Preparation of poly(amino‐amide) particles complexed with ZnO particles using silane coupling agents

Poly(amino‐amide) particles were prepared by reacting 4,4′‐diphenyldicarbonyl chloride and 3,3′‐diaminobenzidine using a precipitation polymerization method with ultrasonic irradiation. The resulting particles had a narrow size distribution with an average diameter of 334 nm and showed excellent dispersion stability in water. The particles obtained were then modified with silane coupling agents (GPES) by reacting the amino groups of the poly(amino‐amide) particles with the epoxide rings of the GPES molecules in N,N‐dimethylformamide or N‐methylpyrrolidone using di‐n‐butyltin dilaurate as a catalyst. The amount of GPES covalently bonded to the poly(amino‐amide) particles was found to depend strongly on the reaction solvent and catalyst used. The resulting particles showed a narrow size distribution and the connections among the particles were not observed. On the other hand, the particles before and after modification showed different thermal properties and dispersion stability in water. The GPES‐modified aromatic polyamide particles were then complexed with ZnO particles with an average diameter of about 20 nm in aqueous acetic acid solution. It was found that the surface of the aromatic polyamide particles was covered with ZnO particles via hydrolysis reaction. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4908–4918, 2009     

Synthesis and characterization of a novel electrochromic aromatic polyamide from AB‐type triphenylamine‐based monomer

A new triphenylamine‐based polyamide I was prepared by direct polycondensation of AB‐type monomer, 4‐amino‐4′‐carboxy‐4″‐methoxytriphenylamine ( 4 ), in the presence of triphenyl phosphite and pyridine as condensation agents. The obtained polyamide I showed excellent solubility in aprotic polar solvents such as NMP, DMAc, DMF, and DMSO and could be cast into transparent film with weight‐average molecular weight (M_w = 63,400) and polydispersity index (PDI = 1.79). The polyamide I exhibited good thermal stability with relatively high glass‐transition temperature (282 °C), 10% weight‐loss temperature above 470 °C under a nitrogen atmosphere, and char yield at 800 °C in nitrogen higher than 64%. It also showed maximum ultraviolet‐visible absorption at 362 nm and exhibited fluorescence emission maxima at 493 nm in NMP solution with fluorescence quantum yield 4.4%. Cyclic voltammogram of polyamide I film cast onto an indium tin oxide coated glass substrate exhibited one oxidative redox couple at 0.72 V (oxidation onset potential) versus Ag/AgCl in acetonitrile solution and revealed good stability of the electrochromic characteristic with a color change from colorless to green at applied potentials ranging from 0.00 to 1.10 V. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1988–2001, 2009     

Thermal oxidative stability and effect of water on gas transport and mechanical properties in PA6‐EVOH films

The thermal oxidative stability and the effect of water on gas transport and mechanical properties of blends of polyamide 6 (PA6) with ethylene‐co‐vinyl alcohol (EVOH) and EVOH modified with carboxyl groups (EVOH‐COOH) have been investigated. The presence of EVOH reduces water vapor and oxygen gas permeability of polyamide, as well as small amounts of EVOH‐COOH further improve barrier properties, especially to oxygen. This has been explained in terms of improved interactions of the blend constituents in the amorphous phase, due to ionic linkages between the polyamide amino groups and the carboxyls of modified EVOH. The permeation to gases was found to increase with the amount of sorbed water. The morphology of the samples was found to have an effect on barrier properties, as the presence of EVOH causes the PA6 α crystalline form to increase, lowering the permeability to oxygen and water vapor. Mechanical properties are strongly affected by water sorption, as tensile modulus and strength decrease with increasing water content. Chemiluminescence (CL), infrared spectroscopy (FTIR), and tensile test were employed in order to assess the correlation between chemical composition and the thermal oxidative stability of the films aged at 110 °C in air. CL experiments suggest that the presence of EVOH and EVOH‐COOH efficiently inhibits the formation of peroxidized species during the processing, and increases the thermal oxidative stability of the films. Infrared spectroscopy showed a build‐up of carbonyl absorption in the range 1700–1780 cm^?1, due to the formation of oxidation products, which is greater in the case of the pure polymer. Tensile tests on films revealed a reduction in ductility as a result of ageing for neat PA6, whereas in comparison the blends exhibit a far better long‐term stability. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 840–849, 2007     

Preparation of submicron‐scale,electrospun cellulose fibers via direct dissolution

