The proposed method greatly reduces fabrication time and cost, and obviates a cation exchange process required in the fabrication of ionic polymer‐metal composite actuators. Also, the self‐metallized silver electrodes exhibit outstanding metal‐polymer adhesion with high conductivity, resulting in substantially larger tip displacements compared with Nafion‐based actuators.

     

Doubly photoresponsive and water‐soluble block copolymers: Synthesis and thermosensitivity

We report the synthesis and investigation of a new type of photoresponsive block copolymers (BCPs). They were designed to comprise two water‐soluble polymers containing two different photoisomerizable moieties (either azobenzene and spiropyran or two different azobenzenes), with the two constituting blocks that, when separated, exhibit a lower critical solution temperature (LCST) in water and can shift their LCST in opposite directions upon photoisomerization (decrease of LCST for one polymer and increase for the other). A variety of such doubly photoresponsive BCPs were synthesized using either azobenzene‐ or spiropyran‐containing poly(N,N‐dimethylacrylamide) (PDMA), poly(N‐isopropylacrylamide) (PNIPAM) and poly[methoxydi(ethylene glycol) methacrylate] (PDEGMMA). Their thermal phase transition behaviors in aqueous solution before and after simultaneous photoreactions on the two blocks were investigated in comparison with their constituting blocks, by means of solution transmittance (turbidity) and variable‐temperature ¹H NMR measurements. The results show that BCPs displayed a single LCST whose shift upon two photoisomerizations appeared to be determined by the competing and opposing photoinduced effects on the two blocks. Moreover, optically controlling the relative photoisomerization degrees of trans azobenzene‐to‐cis azobenzene and spiropyran‐to‐merocyanine could be used to tune the LCST of BCP solution. This study demonstrates the potential of exploring a more complex photoreaction scheme to optically control the solution properties of water‐soluble thermosensitive BCPs. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4055–4066, 2010     

Effect of 1,4‐dioxane on synthesis of macroporous poly(N‐isopropylacrylamide) hydrogels

Thermosensitive Poly(N‐isopropylacrylamide) (PNIPA) hydrogels were synthesized by a free radical solution polymerization in three different ways. Normal hydrogels were prepared at room temperature and normal cryogels were prepared at subzero temperature. A cation surfactant dodecyl dimethyl benzyl ammonium bromide (DDBAB) was used during preparation of novel cryogels in freezing state. The response rates of normal hydrogels were very slow, whereas the rates of both normal and novel cryogels were very fast because of the macroporous structure of the cryogels. Mixed solvents which were composed of pure water and 1,4‐dioxane at various concentrations were used instead of pure water during the polymerization. The effects of the mixed solvent on morphology, swelling ratio, and deswelling/reswelling kinetics of the three kinds of hydrogels were investigated. For normal hydrogels and normal cryogels, there was no remarkable difference no matter the mixed solvent or pure water was used. However, the properties of the resulted novel cryogels were much different with the concentration of dioxane. Finally, the resulted hydrogels were used for concentrating emulsified paraffin. The different separation performance was attributed to the different structure of gel matrix. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6594–6603, 2008     

Preparation of polypyrrole‐graft‐poly(N‐isopropylacrylamide)/silver nanocomposites from pyrrolyl‐capped macromonomer by AgNO3 and their stimuli responsibility of light emission

Pyrrolyl‐capped poly(N‐isopropylacrylamide) macromonomers (Py‐PNIPAM) were prepared through reversible addition‐fragmentation‐transfer polymerization with benzyl 1‐pyrrolylcarbodithioate as chain‐transfer agent. Polymerizations of Py‐PNIPAM with/without pyrrole using AgNO₃ as oxidizing agent and dimethylforamide as solvent resulted in graft copolymers of polypyrrole‐graft‐poly(N‐isopropylacrylamide) (PPy‐g‐PNIPAM) as well as silver nanoparticles, leading to the formation of PPy‐g‐PNIPAM/silver nanocomposites. The resulting nanocomposites were soluble in water when the content of PPy was low, and when the molar ratio of Py/Py‐PNIPAM increased to 30, the resulting products became insoluble in water. The resulting nanocomposites had special optical properties because of PPy as well as the temperature‐responsible PNIPAM. The chemical structure and composition of nanocomposite were characterized by ¹H nuclear magnetic resonance spectroscopy, gel permeation chromatograms, fourier transform infrared spectroscopy, and X‐ray diffraction. Their optical properties were characterized by UV–vis and fluorescence spectroscopy. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6950–6960, 2008     

