Structure and properties of polyimide‐g‐nylon 6 and nylon 6‐b‐polyimide‐b‐nylon 6 copolymers

Polyimide‐g‐nylon 6 copolymers were prepared by the polymerization of phenyl 3,5‐diaminobenzoate with several diamines and dianhydrides with a one‐step method. The polyimides containing pendant ester moieties were then used as activators for the anionic polymerization of molten ε‐caprolactam. Nylon 6‐b‐polyimide‐b‐nylon 6 copolymers were prepared by the use of phenyl 4‐aminobenzoate as an end‐capping agent in the preparation of a series of imide oligomers. The oligomers were then used to activate the anionic polymerization of ε‐caprolactam. In both the graft and copolymer syntheses, the phenyl ester groups reacted quickly with caprolactam anions at 120°C to generate N‐acyllactam moieties, which activated the anionic polymerization. All the block copolymers had higher moduli and tensile strengths than those of nylon 6. However, their elongations at break were much lower. The graft copolymers based on 2,2′‐bis[4‐(3,4‐dicarboxyphenoxy)phenyl]propane dianhydride and 2,2′‐bis[4‐(4‐aminophenoxy)phenyl]propane displayed elongations comparable to that of nylon 6 and the highest moduli and tensile strengths of all the copolymers. The thermal stability, moisture resistance, and impact strength were dramatically increased by the incorporation of only 5 wt % polyimide into both the graft and block copolymers. The graft and block copolymers also exhibited improved melt processability. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 300–308, 2006     

Preparation and characterization of polyimide‐g‐nylon 6 copolymers from nonfunctionalized polyimides

In this research, the anionic polymerization of ?‐caprolactam was carried out in the presence of small amounts of several different polyimides to generate polyimide‐g‐nylon 6 copolymers. The polyimides, which were prepared from 2,2′‐bis[4‐(3,4‐dicarboxyphenoxy)phenyl]propane dianhydride and commercially available diamines with a one‐step method, were first dissolved in molten ?‐caprolactam. Phenylmagnesium bromide was then added at 120°C. Under these conditions, caprolactam anions were formed that attacked the five‐membered imide rings to form N‐acyllactam moieties, which activated the anionic polymerization of caprolactam. In essence, nylon 6 chains grew from the polyimide backbones. Probably because of a high activation energy, the process was relatively slow, requiring 1 h at 120°C. The introduction of 5 wt % polyimide into the graft copolymers produced significant increases in the tensile modulus and tensile strength in comparison with those of low‐ and high‐molecular‐weight nylon 6. The elongation to break, however, was reduced. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 292–299, 2006     

Anionic polymerization and properties of graft copolymers consisting of alternating styrene/maleimide copolymer main chains and polyamide 6 grafts

This article is focused on the synthesis of a new type of graft PA6, which contained alternating styrene/maleimide copolymer main chains and PA6 grafts, by anionic polymerization. The preprepared styrene/maleimide copolymers with acylated caprolactam (ACL) pendants were used as macroactivators for the polymerization of molten ε‐caprolactam (CL). Because of the low activating energy for the initial nucleophilic attack of CL anion on the N‐ACL, the polymerization took place in a few minutes. The macroactivators were characterized by ¹H‐NMR. And the thermal properties, dimensional stability, crystallinity, and solvent resistance ability of the graft PA6 were studied, using DSC, TGA, XRD, water absorption measurement, and solubility experiment. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

A novel approach to the preparation of thermoplastic polyurethane elastomer and polyamide 6 blends by in situ anionic ring‐opening polymerization of ε‐caprolactam

Blends of thermoplastic polyether‐based urethane elastomer (TPEU) and monomer casting polyamide 6 (MCPA6) were prepared using ε‐caprolactam as reactive solvent, with caprolactam sodium as a catalyst in the presence of TPEU, with TPEU content varying from 2.5% to 10% by weight. In situ anionic ring‐opening polymerization and in situ compatibilization to prepare TPEU/MCPA6 blends were carried out in one step. The TPEU chains, which underwent thermal dissociation in amine solvents to bear isocyanate groups, acted as macroactivator to initiate MCPA6 chain growth from the TPEU chains and form graft copolymers of TPEU‐co‐MCPA6 to improve compatibility between TPEU and MCPA6. The structure and thermal properties were characterized by means of Fourier transform infrared spectroscopy, ¹H‐NMR spectroscopy, differential scanning calorimetry and scanning electron microscopy. Copyright © 2006 Society of Chemical Industry     