Cellulose nonwoven mats of submicron‐sized fibers (150 nm–500 nm in diameter) were obtained by electrospinning cellulose solutions. A solvent system based on lithium chloride (LiCl) and N,N‐dimethylacetamide (DMAc) was used, and the effects of (i) temperature of the collector, (ii) type of collector (aluminum mesh and cellulose filter media), and (iii) postspinning treatment, such as coagulation with water, on the morphology of electrospun fibers were investigated. The scanning electron microscopy (SEM) and X‐ray diffraction studies of as‐spun fibers at room temperature reveal that the morphology of cellulose fibers evolves with time due to moisture absorption and swelling caused by the residual salt and solvent. Although heating the collector greatly enhances the stability of the fiber morphology, the removal of salt by coagulation and DMAc by heating the collector was necessary for the fabrication of dry and stable cellulose fibers with limited moisture absorption and swelling. The presence and removal of the salt before and after coagulation have been identified by electron microprobe and X‐ray diffraction studies. When cellulose filter media is used as a collector, dry and stable fibers were obtained without the coagulation step, and the resulting electrospun fibers exhibit good adhesion to the filter media. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1673–1683, 2005     

Nanofibers prepared by electrospinning from solutions of biobased polyamide 4

A successful preparation of polyamide 4 nanofibers via electrostatic spinning with diameters close to 100 nm is described. Polyamide 4 was prepared by the anionic ring‐opening polymerization of 2‐pyrrolidone and characterized. The effect of the system parameters (i.e., molar mass of the polymer, the solvent system) and the process parameters (i.e., the electrode‐to‐collector distance) during the electrostatic spinning have been studied. The morphology of the polyamide 4 fiber layers is given except molar mass of the polymer and the concentration of its solution primarily by the conformation of polyamide chains due to polyelectrolyte effect which was confirmed by viscosity measurements. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2203–2210     

Temperature‐sensitive hydrogel microspheres formed by liquid–liquid phase transitions of aqueous solutions of poly(N,N‐dimethylacrylamide‐co‐allyl methacrylate)

Poly(N,N‐dimethylacrylamide‐co‐allyl methacrylate) (DMA‐co‐AMA) copolymers were prepared by the copolymerization of N,N‐dimethylacrylamide with allyl methacrylate (AMA). The methacryloyl group of AMA reacted preferentially, and this resulted in pendant allyl groups along the copolymer chains. Aqueous solutions of these DMA‐co‐AMA copolymers were thermoresponsive and showed liquid–liquid phase transitions at temperatures that depended on the AMA content. Hydrogel microspheres were prepared from these thermally phase‐separated liquid microdroplets by the free‐radical crosslinking of the pendant allyl groups. The morphologies of the resulting thermoresponsive microspheres as a function of the reaction temperature and the amount of the initiator were examined. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1641–1648, 2005     

Poly(styrene‐co‐glycerol dimethacrylate): Synthesis,characterization, and application as a resin for gel‐phase peptide synthesis

An efficient cross‐linked polymer support for solid‐phase synthesis was prepared by introducing glycerol dimethacrylate cross‐linker to polystyrene network using free radical aqueous suspension polymerization. The support was characterized by various spectroscopic methods. Morphological feature of the resin was analyzed by microscopy. The polymerization reaction was investigated with respect to the effect of amount of cross‐linking agent, which in turn vary the swelling, loading, and the mechanical stability of the resin. The solvent uptake of the polymer was studied in relation to cross‐linking and compared with Merrifield resin. The stability of the resin was tested in different synthetic conditions used for solid‐phase peptide synthesis. Hydroxy group of the support was derivatized to chloro and then amino groups using different reagents and reaction conditions. Efficiency of the support was tested and compared with TentaGel? resin by following different steps involved in the synthesis of the 65–74 fragment of acyl carrier protein. The results showed that the poly(styrene‐co‐glycerol dimethacrylate) (GDMA‐PS) is equally efficient as TentaGel resin in peptide synthesis. The purity of the peptides was analyzed by HPLC and identities were determined by mass spectroscopy and amino acid analysis. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4382–4392, 2005     

