Formation of crystalline macrocyclic phases during electrophilic precipitation-polycondensation syntheses of poly(arylene ether ketone)s

Elongated crystalline particles formed as by-products during poly(arylene ether ketone) synthesis by electrophilic precipitation-polycondensation of 4,4′-diphenoxybenzophenone with terephthaloyl chloride or isophthaloyl chloride, thought previously to be polymer-whiskers, have now been identified as macrocyclic phases. Single crystal X-ray analysis of the needle-like particles formed in the reaction with terephthaloyl chloride, using the microdiffraction technique with synchrotron radiation, revealed that they consist of a macrocylic compound containing ten phenylene units, i.e. the [2+2] cyclic dimer. An analogous structure has also been demonstrated for the corresponding macrocycle derived from the reaction of 4,4′-diphenoxybenzophenone with isophthaloyl chloride. Chloroform extraction of the products of the two polycondensations dissolved the macrocyclic material (but not the linear polymer), and analysis of the extracts by MALDI-TOF mass spectrometry demonstrated the presence in both cases of homologous families of macrocyclic products. Higher yields of macrocycles were obtained under pseudo-high dilution conditions, enabling the [2+2] cyclodimers from reactions of 4,4′-diphenoxybenzophenone with both terephthaloyl and isophthaloyl chloride to be isolated as pure compounds and fully characterised.     

Emulsion atom transfer radical polymerization of 2-ethylhexyl methacrylate

The emulsion atom transfer radical polymerization (ATRP) of 2-ethylhexyl methacrylate (EHMA) was carried out with ethyl 2-bromoisobutyrate (EBiB) as an initiator and copper bromide (CuBr)/4,4′-dinonyl-2,2′-bipyridyl (dNbpy) as a catalyst system. The effects of surfactant type and concentration, temperature, monomer/initiator ratio, and CuBr₂ addition on the system livingness, polymer molecular weight control, and latex stability were examined in detail. It was found that the polymerization systems with Tween 80 and Brij 98 as surfactants at 30 °C gave the best latex stability. The polymer samples prepared under these conditions had narrow molecular weight distributions (M_w/M_n=1.1-1.2) and linear relationships of number-average molecular weight versus monomer conversion.     

Synthesis and properties of polyimides from isomeric bis(dicarboxylphenylthio)diphenyl sulfone dianhydrides

4,4′-Bis(3,4-dicarboxyphenylthio)diphenyl sulfone dianhydride(4,4′-PTPSDA) and 4,4′-bis(2,3-dicarboxyphenylthio)diphenyl sulfone dianhydride(3,3′-PTPSDA) were synthesized from chlorophthalic anhydrides and bis(4-mercaptophenyl)sulfone. Their structures were determined via IR spectra, ¹H NMR and elemental analysis. A series of polyimides were prepared from isomeric PTPSDAs and aromatic diamines in 1-methyl-2-pyrrolidinone (NMP) via the conventional two-step method. Polyimides based on 4,4′-PTPSDA and 3,3′-PTPSDA have good solubility in polar aprotic solvents and phenols. The 5% weight-loss temperatures of isomeric polyimides were near 500 °C in N₂. DMTA and DSC analyses indicated that the glass-transition temperatures of polyimides from 3,3′-PTPSDA are higher than those of polyimides from 4,4′-PTPSDA. The wide-angle X-ray diffraction showed that all polyimides are amorphous. The polyimides from 3,3′-PTPSDA showed higher permeability but lower permselectivity compared with those from 4,4′-PTPSDA.     

Crosslinkable fully aromatic poly(aryl ether ketone)s bearing macrocycle of aryl ether ketone

A novel bisphenol monomer, (3-methoxy)phenylhydroquinone, was synthesized via a three-step synthetic procedure. The cyclization of the bisphenol monomer and 4,4-difluorobenzophenone was carried out under pseudo high dilution condition. Two types of fully aromatic poly(aryl ether ketone)s were prepared by copolymerization of macrocycle of aryl ether ketone (MACEK) containing hydroxyphenyl, 4,4′-(hexafluoroisopropylidene)diphenol (HFBPA), and 4,4-difluorobenzophenone. The copolymers have high molecular mass, good solubility and high glass transition temperatures. The copolymers are crosslinkable in the presence of basic initiator and the glass transition temperatures of the copolymers increased greatly after the curing. These cured copolymers exhibit excellent thermal stability, and the 5% weight loss temperatures are around 500 °C in nitrogen.     

