Effect of the NCO/OH ratio on the properties of Mesua Ferrea L. seed oil‐modified polyurethane resins

A series of polyurethane resins with varying NCO/OH ratios (0.8–2.0) has been synthesized from the monoglyceride of Mesua Ferrea L. seed oil, poly(ethylene glycol) (M_n, 200 g mol^?1) and 2,4‐toluene diisocyanate in the presence of dibutyl tin dilaurate as the catalyst. The effects of the NCO/OH ratios of the synthesized resins on the physical properties, such as hydroxy values, acid values, saponification values, iodine values, specific gravities and isocyanate values have been studied. The formation of the polyurethane resins was confirmed by viscosity measurements, and FTIR, UV and ¹H NMR spectroscopic studies. Performance characteristics, such as impact resistance, flexibility, gloss, hardness, adhesive strength and chemical resistance, of the cured resins were investigated as a function of the varying NCO/OH ratios, with an influence of these ratios being observed for most of the above properties. Thermogravimetric analysis (TGA) demonstrated that the thermal stabilities of the cured resins increased with an increase in the NCO/OH ratios. The amounts of char residues at 550 °C were also found to be greater for higher NCO/OH ratios of the oil‐modified polyurethane resins. Copyright © 2005 Society of Chemical Industry     

Synthesis and characterization of organic/inorganic epoxy nanocomposites from poly(aminopropyl/phenyl)silsesquioxanes

Organic/inorganic epoxy nanocomposites containing diglycidyl ether of bisphenol A (DGEBA), 4‐methylhexahydrophthalic anhydride (MHHPA) and poly(aminopropyl/phenyl) silsesquioxanes (PAPPS) were prepared and characterized. PAPPS were synthesized via fluoride‐catalyzed cage formation from random‐structured poly(phenyl)silsesquioxane (PPS) and 3‐aminopropyltriethoxysilane (APTES) in tetrahydrofuran (THF) using tetrabutylammonium fluoride (TBAF) catalyst containing substantial water. The PPS/APTES stoichiometric ratios were varied. The FTIR, ¹H, solid‐state 29 Si‐NMR studies show that PAPPS probably consists of cages, partial cages, and some linear structures containing phenyl and aminopropyl functional groups. The amine content was determined by back titration and elemental analysis. In comparison with neat epoxy, incorporation of these materials can improve the resultant thermal stabilities, raise glass transition temperatures (T_gs), and reduce coefficients of thermal expansion (CTEs) of epoxy nanocomposites as confirmed by TG/DTA, DMA and TMA tests, respectively. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Improving thermal and flame‐retardant properties of epoxy resins by a new imine linkage phosphorous‐containing curing agent

A new reactive phosphorus‐containing curing agent with imine linkage called 4, 4′‐[1, 3‐phenyl‐bis(9, 10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐yl)dimethyneimino)]diphenol (2) was synthesized both via two‐pot and one‐pot procedure. The chemical structure of this curing agent was confirmed by FTIR, ¹H, ¹³C, and ³¹P NMR spectra. A series of thermosetting systems were prepared by using conventional epoxy resins (E51), 4, 4′‐diaminodiphenyl methane (DDM) and (2). Resins with different phosphorus contents were obtained by changing the DDM/(2) molar ratios. Their dynamic mechanical thermal, thermal and flame‐retardant properties were evaluated by dynamic mechanical thermal analysis (DMTA), thermogravimetric analysis (TGA), and limiting oxygen index (LOI), respectively. All samples had a single T_g, which showed that these epoxy resins were homogeneous phase. Both the two char yields under nitrogen and air atmospheres increased with increasing content of (2) and the LOI values increased from 24.5 for standard resin to 37.5 for phosphorus‐containing resin, which indicated that incorporation of (2) could impart good thermal stability and excellent flame retardancy to the conventional epoxy thermosets. POLYM. ENG. SCI., 56:441–447, 2016. © 2016 Society of Plastics Engineers     

Novel propargylether‐terminated monomers containing pyridine and phenyl pendent group: Synthesis,cure, and properties

Two novel propargylether‐terminated resins containing pyridine and bulky phenyl pendent group were prepared from propargyl bromide and different diphenols, and highly thermal stable polymers were obtained by the thermal cure of the monomers. The chemical structures of these novel monomers were well confirmed by FTIR, ¹H‐NMR and elemental analysis. Curing and thermal behavior of the resins were investigated using differential scanning calorimetry (DSC) and dynamic thermogravimetry in argon atmosphere. DSC curves of these two monomers showed a single endothermic peak corresponding to the conformation of chromene ring and homopolymerization of the chromene ring. The temperature at 5% weight loss (T_d5) was higher than 440°C under argon and the highest glass transition temperature (T_g) reached 362°C. The rheological behavior and solubility of the monomer were also investigated. The monomers showed excellent flow‐ability, broad processing window, and great solubility. These results showed that the two resins could be ideal candidates for high‐temperature resistant resins. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40469.     