A new macroinitiator for the synthesis of triblock copolymers PA12‐b‐PDMS‐b‐PA12

A new PDMS macroinitiator is proposed for the anionic ring‐opening polymerization of lactams. This α,ω‐dicarbamoyloxy caprolactam PDMS macroinitiator was readily obtained in quantitative yield, by an original synthesis scheme in two steps, which involved the scarcely reported reaction of isocyanates with silanol groups. It was then shown that this bifunctional macroinitiator enabled to synthesize triblock copolymers PA12‐b‐PDMS‐b‐PA12 by polymerization of lauryl lactam (LL) at high temperature (200°C) in inert atmosphere under conditions compatible with reactive extrusion processes. Another related high molar weight α,ω‐diacyllactam PDMS macroinitiator was also successfully used in the polymerization of LL under the same conditions, therefore overcoming the limitations formerly reported for this type of macroinitiators during the polymerization ε‐caprolactam (ε‐CL) at a much lower temperature (80°C). Triblock copolymers with a wide range of PA12 /molar weights (M_n: ～ 10,800–250,000 Da) were eventually obtained by using both types of macroinitiators. DMTA and DSC analyses showed that their thermal properties were strongly dependent upon their respective contents in soft and hard blocks. Such triblock copolymers already appear very promising for the highly effective in situ compatibilization of PA12/PDMS blends as shown by recent complementary results obtained in our laboratory. © 2006 Wiley Periodicals, Inc. J Appl PolymSci 102: 2818–2831, 2006     

Synthesis of water‐soluble polyphenol‐graft‐poly(ethylene oxide) copolymers via enzymatic polymerization and anionic polymerization

Water‐soluble polyphenol‐graft‐poly(ethylene oxide) (PPH‐g‐PEO) copolymers were prepared using grafting‐through methodology. Polyphenol chains were synthesized via enzymatic polymerization of phenols, and the graft chains were synthesized via living anionic polymerization of ethylene oxides. The polymers were characterized using gel permeation chromatography, static light scattering and ¹H NMR, infrared and ultraviolet spectroscopies. The PPH‐g‐PEO graft copolymers are soluble in several common solvents, such as water, ethanol, N,N‐dimethylformamide, tetrahydrofuran and methylene dichloride. The solubility of the PPH‐g‐PEO graft copolymers is improved significantly compared with that of polyphenol. Copyright © 2009 Society of Chemical Industry     

Kinetic studies of the polymerization of nylon-6 block copolymers

The kinetics of the activated anionic polymerization of caprolactam to nylon-6 and its copolymers has been studied. Nylon-6 block copolymer and nylon-6 were prepared at various initial reaction temperatures (140°C to 165°C) by anionic polymerization in an adiabatic dewar flask. Different concentrations of poly(ethylene oxide) (PEO) in 4,4′-diphenyl methane diisocyanate (MDI)-capped PEO and 1 mole percent MDI, in a caprolactam solution, were used as the activators with the catalyst, the sodium salt of caprolactam. The kinetics of the reaction were analyzed from an adiabatic temperature rise. A new method was applied to determine the rate parameters. The activation energy, E_a, of nylon-6 and nylon-6 block copolymers were found to be 22 kcal/mole. The collision frequency factor, A_o, steadily decreased and the autocatalytic constant, B_o, decreased to a constant value of 16 with the introduction of PEO. However, it was found that the order of reaction, n, was almost a constant value at the second order for all experiments.     

