Preparation and properties of novel thermally stable pyridine‐based poly(amide imide amide)s

The 2,6‐bis(4‐nitrobenzamido)pyridine was prepared via reaction of 2,6‐diaminopyridine with two moles of 4‐nitrobenzoyl chloride in the presence of propylene oxide. Catalytic reduction of nitro groups of 2,6‐bis(4‐nitrobenzamido)pyridine with hydrazine yielded 2,6‐bis(4‐aminobenzamido)pyridine. Reaction of this diamine with two moles of trimellitic anhydride afforded a diacid with preformed amide and imide structures. Poly(amide imide amide)s were prepared by direct polycondensation reactions of the diacid with different diamines in the presence of triphenyl phosphite. All the precursors and polymers were fully characterized using common spectroscopic methods and elemental analysis and physical properties of the polymers including solution viscosity, thermal stability, thermal behavior, and solubility were studied. According to the obtained results the polymers showed high thermal stability and enhanced solubility. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

PFG‐NMR measurement of self‐diffusion coefficients of long‐chain α‐olefins and their mixtures in semi‐crystalline polyethylene

The self‐diffusion coefficients of C6–C16 long‐chain α‐olefins and their mixtures in semi‐crystalline polyethylene were measured through the pulsed field gradient nuclear magnetic resonance (PFG‐NMR). The effects of chain length, polyethylene (PE) type, and co‐monomer type in PE on the diffusion coefficients were investigated. Moreover, the influence of halohydrocarbon, cycloalkanes, and arene solvents on the diffusion coefficients of C12 α‐olefin in PE was characterized. The results have demonstrated that the diffusion coefficient of the single‐component α‐olefin in PE decreases exponentially with the increase of the carbon number of α‐olefin, and the crystallinity and crystal morphology of PE play a more important role than the co‐monomer type in determining the diffusion coefficients of α‐olefins. In addition, the apparent diffusion coefficients were used to represent the diffusion behaviors of the α‐olefin mixtures in PE. Owing to the presence of other hydrocarbon solvents, namely trichloromethane, cyclohexane, and benzene, the diffusion coefficients of C12 long‐chain α‐olefin in PE are significantly enhanced, and such promoting effect of the hydrocarbon solvents in polyolefin elastomer (POE) is much stronger than those in high‐density polyethylene (HDPE) and linear low‐density polyethylene (LLDPE). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44143.     

Synthesis and thermal properties of bismaleimides with mesogen aromatic amide–ester and flexible polymethylenic group

Four bismaleimides with mesogen “amide–ester” aromatic and flexible polymethylenic group variable length (8 ≤ n ≤ 11) were synthesized in two stages, producing yields exceeding 80%. These bismaleimides (BMIs) were obtained after several purifications by dissolution—precipitation in dimethylformamide–methanol (1/4) with over 94% purity (high‐performance liquid chromatography). These pure BMIs were characterized by nuclear magnetic resonance, Fourier transform infrared spectroscopy, and elemental analysis and studied by differential scanning calorimetry, thermogravimetric analysis, polarized light microscopy, and X‐ray diffraction. Solubilities and thermal properties show effects of parity. The even BMIs are more difficult to solubilize than the odd BMI. The melting points of the even BMI (approximately, 220°C) are far higher than those of odd BMI (approximately, 160°C). Crosslinking temperatures of even BMI are close to 230°C, whereas odd BMI crosslinking temperatures are higher (approximately, 250°C). Even BMIs give rise to a liquid crystal state upon melting. Under the same conditions, odd BMIs give rise to an amorphous state; however, after crosslinking, the four bismaleimides give rise to an ordered liquid crystal state of smectic type. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Identification of relationship between the synthesis/process parameters and properties of a sol–gel‐derived polymer nanocomposite system

A Ti‐containing silicate‐based epoxy‐functional polymer nanocomposite system was synthesized by a sol–gel route with or without the introduction of a reflux process, which was followed by UV‐induced epoxy polymerization. Influences of synthesis and process parameters, including Ti content, sol ageing, reflux process, and UV‐irradiation on various properties of the system were detailed. It was demonstrated that the introduction of a reflux process during the sol–gel synthesis could significantly modify the chemical and physical properties of the resultant material system along with other parameters such as Ti content. Overall results showed that the synthesis and process parameters examined could be employed to modify the microstructure, and to tune the final properties of this polymer nanocomposite system. The technique described herein, therefore, could be used to develop a new process regime to obtain materials of this type with desired properties, which might potentially be employed in certain applications such as dental restoration. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and characterizations of hydrophobically associating water‐soluble polymer with nonionic surfmer