Synthesis,complex formation,and dilute‐solution associative behavior of linear poly(methacrylic acid)‐graft‐poly(2‐ethyl‐2‐oxazoline)*

Poly(methacrylic acid) (PMA) and poly(2‐ethyl‐2‐oxazoline) (PEOZO) are a polyacid/polybase pair capable of forming reversible, pH‐responsive, hydrogen‐bonding complexes stabilized by hydrophobic effects in aqueous media. Linear PMA was modified with long‐chain (number‐average molecular weight: 10,000) PEOZO via statistical coupling reactions in organic media to prepare a series of PMA‐graft‐PEOZO copolymers. Potentiometric titrations revealed that the presence of tethered PEOZO markedly increases the pK_a values for PMA‐g‐PEOZO copolymers as compared with simple PMA/PEOZO mixtures at degrees of ionization, α, between 0.0 and 0.1. The dilute‐solution PMA–PEOZO intramolecular association has been probed by monitoring the PEOZO NMR spin–spin (T₂) relaxation as a function of pH. Covalently attached PEOZO side chains participate in complexation at higher values of α than untethered PEOZO. Surprisingly, most PEOZO side chains did not take part in hydrogen bonding at low α, and the highest level of PEOZO incorporation induced a decrease in the number of PMA/PEOZO hydrogen bonds. The polymer self‐diffusion as a function of α was measured with dynamic light scattering. At low pH, the copolymers had no charge and they were in a collapsed form. At high pH, the expected conformational expansion of the PMA units was enhanced at moderate levels of PEOZO incorporation. However, the highest PEOZO incorporation induced the onset of intramolecular associations between PEOZO units along the copolymer chains. Low shear rheometry and light scattering measurements were used in conjunction with the T₂ NMR measurements to propose a model consistent with the aforementioned behavior. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2520–2533, 2004     

Shape‐memory polymer networks from oligo(ϵ‐caprolactone)dimethacrylates

Polymer networks showing a thermally induced shape‐memory effect were prepared through the crosslinking of oligo(?‐caprolactone)dimethacrylates under photocuring with or without an initiator. The influence of the molecular weight of the oligo(?‐caprolactone)dimethacrylates and the initiator concentration on the macroscopic properties of the polymer networks was investigated. The isothermal and nonisothermal crystallization behavior of the polymer networks was evaluated as a basic principle of the functionalization process. Shape‐memory properties such as the strain fixity and strain recovery rate were quantified with cyclic thermomechanical tensile experiments for different maximum elongations. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1369–1381, 2005     

Multisensitive polymers based on 2‐vinylpyridine and N‐isopropylacrylamide *

Poly(2‐vinylpyridine) (P2VP) containing functionalized end groups was synthesized using nitroxyl‐mediated radical polymerization with a hydroxy‐functionalized stable free radical. It was shown that P2VP could be synthesized with variable molar masses and low polydispersities. The transformation of the hydroxy groups to an acrylic ester led to the formation of macromonomers. A free‐radical copolymerization of these macromonomers with N‐isopropylacrylamide gave a graft copolymer with a poly(N‐ispopropylacrylamide) backbone and P2VP side chains. Polymers containing different amounts of the monomers were synthesized. It was possible to vary both the amount of P2VP side chains at a constant chain length of the macromonomer and the chain length at a nearly constant chain number. The behavior of the multifunctional macromolecules at different temperatures and pH values was investigated using dynamic light scattering and DSC. The macromolecules were found to retain the specific properties of the homopolymers. The hydrodynamic radii of the synthesized graft copolymers were both dependent on the temperature and pH value. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3797–3804, 2001     