Improved processibility of silicone composites by MQ silicone resins

Processibilities of silicone composites were always a problem for their high content of SiO₂ powders. This article found that the substitution of silicone resins for linear polydimethylsiloxanes (PDMS) made processibilities easier. Three silicone resins (MQ1.0, MQ1.1, and MQ1.2) with clarified chemical structures (by FT IR, ²⁹Si NMR, and GPC) were adopted. Their shearing viscosities [η()] were greatly higher than PDMS with higher molecular weight, which could be assigned to stronger molecular interactions as surface tension and flowing activation energy ΔE indicated. On the contrary, η() of MQ‐PDMS binary blends greatly decreased to that even lower than either components (about 85% utmost decrease comparing to PDMS), for the variation of molecular interaction rather than dilution effect. Furtherly, when PDMS were partly replaced with MQ resins, process time of PDMS–SiO₂ silicone composites were greatly shortened (from >6 to 2 h), while with better SiO₂ dispersion (Mooney viscosity greatly decreased from 30.0 to 5.0 MU). Better dispersion of SiO₂ fillers in composites could be confirmed by SEM and mechanical properties. For the better dispersion, mechanical properties of composites were improved with higher elastic modulus, higher tensile strength, and higher hardness, especially with higher elongation at break (utmost increased from 190% to 277%). © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46445.     

Star‐shaped POSS–methacrylate copolymers with phenyl–triazole as terminal groups,synthesis, and the pyrolysis analysis

Star‐shaped polyhedral oligomeric silsesquioxane (POSS)–methacrylate hybrid copolymers with phenyl–triazole as terminal groups had been designed and synthesized via sequential atom transfer radical polymerization (ATRP), azidation, and phenylacetylene‐terminated procedures, and the hybrid copolymers here could be denoted as POSS–(PXMA‐Pytl)₈, where X can be M, B, L, and S, represented four different methacrylate monomers, such as methacrylate (MMA), butyl methacrylate (BMA), lauryl methacrylate (LMA), and stearyl methacrylate (SMA), respectively. Thermal gravimetric analysis (TGA) and in situ Fourier transform infrared spectroscopy (FTIR) were applied for studying the thermal stability and degradation mechanism, and it was found that all of the POSS–(PXMA‐Cl)₈ and POSS–(PXMA‐Pytl)₈ copolymers exhibited excellent thermal stabilities, which had great potential in heat‐resistant material application. Different tendencies of decomposition temperatures at 5% and 10% weight loss (T₅ and T₁₀) dependent on the side‐chain length and terminal group species were investigated respectively. The longer alkyl side chains of the monomers, the lower thermal stabilities, and enhanced T₅ and T₁₀ were also shown with the introduction of phenyl–triazole groups instead of chlorine groups. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40652.     

Curing kinetics and structural changes of a of di[(N‐m‐acetenylphenyl) phthalimide] ether/[(methyl) diphenylacetylene] silane copolymer

Differential scanning calorimetry, Fourier transform infrared (FTIR) spectroscopy, and ¹³C‐NMR were used to characterize the curing kinetics and structural changes of a copolymer of di[(N‐m‐acetenylphenyl) phthalimide] ether (DAIE) and [(methyl) diphenylacetylene] silane (MDPES). The results show that the apparent activation energy (E) and reaction order (n) calculated according to the Kissinger method were nearly the same as those calculated according to the Ozawa method. E was 160.4 kJ/mol and n was 0.96 with the Kissinger method, and E was 158.1 kJ/mol and n was 0.95 with the Ozawa method. The FTIR and solid‐state ¹³C‐NMR results also indicate that with increasing curing temperature, the peaks assigned to Si? H and C?C bonded to phenylene carbons decreased, broadened, and finally vanished, whereas the peaks assigned to the C?C carbons and phenyl carbons increased and broadened. Crosslinking reactions in the curing of the DAIE/MDPES copolymer were possible due to the hydrosilylation reaction and the Diels–Alder reaction. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2126–2130, 2006     