Synthesis of novel maleimide-terminated thioetherimide oligomer and its bulk copolymerization with reactive solvents

This paper reports the synthesis of a novel maleimide-terminated thioetherimide oligomer and its copolymerization with reactive solvents bearing vinyl. Starting from 3-chlorophthalic anhydride and 4-chlorophthalic anhydride, 2,2′,3,3′-thiodiphenyl tertracaboxylic dianhydride (3,3′-TDPA) and 3,3′,4,4′-thiodiphenyl tertracaboxylic dianhydride (4,4′-TDPA) were synthesized. Thereby, a novel maleimide-terminated thioetherimide oligomer was prepared from. 3,3′-TDPA, 4,4′-TDPA, 3,3′-dimethyl-4,4′-diaminodiphenylmethane (DMMDA) and maleic anhydride. Binary and ternary copolymer resin were derived from corresponding binary and ternary homogeous solution consisting of thioetherimide oligomer, reactive solvent N-vinylpyrrolidone (NVP) or N,N′-dimethylacrylamide (DMAA) and divinylbenzene (DVB) as modifier, initiated either by gamma ray irradiation or by benzoyl peroxide (BPO). Thermal and mechanical properties of copolymer resin are determined and compared in terms of the kind of reactive solvent, addition of modifier DVB. The effect of initiation approach on property of final copolymer resin were studied. Phase separation and sub-transition of ternary copolymer resin induced by BPO are observed, which could be accounted for by thermal movement of DMAA molecules during thermal initiation. Structure-property relationship of copolymer resin was discussed. The effect of monomer molar ratio of 3,3′-TDPA and 4,4′-TDPA on thermal and mechanical properties were investigated.     

Novel polyimides derived from 2,3,3′,4′-benzophenonetetracarboxylic dianhydride

A series of polyimides (PIs) based on 2,3,3′,4′-benzophenonetetracarboxylic dianhydride (2,3,3′,4′-BTDA) and 3,3′,4,4′-BTDA were prepared by the conventional two-step process. The properties of the 2,3,3′,4′-BTDA based polyimides were compared with those of polyimides prepared from 3,3′,4,4′-BTDA. It was found that PIs from 2,3,3′,4′-BTDA have higher glass transition temperature and better solubility without sacrificing their thermal properties. Furthermore the rheological properties of PMR-15 type polyimide resins based on 2,3,3′,4′-BTDA showed lower melt viscosity and wider melt flow region (flow window) compared with those from 3,3′,4,4′-BTDA. The structure-property relations resulted from isomerism were discussed.     

Photocrosslinking of poly(ethylene terephthalate) copolymers containing photoreactive comonomers

Poly(ethylene terephthalate) (PET) copolymers containing 4,4′-, 3,5-, and 2,4-benzophenone dicarboxylate chromophores have been synthesized by transesterification of PET with benzophenone 4,4′-dicarboxylic acid (4,4′-BDA), dimethyl benzophenone 4,4′-dicarboxylate (4,4′-BDE), dimethyl benzophenone 3,5-dicarboxylate (3,5-BDE) and dimethyl benzophenone 2,4-dicarboxylate (2,4-BDE). The benzophenone segments in the backbone induce photocrosslinking upon UV irradiation in the solid state most probably by a hydrogen atom abstraction mechanism. The crosslinking rate depends upon the concentration and the structure of chromophores as evidenced by gel content measurements. The photocrosslinking efficiency of 4,4′-benzophenone dicarboxylate containing polymers is higher than for 2,4- or 3,5-benzophenone dicarboxylate containing polymers. Photocrosslinked PET copolymers show increased glass transition temperatures and broadening of melting transitions.     

Efficiency of ligands in atom transfer radical polymerization of lauryl methacrylate and block copolymerization with methyl methacrylate

Atom transfer radical polymerization of lauryl methacrylate (LMA) was carried out in the presence of various ligands using ethyl-2-bromoisobutyrate as initiator and CuBr as catalyst in toluene at 95 °C. The ligands used were 2,2′-bipyridyl,4,4′-dimethyl-2,2′-bipyridyl, N,N,N′,N′,N″-pentamethyldiethylenetriamine (PMDETA) and N-(n-propyl)-2-pyridylmethanimine (PPMI). Controlled polymerization was observed with PMDETA and PPMI ligands and poly(LMA)s with narrow molecular weight distribution (MWD) (M_w/M_n≤1.2) were obtained. The first-order time-conversion plot showed the presence of termination in the presence of PMDETA. A linear first-order time-conversion plot with a small induction period (∼10 min) was observed in the presence of PPMI ligand. Di-block copolymers of LMA and methylmethacrylate with controlled molecular weight and narrow MWDs were synthesized via sequential monomer addition.     

