NOTE: Synthesis and Characterization of a Poly(acrylamide) with Pendant 1,4-piperazine-2,5-dione Moieties via Post-polymerization Cyclization

A poly(acrylamide) was synthesized from N ^α -Boc-N ^? -acrolyl-l-lysylglycine methyl ester via radical polymerization. This polymer typically had Mn ～ 100,000 g/mol, Mw ～ 300,000 g/mol, and a T_g of 93°C. Removal of Boc with TFA and cyclization with DABCO? in DMSO at 65°C afforded a soluble piperazinedione-containing polymer that had a T_g of 157°C and thermal stability up to 300°C. These results demonstrate a viable and efficient synthetic route to piperazinedione-containing polyacrylamides of high molecular weight. Related polymers that incorporate substituted indane moieties could be useful high T_g materials for fabrication of LC and NLO devices.     

Poly(imino imino ether ether ketone ketone) as novel soluble heat-resistant polymer

In this paper, we introduce a novel high-performance polymer, poly(imino imino ether ether ketone ketone), which has been synthesized by the palladium-catalyzed C-N cross coupling reaction of 1,4-bis-(4-bromobenzoyl) benzene and 1,3-bis-(4-aminophenoxy) benzene. The structure of the polymer is characterized by means of ¹H NMR spectroscopy and elemental analysis, and the results show a good agreement with the proposed structure. Compared with traditional poly(ether ether ketone)s, the solubility of the synthesized polymer in common organic solvents was higher; it also exhibited high glass transition temperature (T _g = 176°C) and good thermal stability with high decomposition temperature (T ₅ = 400°C).     

Synthesis and second-order nonlinear optical properties of a crosslinkable functionalized hyperbranched polymer

A new implementation of copper-free thermal Huisgen 1,3-dipolar crosslinking reaction into a high T_g hyperbranched polyimide polymer in order to stabilize the electro-optic (EO) activity of second-order non linear materials is reported. Towards this goal, two different synthetic approaches were explored. The first strategy is based on the post-functionalization of the polymer with mixtures of DR1 azido derivative and propargylic alcohol, whereas, the second consists in the preparation of two complementary functionalized hyperbranched polymers that are mixed just before the preparation of films. Materials exhibit good second-order nonlinear optical coefficients (d₃₃) close to 30 pm/V at the fundamental wavelength of 1064 nm. Moreover, the thermal stability of the NLO properties of these materials reaches temperatures as high as 150 °C, and probably higher. This represents the highest thermal stability of crosslinkable EO polymers based on the crosslinking Huisgen reaction.     

Structure-property study of polyimides derived from PMDA and BPDA dianhydrides with structurally different diamines

A series of aromatic diamines were polymerized with two aromatic dianhydrides, pyromellitic dianhydride and 3,3^′,4,4^′-biphenyltetracarboxylic dianhydride, and the resulting poly(amic acid)s were thermally cyclodehydrated to aromatic polyimides. The polyimides were characterized by determining the glass transition temperatures (T_g), thermal stability, coefficients of thermal expansion, and wide-angle X-ray diffraction. Structure-property relationships are elucidated and discussed in terms of the structural fragments in the polymer chain. The PMDA-based polyimides generally revealed a higher T_g than the corresponding BPDA-based analogues. Generally, the dilution of the imide content by the insertion of oxyphenylene segments into the diamines significantly reduced the T_g. The introduction of m- or o-phenylene units into the polymer backbone usually resulted in a decrease in T_g. The attachment of pendant groups on the backbone may lead to decreased or increased T_gs, depending on the structure of pendant groups. As evidenced by X-ray diffraction, the polyimides derived from rigid, rod-like diamines or the diamines having two or three p-oxyphenylene showed a higher crystalline tendency. The presence of aliphatic pendant groups slightly reduced the thermal stability of the polyimides. The other structural changes did not show a dramatic influence on the thermal stability. Some polyimides obtained from p- or m-phenylenediamine had low thermal expansion coefficients below 2×10−5°C⁻¹.     

Conductivity and thermal behavior of proton conducting polymer electrolyte based on poly (N-vinyl pyrrolidone)

The polymer electrolytes based on poly N-vinyl pyrrolidone (PVP) and ammonium thiocyanate (NH₄SCN) with different compositions have been prepared by solution casting technique. The amorphous nature of the polymer electrolytes has been confirmed by XRD analysis. The shift in T_g values and the melting temperatures of the PVP-NH₄SCN electrolytes shown by DSC thermo-grams indicate an interaction between the polymer and the salt. The dependence of T_g and conductivity upon salt concentration have been discussed. The conductivity analysis shows that the 20 mol% ammonium thiocyanate doped polymer electrolyte exhibit high ionic conductivity and it has been found to be 1.7 × 10⁻⁴ S cm⁻¹, at room temperature. The conductivity values follow the Arrhenius equation and the activation energy for 20 mol% ammonium thiocyanate doped polymer electrolyte has been found to be 0.52 eV.     