Tracer‐compatibilizer: Synthesis and applications in polymer blending processes

This article reports on a route to synthesizing fluorescent labeled graft copolymers, on the one hand; and on a concept of tracer‐compatibilizer for facile build‐up of emulsification curves of polymer blends, on the other hand. For these purposes, blends composed of polystyrene (PS) and polyamide 6 (PA6) are chosen. The synthesis of the corresponding tracer‐compatibilizer consists of three steps: (1) copolymerization of styrene with 3‐isopropenyl‐α,α'‐dimethybenzyl isocyanate (TMI); (2) conversion of a fraction of the isocyanate moieties of the resulting copolymer into anthracene ones upon reacting with 9‐(methylamino‐methyl)anthracene (MAMA); and (3) polymerization of ε‐caprolactam (CL) from the remaining isocyanate moieties. The resulting fluorescent labeled graft copolymer, denoted as PS‐g‐PA6‐Ant, is used to build up emulsification curves of PS/PA6 blends in a twin screw extruder (TSE), showing great usefulness of the concept of tracer‐compatibilizer. POLYM. ENG. SCI. 2012. © 2011 Society of Plastics Engineers     

Follow‐up of the course of the anionic ring‐opening polymerization of lactams onto an isocyanate‐bearing polymer backbone in the melt

In this study, a batch mixer was used as a rheoreactor to carry out and follow up in real time the rate of the anionic polymerization of ε‐caprolactam onto a 3‐isopropenyl‐α,α‐dimethylbenzene isocyanate bearing polypropylene (PP‐g‐TMI) in the presence of sodium ε‐caprolactam as a catalyst. The isocyanate group in the PP‐g‐TMI was capable of activating the anionic polymerization, leading to the formation of a graft copolymer with polypropylene as the backbone and polyamide 6 as the grafts. The polymerization rate was related to the viscosity increase of the polymerization system. The latter then resulted in a concomitant torque increase. It was shown that torque was a rapid, convenient, and approximate measure of the polymerization rate. The use of the torque allowed for rapid and approximate evaluation of the effects of chemical and operating conditions on the polymerization rate without the need to determine the monomer conversions. Torque profiles were also a very useful piece of information for the design of a reactive extrusion process for the same type of polymerization system. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4394–4403, 2006     

Preparation of PS-g-PA6 copolymers by anionic polymerization of ε-caprolactam using PS precursors with N-carbamated caprolactam pendants as macroactivators

The graft copolymer of polystyrene and polyamide 6 (PS-g-PA6) was investigated by anionic polymerization of ε-caprolactam (CL), using the free radical copolymer of styrene and a kind of allyl monomer containing N-carbamated caprolactam group as macroactivator (PS-CCL). CL monomers were grafted onto PS-CCL backbone via initiating N-carbamated caprolactam (CCL) pendants along its backbone to form the graft copolymer in the presence of catalyst sodium caprolactamate. The macroactivator was characterized by Fourier-transform infrared spectroscopy and nuclear magnetic resonance, and the graft copolymer by the selective solvent extraction technique using methanol and chloroform as solvents. PS-g-PA6 copolymers with different PS content were synthesized to study the effect of PS on morphology, crystallinity, dimensional stability, and thermal properties, using scanning electron microscopy, X-ray diffraction, water absorption measurement, thermogravimetric analysis, and differential scanning calorimetry. The results show the percentage crystallinity of graft copolymer decreases with increasing PS content, but the addition of PS scarcely influences the crystalline structure of PA6. The graft copolymer has improved thermal properties and dimensional stability. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis of graft copolymer polyethylene‐ graft‐poly(ethylene oxide) by a new anionic graft‐from polymerization

A series of amphiphilic graft copolymers, PE‐graft‐PEO, containing hydrophobic polyethylene (PE) as the backbone and hydrophilic poly(ethylene oxide) (PEO) as the side‐chain, have been synthesized by a novel route. The graft structure and the molecular weight, as well as the molecular weight distribution of the graft copolymer can easily be controlled. The molecular weight of the side‐chain PEO is proportional to the reaction time and the monomer concentration, which indicates the ‘living’ character of the anionic polymerization of ethylene oxide. The produced copolymers PE‐graft‐PEO were characterized by ¹H NMR and DSC measurements. Copyright © 2004 Society of Chemical Industry     