Bis[4‐(4‐maleimidephen‐oxy)phenyl]propane/N,N‐4,4′‐bismaleimidodiphenylmethyene blend modified with diallyl bisphenol A

In this article, 2,2′‐bis[4‐(4‐maleimidephen‐oxy)phenyl)]propane (BMPP) resin and N,N‐4,4′‐bismaleimidodiphenylmethyene (BDM) resin blends were modified by diallyl bisphenol A (DABPA). The effects of the mole concentration of BMPP on mechanical properties, fracture toughness, and heat resistance of the modified resins were investigated. Scanning electron microscopy was used to study the microstructure of the fractured modified resins. The introduction of BMPP resin improves the fracture toughness and impact strength of the cured resins, whose thermal stabilities are hardly affected. Dynamic mechanical analysis shows that the modified resins can maintain good mechanical properties at 270.0°C, and their glass transition temperatures (T_g) are above 280.0°C. When the mole ratio of BDM : BMPP is 2 : 1(Code 3), the cured resin performs excellent thermal stability and mechanical property. Its T_g is 298°C, and the Charpy impact strength is 20.46 KJ/m². The plane strain critical stress intensity factor (K_IC) is 1.21 MPa·m^0.5 and the plane strain critical strain energy release rate (G_IC) is 295.64 J/m². Compared with that of BDM/DABPA system, the K_IC and G_IC values of Code 3 are improved by 34.07% and 68.10%, respectively, which show that the modified resin presented good fracture toughness. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40395.     

Synthesis,characterization, and preliminary antimicrobial evaluation of bisphenol‐A formaldehyde resin coordinated with transition metal complexes of ethylenediamine

Coordination polymers containing bisphenol‐A, formaldehyde, and transition metal complexes of ethylenediamine [M(en)₂] were synthesized by the reaction of bisphenol‐A, formaldehyde, and M(en)₂ complex in alkaline medium, using M for Fe⁺³, Co⁺², Ni⁺², Cu⁺², and Zn⁺². The materials were characterized by elemental analysis, FTIR, UV–Vis, ¹H‐NMR spectra, TGA, and magnetic susceptibility measurement. The geometry of the central metal ions was determined by electronic spectral studies and magnetic moment measurement. The M N and C N bonds were confirmed by the IR spectra of the polychelates. The ¹H‐NMR spectra of the chelating resins confirmed polycondensation with well‐defined peaks for bridging methylene functions. Complexation studies with transition metal ions revealed effective coordination of the bisphenol‐A formaldehyde resin. The antimicrobial activities of these chelated resins were screened against E. coli, S. dysantrea (bacteria), and C. albicans, A. niger (fungi) by using agar well diffusion method. All the polymeric chelates show promising antimicrobial activities. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation,characterization, and thermal properties of controllable metal–imidazole complex curing agents for epoxy resins

A series of complexes incorporating the epoxy–imidazole adduct of phenyl glycidyl ether with 2‐ethyl‐4‐methylimidazole (PGE‐EMI), has been prepared with the acetato and chloro transition metal salts of Mn, Co, Ni, Cu, Zn, and Ag. These complexes have been characterized using spectroscopic methods (IR, UV‐Vis, ¹H‐ and ¹³C‐NMR, where appropriate) and their thermal stabilities have been determined using elevated temperature NMR techniques. These high‐temperature NMR results indicated that the chloro complexes studied (of Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺) exist in equilibrium (i.e., they dissociate reversibly in a solution of dimethylsulphoxide, DMSO, at elevated temperatures), while the corresponding acetato complexes dissociate irreversibly. For the silver complexes, thermogravimetric analysis (TGA) was used to monitor the dissociation, showing that the weight loss recorded was consistent with the dissociation of the metal salt to liberate the PGE–imidazole ligand. The thermal stabilities of the metal complexes were influenced by changing both the transition metal (e.g., from Mn to Zn) and varying the anion (e.g., from acetate to chloride). From ¹H‐NMR analysis, a decrease of ca. 10°C was observed in the thermal dissociation of the acetato complexes when compared with the chloro complexes, showing that the series of PGE‐EMI complexes with acetate anions is less thermally stable than the corresponding chlorides. This finding suggests that these PGE‐EMI complexes may be modified to accommodate their use in a variety of different curing schedules when used to cure epoxy resins. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 201–217, 2000     

