Long chain branched poly(butylene succinate‐co‐terephthalate) copolyesters using pentaerythritol as branching agent: Synthesis,thermo‐mechanical,and rheological properties

Incorporating long chain branching (LCB) structure into biodegradable copolyesters can effectively improve their melt strength and film blowing processability. However, branching also results in deterioration of crystallizability which is also important for copolyester properties and processing. In this study, pentaerythritol (PER) was used as branching agent (BA) instead of previous used in‐situ BA, diglycidyl 1,2,3,6‐tetrahydrophthalate (DGT), to synthesize LCB poly(butylene succinate‐co‐terephthalate) (PBST) copolyesters. The chain structure was characterized and the effects of branching on thermal transition, mechanical, and rheological properties were investigated. Similar to DGT, copolymerizing small amount of PER (0.1–0.4 mol %) generates LCB structure and, therefore, improves the melt elasticity or strength and tensile modulus but reduces the elongation at break. Differing from DGT, PER showed higher branching efficiency, and PER‐branched PBSTs exhibited unchanged or even improved crystallization ability compared with linear PBST. The improved melt strength coupled with good crystallizability will endow PER‐branched PBSTs with better film blowing processability. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44544.     

Partial crosslinking method for poly(2,6‐dimethyl‐1,4‐phenylene oxide)–poly(vinyl alcohol) membranes to obtain optimized stability and permeability

A partial crosslinking method was developed to modify hydrophilic membranes. The membrane was sandwiched between two porous plates to protect part of the areas, then immersed into a crosslinking solution such as glutaraldehyde, and finally, set free from the plates. The protected and unprotected areas were alternatively distributed to form a heterogeneous membrane. The unprotected areas were crosslinked to enhance the membrane stability, whereas the protected areas retained their original permeability. Three types of hydrophilic base membranes were selected and prepared from poly(2,6‐dimethyl‐1,4‐phenylene oxide) and poly(vinyl alcohol). The base membranes were partially crosslinked (5.56% of the direct area with enlarged areas) to investigate their stability and diffusion dialysis (DD) performances. The partially crosslinked membranes had remarkably reduced water uptake and swelling degrees compared with the base membranes (72.4–250.4 vs 178.2%–544.4% and 94.0%–408.0% vs. 163.8%–814.8%). Meanwhile, the membranes still retained high DD performances for separating HCl–FeCl₂ or NaOH–NaAlO₂ solutions. The dialysis coefficients of HCl and NaOH were much higher than those of the fully crosslinked membranes (0.0209 vs. 0.0109 m/h and 0.0059–0.0085 vs. 0.0017–0.0022 m/h). Hence, partial crosslinking was effective in optimizing the membrane hydrophilicity and permeability. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45305.     

Preparation and properties of emulsifier‐/solvent‐free polyurethane‐acrylic hybrid emulsions for binder materials: Effect of the glycidyl methacrylate/acrylonitrile content

To obtain binder materials, emulsions of emulsifier‐/solvent‐free waterborne polyurethane‐acrylic hybrids with a fixed acrylic monomer content (30 wt %) were prepared in this study. This study focused on the effect of glycidyl methacrylate (GMA)/acrylonitrile (AN) wt % on the shelf stability, mean particle size and viscosity of hybrid emulsion samples, water swelling %/dynamic mechanical thermal properties/mechanical properties of hybrid film samples, and the failure mode and adhesive strength of binder materials prepared in this study. Characterization of the chemical structures of prepolymers, hybrid materials (binder materials), and atmospheric pressure plasma‐treated polyethylene (PE) has been performed by means of Fourier transformed infrared spectroscopy to determine the presence/disappearance/peak intensity change of functional groups. Various properties such as mean particle size, viscosity, T_g, water swelling %, hardness and mechanical properties, and failure mode and adhesive strength for leather/leather, control PE/leather, and plasma‐treated PE/leather were found to be significantly dependent on the weight ratio of GMA/AN. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44497.     