In this article, a hydrophobically associating copolymer (2‐acrylamido)‐2‐methylpropanesulfonic acid (AMPS)/AA‐EO₂₅C₁₂ was synthesized by AMPS and nonionic surfmer AA‐EO₂₅C₁₂ through free radical copolymerization. The structure of copolymer was characterized by FT‐IR and ¹H‐NMR. The properties of copolymer were studied and the results indicated that the copolymer exhibits good thickening ability due to intermolecular hydrophobic associations as the apparent viscosity of the copolymer solution increases sharply with increasing polymer concentration. Compared with homopolymer PAMPS, the rheological test indicates that the copolymer solution shows shear thickening behavior at low shear rate region. Besides, the copolymer exhibits interfacial activity as it can reduce the interfacial tension to 10° level, and ability to form emulsion with good stability, which is due to successfully introducing the structure of nonionic surfmer AA‐EO₂₅C₁₂ to the polymer chain. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43195.     

Preparation and ionic conductive properties of all‐solid polymer electrolytes based on multiarm star block polymers

A series of star block polymers with a hyperbranched core and 26 arms are successfully synthesized by atom transfer radical polymerization of styrene (St), and poly(ethylene glycol) methyl ether methacrylate from a hyperbranched polystyrene (HBPS) multifunctional initiator. All‐solid polymer electrolytes composed of these multiarm star polymers and lithium salts are prepared. The influences of polyoxyethylene (PEO) side‐chain length, PEO content, lithium salt concentration and type, and the structure of polymer on ionic conductivity are systematically investigated. The resulting polymer electrolyte with the longest PEO side chains exhibits the best ionic conductive properties. The maximum conductivity is 0.8 × 10^?4 S cm^?1 at 25°C with EO/Li = 30. All the prepared multiarm star block polymers possess good thermal stability. The mechanical property is greatly improved owing to the existence of polystyrene blocks in the multiarm star polymer molecules, and flexible films can be obtained by solution‐casting technique. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

An m‐phenylenediamine‐based benzoxazine with favorable processability and its high‐performance thermoset

A novel aromatic diamine‐based benzoxazine (P‐mPDA) is successfully synthesized from m‐phenylenediamine (m‐PDA), 2‐hydroxybenzaldehyde, and formaldehyde. The polymerization behavior of P‐mPDA and the properties of its thermoset are studied. The results indicate that P‐mPDA owns favorable processability including low polymerization temperature, low liquefying temperature, and wide processing window. Even lower polymerization temperature (polymerization onset temperature as low as 80 °C) can be achieved by the promotion of catalysts. The ring‐opening polymerization of P‐mPDA first generates polybenzoxazine with N, O‐acetal‐type structure and arylamine Mannich‐type structure, following which rearrangement from N, O‐acetal‐type structure to phenolic Mannich‐type structure proceeds at elevated temperature. Furthermore, the polymerized P‐mPDA shows outstanding performance such as extremely high glass transition temperature (T_g) of 280 °C, high char yield above 53% at 800 °C under nitrogen and excellent mechanical property. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43368.     

Influence of hydrogen‐bonding interaction introduced by filled oligomer on bulk properties of blended polyimide films

Specific structure oligomer is designed and synthesized to fill “blank interaction points” left among polyimide (PI) rigid‐rod structure in order to further enhance the interaction between PI macromolecules. An oligomer, 4,4′‐bisbenzamide diphenyl ether (BADE) containing amide groups as proton donor, was blended with polyamic acid (PAA) solution to modify PI of pyromellitic dianhydride and 4,4′‐oxydianiline. Fourier transform infrared and dynamic mechanical analyses show that hydrogen‐bonding interaction occurs between N? H groups and PI chains. This resulted interchain interaction increases the tensile strength of blended PI films from 115.9 to 135.6 MPa, about 17.0% improvement, with BADE content surprisingly up to 20 wt %. BADE is uniformly dispersed without aggregation within a saturated amount of 20 wt % through wide angle X‐ray diffraction and morphology characterization. Moreover, rheological measurements indicate that the processability of PAA solution is maintained after introduction of BADE. The obtained PI films still have excellent thermal stability. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40498.     