Synthesis of pH‐ and thermoresponsive poly(2‐n‐propyl‐2‐oxazoline) based copolymers

Polymers that possess lower critical solution temperature behavior such as poly(2‐alkyl‐2‐oxazoline)s (PAOx) are interesting for their application as stimulus‐responsive materials, for example in the biomedical field. In this work, we discuss the scalable and controlled synthesis of a library of pH‐ and temperature‐sensitive 2‐n‐propyl‐2‐oxazoline P(nPropOx) based copolymers containing amine and carboxylic acid functionalized side chains by cationic ring opening polymerization and postpolymerization functionalization strategies. Using turbidimetry, we found that the cloud point temperature (CP) is strongly dependent on both the polymer concentration and the polymer charge (as a function of pH). Furthermore, we observed that the CP decreased with increasing salt concentration, whereas the CP increased linearly with increasing amount of carboxylic acid groups. Finally, turbidimetry studies in PBS‐buffer indicate that CPs of these polymers are close to body temperature at biologically relevant polymer concentrations, which demonstrates the potential of P(nPropOx) as stimulus‐responsive polymeric systems in, for example, drug delivery applications. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1573–1582     

Coordination of nickel and copper dithiolate to 2,2′‐bipyridine‐based π‐conjugated polymers

π‐Conjugated polymers (Poly1–Poly3) containing a 2,2′‐bipyridine (bpy) unit were subjected to coordination to nickel and copper dithiolate for the purpose of manipulating the photophysical properties. The absorption maximum peak of Poly1 [maximum wavelength (λ_max) = 446 nm] redshifted by 36 nm upon the coordination of bpy to NiCl₂, which produced Poly1–NiCl₂. A further bathochromic shift was observed in the spectrum of Poly1–mntNi [mntNi = (maleonitrile dithiolate)nickel; λ_max = 499 nm] bearing the dithiolate ligand, which stemmed from the extension of the conjugated system over the nickel dithiolate moiety through the bpy unit. An increase in the [Ni]/[bpy] ratio in Poly1–mntNi rendered the original maximum peak at 446 nm smaller and the lower energy charge‐transfer peak at 499 nm larger; the isosbestic points remained at 380 and 475 nm. The green fluorescence (λ_max = 504 nm) emitted from Poly1 markedly diminished upon the coordination of nickel dithiolate because of the effective energy transfer. The absorption maximum peak of Poly1–mntNi in chloroform at 499 nm blueshifted to 471 nm when the volume ratio of the chloroform/N,N‐dimethylformamide solvent reached 10:90. The coordination of nickel dithiolate to Poly2 and Poly3 also brought about redshifts of the absorption maximum peaks of as much as 55 and 61 nm, respectively. The absorption maximum peak of Poly1–(phenyldithiolate)nickel(pdtNi) (λ_max = 474 nm) redshifted by 28 nm in comparison with that of Poly1, whereas the magnitude of the shift of Poly1–bis(thiophenoxide)nickel(btpNi) bearing two thiophenoxide ligands was 20 nm. Poly1–mntCu with a tetrahedral copper center was also investigated. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2631–2639, 2004     

Synthesis of imidazole‐terminated hyperbranched polymers with POSS‐branching points and their pH responsive and coordination properties

An imidazole‐terminated hyperbranched polymer with octafunctional POSS branching units denoted as POSS‐HYPAM‐Im was prepared by the polymerization of excess amounts of tris(2‐aminoethyl)amine with the first‐generation methyl ester‐terminated POSS‐core poly(amidoamine)‐typed dendrimer, reacting with methyl acrylate, and ester‐amide exchange reaction with 3‐aminopropylimidazole. The imidazole‐terminated hyperbranched poly(amidoamine) denoted as HYPAM‐Im was also synthesized with 1‐(3‐aminopropyl)imidazole from a methyl ester‐terminated hyperbranched poly(amidoamine) by the ester‐amide exchange reaction. The transmittance of the POSS‐HYPAM‐Im solution drastically decreased when the solution pH was greater than 8.2. On the other hand, the transmittance of the HYPAM‐Im solution gradually decreased when the solution pH at 8.5 and was greater than 9. Spectrophotometric titrations of the hyperbranched polymer aqueous solutions with Cu²⁺ ions indicated the variation of the coordination modes of POSS‐HYPAM‐Im from the Cu²⁺–N₄ complex to the Cu²⁺–N₂O₂ complex and the existence of the only one complexation mode of Cu²⁺–N₄ between Cu²⁺ ion and HYPAM‐Im with increasing the concentrations. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2695–2701     