Transport properties and mechanical behavior of poly(methyl‐phenylsiloxane) membranes as a function of methyl to phenyl groups ratio

Membranes based on dimethyl and methyl‐phenylsiloxane were synthesized and then fully characterized. Transport properties and mechanical behavior were determined as a function of different methyl/phenyl group ratios and the effects of these groups on results were established. Membrane transport properties were evaluated from n‐hexane absorption studies. Static tensile stress–strain deformation measurements, stress–hysteresis determination, and stress–relaxation studies were performed to assess the mechanical behavior of these membranes. The results indicate that both physical–mechanical and transport properties are strongly affected by the methyl group content. The increase of the phenyl groups in the polymer chain impairs mechanical properties as a result of which decrease in crosslinking degree and gas permeability due to the diminution in free volume and penetrant solubility. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1624–1633, 2002     

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.     

A new SiC precursor with high ceramic yield: Synthesis and characterization of CHxMeSiH2-containing poly(methylsilane-carbosilane)

A new poly(methylsilane-carbosilane) (PMSCS) for silicon carbide precursor was prepared using Wurtz-type copolymerization of methyldichlorosilane (MeHSiCl₂), chloromethyldichloromethylsilane (ClCH₂MeSiCl₂), and (dichloromethyl)methylsilane (Cl₂CHMeSiH₂), with (chloromethyl)methylsilane (ClCH₂MeSiH₂) or trimethylchlorosilane (Me₃SiCl) as terminated reagent. The ceramic yield of PMSCS was markedly increased by introduction of Cl₂CHMeSiH₂ comonomer and capped with ClCH₂MeSiH₂. The H₂MeSiCH₂-capped PMSCS with CHMeSiH₂ structure unit in main chain produced SiC ceramic with 1.21 of C/Si atomic ratio in a ceramic yield of 78 wt % upon pyrolyzed at 1000 °C. The excellent pyrolytic properties, combining with its economical preparation, good storage stability in air, and favorable processabilty, make the CH_xMeSiH₂-containing PMSCS a new cost-effective SiC ceramic precursor. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47618.     

Preparation and characterization of the ethylene‐vinyl acetate copolymer partially hydrolyzed assisted by microwave radiation

Ethylene‐vinyl acetate copolymer (EVA) was modified by hydrolysis using dielectric heating. The modified EVA was characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis (TG), ¹H Nuclear magnetic resonance (NMR), gel permeation chromatography, and small‐angle X‐ray scattering. The results showed that the EVA was hydrolyzed with degree between 36.1 and 42.6% according to ¹H NMR and TG results. The relative reaction rate for the sample prepared in the oil bath was ～9%/h, while in the dielectric was ～150%/h for 15 min. This significant improvement was due to the specific effect of microwave‐assisted reactions through dipole rotation and ionic polarization contributions. The hydrolysis reaction promoted a reduction of the pendent group size of EVA backbone. This change directly contributed to increasing melt temperature, crystallization temperature, melt and crystallization enthalpies. Also, decreased the long period, increased the volume crystallinity, and caused reductions amorphous/crystalline interface and two‐phase model deviations. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44558.     

Ionic nanocomposite networks in poly(styrene‐co‐methacrylic acid) copolymers with calcium carbonate

To create reversible supramolecular ionic networks, ionic cross‐links were formed from acid pendant functions in poly(styrene‐co‐methacrylic acid) copolymers by the addition of calcium carbonate. The random dispersion of acid functions in the polystyrene chain is ensured by NMR analysis. The partial reaction of the calcium carbonate with the carboxylic acids is highlighted by a limewater test. The influence of methacrylic acid and calcium‐carbonate contents on the formation of an ionic network has been studied through solubility tests. Two main effects were obtained: the exfoliation of the unreacted calcium carbonate characterized by TEM is due to ionic interactions at the surface of nanometric particles that form the first level of organization of the calcium carbonate. Another part of the calcium carbonate reacts with carboxylic acid and is detached from particles to form clusters as shown by x‐ray analysis. Finally, by analyzing the dynamic rheological spectrum, the conclusion that the strength of the ionic bonds arises with the calcium content is made. The interest of such an approach with a wide range of observed phenomena in the material is a one‐batch process to make thermoreversible nanocomposite networks. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Hydrophilic and hydrophobic poly(l‐lactic acid) films by building porous topological surfaces