Synthesis and nonlinear optical properties of novel Y‐type polyurethane containing tricyanovinylthiazole with enhanced thermal stability of second harmonic generation

A novel Y‐type poly[iminocarbonyloxyethyl‐5‐methyl‐4‐{2‐thiazolylazo‐4‐(1,2,2‐tricyanovinyl)}resorcinoxyethyloxycarbonylimino‐(3,3′‐dimethoxy‐4,4′‐biphenylene)] 4 containing 5‐methyl‐4‐{5‐(1,2,2‐tricyanovinyl)‐2‐thiazolylazo}resorcinoxy groups as nonlinear optical (NLO) chromophores, which constitute part of the polymer backbone, was prepared and characterized. Polyurethane 4 is soluble in common organic solvents such as acetone and N,N‐dimethylformamide. It showed a thermal stability up to 250 °C in thermogravimetric analysis thermogram and the glass‐transition temperature (T_g) obtained from differential scanning calorimetry thermogram was around 118 °C. The second harmonic generation coefficient (d₃₃) of poled polymer films at 1560 nm fundamental wavelength was around 8.43 × 10^?9 esu. The dipole alignment exhibited a thermal stability even at 12 °C higher than T_g, and there was no SHG decay below 130 °C due to the partial main‐chain character of the polymer structure, which is acceptable for NLO device applications. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1166–1172, 2010     

Thermal study and evaluation of new menthol-based ionic liquids as polymeric additives

Thermal properties of new ionic liquids (ILs) were investigated by thermogravimetry (TG/DTG) and differential scanning calorimetry (DSC). Chlorides, tetrafluoroborates and hexafluorophosphates of (−)mentholpyrrolidinium and (−)-mentholimidazolium cations revealed good thermal stability at air atmosphere. Morphological characteristics of poly(methyl methacrylate) (PMMA) matrices doped with 10% of these ILs were also investigated by DRX and water absorption test. Into the matrix, they exhibited a very satisfactory pattern concerning the polymer thermal stabilization. DSC results show that some of these ILs also present plasticizer features since they can lower the polymer glass transition temperature (T _g) up to 317.15 K.     

Synthesis and characterization of novel alternating fluorinated copolymers bearing oligo(ethylene oxide) side chains

The synthesis and characterization of novel poly(CTFE‐g‐oligoEO) graft copolymers [chlorotrifluoroethylene (CTFE) and ethylene oxide (EO)] are presented. First, vinyl ether monomers bearing oligo(EO) were prepared by transetherification of ω‐hydroxyoligo(EO) with ethyl vinyl ether catalyzed by a palladium complex in 70–84% yields. Two vinyl ethers of different molecular weights (three and 10 EO units) were thus obtained. Then, radical copolymerization of the above vinyl ethers with CTFE led to alternating poly(CTFE‐alt‐VE) copolymers that bore oligo(OE) side chains in satisfactory yields (65%). These original poly(CTFE‐g‐oligoEO) graft copolymers were characterized by ¹H, ¹⁹F, and ¹³C NMR spectroscopy. Their molecular weights reached 19,000 g mol^?1, and their thermal properties were investigated while their glass transition temperatures ranged between ?42 and ?36 °C. Their thermogravimetric analyses under air showed decomposition temperatures of 270 °C with 10% weight loss (T_d,10%). These novel copolymers are of potential interest as polymer electrolytes in lithium ion batteries, showing room temperature conductivities ranging from 4.49 × 10^?7 to 1.45 × 10^?6 S cm^?1 for unplasticized material. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthesis and nonlinear optical properties of novel Y-type polyimides with enhanced thermal stability of dipole alignment

2,3-Bis-(3,4-dicarboxyphenylcarboxyethoxy)-4′-nitrostilbene dianhydride (4) was prepared and reacted with 1,4-phenylenediamine, 4,4′-oxydianiline, 4,4′-diaminobenzanilide and 4,4′-(hexafluoroisopropylidene)dianiline to yield novel polyimides 5-8 containing 2,3-dioxynitrostilbenyl groups as NLO-chromophores, which constituted parts of the polymer backbones. The resulting polyimides 5-8 were soluble in polar solvents such as acetone and DMF. Polymers 5-8 showed a thermal stability up to 300 °C in TGA thermograms with T_g values obtained from DSC thermograms in the range of 135-160 °C. The SHG coefficients (d₃₃) of poled polymer films at the 1064 cm⁻¹ fundamental wavelength were around 5.26 × 10⁻⁹ esu. The dipole alignment exhibited exceptionally high thermal stability even at 30 °C higher than T_g and there was no SHG decay below 170-190 °C due to the partial main chain character of polymer structure, which was acceptable for NLO device applications.     

