Coionomeric mixtures of polyhydroxyethers and ethylene methacrylic acid copolymers. I. Effects of cation concentration and ABA oligomeric miscibilisers on morphology and properties

Mixtures of a phenoxy polymer (polyhydroxyether of bis-phenol A) and a polyolefin ionomer (sodium ionomer of ethylene methacrylic acid copolymer) were compatibilized by the addition of small amounts of sodium ethoxide and/or by the incorporation of varying amounts of A-B-A block oligomers. The latter were produced by reacting several bis-phenol A epoxy resins, varying in molecular weight, with montanic acid in order to provide segments soluble in each of the two polymer components of the blend. Chemical miscibilization by the addition of sodium ethoxide changed the morphology into one containing larger amounts of cocontinuous phases, while the incorporation of substantial amounts of A-B-A oligomer brought about primarily the formation of irregular and highly elongated particles. The mixtures were found to exhibit the typical properties of ionomers which were enhanced by the addition of sodium ethoxide. Furthermore sufficient evidence was gathered to establish that the ionomeric aggregates are shared by both polymer components of the blend, from which the term coionomeric mixture is derived. © 1993 John Wiley & Sons, Inc.     

Preparation of poly(ethylene terephthalate)/organoclay nanocomposites using a polyester ionomer as a compatibilizer

In this work, poly(ethylene terephthalate)/organically modified montmorillonite (PET/o‐MMT) nanocomposites were prepared via direct melt compounding in a twin‐screw extruder. The main objective was to study the effects of using a polyester ionomer (PETi) as a compatibilizer to promote the intercalation and/or exfoliation of the o‐MMT in the PET. The o‐MMT content was 0, 1, 3, or 5 wt % and the PETi/o‐MMT mass ratio was 0/1, 1/1, or 3/1. The PETi was efficient to promote the intercalation/exfoliation of the o‐MMT in the PET matrix, as revealed by wide angle X‐ray scattering and transmission electron microscopy. Rheological characterization showed that the PET/o‐MMT nanocomposites exhibited a higher complex viscosity at low frequencies than PET, which is characteristic of materials presenting yield strength. Moreover, the higher the content and/or the degree of intercalation/exfoliation of the o‐MMT, the more the nanocomposite behaved like a solid because of a percolated structure formed by the o‐MMT layers, and the more the storage and loss modulus, G′ and G″, became independent of the frequency at low frequencies. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3084–3091, 2007     

Plastic deformation of ethylene/methacrylic acid copolymers and ionomers

A material strained beyond its yield point typically suffers substantial irrecoverable deformation. Surprisingly, this is not the case for ethylene/methacrylic acid (E/MAA) copolymers and ionomers, for which significant permanent deformation does not result until the applied strain exceeds 50–150%, far beyond the yield strain of 5–10%. At room temperature, strain recovery is complete on the order of hours or days following the removal of the applied load. Interestingly, the onset of permanent deformation coincides with a broad maximum or shoulder in the plot of stress versus strain. Two‐dimensional X‐ray scattering studies of both initially isotropic samples and highly aligned blown films reveals that this “second yield shoulder,” commonly observed in the stress–strain curves of ethylene/α‐olefin copolymers, is fundamentally associated with polyethylene crystal fracture, resulting in fragments of reduced lateral extent. Connections formed between these crystalline fragments lock in the deformed conformations of the amorphous intercrystalline segments, preventing the specimen from retracting to its initial dimensions. Additional recovery is possible through heating; complete melting of the deformed specimens results in full recovery up to applied strains of 200%, beyond which strain‐induced chain disentanglement begins. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1588–1598, 2009     

Block copolymers of poly(ethylene terephthalate–polybutylene terephthalate). I. Preparation and crystallization behavior