Surface wettability of thin films is significant for their functional properties. Poly(l ‐lactic acid) (PLLA) is proposed as film matrix for building porous topological surfaces. By controlling the dope composition and ambient conditions, the films with ordered pores at micrometer scale are obtained. The results demonstrate that the hydrophilic or hydrophobic surface can be realized by building the porous topological surfaces. Increasing polymer concentration can lead to decreased pore size. The transition behavior of surface pores from discrete bowl‐like to interconnected honeycomb‐like structure with the increasing humidity is observed. The contact angle of top surface of film is higher than that of bottom surface, which verified the different roughness performance. The morphology and scale of topological structure are markedly related with the template effect of water droplets. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44572.     

Strain rate dependent mechanical properties of a high‐strength poly(methyl methacrylate)

Strain rate dependency is an important issue for the mechanical response of materials in impact events. Dynamic mechanical properties of a high‐strength poly(methyl methacrylate) (PMMA) were studied by using split Hopkinson pressure bar technology. The maximum stress is enhanced with the increase of strain rate, and then keeps a constant with the further increase of strain rate, which is accompanied with a linear increase of fracture energy density. The critical data of strain rate and maximum stress were determined. Eyring's equation was applied for analyzing the influence factors, which relate to the hardening induced by strain rate and softening caused by adiabatic temperature rise. Inherent physical mechanisms were clarified and the strategies for designing advanced impact‐resistant polymers were proposed. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46189.     

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     

Gloss reduction and morphological properties of polycarbonate and poly(methyl methacrylate‐acrylonitrile‐butadiene‐styrene) blends with SAN‐co‐GMA as a reactive compatibilizer

The gloss properties of the polycarbonate (PC)/poly(methyl methacrylate‐acrylonitrile‐butadiene‐styrene) (MABS) blend with styrene‐acrylonitrile‐co‐glycidyl methacrylate (SAN‐co‐GMA) as a compatibilizing agent were investigated. For the PC/poly(MABS)/SAN‐co‐GMA (65/15/20, wt %) blend surface, the reduction of gloss level was observed most significantly when the GMA content was 0.1 wt %, compared with the blends with 0.05 wt % GMA or without GMA content. The gloss level of the PC/poly(MABS)/SAN‐co‐GMA (0.1 wt % GMA) blend surface was observed to be 35, which showed 65% lower than the PC/poly(MABS)/SAN‐co‐GMA blend without GMA content. The gloss reduction was most probably caused by the insoluble fractions of the PC/poly(MABS)/SAN‐co‐GMA blend that were formed by the reaction between the carboxylic acid group in poly(MABS) and epoxy group in SAN‐co‐GMA. The results of optical and transmission electron microscope analysis, spectroscopy study, and rheological properties supported the formation of insoluble structure of the PC/poly(MABS)/SAN‐co‐GMA blend when the GMA content was 0.1 wt %. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46450.     

Polypropylene with high melt flow rate and high isotacticity prepared by phosphate‐mixed external donors

High melt flow rate (MFR) of polypropylene can improve its processability and its high isotacticity is favor of keeping good mechanical properties of polypropylene. In this study, as a convenient and effective method, the mixture of phosphate and alkoxysilane as mixed external donors for Ziegler‐Natta catalyst is used to improve MFR of polypropylene. The MFR of polypropylenes prepared by mixed external donors is three to five time higher than that prepared by dicyclopentyl dimethoxysilane (Donor‐D) alone, which is attributed to broad molecular weight distribution and low molecular weight of polypropylene prepared by mixed external donors. In addition, isotacticity and lamella thickness of polypropylene prepared by mixed external donors containing triisopropyl phosphate or phenyl‐phosphonic acid dipentyl ester are very close to that prepared by Donor‐D, which lead to keep high thermal properties and good mechanical properties for the polypropylenes. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44704.     