ATRP of butyl acrylates from functionalized carbon black surfaces

The functionalization of carbon black surface with atom transfer radical polymerization (ATRP) initiating sites and subsequent ATRP of n‐butyl acrylate (n‐BA) and t‐butyl acrylate (t‐BA) from the surface of carbon black is reported. The polymerizations were carried out using CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine as the primary catalytic system in anisole at 70 °C. The initiator density on carbon black surface was tuned and the effect of initiator density on the polymers grafted on the surface was illustrated. Polymerizations were also performed in the presence of a sacrificial initiator to indirectly monitor the molecular weight evolution of polymers formed in the system. Block copolymerization of t‐BA initiated from poly(n‐BA) grafted carbon black was conducted to achieve water‐dispersible carbon black composites after cleavage of the t‐butyl groups. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4695–4709, 2005     

Synthesis and properties of a bisphenol A based phthalonitrile resin

A multiple aromatic ether linked phthalonitrile was synthesized and characterized. The oligomeric phthalonitrile monomer was prepared from the reaction of an excess amount of bisphenol A with 4,4′‐difluorobenzophenone in the presence of K₂CO₃ as the base in an N,N‐dimethylformamide/toluene solvent mixture, followed by end capping with 4‐nitrophthalonitrile in a two‐step, one‐pot reaction. The monomer properties were compared to those of the known resin 2,2‐bis[4‐(3,4‐dicyanophenoxy)phenyl]propane after being cured in the presence of bis[4‐(4‐aminophenoxy)phenyl]sulfone. Rheometric measurements and thermogravimetric analysis showed that the oligomeric phthalonitrile resin maintained good structural integrity upon heating to elevated temperatures and exhibited excellent thermal properties along with long‐term oxidative stability. The ether‐linked phthalonitrile resin absorbed less than 2.5% water by weight after exposure to an aqueous environment for extended periods. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4136–4143, 2005     

Synthesis and characterization of novel biodegradable unsaturated poly(ester amide)s

A series of novel biodegradable unsaturated poly(ester amide)s (UPEAs) were synthesized through the solution polycondensation of two unsaturated monomers, di‐p‐nitrophenyl fumarate and L ‐phenylalanine 2‐butene‐1,4‐diol diester p‐toluene sulfonate, and four other saturated monomers in different combinations. The UPEAs were obtained in fairly good yields with N,N‐dimethylacetamide (DMA) as the solvent. The number‐average and weight‐average molecular weights of the UPEAs, measured by gel permeation chromatography, ranged from 10 to 30 kg/mol, they had a rather narrow molecular weight distribution of 1.40. The chemical structures of the novel biodegradable UPEAs were confirmed by both IR and NMR spectra. The UPEAs had higher glass‐transition temperatures than saturated PEAs of similar structures, and their glass‐transition temperatures were affected more by the CC double bond located in the diamide part than by those in the diester part. The solubility of the polymers was poor in water but better in DMA and dimethyl sulfoxide. With the availability of these inherent CC double bonds in the UPEA backbones, these UPEAs have the functionality of CC bonds, such as photochemical reactivity or the ability to react with or be modified by other bioactive or other environmentally sensitive compounds, and this can easily extend their applications to biomedical and pharmaceutical areas. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1463–1477, 2005     

Investigation of the sub‐melting‐temperature exotherm in melt‐quenched polyamide‐6/clay nanocomposites

A sub‐melting‐temperature exotherm in a polyamide‐6/clay nanocomposite (containing 3 wt % montmorillonite) was investigated with differential scanning calorimetry. It existed only via air‐quenching from the melt; it did not exist at higher or lower heating rates. The exotherm could be ascribed to frozen‐in stresses in the interlamellar regions through hydrogen bonding. A combination of larger internal stresses and larger crystallinity was necessary to produce this exotherm. Its appearance was closely connected to the addition of montmorillonite. During the air‐quenching process, montmorillonite not only greatly accelerated the crystallization rate of polyamide‐6 but also further intensified the internal stresses produced during the quenching process. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 378–382, 2005     

Crystalline structure and thermal behavior of nylon‐10,14

The structure and morphology of a novel polyamide, nylon‐10,14, and its lamellar crystals from dilute solution were examined by transmission electron microscopy and wide‐angle X‐ray diffraction (WAXD). Both the electron‐diffraction pattern and WAXD data demonstrated that nylon‐10,14 adopts the structure of a triclinic lattice similar to that of the traditional nylon‐66 but with a corresponding increase of the c parameter to 3.23 nm. In addition, the thermal behavior of melt‐crystallized nylon‐10,14 was investigated by dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). The glass‐transition temperature of nylon‐10,14 determined by the DMA data was 46.6°C. DSC indicated that the multiple melting behavior of isothermally crystallized nylon‐10,14 probably results from the melt and recrystallization mechanism. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1422–1427, 2003     