Synthesis and characterization of a propargyl‐substituted polycarbosilane with high ceramic yield

A propargyl‐substituted polycarbosilane (PCS), namely, propargyl‐substituted hyperbranched hydrodipolycarbosilane (PHPCS), was prepared by a modified synthesis route, which involved Grignard coupling of partially methoxylated Cl₃SiCH₂Cl and CHCCH₂Cl, followed by reduction with lithium aluminum hydride. The resultant PHPCSs were characterized by gel permeation chromatography, Fourier transform infrared (FTIR) spectroscopy, and NMR. Moreover, the thermal properties of the PHPCSs were investigated by thermogravimetric analysis. The ceramic yield of PHPCS at 1400°C was about 82.5%, which was about 10 wt % higher than that of hyperbranched hydrodipolycarbosilane without the substitution of propargyl groups. The PHPCS‐derived ceramics were characterized by X‐ray diffraction (XRD), FTIR spectroscopy, and elemental analysis. The XRD and FTIR results indicate that the heat treatment significantly influenced the evolution of crystalline β‐SiC. It can be convenient to get near‐stoichiometric ceramics from PHPCS through the control of feed ratios of the starting materials. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121:3400–3406, 2011     

Synthesis and aqueous solution properties of novel thermosensitive polyacrylamide derivatives

A series of novel thermosensitive polymers were synthesized with acrylamide and thermosensitive macromonomers by radical polymerization in water solution. The structures of the copolymers were characterized by ¹H‐NMR. The effects of the polymer concentration, NaCl concentration, shear rate, and chemical structure on the thermothickening behavior of the polymer solution were investigated by advanced rheometry. The luminous transmittance of the solution with various polymer concentrations was tested by visible spectrometry. The results show that the thermothickening behavior was due to the phase separation of the polymer solution or intramolecular repulsions between the hydrophobic side chains and hydrophilic backbone at high temperatures. Finally, the thermothickening properties of the novel copolymer were studied under conditions simulating an underground oil reservoir. This novel copolymer is expected to be used as an oil‐displacing agent to enhance oil recovery in the future. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 766‐775, 2013     

Interaction and properties of epoxy‐amine system modified with poly(phthalazinone ether nitrile ketone)

An epoxy based on the tetraglycidyl 4,4′‐diaminodiphenyl‐ methane (TGDDM)/bisphenol A type novolac(F‐51) cured with 4,4′‐diaminidiphenysulfone (DDS) has been modified with Poly (phthalazinone ether nitrile ketone)(PPENK). The interaction between the PPENK and epoxy resin have been investigated by differential scanning calorimetry (DSC), FT‐IR, and dynamic mechanical analysis (DMA). The thermal and mechanical properties were characterized by thermogravimetric analysis (TGA), thermomechanical analysis (TMA), flexural, impact strength, and the critical stress intensity factor tests. The results showed that a large number of physical crosslinks formed by intermolecular and intramolecular hydrogen bonding indeed existed in the TGDDM/F‐51/PPENK blends. These interactions gave good compatibility between PPENK and epoxy resin. So that any phase separation had not been detected by DMA and scanning electron microscope (SEM). Beyond that the interaction could also be a benefit to the thermal and mechanical properties. Compared with the neat epoxy resin, the critical stress intensity factor values reached the maximum at 10‐phr PPENK, as well as the impact strength. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42938.     

Synthesis and properties of poly(ether imide)s derived from 2,5‐bis(3,4‐dicarboxyphenoxy)biphenyl dianhydride and aromatic ether–diamines

A series of poly(ether imide)s (PEIs) with light colors and good mechanical properties were synthesized from 2,5‐bis(3,4‐dicarboxyphenoxy)biphenyl dianhydride and various aromatic ether–diamines via a conventional two‐step polymerization technique that included ring‐opening polyaddition at room temperature to poly(amic acid)s (PAAs) followed by thermal imidization. The precursor PAAs had inherent viscosities ranging from 0.71 to 1.19 dL/g and were solution‐cast and thermally cyclodehydrated to flexible and tough PEI films. All of the PEI films were essentially colorless, with ultraviolet–visible absorption cutoff wavelengths between 377 and 385 nm and yellowness index values ranging from 10.5 to 19.9. These PEIs showed high thermal stabilities with glass‐transition temperatures of 206–262°C and decomposition temperatures (at 10% weight loss) higher than 478°C. They also showed low dielectric constants of 3.39–3.72 (at 1 MHz) and low water absorptions below 0.85 wt %. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Shape‐memory behavior of high‐strength amorphous thermoplastic poly(para‐phenylene)