Hydrophobic and tribological behaviors of a poly(p‐phenylene benzobisoxazole) fabric composite reinforced with nano‐TiO2

1H,1H,2H,2H‐Perfluorooctyl trichlorosilane (PFTS) was used to modify TiO₂ nanoparticles, and hydrophobic PFTS–TiO₂ nanoparticles were obtained by an ultrasonic reaction method. The PFTS–TiO₂ surface morphological and hydrophobic properties were analyzed with scanning electron microscopy (SEM), Fourier transform infrared spectrometry, and contact angle (CA) testing. Then, the poly(p‐phenylene benzobisoxazole) fabric–phenolic composite filled with PFTS–TiO₂ as a lubricant additive was fabricated by a dip‐coating process. The tribological properties of the composite were investigated, and the wear surface morphology was observed by SEM. The experimental results show that the water CA of the composite filled with PFTS–TiO₂ was 158°, and the composite containing 4 wt % PFTS–TiO₂ exhibited excellent antifriction and abrasion resistance. The hydrophobic surface of the composite showed excellent durable performance with a static water CA of 126.7° after abrasion. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45077.     

Waterborne poly(urethane‐urea) gas permeation membranes for CO2/CH4 separation

In this work, dense membranes from aqueous dispersions of poly(urethane‐urea) (PUU) based on poly(propylene glycol) (PPG) and a block copolymer composed of poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG), EG‐b‐PG, with 7 wt % of the former were obtained. Nonpolluting formulations were synthesized with proportions of PPG and EG‐b‐PG as 1:0, 1:1, 1:3, and 3:1 in terms of equivalent number ratios. The effect of small and gradual increases in PEG segments was evaluated for the permeability of pure CO₂, CH₄, and N₂, at room temperature. Slight increases in PEG‐based segments in PUU promoted some remarkable properties, which led to a simultaneous increase in CO₂ permeability and ideal selectivity for CH₄ (300%) and N₂ (380%). Infrared spectroscopy showed that the PEG portions induced hydrogen bonds between ? NH of urethane and ether groups in the PEG portions, which promoted ordering of the flexible segments, confirmed by X‐ray diffractometry and small‐angle X‐ray scattering. Diffractometry techniques also confirmed the absence of crystalline domains, as did dynamic mechanical analysis. The produced membranes showed performance above Robeson's 2008 upper bound and seemed to be a superior polymeric material for CO₂/CH₄ and CO₂/N₂ separation. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46003.     

Surface modification of ion‐exchange membranes: Methods,characteristics, and performance

Considerable effort has been made to improve ion‐exchange membrane (IEM) properties in order to achieve better performance of IEM‐based processes in various applications. Surface modification is one of the effective ways to improve IEM properties. Various methods have been used to modify IEM surfaces, for example, plasma treatment, polymerization, solution casting, electrodeposition, and ion implantation. These methods are able to produce a thin and fine distributed layer and also to modify the chemical structure of the surface. The new layer can be adsorbed, deposited, or chemically bonded on a membrane surface. By using these methods, IEM properties are improved, and the desired or specific characteristics such as high monovalent ion permselectivity, low fuel crossover, and anti‐organic‐fouling property can be obtained. In this paper, methods for surface modification of IEMs are reviewed. Moreover, the effects of modification on IEM properties and performance are discussed. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45540.     