The effect of the length of the oxyethylene chain on the conductivity of the polyurethaneurea electrolyte

Polyurethaneureas (PUU), which were synthesized from 4,4′-diphenylmethane diisocyanate (MDI), poly(ethylene glycol) (PEG), and 3,5-diaminobanzoic acid (DABA), were used as polyelectrolytes in this study. Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR) were used to monitor the effect of the various kinds of PEG on the changes in morphology of PUU electrolytes corresponding to the concentration of lithium perchlorate (LiClO₄) dopants. The results of DSC and FT-IR indicate the Li⁺ ions coordinate with the soft and hard segments. Additionally, the crystallinity of the PEG soft segment and the ordered hydrogen-bonded urea carbonyl groups decreased with increasing salt concentration. Impedance spectroscopy (IS) measurements show that the PUU electrolyte with the high phase separation degree has the high ionic conductivity. The hard-segment T_g and the soft-segment T_m influence the conductivity behavior of polyelectrolytes with increasing measurement temperature.     

Synthesis of cationic polyacrylamide by aqueous two‐phase polymerization in poly(ethylene glycol) chloride solution

Aqueous two‐phase copolymerization of acrylamide(AM) and acryloyloxyethyl trimethyl ammonium chloride (DAC) was performed in poly(ethylene glycol) (PEG) solution and in PEG chloride(Cl‐PEG) solution, respectively. Series of cationic polyacrylamide(CPAM) aqueous dispersion were prepared using potassium persulfate (KPS) as initiator. The effect of total amount of monomers, the dosage of initiator, the content of dispersant, the mass ratio of AM to DAC, and the temperature on the conversion, molecular weight, cationic degree, and stability of aqueous dispersion were studied in detail. It is found that the increase of initiator and reaction temperature resulted in the increase of the final conversion, whereas the increase of DAC and PEG concentration resulted in the decrease of the final conversion. The optimum reaction conditions of synthesis were as follows: (1) PEG‐H₂O system: PEG 7.5 g, AM 8 g, DAC 2 g, KPS 0.05 g, H₂O 100 mL, 70°C. In this process conditions, the molecular weight of CPAM was 3.21 × 10⁶, the cationic degree of CPAM was 24.4%, the storage stability of the aqueous dispersion was over 3 months. (2) Cl‐PEG‐H₂O system: Cl‐PEG 7.5 g, AM 8 g, DAC 2 g, KPS 0.05 g, H₂O 100 mL, 65°C. In this process conditions, the molecular weight was 3.68 × 10⁶, the cationic degree was 23.3%, and the storage stability of the aqueous dispersion was over 6 months. In general, the stability of CPAM aqueous dispersion in Cl‐PEG system is much better than in PEG system. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Polymer encapsulation of surface-modified carbon blacks using surfactant-free emulsion polymerisation

Polymer encapsulations of two different grades of water-dispersible, surface-sulfonated carbon black, Sterling-4620 with an aggregate size of 260 nm and Black Pearls-800 (BP-800) with an aggregate size of 45.7 nm, were carried out using surfactant-free emulsion polymerisation of butyl acrylate, methyl methacrylate and allyl methacrylate. High levels of initiator were required because carbon black acts as an efficient radical trap. Although polymerisation in the presence of Sterling-4620 proceeded satisfactorily using ammonium persulfate (APS), the much larger specific surface area of BP-800 inhibited polymerisation with APS and the sodium salt of 4,4′-azobis(4-cyanopentanoic acid), a non-oxidising initiator, was necessary for effective polymerisation in the presence of BP-800. Several polymer-encapsulated Sterling-4620 and BP-800 products were prepared successfully using different amounts and compositions of polymer, and have been characterised using solvent extraction, pyrolysis, thermogravimetry, infrared spectroscopy, transmission electron microscopy, differential scanning calorimetry and dynamic mechanical thermal analysis.     