The purpose of this study was to investigate the shape‐memory behavior of poly(para‐phenylene) (PPP) under varying programming temperatures, relaxation times, and recovery conditions. PPP is an inherently stiff and strong aromatic thermoplastic, not previously investigated for use as a shape‐memory material. Initial characterization of PPP focused on the storage and relaxation moduli for PPP at various frequencies and temperatures, which were used to develop continuous master curves for PPP using time–temperature superposition (TTS). Shape‐memory testing involved programming PPP samples to 50% tensile strain at temperatures ranging from 155°C to 205°C, with varying relaxation holds times before cooling and storage. Shape‐recovery behavior ranged from nearly complete deformation recovery to poor recovery, depending heavily on the thermal and temporal conditions during programming. Straining for extended relaxation times and elevated temperatures significantly decreased the recoverable deformation in PPP during shape‐memory recovery. However, PPP was shown to have nearly identical full recovery profiles when programmed with decreased and equivalent relaxation times, illustrating the application of TTS in programming of the shape‐memory effect in PPP. The decreased shape recovery at extended relaxation times was attributed to time‐dependent visco‐plastic effects in the polymer becoming significant at longer time‐scales associated with the melt/flow regime of the master curve. Under constrained‐recovery, recoverable deformation in PPP was observed to have an exponentially decreasing relationship to the bias stress. This study demonstrated the effective use of PPP as a shape‐memory polymer (SMP) both in mechanical behavior as well as in application. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42903.     

Thermal and mechanical properties of poly(N‐isopropylacrylamide)‐based hydrogels as a function of porosity and medium change

Poly(N‐isopropylacrylamide) (PNIPAAm) has been a well‐known stimuli–responsive material and has been used in multiple novel applications. One of the key attributes to make the hydrogel more attractive is to control the response time and temperature. This work focused on comparing the physical properties, such as response time, transition temperature, heat of fusion, and mechanical strength, of macroporous and microporous PNIPAAm hydrogels, respectively. It was found that the macroporous hydrogels synthesized from a low‐temperature polymerization with addition of tetramethyl orthosilicate exhibited a faster response time and superior mechanical strength. Furthermore, to modulate the transition temperature, both the macroporous and microporous hydrogels were subjected to different qualities of media by introducing a cosolvent (methanol) or an anionic surfactant (sodium dodecyl sulfate). Interestingly, addition of a cosolvent demonstrated a more pronounced effect on the macroporous hydrogel, whereas the surfactant resulted in a more pronounced effect on the microporous hydrogel. Such results revealed that based on their porosity; there were appreciable differences when the PNIPAAm hydrogels interacted with media molecules. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42776.     

Enthalpy relaxation of photopolymerized multilayered thiol‐ene films

Multilayered thiol‐ene network films with two and three different components were fabricated by spin coating and photopolymerization. The distinctive glass transition temperatures of each layer component were observed at corresponding glass transition regions of each bulk sample. Sub‐T_g aging of 10‐, 21‐, and 32‐layered thiol‐ene films was investigated in terms of enthalpy relaxation. Enthalpy relaxation of each layer component occurred independently and presented the characteristic time and temperature dependency. Overlapped unsymmetrical bell‐shaped enthalpy relaxation distribution having peak maximum at T_g‐10°C of each layer component was observed, resulting in broad distribution of enthalpy relaxation over wide temperature range. In addition, enthalpy relaxation of each layer component in the multilayered thiol‐ene films was significantly accelerated comparing to that of bulk thiol‐ene samples. Dynamic mechanical thermal properties of multilayered thiol‐ene films also showed two and three separated glass transition temperature. However, for 32‐layered thiol‐ene film consisting of three different layer components, glass transition and damping region are overlapped and the width is extended more than 100°C. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Thermal stability and degradation of biological terpolyesters over a broad temperature range

Because of high susceptibility to thermal degradation during conventional melt processing of poly(3‐hydroxybutyrate) (P3HB) homopolymer, incorporation of a second or third monomer unit in the polyester backbones is expected to reduce the melting temperature and crystallinity, resulting in a controlled thermal degradation with improved stability. In this work, random poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate‐co‐4‐hydroxyvalerate) (P3HB3HV4HV) terpolyesters biologically synthesized by Cupriavidus necator were investigated for the thermal stability and degradation over a broad temperature range (100–300°C) in comparison with P3HB homopolyester. The work revealed that below the complete melting point (around 150°C), the terpolyester exhibited a high thermal stability and became an amorphous semisolid suitable for conventional thermal processing. Size exclusion chromatography plus nuclear magnetic resonance analysis was used to examine the thermal degradation products and the vulnerability of different monomer units at high temperatures (240–290°C). We found that 3HV unit in P3HB3HV4HV copolymers was more vulnerable to thermal degradation than 3HB unit under air. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41715.     