Evaluation of (4‐Arylpiperidin‐1‐yl)cyclopentanecarboxamides As High‐Affinity and Long‐Residence‐Time Antagonists for the CCR2 Receptor

Animal models suggest that the chemokine ligand 2/CC‐chemokine receptor 2 (CCL2/CCR2) axis plays an important role in the development of inflammatory diseases. However, CCR2 antagonists have failed in clinical trials because of a lack of efficacy. We previously described a new approach for the design of CCR2 antagonists by the use of structure–kinetics relationships (SKRs). Herein we report new findings on the structure–affinity relationships (SARs) and SKRs of the reference compound MK‐0483, its diastereomers, and its structural analogues as CCR2 antagonists. The SARs of the 4‐arylpiperidine group suggest that lipophilic hydrogen‐bond‐accepting substituents at the 3‐position are favorable. However, the SKRs suggest that a lipophilic group with a certain size is desired [e.g., 3‐Br: K_i=2.8 nM , residence time (t_res)=243 min; 3‐iPr: K_i=3.6 nM , t_res=266 min]. Alternatively, additional substituents and further optimization of the molecule, while keeping a carboxylic acid at the 3‐position, can also prolong t_res; this was most prominently observed in MK‐0483 (K_i=1.2 nM , t_res=724 min) and a close analogue (K_i=7.8 nM ) with a short residence time.     

Effects of the coagulation temperature on the properties of wet‐spun poly(vinyl alcohol)–graphene oxide fibers

Graphene oxide (GO) as a positive reinforcement filler was dispersed into a poly(vinyl alcohol) (PVA) dope and wet‐spun into composite fibers. The effects of two EtOH coagulation baths maintained at ?5 and 25 °C, respectively, on the morphology, structure, and mechanical properties of the composite fibers were investigated. The results show that gel spinning at ?5 °C led to a relatively large shrinkage ratio, thin diameter, and low porosity of the as‐spun fibers. Simultaneously, the low coagulation temperature also greatly contributed to the formation and preservation of the liquid‐crystalline phase of the GO sheets and interrupted the crystalline zone of PVA less. As a result, either the tenacity or the elongation at break of the fibers spun at ?5 °C was higher than those of the fibers spun through a coagulation bath at 25 °C. In particular, 1 wt % GO showed the highest reinforcement effects among all of the wet‐spun composite fibers. Hence, controlling the gelling–demixing process at a low temperature will provide more instructive insights for tailoring functional industrial textiles with excellent mechanical properties. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45463.     

PANI/PPY blend thin films electrodeposited for use in EGFET sensors

Galvanostatic electrodeposited thin films of polyaniline (PANI)/polypyrrole (PPY) blend were tested as chemical sensors and evaluated according to the relative monomer concentration in polymerization solution aiming to obtain a reliable reference field‐effect transistor able to be used as contrast sensing film. The blend material presented properties that can be controlled by the polymerization process. The films were produced using aniline (0.25 M) and pyrrole (0.25 M) mixed in five different proportions (90/10, 70/30, 50/50, 30/70, 10/90) with HCl (1.0 M) in an aqueous solution. The current density was 1 mA/cm² for 300 s. The films were analyzed by their chronopotentiometric curves, thickness, reflectance spectroscopy, optical color parameters, and surface morphology. The characteristics and properties analyzed were correlated to the relative monomer concentration in the polymerization solution. The polymerization of PANI is favorable in aqueous acid solution compared to PPY, which resulted in thin films with properties varying from PANI down to PPY. The blend films presented controllable sensitivity when applied as sensing stage in field‐effect transistor devices as function of the relative monomer concentration. The sensitivity varied from 57 ± 1 mV/pH for the PANI sample, down to 25 ± 1 mV/pH for the PPY sample, presenting an exponential behavior. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46625.     

Autonomic self‐healing of poly(vinyl butyral)

The self‐healing behavior of poly(vinyl butyral) (PVB) is evaluated below the glass transition temperature T_g. It is found that PVB shows autonomic self‐healing even at room temperature, although T_g is around at 76°C. Furthermore, a large amount of water is found to be adsorbed on the surface of the film. This is attributed to the surface localization of hydroxyl group in PVB, which is confirmed by X‐ray photoelectron spectroscopy. Since the surface is plasticized by water, the scar applied by a razor blade is healed even in the glassy state of the bulk. Moreover, the healing efficiency is enhanced at high humidity condition, owing to the pronounced plasticizing effect by water. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42008.