Preparation and performance of high refractive index silicone resin‐type materials for the packaging of light‐emitting diodes

A novel high refractive index and highly transparent silicone resin‐type material for the packaging of high‐power light‐emitting diodes (LEDs) is introduced, which was synthesized by hydrosilylation of vinyl end‐capped methylphenyl silicone resin and methylphenyl hydrosilicone oil catalyzed by Karstedt's catalyst. The vinyl end‐capped methylphenyl silicone resins were prepared by hydrolysis?polycondensation method from methylphenyl diethoxysilane (MePhSi(OEt)₂), phenyl triethoxysilane (PhSi(OEt)₃), and vinyl dimethylethoxy silane (Me₂ViSiOEt) in toluene/water mixture catalyzed by cation‐exchange resin. The vinyl end‐capped methylphenyl silicone resins were characterized by ¹H‐NMR and Fourier‐transform infrared. The performances of the cured silicone resin‐type materials for LED packaging have been examined in detail. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis,Characterization, and Properties of Multifunctional Epoxy Maleimide Resins

Summary: Novel multifunctional formaldehyde resins bearing diaminodiphenylmethane groups are synthesized by the polymerization of a mixture of diaminodiphenylmethane (DDM), o‐cresol (o‐Cz), and cyclohexanone (CH_x) with formaldehyde (FA) (at a molar ratio of monomers/formaldehyde, 1/1), in the presence of acid catalyst (HCl). The obtained resins are epoxidated with a large excess of epichlorohydrin and transformed into multifunctional epoxy resins. The multifunctional epoxy maleimide resins are obtained by reaction of the epoxy resins with carboxy phenyl maleimide in the presence of triethylamine as a catalyst. The resultant resins are characterized by IR and NMR spectroscopy, elemental, and thermal analysis. The curing and thermal behavior of these epoxy maleimide resin/DDM systems are investigated using differential scanning calorimetry (DSC) and thermogravimetry (TG) techniques. The activation energies of the curing reactions are situated in the range of 53–90 kJ · mol^?1. The cured products have good thermal properties, and activation energies of degradation reactions have values between 42–74 kJ · mol^?1.

The curing reaction of multifunctional epoxy maleimide resins with DDM.     

Synthesis,characterization, and metal ion uptake studies of chelating resins derived from formaldehyde/furfuraldehyde condensed phenolic schiff base of 4,4′‐diaminodiphenylmethane and o‐hydroxyacetophenone

The synthesis, characterization, and metal ion uptake studies of two chelating resins with multiple functional groups are reported. The chelating resins were synthesized by condensing a phenolic Schiff base derived from 4,4′‐diaminodiphenylmethane and o‐hydroxyacetophenone with formaldehyde or furfuraldehyde. The resins readily absorbed transition metal ions, such as Cu²⁺ and Ni²⁺, from dilute aqueous solutions. The Schiff base, resins, and metal polychelates were characterized by various instrumental techniques, such as elemental‐analysis, ultraviolet–visible spectroscopy proton and carbon‐13 nuclear magnetic resonance spectroscopy (¹H‐NMR and ¹³C‐NMR, respectively), X‐ray diffraction (XRD), and thermogravimetric–differential thermogravimetric analyses (TG–DTG). The ¹H‐NMR and ¹³C‐NMR studies were used to determine the sites for aldehyde condensation with the phenolic moiety. Fourier transform infrared data provided evidence for metal–ligand bonding. Thermogravimetric analysis was employed to compare the relative thermal stabilities of the resins and the polychelates. The TG data were fitted into different models and subjected to computational analysis to calculate the kinetic parameters. The XRD data indicate that the incorporation of metal ion into the resin matrix significantly enhanced the degree of crystallinity of the material. The extent of metal‐ion loading into the resins was studied in competitive and noncompetitive conditions, varying the time of contact, metal ion concentrations, and pH of the reaction medium in a suitable buffer medium. The furfuraldehyde‐condensed resin was more effective in removing metal ions than the formaldehyde‐condensed resins. The resins were selective for Cu²⁺, resulting in separation of Cu²⁺ and Ni²⁺ from the mixture at pH 5.89. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 570–581, 2003     

Synthesis and properties of novel phosphorus‐containing bismaleimide/epoxy resins