Interfacial crystallization of low‐crystallinity elastomer incorporated by multi‐walled carbon nanotubes: Mechanical reinforcement,structural evolution and enhanced thermal stability

In this paper, we report interfacial crystallization in olefin block copolymer (OBC) with low crystallinity incorporated by multi‐walled carbon nanotubes (MWCNTs). A hybrid shish‐kebab (HSK) superstructure in nanocomposites is observed that MWCNTs act as central shish and OBC crystals grow perpendicular to the nanotubes axis. The mechanical properties of nanocomposites are significantly improved with incorporation of MWCNTs. The most ideal reinforcing and toughening effect is both observed in nanocomposites with MWCNTs content of 1 wt % that can increase tensile strength by 122% as well as elongation at break by 36%. Efficient load transfer are confirmed with in‐situ Raman spectra that G’ band of MWCNTs in OBC matrix exhibit a downshifting trend and symmetric broadening of line shape which reveals additional macroscale strain from axial extension of MWCNTs in nanocomposites, thus suggesting a certain load is carried by HSK superstructure. The structural evolution of OBC and nanocomposites are investigated by in‐situ wide‐angle X‐Ray Diffraction (WAXD). The Herman's orientation factor of nanocomposites with 2 wt % MWCNTs incorporation is lower than that of neat matrix at mall and intermediate strains, indicating a heterogeneous stress distribution and low compliance of HSK superstructure, which is consistent with in‐situ Raman results. Moreover, the nanocomposites presents significantly enhanced thermal stability. The onset decomposition temperature of nanocomposites with 3 wt % MWCNTs can be 60.2°C higher than that of neat OBC. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42368.     

Effect of coupling agent on structure and properties of micro–nano composite fibers based on PET

Poly(ethylene terephthalate) (PET)/carbon black (CB) micro–nano composite fibers were manufactured by melt spinning method. To achieve good dispersion, nano‐CB particles were modified by coupling agent (CA). The effect of CA on structure and properties of the fibers were investigated via scanning electron microscopy (SEM), tensile testing, differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD), sonic orientation, and birefringence, respectively. At 2 wt % CA dosage, CB particles present the optimal dispersion in the fibers, shown in SEM images. Besides, the fibers possess the maximum breaking strength, the lowest crystallization temperature, and the highest crystallinity. After CA modification, the superior interfacial structure between PET and CB is beneficial to improve mechanical properties of the fibers. The well dispersed CB particles provide more heterogeneous nucleation points, resulting in the highest crystallinity. Furthermore, the fibers with 2 wt % CA dosage possess the maximum orientation and shrinkage ratio. According to Viogt–Kelvin model, the thermal shrinkage curves of the fibers can be well fitted using single exponential function. The three‐phase structure model of crystal phase–amorphous phase–CB phase was established to interpret the relationship among shrinkage, orientation, and dispersion of CB particles. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43846.     

Solution properties of a novel ampholytic polyphenylene sulfide

A polyampholyte was prepared from polyphenylene sulfide (PPS) by sulfonation, followed by bromination, and then the substitution of bromine by a quaternary ammonium group and tertiary amine group. The aqueous solution properties of the polyelectrolyte and polyampholyte with different ionic groups were investigated by viscometric measurement and rheological behavior measurement. The results show that the viscosities of the polyelectrolyte and polyampholyte were not only dependent on the nature of acid and base substituents along the polymer chain but also on the external factors, such as pH and small‐molecule electrolytes. In pure water, the rheological behavior of the polyelectrolyte showed an obvious critical shear rate in this circumstance; the polyampholyte showed a relatively stable shear rate compared with the polyelectrolyte. However, in salt‐saturated water, the viscosity decreased quickly with increasing shear rate. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effects of nano‐TiO2 on the properties and structures of starch/poly(ε‐caprolactone) composites

Poor physical properties resulting from low interfacial interactions between hydrophilic biopolymers and hydrophobic thermoplastic matrices have been one of the biggest obstacles in preparing quality biomass materials. This study concentrates on the effects of nano‐TiO₂ on the properties and structure of starch/poly (ε‐caprolactone) (PCL) composites. The molecular and crystal structures of the composites were characterized by using Fourier transform infrared spectroscopy, differential scanning calorimeter (DSC), X‐ray diffraction (XRD), and field emission scanning electron microscope. The results indicated that an interpenetrating network structure formed by adding nano‐TiO₂ into starch/PCL composites. The DSC and XRD analysis indicated that the crystallinity degree and the crystallization rate of the composites reduced, whereas the crystal form and crystal size were unchanged. The results also showed that the mechanical properties and water resistance of the composites were improved significantly with the addition of nano‐TiO₂, whereas their transparency decreased. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4129–4136, 2013