Synthesis and characterization of thermotropic liquid crystalline poly(azomethine ether)s

Two series of monomers, namely 4,4′-diformyl-α,ω-diphenoxydecane and 4,4′-diformyl-3,3-methoxy-α,ω-diphenoxydecane, were prepared from 1,10-dibromodecane with p-hydroxybenzaldehyde and 4-hydroxy-3-methoxybenzaldehyde (vanillin), respectively. The poly(azomethine ether)s were prepared by solution polycondensation using 4,4′-diformyl-α,ω-diphenoxydecane, 4,4′-diformyl-3,3-methoxy-α,ω-diphenoxydecane with various diamines. The monomers and polymers were characterized by intrinsic viscosity, FT-IR, ¹H, and ¹³C NMR spectroscopy. The thermogravimetric analysis reveals that the polymers are stable up to 320-500 °C and decomposed with good char yield. The thermotropic liquid crystalline properties of the polymers were examined by differential scanning calorimetry (DSC) and their textures observed under hot stage optical polarized microscopy (HOPM). All the polymers were exhibited thermotropic liquid crystalline properties except tetramethylene diamines-based polymers.     

Synthesis and nonvolatile memory characteristics of thermally, dimensionally and chemically stable polyimides

A series of soluble poly(amic acid) precursors were prepared from a new carbzole-containing monomer, 3,3′-bis[9-carbazole(ethyloxy)biphenyl]-4,4′-diamine (HAB-CBZ) by polycondensation with four different aromatic dianhydrides: pyromellitic dianhydride (PMDA), 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), 3,3′,4,4′-diphenylethertetracarboxylic dianhydride (ODPA), and 3,3′,4,4′-diphenylsulfonyltetracarboxylic dianhydride (DSDA). From the precursors, nanoscale thin films of polyimides (PIs) were prepared by spin-coating and subsequent thermal imidization. All the PIs exhibited excellent thermal and dimensional stability. In particular, the PIs based on the PMDA and BPDA units revealed excellent chemical resistance to organic solvents, in addition to the high thermal and dimensional stability, which are required for the fabrication of high performance memory devices in three-dimensionally multi-stack structure. Devices fabricated with nanoscale thin PI films exhibited excellent unipolar write-once-read-many-times (WORM) memory behavior with a high ON/OFF current ratio of up to 10¹⁰. The active PI films were found to operate at 2.2-3.3 V, depending on the chemical structures. This study found that the imide rings as local charge trap sites are necessary to enhance the memory performance in addition to carbazole moiety. All the results collectively indicate that the thermally, dimensionally and chemically stable PIs of this study are a promising material for the mass production at low cost of high performance, programmable nonvolatile WORM memory devices that can be operated with low power consumption in unipolar switching mode.     

Copolyimides with trifluoromethyl or methoxy substituents. NMR characterization

In the first stage, a series of aromatic diamine compounds such as 2-methoxy-5,4′-diaminodiphenyl ether (ODAOMe) and 2-trifluomethyl-4,4′-diaminodiphenyl ether (ODACF₃) were synthesized. These aromatic diamines and 4,4′-diaminodiphenyl ether (ODA) were then used to prepare copolyimides with 4,4′-oxydiphthalic anhydride (ODPA) and bicyclo[2.2.2]-oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BCDA). Both chemical composition and the arrangements of repetitive units were characterized by ¹H and ¹⁹F NMR. It was shown that solubility and thermal stability are related to the BCDA fraction in the copolymers and to the chemical structure of the diamine.     

Bifunctional initiators

Summary Acrylamide was polymerized by both thermolysis and photolysis of the 4,4-azo-bis-(4-cyanovaleryl)-bis-(m-chlorobenzoyl) diperoxide as initiator. The molecular weight and the conversion depend on polymerization duration and initiator concentration. The sequential character of the initiator was proved by the two stage polymerization of acrylamide when the obtained molecular weights were twice as compared to those of the one stage process.     

Copolymer of cyclohexanone-formaldehyde resin and polystyrene

The reaction product of cyclohexanone-formaldehyde resin with an acid chloride of a radical initiator, 4,4′-azo-bis(4-cyano pentanoic acid) was used as initiator for styrene polymerization to form a cyclohexanone-formaldehyde resin/polystyrene copolymer. The copolymer showed similar solubility as polystyrene.     

Acrylamide-styrene copolymerization with the 4,4′-azo-bis-(4-cyanovaleryl)-bis-(m-chlorobenzoyl) diperoxide azoperoxy initiator

Summary The copolymerization of acrylamide with acrylic acid by use of 4,4-azo-bis-(4-cyanovaleryl)-bis-(m-chlorobenzoyl) diperoxide as initiator was studied. The thermolysis or photolysis of the mentioned initiator was studied. The thermolysis or photolysis of the mentioned initiator was used to prepare polystyrene with final peroxidic groups, which was further reacted with acrylamide to yield poly(styrene-acrylamide).     