Thermo‐mechanical Properties of PEO‐PU/PAN Semi‐Interpenetrating Polymer Networks and their LiClO4 Salt‐Complexes

This paper is an investigation on the thermo‐mechanical properties of a new class of materials, which holds promise for its potential use as solid polymer electrolytes, i.e., SPE material. A series of poly(ethylene oxide)‐polyurethane/poly(acrylonitrile) (PEO‐PU/PAN) semi‐IPNs, along with their LiClO₄ salt complexes, were characterized for their thermal, mechanical and dimensional stability using DSC, TG‐DTA, UTM and DMTA. The glass transition temperature (T_g) of both the undoped and doped semi‐IPNs, obtained by DSC, remained well below room temperature (～?50°C to ?35°C), satisfying one of the essential requirements to serve as a SPE host matrix. The crystallization process in the PEO segments of the PEO‐PU/PAN semi‐IPNs was prevented at higher salt concentrations, which is attributed to the Li⁺ ion mediated pseudo‐crosslinks. Good thermal stability of the semi‐IPNs was evident from the degradation onset temperature (T₀～240°C) with a three‐stage degradation process, which is independent of the PAN content as observed from differential thermogravimetric studies. The incorporation of PAN in the PEO‐PU networks results in improved mechanical properties, such as tensile strength and modulus while retaining the flexibility of the semi‐IPNs. The peak temperatures and storage modulus obtained from DMTA correlates well with the observations of DSC and tensile measurements.     

Hydrogen-bonded network: An effective approach to improve the thermal stability of organic/polymer electro-optic materials

Preparation of PMMA-co-PHPMN-(4-hydroxyphenyl)maleimide was prepared according tothe literature [1]. The monomer mixtures, comprising of 0.6g N-(4-hydroxyphenyl)maleimide, 0.4 g MMA and 0.004 g , ′-azobisisobutyronitrile (AIBN) were dissolved in 2 mLDMF. Air above the monomers was swept out using thefreeze-pump-thaw procedure three times and filled with     

Molecular design,synthesis, and properties of Y‐type nonlinear optical polyester containing tricyanovinylthiophene with enhanced thermal stability of second harmonic generation

1‐{3,4‐Di‐(2‐hydroxyethoxy)phenyl}‐2‐(2‐thiophenyl)ethene (5) was prepared and condensed with terephthaloyl chloride to yield polyester (6). Polymer 6 was reacted with tetracyanoethylene to give a new Y‐type polyester (7) containing 1‐(3,4‐dioxyethoxy)phenyl‐2‐{5‐(2,2,3‐tricyanovinyl)‐2‐thiophenyl)}ethenyl groups as NLO‐chromophores, which are components of the polymer backbones. Polyester 7 is soluble in common organic solvents such as N,N‐dimethylformamide and acetone. Polymer 7 showed a thermal stability up to 300 °C in thermogravimetric analysis with glass transition temperature (T_g) obtained from differential scanning calorimetry near 126 °C. The second harmonic generation (SHG) coefficient (d₃₃) of poled polymer film at the 1560 nm fundamental wavelength was around 6.57 × 10^?9 esu. The dipole alignment exhibited high thermal stability up to the T_g, and there was no SHG decay below 125 °C due to the partial main‐chain character of polymer structure, which is acceptable for NLO device applications. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1911–1919, 2009     

Open spaces and molecular motions of polyether-based network polymers probed by positron annihilation

The lifetimes of positrons have been measured for network polymers based on polyethers. From the temperature dependence of the lifetime of ortho-positronium (o-Ps), τ₃, for the network polymer of poly(ethylene oxide-co-propylene oxide) [P(EO/PO)], an onset temperature for limited local motions of molecules, T_γ, and the glass transition temperature, T_g, were determined to be 57 and 201 K, respectively. For the network polymer of poly[EO-co-2-(2-methoxyethoxy)ethyl glycidyl ether] [P(EO/MEEGE)], T_γ and T_g were determined to be 57 and 185 K, respectively. For both specimens, above 270 K, the observed linear temperature dependence of τ₃ was attributed to the thermal expansion of open spaces in a liquid state. In the temperature range between T_γ and 270 K, for the P(EO/MEEGE) network, τ₃ was longer and its intensity was smaller than those for the P(EO/PO) network. These results were attributed to the increase in the size of open spaces for the P(EO/MEEGE) network polymer and the blocking of these regions by motions of side chains and chain ends. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1919–1925, 1998     