Poly(2,5‐dihydroxy‐1,4‐phenylene benzobisthiazole)/poly(1,4‐phenylene benzobisthiazole) copolymers: Chain packing and properties

Crystal‐packing, optical, and electrical properties of poly(2,5‐dihydroxy‐1,4‐phenylene benzobisthiazole) (DiOH‐PBZT) and copolymers of DiOH‐PBZT/poly(1,4‐phenylene‐benzobisthiazole) (PBZT) were examined. Intramolecular hydrogen bonds between the hydroxyl units and the neighboring nitrogen atoms, as evidenced by the IR spectra, led to the formation of a pseudoladder chain structure and changed the chain packing. The (200) and (010) planes were both affected by the copolymer composition, with the (200) plane spacing increasing from 5.895 to 6.482 Å and the (010) plane spacing decreasing from 3.539 to 3.404 Å with the transition from the unsubstituted PBZT homopolymer to the DiOH‐PBZT homopolymer. The cell dimensions of the copolymers were simple averages of those of the individual homopolymers, suggesting the isomorphic crystal structure formation of the two units. The c‐axis spacing, however, remained unchanged. The increase in the conjugation length of the copolymers as the dihydroxy content increased was confirmed by the bathochromic shift of the absorption band in the ultraviolet–visible spectra. The intrinsic conductivities of the copolymers were 3 orders of magnitude higher than that of the unsubstituted PBZT. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 559–565, 2001     

Triblock Copolymer Based on Poly(propylene oxide) and Poly(1‐[11‐acryloylundecyl]‐3‐methyl‐imidazolium bromide)

The controlled atom transfer radical polymerization of an ionic liquid, 1‐(11‐acryloylundecyl)‐3‐methyl imidazolium bromide (ILBr), from both ends of a telechelic poly(propylene oxide) (PPO) macroinitiator, end‐functionalized with bromoisobutyryloyl is reported. The resulting highly water‐soluble triblock, poly(ILBr‐b‐PO‐b‐ILBr) is multistimuli responsive. This new class of triblocks exhibits classical surface activity in lowering surface tension at the air–water interface and in modifying wetting in waterborne coatings. It also immunizes model colloids against coagulation induced by Debye–Hückel (indifferent electrolyte) electrostatic screening. Further, sol–gel thermoreversibility is unexpectedly found as an additional form of stimuli responsiveness.     

Stimulus‐responsive polymers based on 2‐hydroxypropyl acrylate prepared by RAFT polymerization

Homopolymerization and diblock copolymerization of 2‐hydroxypropyl acrylate (HPA) has been conducted using reversible addition fragmentation chain transfer (RAFT) chemistry in tert‐butanol at 80 °C. PHPA homopolymers were obtained with high conversions and narrow molecular weight distributions over a wide range of target degrees of polymerization. Like its poly(2‐hydroxyethyl methacrylate) isomer, PHPA homopolymer exhibits inverse temperature solubility in dilute aqueous solution, with cloud points increasing systematically on lowering the mean chain length. The nature of the end groups is shown to significantly affect the cloud point, whereas no effect of concentration was observed over the PHPA concentration range investigated. Various thermoresponsive PHPA‐based diblock copolymers were prepared via one‐pot syntheses in which the second block was either permanently hydrophilic or pH‐responsive. Preliminary studies confirmed that poly(ethylene oxide)‐poly(2‐hydroxypropyl acrylate) (PEO₄₅‐PHPA₄₈) and poly(2‐hydroxypropyl acrylate)‐ poly(2‐hydroxyethyl acrylate) (PHPA₄₉‐PHEA₆₈)diblock copolymers formed well‐defined PHPA‐core micelles in 10 mM sodium nitrate solution at 40 °C and 70 °C with mean hydrodynamic diameters of 20 nm and 35 nm, respectively. In contrast, most other PHPA‐based diblock copolymers investigated formed larger colloidal aggregates in 10 mM NaNO₃ solution at elevated temperatures. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2032–2043, 2010     