A novel soluble phosphorus‐containing bismaleimide (BMI) monomer, bis(3‐maleimidophenyl)phenylphosphine oxide (BMIPO), was synthesized by the imidization of bis(3‐aminophenyl) phenylphosphine oxide, in which its structural characterization was identified with ¹H‐NMR, ¹³C‐NMR, and Fourier transform infrared spectra. The BMIPO resin, with five‐membered imide rings and high phenyl density, was an excellent flame retardant with a high glass‐transition temperature (T_g), onset decomposition temperature, and limited oxygen index. In phosphorus‐containing BMI/epoxy/4,4′‐methylene dianiline (DDM)‐cured resins, homogeneous products were obtained from all proportions without phase separation. Because of the higher reactivity of BMIPO/DDM relative to that of 4,4′‐bismaleimidodiphenylmethane (BMIM)/DDM, the increase in the BMIPO/BMIM ratio in this blending resin increased the recrosslinking hazards of the postcuring stage and so lowered the T_g value and thermal stability. The thermal stability of the BMI/epoxy‐cured system was lower than that of the epoxy‐cured system because of the introduction of a phosphide group into BMIPO, whereas for the T_g value and flame retardancy, the former was significantly higher than the latter: the higher the BMIPO content in the blend, the higher the flame retardancy. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2080–2089, 2002; DOI 10.1002/app.10607     

Preparation and properties of halogen-free flame retardant epoxy resins with phosphorus-containing siloxanes

Novel epoxy resin modifiers, DOPO–TMDS and DOPO–DMDP were synthesized by addition reaction of divinylsiloxane with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO). Halogen-free flame retardant epoxy resins were obtained through modification of o-cresol novolac epoxy resin cured by phenol novolac resin using DOPO–TMDS and DOPO–DMDP which were characterized by ¹H NMR, ¹³C NMR, ³¹P NMR and FT-IR measurements. Effects of the phosphorus-containing siloxanes on thermal stabilities, mechanical properties and flame retardant properties of the epoxy resins were investigated. The cured epoxy resins exhibited better mechanical properties and greatly improved flame retardant properties due to the presence of phosphorus-containing siloxanes. The cured epoxy resins with phosphorus loading of 2.0 wt% showed LOI values of 32–33 and achieved UL94V-0 ratings.     

Synthesis and characterization of siloxane-modified epoxy resin

Epoxy resins of the EBS, a bis-p-phenol S modified diglycidyl ether of bis-p-phenol A and the ESBS, a siloxane modified EBS epoxy resin were prepared. Both structures of EBS and ESBS were elucidated with IR,¹H NMR, and¹³C NMR. The near perpendicular comformation of two phenyl rings of sulfone has been introduced into the epoxy resins of EBS und ESBS for Me increase of Me T_g. Some curing and thermal characteristics of these modified EBS and ESBS epoxy resins were studied. The curing patterns of ESBS and ESBS indicated the similarity with that of the DGEBA epoxy resins. T_g measurements resulted an increasing order of We ESBS (T_g of 141 °C), EBS (T_g of 135 °C) and then followed by Epons 1004 (T_g of 104 °C), 1001 (T_g of 101 °C) and 828 (T_g of 100 °C) in samples tested under the same conditions. Thus the substantial improvement of the thermal stability of the modified epoxy resins was indicated. Compatibility characteristics of the EBS and ESBS as indicated by the SEM/EDS is that an ESBS up to 30 % of the siloxane content was found to be compatible but not miscible with the Epon, a phenolic epoxy resin of DGEBA.     

Synthesis of a novel curing agent containing organophosphorus and its application in flame‐retarded epoxy resins

A novel amine‐terminated and organophosphorus‐containing compound m‐aminophenylene phenyl phosphine oxide oligomer (APPPOO) was synthesized and used as curing and flame‐retarding agent for epoxy resins. Its chemical structure was characterized by Fourier transform infrared (FTIR) spectroscopy, ¹H nuclear magnetic resonance (¹H NMR), ¹³C nuclear magnetic resonance, and ³¹P nuclear magnetic resonance. The flame‐retardant properties, combusting performances, and thermal degradation behaviors of the cured epoxy resins were investigated by limiting oxygen index (LOI), vertical burning test (UL‐94), cone calorimeter test, and thermogravimetric analysis. The EPO/APPPOO thermosets passed V‐1 rating with the thickness of 3.0 mm and the LOI value reached 34.8%. The thermosets could pass V‐2 rating when the thickness of the samples was 1.6 mm. The cone calorimeter test demonstrated that the parameters of EPO/APPPOO thermosets including heat release rate and total heat release significantly decreased compared with EPO/PDA thermosets. Scanning electron microscopy revealed that the incorporation of APPPOO into epoxy resins obviously accelerated the formation of the compact and stronger char layer to improve flame‐retardant properties of the cured epoxy resins during combustion. The mechanical properties and water resistance of the cured epoxy resins were also measured. After the water‐resistance test, EPO/APPPOO thermosets still remained excellent flame retardant and the water uptake was only 0.4%. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41159.     