Ultrafine electrospun polyamide‐6 fibers: Effect of emitting electrode polarity on morphology and average fiber diameter

Electrostatic spinning or electrospinning is now a well‐known process for fabricating ultrafine fibers with diameters in the submicrometer down to nanometer range from materials of diverse origins. The polarity of the emitting electrode (i.e., the one that is in contact with the polymer solution or melt) can be either positive or negative. In the present contribution, the effects of emitting electrode polarity and some processing parameters (i.e., polyamide‐6 (PA‐6) concentration, molecular weight of PA‐6, electrostatic field strength, solution temperature, solvent type, and addition of an inorganic salt) on morphological appearance and average size of the as‐spun PA‐6 fibers were investigated. Scanning electron micrographs showed obvious morphological difference between the fibers obtained under positive and negative polarity of the emitting electrode. The main differences were that the cross section of the as‐spun PA‐6 fibers obtained under the negative electrode polarity was flat, while that of those obtained under the positive one appeared to be round and that the average size of the fibers obtained under the negative electrode polarity was larger than that of those obtained under the positive one. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3699–3712, 2005     

Preparation by controlled radical polymerization and self‐assembly via base‐recognition of synthetic polymers bearing complementary nucleobases

The radical polymerization of three monomers bearing nucleobases 1‐(4‐vinylbenzyl)thymine (VBT), 1‐(4‐vinylbenzyl)uracil (VBU) and 9‐(4‐vinylbenzyl)adenine (VBA) was investigated. The corresponding homopolymers could be prepared in high yields via conventional radical polymerization. However, the resulting polymers were found to be only soluble in a few polar solvents. On the other hand, copolymers of dodecyl methacrylate (DMA) with either VBT or VBA could be prepared via both free radical polymerization and atom transfer radical polymerization and could be dissolved in a large variety of organic solvents. Moreover, the formed complementary copolymers P(VBT‐co‐DMA) and P(VBA‐co‐DMA) were found to self‐assemble in dilute solutions in dioxane or chloroform via base recognition, as evidenced by a significant hypochromicity effect in UV spectroscopy. Nevertheless, at higher concentrations in chloroform, both dynamic light scattering and optical microscopy indicate that P(VBT‐co‐DMA), P(VBA‐co‐DMA), or P(VBT‐co‐DMA)/P(VBA‐co‐DMA) mixtures spontaneously self‐assemble into micron size spherical aggregates. ¹H NMR and FTIR studies confirmed that the self‐assembly process is driven in all cases via H‐bond formation. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4805–4818, 2005     

Halo formation in asymmetric polyetherimide and polybenzimidazole blend hollow fiber membranes

For the first time, we have reported a halo (ring) formation occurred in the cross‐section of integrally skinned asymmetric membranes. These membranes were wet‐spun from solutions containing 30 and 33 wt % of 95/5 and 90/10 polyetherimide (PEI)/polybenzimidazole (PBI). Both Imaging X‐ray Photoelectron Spectroscopy (XPS) and Dynamic Mechanical Analyzer's (DMA) data suggest PEI and PBI form miscible blends the “halo” is not chemically different from the matrix and is most likely a physical phenomenon of unique pore morphology. In other words, uniform porosity was created in the middle of hollow fiber cross‐section area, which performs as a filter for light transmission. We found that the addition of PBI in PEI/DMAc solution not only depresses the macrovoid formation, but also changes the precipitation path: nucleation growth vs. spinodal decomposition. The formation of a halo within a membrane is possibly due to the fact that a uniform nucleation growth occurs in the ring region during the early stage of phase separation because of high solution viscosity and diffusion controlled solvent‐exchange process, and then separation grows in the mechanism of spinodal decomposition from small amplitude composition fluctuations. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1575–1585, 1999     

Hydration in a new semiaromatic polyamide observed by humidity‐controlled dynamic viscoelastometry and X‐ray diffraction