Functional amphiphilic block copolyethers as carriers of caffeic acid phenethyl ester

Amphiphilic diblock copolymers consisting of hydrophilic polyglycidol (PG) and hydrophobic poly(allylglycidyl ether) (PAGE) were prepared by sequential anionic ring‐opening polymerization of allylglycidyl ether and ethoxyethyl glycidyl ether followed by removal of the protective ethoxyethyl groups. The polymerization was initiated by partially deprotonated dodecanol and performed in solvent‐free conditions. The copolymers were composed of a hydrophobic dodecyl residue attached to a block of PAGE with a fixed degree of polymerization (dp = 44) and differing in length of the PG block (dp = 16 and 66, corresponding to PG contents of 25 and 60 mol%, respectively). The two copolymers were spontaneously soluble in water. Above a certain critical concentration, they formed well‐defined self‐assembled nanoparticles. Their characterization parameters were determined by static and dynamic light scattering. The aggregates of the more hydrophobic copolymer, C₁₂‐PAGE‐PG25, were characterized by considerably larger dimensions and molar mass, reaching 78.6 nm and 253.0 × 10⁶ g mol^?1, respectively, than those of the more hydrophilic copolymer, C₁₂‐PAGE‐PG60. The hydrophobic moieties were proved to create a favorable environment for solubilization of caffeic acid phenethyl ester (CAPE) (the main active ingredient of propolis with cytotoxic and antioxidant activities), whereas the numerous hydroxyl groups from the PG moieties brought additional benefits related to the biocompatibility of the copolymers. Preliminary experiments with L929 fibroblast cells showed that the aggregates displayed no signs of toxicity in the applied in vitro test system, suggesting their appropriateness as a drug delivery platform. The CAPE‐loaded aggregates, however, showed dose‐dependent cytotoxic effects, indicating that CAPE retained its cytotoxic activity. © 2019 Society of Chemical Industry     

Polyamide‐6‐b‐polybutadiene block copolymers: Synthesis and properties

Polyamide‐6 (PA6)/polybutadiene (PB) block copolymers were synthesized with macroactivators (MAs) based on hydroxyl‐terminated polybutadiene functionalized with diisocyanates and having three N‐acyllactam chain‐growing centers per molecule. Two different diisocyanates, hexamethylene diisocyanate and isophorone diisocyanate, were applied as precursors for the MAs. The sodium salt of ε‐caprolactam was chosen as an initiator. The influence of the MA type and concentration on the anionic ring‐opening polymerization of ε‐caprolactam at 180°C was studied. A large percentage of the gel fraction in the copolymers was estimated, indicating crosslinked macromolecules. The structure and phase behavior of the copolymers were investigated with differential scanning calorimetry, wide‐angle X‐ray scattering, thermogravimetric analysis, and dynamic mechanical thermal analysis. In the copolymers, only the PA6 chains crystallized, and the crystallinity depended on the PB content. Different glass‐transition temperatures for the PB blocks and PA6 blocks were observed, indicating microphase separation in the copolymers. The mechanical properties of the copolymers were studied by notched impact testing and hardness measurements. The impact strength increased linearly with the soft component concentration up to 10 wt % and reached values six times higher than those of the PA6 homopolymer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 711–717, 2003     

Polyamide 6/ethylene‐butylene elastomer blends generated via anionic polymerization of ε‐caprolactam: Phase morphology and dynamic mechanical behavior