Enzymatic Degradation of Semi‐IPN Hydrogels Based on N‐Isopropylacrylamide and Dextran at a Specific Temperature Range

The temperature‐dependent enzymatic degradation of semi‐IPN hydrogels consisting of dextran grafted with thermo‐responsive chains (lower cloud point) and a thermo‐responsive crosslinked matrix (higher cloud point) was examined. Enzymatic degradation of the semi‐IPN hydrogel was significantly inhibited below the lower and above the higher cloud point. Only between both cloud points, enzymatic degradation proceeded. The designed semi‐IPN hydrogel is therefore advantageous to achieve enzymatic degradation at a specific temperature range.     

Donor–acceptor photovoltaic polymers based on 1,4‐dithienyl‐2,5‐dialkoxybenzene with intramolecular noncovalent interactions

Donor–acceptor (D–A) conjugated polymers bearing non‐covalent configurationally locked backbones have a high potential to be good photovoltaic materials. Since 1,4‐dithienyl‐2,5‐dialkoxybenzene ( TBT ) is a typical moiety possessing intramolecular S…O interactions and thus a restricted planar configuration, it was used in this work as an electron‐donating unit to combine with the following electron‐accepting units: 3‐fluorothieno[3,4‐b]thiophene ( TFT ), thieno‐[3,4‐c]pyrrole‐4,6‐dione ( TPD ), and diketopyrrolopyrrole ( DPP ) for the construction of such D–A conjugated polymers. Therefore, the so‐designed three polymers, PTBTTFT , PTBTTPD , and PTBTDPP , were synthesized and investigated on their basic optoelectronic properties in detail. Moreover, using [6,6]‐phenyl‐C₇₁‐butyric acid methyl ester (PC₇₁BM) as acceptor material, polymer solar cells (PSCs) were fabricated for studying photovoltaic performances of these polymers. It was found that the optimized PTBTTPD cell gave the best performance with a power conversion efficiency (PCE) of 4.49%, while that of PTBTTFT displayed the poorest one (PCE = 1.96%). The good photovoltaic behaviors of PTBTTPD come from its lowest‐lying energy level of the highest occupied molecular orbital (HOMO) among the three polymers, and good hole mobility and favorable morphology for its PC₇₁BM‐blended film. Although PTBTDPP displayed the widest absorption spectrum, the largest hole mobility, and regular chain packing structure when blended with PC₇₁BM, its unmatched HOMO energy level and disfavored blend film morphology finally limited its solar cell performance to a moderate level (PCE: 3.91%). © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 689–698     

N‐vinylcaprolactam‐based microgels: Synthesis and characterization

Poly(N‐vinylcaprolactam) (PVCL) is well known for its thermoresponsive behavior in aqueous solutions. PVCL combines useful and important properties; it is biocompatible polymer with the phase transition in the region of physiological temperature (32–38 °C). This combination of properties allows consideration of PVCL as a material for design biomedical devices and use in drug delivery systems. In this work, PVCL based temperature‐sensitive crosslinked particles (microgels) were synthesized in a batch reactor to analyze the effect of the crosslinker, initiator, surfactant, temperature, and VCL concentration on polymerization process and final microgels characteristics. The mean particle diameters at different temperatures and the volume phase‐transition temperature of the final product were analyzed. To obtain information about the inner structure of microgel particles, semicontinuous polymerizations were carried out and the evolution of the hydrodynamic average particle diameters at different temperatures of the microgel synthesized was investigated. In the case of microgel particles obtained in a batch reactor the size and the swelling‐de‐swelling behavior as a function of the temperature of the medium can be tuned by modulating the reaction variables. When the microgel particles were synthesized in a semibatch reactor different swelling‐de‐swelling behaviors were observed depending on particles inner structure. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2510–2524, 2008