Facile preparation of poly(N-isopropylacrylamide)-based hydrogels via aqueous Diels-Alder click reaction

The study reports a facile method of preparing poly(N-isopropylacrylamide)- based hydrogels by means of the Diels-Alder reaction. First, polymeric dienes were synthesized by free radical copolymerization between N-isopropylacrylamide (NIPA) and furfuryl methacrylate (FM), with 2, 2′-azobisisobutyronitrile (AIBN) as an initiator, and polymeric dienophile was obtained by a coupling reaction of poly(ethylene glycol) (PEG) and N-maleoyl-l-leucine (LMI) under N, N′-dicyclohexylcarbodiimide (DCC). Afterwards, the resultant dienes and dienophiles were dissolved in water and put in a refrigerator remaining a temperature of 9 °C, gelation via Diels-Alder reaction was observed after some time. The samples obtained at different steps were characterized by FTIR, NMR, GPC, SEM, CD, etc. It was found that LCST of copolymers decreases with the increase of FM content in copolymers. And the disassembly time of the hydrogels is closely related to the temperature and the solvents used. The swelling behavior study by gravimetric measurement indicates the hydrogels possess thermosensitivity and exhibit considerable swelling in water. Due to the simplicity of synthesis and no need for initiator or catalyzer and organic solvent, the strategy described here could find a promising application in the preparation of hydrogels.     

Copolyimides from 2,3,3′,4′-biphenyltetracarboxylic dianhydride and pyromellitic dianhydride with 4,4′-oxydianiline

A series of copolyimides were prepared via the polyamide acids (polyamic acids) from the reaction of 2,3,3′,4′-biphenyltetracarboxylic dianhydride (a-BPDA) and pyromellitic dianhydride (PMDA) with 4,4′-oxydianiline (4,4′-ODA) at dianhydride molar ratios of 9:1, 7:3, 1:1, 3:7 and 1:9. Homopolymers and a 1:1 polymer blend were also prepared. Films from the 7:3, 1:1 and 3:7 molar ratio polyamide acids reacted for 5-6 h at ambient temperature were brittle, whereas films from the same polyamide acids reacted for 24-48 h at ambient temperature were fingernail creaseable. The difference was apparently due to the initial formation of incompatible block domains that underway randomization upon longer reaction time. The differential scanning calorimetric (DSC) curves of some of the brittle films quenched after heating to 400 °C had two apparent glass transition temperatures (T_gs), indicative of two block domains. The creaseable films quenched after heating to 400 °C had single T_gs. Wide-angle X-ray diffraction showed all films to be amorphous even though the initial DSC curves showed strong endothermic peaks, generally associated with crystalline melts. These strong endotherms near the T_g region were thought to be due to relaxation of regions in the highly stressed films. Films of copolyamide acids from the reaction of 1:1 molar ratios of 3,3′,4,4′-oxydiphthalic anhydride/a-BPDA and 3,3′,4,4′-biphenyltetracarboxylic dianhydride/a-BPDA with 4,4′-ODA reacted for 6 h were fingernail creaseable. The chemistry and the properties of the copolymers are compared with those of the homopolymers.     

Magnetoelectrochemistry of 4,4′-bis(dimethylamino)biphenyl and 4,4′-dinitrobiphenyl azacrown macrocyclic lactams

The voltammetric behaviour at carbon fibre microelectrodes under the application of static magnetic fields of two series of macrolactams containing in their structure 4,4′-bis(dimethylamino)biphenyl or 4,4′-dinitrobiphenyl groups in MeCN solution is described. The response of 4,4′-dinitrobiphenyl receptors is dominated by two successive one-electron reduction processes at −0.9 and −1.6 V versus AgCl/Ag. 4,4′-bis(dimethylamino)biphenyl-containing receptors display two one-electron oxidations above +0.8 and +1.0 V. In both cases, a dihedral/planar interconversion precedes the second electron transfer step. Upon application of moderate (0.05-0.2 T) static magnetic fields to the electrochemical cell, the rate of such dihedral/planar interconversion is lowered for both the reduction of 4,4′-dinitrobiphenyl receptors and the oxidation of 4,4′-bis(dimethylamino)biphenyl lactams. The electrochemical response of N-methylated receptors, for which different cisoid-cisoid, cisoid-transoid, and transoid-transoid forms exist, exhibits a significant peak splitting that can be associated to the presence of such conformational isomers. Application of magnetic fields produces a relative enhancement of some peaks that can be interpreted in terms of differential magnetoconvection involving such conformational isomers.