Block copolymers of two crystallizable compounds, poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT), were developed with PET as the major component and the amount of PBT varying from 1.0 to 20.0 wt %. These block copolymers were prepared by end-group coupling of preformed oligomers. All polymers prepared were of equivalent molecular weight as determined by the intrinsic viscosity method. Thermal properties were determined by differential thermal analysis (DTA), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). With increasing PBT content, the block copolymers showed a general decrease in the values of glass transition temperature, melting temperature, initial decomposition temperature, and maximum decomposition temperature. The heat of fusion and heat of crystallization first increased and then decreased slightly. Rates of crystallization were determined by measuring density as a function of time of isothermal crystallization carried out at 95°C. It was found that small amounts of PBT increased the crystallization rate considerably over that of PET. Random copolymers did not show this phenomenon and behaved more like pure PET. The crystallization behavior of block copolymers was analyzed by the Avrami equation and Avrami exponents were determined. Results were explained on the basis that the faster-crystallizing PBT blocks crystallized first and provided built-in nucleation sites for the subsequent crystallization of PET, thus resulting in a relatively fast-crystallizing copolyester.     

Role of ionic interactions in the compatibility of polyester ionomers with poly(ethylene terephthalate) and nylon 6

Water absorption and other properties of polyamides can potentially be modified by blending with polyesters. The compatibility of a polyester ionomer melt‐blended with nylon‐6 is studied in this article, examining the effect of blending upon crystallization behaviors, morphology, thermal/mechanical properties, and water absorption. Comparisons of the crystallization behaviors of the ionomer/nylon‐6 blends with poly(ethylene terephthalate)/nylon‐6 blends suggest increased compatibility due to greater interactions between the two phases. The results indicate that the presence of a significant amount of the ionomeric groups is required to improve polyester compatibility with polyamides. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2091–2103, 2006     

Swelling-assisted modification of poly(ethylene terephthalate) by methacrylic acid

When a poly(ethylene terephthalate), PET, film is heated in an aqueous solution of methacrylic acid in the presence of hydrogen peroxide as an initiator, it is found that the weight of the film is increased. The amount of methacrylic acid that may be added onto the film is dependent upon the concentration of the monomer, the initiator, and the temperature at which the reaction occurs. Pretreatment of the film with 1,1,2,2,tetrachloroethane causes swelling and the amount of add-on is increased as the swelling level increases. Methacrylic-acid-modified PET films hydrolyze at room temperature in aqueous sodium hydroxide; the rate of hydrolysis is dependent upon the amount of add-on and the concentration of the base. This procedure leads to a chemically induced blend of polymethacrylic acid and poly(ethylene terephthalate), and grafting of the monomer onto the polymer film does not occur. © 1995 John Wiley & Sons, Inc.     

Block copolymers of poly(ethylene terephthalate)-poly(butylene terephthalate). II. Small-angle light-scattering studies

Small-angle light-scattering (SALS) studies were carried out on block copolymers of poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT), the synthesis and characterization of which have been reported in an earlier paper. Samples were crystallized isothermally from the melt at 95°C for predetermined crystallization times in order to follow the formation and growth of crystalline superstructure. During the early stages of crystallization, the block copolymers showed unusual H_v patterns with the four lobes along the polarizer directions, while at later stages they showed the usual H_v patterns with the four lobes at 45° to the polarizer directions. The unusual patterns are characteristic of PBT superstructure, while the usual patterns are characteristic of PET superstructure. These results show that PBT, which is the faster-crystallizing component, crystallizes first and provides nucleation sites for the crystallization of PET, which crystallizes later. Similar behavior was not observed in PET homopolymer and random copolymers of equivalent compositions. In each case the spherulite size increased with the time of crystallization. The ultimate spherulite size decreased with increasing PBT content in the block copolymer, thus showing an increase in nucleation density. It was demonstrated that light scattering is a useful tool to characterize block copolymers of two crystalline components which have different types of superstructure.     