Synthesis,characterization, and properties of silicone–epoxy resins

Silicone–epoxy (SiE) resins were synthesized through the hydrolytic condensation of 2‐(3,4‐epoxycyclohexylethyl) methyldiethoxysilane (EMDS) and the cohydrolytic condensation of EMDS with dimethyldiethoxysilane. Structural characterization was carried out by ¹H‐NMR, ²⁹Si‐NMR, and mass spectrometry analysis; the resins were linear oligomers bearing different numbers of pendant epoxy groups, and the average number of repeat Si O units ranged from 6 to 11. Methyhexahydrophthalic anhydride was used to cure the SiE resins to give glassy materials with high optical clarity. The cured SiE resins showed better thermal stability and higher thermal and UV resistances than a commercial light‐emitting diode package material (an epoxy resin named CEL‐2021P). The effect of the epoxy value on the thermal and mechanical properties and the thermal and UV aging performances of the cured SiE resins were investigated. The SiE resins became more flexible with decreasing epoxy value, and the resin with the moderate epoxy value had the highest thermal and UV resistances. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Bismaleimide‐modified methyl‐di(phenylethynyl)silane blends and composites: Cure characteristics,thermal stability,and mechanical property

Reactive blends of organic‐inorganic hybrid monomer, methyl‐di(phenylethynyl)silane (MDPES) and a modified bismaleimide resin (BMI/DBA) have been prepared. The thermal and oxidative stabilities of MDPES‐BMI/DBA blends were characterized by thermogravimetric analysis, derivative thermogravimetry, differential thermal analysis, dynamic mechanical analysis, and flexural strength retention at 240°C. Scanning electron microscopy was employed to study the surface morphology of MDPES‐BMI/DBA composite after thermal oxidative treatment. With the increase of concentration of BMI/DBA, flexural strength of composites increased from 78 to 331 MPa. The results showed that MDPES‐BMI/DBA blends exhibited excellent thermal and thermal oxidative properties, and the interface between MDPES and glass fiber was improved by the incorporation of BMI/DBA. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis,structures, and density functional theory computational study of thiophene‐containing and fluorodecorated imine‐linked polymers

A new series of extended–conjugated and thermally stable thiophene‐containing imine‐linked polymers were synthesized via a Schiff‐base condensation reaction between aryl aldehydes and 2,6‐diaminopyridine building blocks. The backbones of the polymers were functionalized with phenyl, fluorosubstituted phenyl, thienyl, and pyridyl aromatic rings. The successful synthesis was confirmed with spectrochemical characterization techniques, including IR, ¹H‐NMR, ¹³C‐NMR, and elemental analyses. The electronic properties of the polymers were investigated with ultraviolet–visible (UV–vis) absorption spectroscopy; the properties were collected experimentally and calculated with density functional theory (DFT) in the gas phase. The maximum absorption calculated from DFT was higher than the experimental values by about 60 nm; this was attributed to the absence of the solvent effect in the DFT case. The frontier molecular orbital ((HOMO) highest occupied molecular orbital and (LUMO) lowest unoccupied molecular orbital), optical band gap (E_g), and total energy (E_T) values of the optimized structures were calculated. Apparently, there was a significant relation between the number of thiophene rings and the resulting E_g and E_T values. As the number of thiophene rings in the polymer chain increased, E_g and E_T decreased, and the thermal stability of the polymers increased. E_g and the absorption band edges were determined experimentally from the UV–vis and transmittance spectra, respectively. Poly(terthienyl–azomethine–pyridine–azomethine), with the highest thiophene content, had the lowest experimental and calculated E_g values (2.10 and 2.63 eV, respectively). In contrast, upon fluorination, poly[(2,5‐dithienyl–1,4‐difluorobenzene)–azomethine–pyridine–azomethine] exhibited the highest E_g (2.81 eV) and absorption band edges (2.94 eV), whereas the thermal stability decreased to 250 °C. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44331.