This paper reports about the polymerization of ε‐caprolactam monomer in the presence of low molecular weight hydroxyl or isocyanate end‐capped ethylene‐butylene elastomer (EB) elastomers as a new concept for the development of a submicron phase morphology in polyamide 6 (PA6)/EB blends. The phase morphology, viscoelastic behavior, and impact strength of the polymerization‐designed blends are compared to those of similar blends prepared via melt‐extrusion of PA6 homopolymer and EB elastomer. Polyamide 6 and EB elastomer were compatibilized using a premade triblock copolymer PA6‐b‐EB‐b‐PA6 or a pure EB‐b‐PA6 diblock reactively generated during melt‐blending (extrusion‐prepared blends) or built‐up via anionic polymerization of ε‐caprolactam on initiating ? NCO groups attached to EB chain ends (polymerization‐prepared blends). Two compatibilization approaches were considered for the polymerization‐prepared blends: (i) the addition of a premade PA6‐b‐EB‐b‐PA6 triblock copolymer to the ε‐caprolactam monomer containing nonreactive EB? OH elastomer and (ii) generation in situ of a PA6‐b‐EB diblock using EB? NCO precursor on which polyamide 6 blocks are built‐up via anionic polymerization of ε‐caprolactam. The noncompatibilized blends exhibit a coarse phase morphology, either in the extruded or the polymerization prepared blends. Addition of premade triblock copolymer (PA6‐b‐EB‐b‐PA6) to a EB? OH /ε‐caprolactam dispersion led to a fine EB phase (0.14 μm) in the PA6 matrix after ε‐caprolactam polymerization. The average particle size of the in situ reactively compatibilized polymerization‐prepared blend is about 1 μm. The notched Izod impact strength of the blend compatibilized with premade triblock copolymer was much higher than that of the neat PA6, the noncompatibilized, and the in situ reactively compatibilized polymerization blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2538–2544, 2004     

Synthesis and characterization of graft copolymers of syndiotactic polystyrene with polybutadiene and 4‐methylstyrene

The basic method for synthesizing syndiotactic polystyrene‐g‐polybutadiene graft copolymers was investigated. First, the syndiotactic polystyrene copolymer, poly(styrene‐co‐4‐methylstyrene), was prepared by the copolymerization of styrene and 4‐methylstyrene monomer with a trichloro(pentamethyl cyclopentadienyl) titanium(IV)/modified methylaluminoxane system as a metallocene catalyst at 50°C. Then, the polymerization proceeded in an argon atmosphere at the ambient pressure, and after purification by extraction, the copolymer structure was confirmed with ¹H‐NMR. Lastly, the copolymer was grafted with polybutadiene (a ready‐made commercialized unsaturated elastomer) by anionic grafting reactions with a metallation reagent. In this step, poly(styrene‐co‐4‐methylstyrene) was deprotonated at the methyl group of 4‐methylstyrene by butyl lithium and further reacted with polybutadiene to graft polybutadiene onto the deprotonated methyl of the poly(styrene‐co‐4‐methylstyrene) backbone. After purification of the graft copolymer by Soxhlet extraction, the grafting reaction copolymer structure was confirmed with ¹H‐NMR. These graft copolymers showed high melting temperatures (240–250°C) and were different from normal anionic styrene–butadiene copolymers because of the presence of crystalline syndiotactic polystyrene segments. Usually, highly syndiotactic polystyrene has a glass‐transition temperature of 100°C and behaves like a glassy polymer (possessing brittle mechanical properties) at room temperature. Thus, the graft copolymer can be used as a compatibilizer in syndiotactic polystyrene blends to modify the mechanical properties to compensate for the glassy properties of pure syndiotactic polystyrene at room temperature. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Mechanical relaxations of nylon–polyurea block copolymers

Dynamic mechanical analysis from ?150 to +150°C has been carried out on seven block copolymers that were prepared by the in situ anionic polymerization of caprolactam in the presence of a preformed polyurea. The various relaxations have been identified and activation energies calculated. Some polymer–polymer miscibility of the polyurea and amorphous nylon copolymer segments is indicated by the compositional dependence of the α relaxation.     