Preparation of nano poly(phenylsilsesquioxane) spheres and the influence of nano-PPSQ on the thermal stability of poly(methyl methacrylate)

The nano poly(phenylsilsesquioxane) spheres (nano-PPSQ) were prepared by the sol?Cgel method and incorporated into poly(methyl methacrylate) (PMMA) by in situ bulk polymerization of methyl methacrylate. The structure of nano-PPSQ was confirmed by transmission electron microscope and thermogravimetry analysis (TG). The interaction between nano-PPSQ and PMMA was investigated by Fourier transform infrared spectra (FT-IR). The influence of nano-PPSQ on the thermal stability of PMMA was investigated by TG and differential scanning calorimetry (DSC) measurements. The results indicated that nano-PPSQ enhanced the thermal stability and the temperatures of glass transition (T _g) of nanocomposites. The effect of the heating rate in dynamic measurements (5?C30?°C?min^?1) on kinetic parameters such as activation energy by TG both in nitrogen and air was investigated. The Kissinger method was used to determine the apparent activation energy for the degradation of pure PMMA and nanocomposites. The kinetic results showed that the apparent activation energy for degradation of nanocomposites was higher than that of pure PMMA under air.     

Preparation and characterization of the soluble NLO polyarylates with enhanced electro-optic properties

Three novel nonlinear optical polyarylate polymers were prepared containing one main-chain polymer (mPAR-chr1) and two side-chain polymers (sPAR-chr1, sPAR-chr2) with different kinds of chromophores. The obtained polymers were characterized and evaluated by UV-Vis, ¹H NMR, DSC and TGA. All the polymers exhibited excellent thermal stability, film forming ability and good electro-optic (EO) activity. The relationship between EO coefficients (r ₃₃) and the chromophore concentration of the three polymers had been also characterized and discussed. There were no obvious differences found in EO activity between main-chain and side-chain polyarylates with the same chromophore (chr1). Due to the stronger electron-withdrawing tricyanopyrroline acceptor and the steric effect of the large dendritic groups of chromophore 2 (chr2), polymer sPAR-chr2 showed the largest EO cofficients (64 pm V^?1) in these new polymers.     

Synthesis and characterization of thermally stable sulfonated polybenzimidazoles

A series of sulfonated polybenzimidazoles (sPBI-IS) with controlled sulfonation degrees (SDs) were synthesized from various stoichiometric ratio mixtures of 5-sulfoisophthalic acid monosodium salt (SIPN), 4,4′-sulfonyldibenzoic acid and 3,3′-diaminobenzidine by solution copolycondensation in poly(phosphoric acid). The resulting sulfonated polymers were characterized by means of FTIR, ¹H NMR and GPC, in addition to TGA and DMA. The number-average molecular weights (M_n) of the sPBI-IS are in the range of 45,500-64,000, and the polydispersity indices (M_w/M_n) vary from 1.9 to 2.4. The synthesized sPBI-IS samples present good solubilities in polar aprotic solvents and they are easy to form the transparent, flexible and tough films by solution casting. These polymer membranes show excellent thermal stabilities and dynamic mechanical properties. The thermal stability of the sodium form sPBI-IS remarkably increases with increasing SD. However, the acidic form sPBI-IS presents less thermal stability than the non-sulfonated sample (sPBI-IS0). The onset decomposition temperature (T_d) and the glass-transition temperature (T_g) of the acidic form sPBI-IS70 are 439 °C and 196 °C, respectively. The sulfonated membranes show higher storage moduli and loss moduli than sPBI-IS0. The resulting sPBI-IS membranes with high hygroscopicity show potential application as the high temperature proton exchange membrane in fuel cell.     