Hydration in a new semiaromatic polyamide, named polyamide 9‐T (PA9‐T), a copolymer of terephthalic acid with n‐ and iso‐nonanediamines, is studied by dynamic viscoelastic analysis under controlled humidity conditions and wide‐angle X‐ray diffraction analysis in comparison with common polyamide nylon 6. The storage modulus of PA9‐T is retained at up to 60 °C with increasing humidity, then dropped with further increases in temperature past 70 °C. The decrease in mechanical properties at 70 °C due to moisture uptake is found to be substantially improved by annealing to develop molecular packing and/or crystallization. In contrast, the storage modulus of very highly crystallized (50% crystallinity) nylon 6 decreases markedly with humidity at low temperatures such as 20 °C. Thus, PA9‐T retains its mechanical properties in humid atmospheres at much higher temperatures than nylon 6. The crystalline X‐ray diffraction peaks for nylon 6 corresponding to (002) + (202) of the α form shift upon absorption of moisture, speculated to be due to the weakening of hydrogen bonds and the subsequent conformational disordering of the chains. Unlike nylon 6, the crystalline peaks of PA9‐T do not shift due to moisture uptake. This is considered to be attributable to that the long aliphatic chain in PA9‐T forms the large hydrophobic domain, rendering PA9‐T less hygroscopic than nylon 6. Additionally, strong hydrogen bonds formed by terephthalamide residues together with a strong stacking force of phenylene groups may also repel water, preventing moisture bind with the amide groups of PA9‐T crystals. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1640–1648, 2005     

Thioxanthone–carbazole as a visible light photoinitiator for free radical polymerization

A thioxanthone (TX) derivative with the additional carbazole chromophore, namely thioxanthone‐carbazole (TX‐C) was synthesized and characterized. The photophysical properties and its efficiency to polymerize methyl methacrylate both in the presence and absence of N,N‐dimethylaniline (DMA) as coinitiator was investigated and compared with that of the commercially available TX. TX‐C was found to display better photophysical properties and in both cases initiate polymerization more efficiently. Detailed real‐time Fourier transform infrared studies revealed that high polymerization rates can be obtained when TX‐C in conjunction with DMA was used. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Nanocomposites of vinyl chloride–acrylonitrile copolymer and silica

Vinyl chloride–acrylonitrile (VC–AN) copolymer was synthesized through emulsion copolymerization. VC–AN copolymer/silica nanocomposites were prepared by solution blending of copolymer and silica in a common solvent, N,N‐dimethylformamide (DMF). The rheology studies show that the shear‐thinning behavior of the VC–AN copolymer solution becomes less distinct as nano particles are introduced. It was also found that the viscosity of the copolymer solution decreases with adding small amount of nano particles. Transmission electron microscopy observations indicate that the UV‐treated silica could disperse well in the copolymer matrix. Differential scanning calorimeter studies suggest that the presence of the silica suppresses crystallization of the AN segments in the copolymers. Because of the interactions between copolymer chains and inorganic particles, the thermal stability and mechanical strength of the VC–AN copolymers are improved considerably. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3127–3134, 2005     

Pd (II)‐catalyzed vinyl addition polymerization of novel functionalized norbornene bearing dimethyl carboxylate groups

Three novel functionalized polynorbornenes (PNB) with pendant dimethyl carboxylate group (carboxylates—acetate, propionate, and butyrate) are synthesized as a vinyl‐type with a palladium (II) catalyst in high yield. The effects of size of substitutents, molar ratio of monomer to catalyst, solvent polarity, reaction time, and temperature on the polymerization of exo‐norbornene dimethyl propionate were systematically investigated. The low molar ratio and temperature, as well as high polarity of solvent, and long reaction time, are favorable for the enhancement of the monomer conversion, especially, the solvent have an obvious effect on the catalyst activity. The resulting poly(cis‐norbornene‐exo‐2,3‐dimethyl carboxylates) (PNB‐dimethyl carboxylates) show good solubility in common organic solvent and high thermal stability up to 360 °C. The glass transition temperature was detected by DMA at 331, 324, and 318 °C for acetate, propionate, and butyrate, respectively. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3391–3399, 2007     

Covalent stabilization of nanostructures: Robust block copolymer templates from novel thermoreactive systems

Structurally robust block copolymer templates with feature sizes of approximately 10 nm were prepared from functionalized poly(methyl methacrylate)‐b‐polystyrene block copolymers. By the inclusion of benzocyclobutene crosslinking groups in the polystyrene block, the covalent stabilization of thin films to both thermal treatment and solvent exposure became possible. In addition, the crosslinking of the poly(styrene‐benzocyclobutene) domains at 220 °C, followed by the removal of poly(methyl methacrylate), provided a robust, crosslinked nanostructure with greater processing and fabrication potential. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1028–1037, 2005