Architecture of nanostructured polymers by segregated domain crosslinking of block‐graft copolymer micelles

Polystyrene‐block‐polyisoprene (PS‐block‐PI; high 3,4‐structure) diblock copolymer was prepared by living anionic polymerization. For transfer into a reactive intermediate, the hydroxylation of the double bonds of PI block was achieved by hydroboration, followed by oxidation. Esterification of the hydroxy‐derivative with stearoyl chloride or decanoyl chloride resulted in block‐graft copolymers composed of PS (flexible chain)‐grafted long alkane (stretched chains). After partial chloromethylation of PS block copolymer, photofunctional N,N‐diethyldithiocarbamate (DC) groups were introduced into such pendant sites by reaction with the corresponding sodium salt. We studied the self‐assemblies of photofunctional block‐graft copolymers in a selective solvent, such as heptane, and constructed nanostructured polymers by crosslinking PS cores under UV irradiation. © 2001 Society of Chemical Industry     

Kinetics of the in situ polymerization and in situ compatibilization of poly(propylene) and polyamide 6 blends

In previous articles, we reported on a novel reactive extrusion process to obtain a compatibilized blend of polymer A and polymer B. It consisted in polymerizing the monomer of polymer A in the presence of polymer B. A fraction of the latter contained initiating sites from which the polymerization of monomer A took place. As such, both polymer A and a graft copolymer of polymer A and polymer B were formed in the process. That process was called in situ polymerization and in situ compatibilization of polymer blends. Its feasibility was illustrated for in situ polymerized and in situ compatibilized poly(propylene) and polyamide 6 (PP/PA6) blends. The latter were prepared by activated anionic polymerization of ?‐caprolactam (CL) in the presence of PP in a batch mixer and a twin‐screw extruder, respectively. A fraction of the PP contained isocyanate groups from which PA6 grafts were formed. Sodium caprolactam (NaCL) was used as the catalyst and a diisocyanate compound was used as the activator. In this study, we report on the effects of various parameters on the kinetics of the anionic polymerization of CL in the presence of PP. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1498–1504, 2004     

Hyperbranched homo and thermoresponsive graft copolymers by using ATRP‐macromonomer initiators

Macromonomer initiators behave as macro cross‐linkers, macro initiators, and macromonomers to obtain branched and cross‐linked block/graft copolymers. A series of new macromonomer initiators for atom transfer radical polymerization (MIM‐ATRP) based on polyethylene glycol (M_n = 495D, 2203D, and 4203D) (PEG) were synthesized by the reaction of the hydroxyl end of mono‐methacryloyl polyethylene glycol with 2‐bromo propanoyl chloride, leading to methacryloyl polyethylene glycol 2‐bromo propanoyl ester. Poly (ethylene glycol) functionalized with methacrylate at one end was reacted with 2‐bromopropionyl chloride to form a macromonomeric initiator for ATRP. ATRP was found to be a more controllable polymerization method than conventional free radical polymerization in view of fewer cross‐linked polymers and highly branched polymers produced from macromonomer initiators as well. In another scenario, ATRP of N‐isopropylacrylamide (NIPAM) was initiated by MIM‐ATRP to obtain PEG‐b‐PNIPAM branched block/graft copolymers. Thermal analysis, FTIR, ¹H NMR, TEM, and SEM techniques were used in the characterization of the products. They had a thermo‐responsive character and exhibited volume phase transition at ～ 36°C. A plasticizer effect of PEG in graft copolymers was also observed, indicating a lower glass transition temperature than that of pure PNIPAM. Homo and copolymerization kinetics were also evaluated. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The reactive compatibilization effect of copolymer macroactivator for immiscible anionic polyamide 6/polystyrene blends via in situ polymerization

In this article, a novel method has been successfully developed to prepare the anionic polyamide 6/polystyrene (APA6/PS) blends. The macroactivator P(St‐co‐IEM) was synthesized by the free radical polymerization of 2‐isocyanatoethyl methacrylate and styrene (St), then the graft copolymer of PS and APA6 (PS‐g‐APA6) can be obtained by the anionic polymerization of ɛ‐caprolactam activated by the macroactivator P(St‐co‐IEM). The X‐ray diffraction analysis, differential scanning calorimetry, scanning electron microscopy analysis, contact angle measurement, water absorption measurement, molau test, thermogravimetric analysis, and mechanical properties test were performed separately to study the effects of P(St‐co‐IEM) on crystallinity, morphology, water resistance, thermal stability, and mechanical properties. The results indicate the synthesis of macroactivator can promote the formation of the γ‐phase. Moreover, it can improve the interfacial compatibility, water resistance, thermal stability, and toughness. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46302.