Synthesis,electrolyte properties and solar cell performance of hyperbranched poly(aryl-ether-urea)s

Hyperbranched poly(aryl-ether-urea)s with phenyl, N,N-dimethylamino ethyl and polyethylene oxide end-groups linked through urethane group – HBPEU-1, HBPEU-2 and HBPEU-3 respectively – were synthesized from an AB₂-type blocked isocyanate monomer and characterized by FT-IR, ¹H-NMR, SEC-MALLS, TGA and DSC techniques. The molecular weight of the polymers were found to be ranged from 4.9 × 10³ ? 1.96 × 10⁴ g/mol. The TGA results showed that the polymers decompose between 175°C – 220°C. In the DSC curves, HBPEU-1 and HBPEU-3 showed T_g at 160°C and 53°C respectively, whereas HBPEU-2 did not showed clear T_g. All the three polymers were converted into polymer electrolytes by doping with LiI/I₂. The doped polymers showed remarkably high ionic conductivity, up to 222 – 277 times compared to the un-doped polymers and the highest conductivity was observed with doped HBPEU-2. The TiO₂ based dye-sensitized solar cells (DSSCs) were fabricated using the doped polymer electrolytes and their performance was tested; HBPEU-2 showed good performance by yielding energy conversion efficiency (η) of 4.5%.     

Electrochemical synthesis and investigation of poly(1,4-bis(2-(3,4-ethylenedioxy)thienyl)benzene) and its application in an electrochromic device

1,4-Bis(2-(3,4-ethylenedioxy)thienyl)benzene, prepared by Stille cross-coupling reaction was successfully electrochemically polymerized to give polymer 1,4-bis(2-(3,4-ethylenedioxy)thienyl)benzene (PEBE). Characterizations of the resulting polymer PEBE were performed by cyclic voltammetry (CV), UV–vis, Fourier transform infrared spectroscopy and scanning electron microscopy. Moreover, the spectroelectrochemical and electrochromic properties of the polymer film were investigated. The resulting polymer film has distinct electrochromic properties and shows three different colors (deep red, gray, and light blue) under various potentials. At the dedoped state of the polymer, the π–π* transition absorption peak is located at 510?nm and the optical band gap (E _g) was calculated as 1.92?eV. The PEBE film shows a maximum optical contrast (ΔT%) of 31.0?% at 500?nm with a response time of 0.85?s. The coloration efficiency of PEBE film was calculated to be 182.2?cm²C^?1. An electrochromic device (ECD) based on PEBE and poly(3,4-ethylenedioxythiophene) was also constructed and characterized. The response time was measured as 0.4?s, and the coloration efficiency of the device was calculated to be 225.4?cm²C^?1. Furthermore, this ECD exhibited satisfactory optical memories and redox stability.     

Determination of ultra-low glass transition temperature via differential scanning calorimetry

A novel method was developed to determine the ultra-low glass transition temperature (T_g) of materials through physical blending via differential scanning calorimetry. According to the Fox equation for polymer blends, a blend of two fully compatible polymers has only one T_g. The single T_g is a function of the T_gs of the two simple polymers. Thus, the ultra-low T_g of one material can be obtained from the T_gs of another polymer and their blends. The error of T_g measurements depends on the measurement error of the T_gs for the blends and another polymer. The method was successfully applied to determine the T_gs of acetyl tributyl citrate (ATBC), tributyl citrate (TBC) and poly(ethylene glycol)s (PEG)s with different molecular weights. The T_gs for ATBC, TBC, PEG-4000 and PEG-800 were ?57.0 °C, ?62.7 °C, ?76.6 °C and ?83.1 °C, respectively. For all the samples, the standard deviation of measurements was less than 3.3 °C, and the absolute error of measurements was theoretically not more than 5.3 °C. These results indicate that this method has acceptable precision and accuracy.     

Sulfur-containing polymers. Synthesis and properties of novel poly(arylene thioether)s based on 2,2-bis(4-mercaptophenyl)propane

Novel poly(arylene thioether)s were synthesised using the one pot polymerisation method from the bis(N,N-dimethyl-S-carbamate) of 2,2-bis(4-mercaptophenyl)propane and activated difluoro aromatic compounds. Each of the polymers, obtained in good yields and with fairly high molecular weights, were characterised by IR, GPC and NMR analyses. In particular, the NMR characterisation was performed using ¹H NMR, ¹³C NMR, DEPT, 2D COSY and 2D HSQC experiments. To study the effect on the thermal properties of replacing the ethereal oxygen atoms with sulfur atoms, we have synthesised the counterparts, the poly(arylene ether)s, with similar molecular weights. We observed that the substitution of the ethereal oxygen atoms with sulfur atoms results in a slightly lower thermal stability for the poly(thioether ketone)s, both under nitrogen and in air, and does not modify the T_g values. For the poly(thioether sulfone), on the other hand, the thermal stability is equal to that of the poly(ether sulfone), while the T_g is 10 °C lower. Furthermore, each sample is completely amorphous, with the exception of one of the poly(thioether ketone)s (sample 1b), which shows the capacity to crystallise, even if with a very slow crystallisation kinetics.