Poly(ethylene terephthalate) copolymers containing nitroterephthalic units. II. Crystallization and conformational studies

The effect of incorporating a nitro side group into the phenylene units of poly(ethylene terephthalate) (PET) on the conformation and crystallizability of this polyester was evaluated. Random poly(ethylene terephthalate‐co‐nitroterephthalate) (PETNT) copolymers containing 5, 10, and 15 mol % nitroterephthalic units were investigated with reference to PET. All the examined copolymers were semicrystalline and were found to adopt the triclinic crystal structure of PET, with the nitrated units being excluded from the crystallites. Both the crystallinity and crystallization rate of PETNT largely decreased with the content of nitrated units, and the O? CH₂? CH₂? O trans‐to‐gauche conformational ratio increased with crystallization, attaining comparable values for all the compositions. The conformation and crystallinity of isothermally crystallized PET and PETNT samples could be correlated with the size of the crystallites generated in each case. However, a different crystal perfecting mechanism seemed to operate for PET and for the PETNT copolymers when they were subjected to annealing. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2759–2771, 2002     

Thermoresponsive copolymers of methacrylic acid and poly(ethylene glycol) methyl ether methacrylate

Copolymers of methacrylic acid (MAA) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) were prepared and their cloud points in aqueous solution were studied as a function of comonomer ratio, solution pH, and presence of hydrophobic comonomers. Under acidic conditions, the cloud point falls below 0 °C for copolymers with between 25% to 60% ether content, because of the formation of hydrophobic H‐bonded ether–acid complexes. The cloud point also decreases with solution pH. For equivalent ether to acid ratios, the cloud point decreases with decreasing PEG chain length, because of the presence of a larger number of hydrophobic methyl and methacrylate groups. Similarly, the cloud point decreases upon incorporation of hydrophobic comonomers such as butyl, lauryl, or glycidyl methacrylates. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6095–6104, 2005     

Inverse emulsion polymerization of acrylamide. II. Synthesis and characterization of copolymers with methacrylic acid

Inverse emulsion copolymerization studies of acrylamide (Am) with methacrylic acid (MAA) are reported. Aqueous monomer solutions were emulsified in toluene with a blend of two surfactants (sorbitan sesquioleate and C18-terminated acrylamide oligomers). Polymerization kinetics in presence of an oil-soluble initiator (AIBN) were determined at 40°C as a function of methacrylic acid content and aqueous-phase pH. Polymerization rates were found to be faster at basic pH than at acidic pH, which appeared to be related to the actual concentration of methacrylic acid in the aqueous phase. Monomer reactivity ratios have been derived as r_A-M = 0.58 ± 0.02 and r_M-A = 4.0 ± 0.10 at pH 4, r_A-M = 0.56 ± 0.005 and r_M-A = 0.15 ± 0.03 at pH 10. These differences were found to have an effect on the molecular characteristics of the copolymers. Initial emulsions and final inverse latexes displayed the same broad size distribution; under basic pH the particle size is relatively insensitive to the ionic comonomer concentration. Poor latex stability is characteristic of copolymer latexes prepared under acidic conditions. Based on these experimental results, some aspects of the polymerization mechanism are discussed.     

Origin of directional tear in blown films of ethylene/methacrylic acid copolymers and ionomers

Blown films of ethylene/methacrylic acid copolymers and ionomers can exhibit pronounced directional tear, meaning that a tear can propagate with much less resistance in a particular direction. However, films blown from the same resin can exhibit different preferred tear directions, which depend on the process conditions. Through wide‐ and small‐angle X‐ray scattering, we demonstrate that this directional tear behavior is a direct result of the orientation of the lamellar polyethylene crystallites in these films; tears propagate more readily between lamellae than through lamellae, as previously recognized for low‐density polyethylene homopolymer. Unlike polyethylene homopolymer, however, an increase in the blowup ratio during the film processing of ethylene/methacrylic acid copolymers and ionomers leads to a 90° rotation of the lamellae that form upon subsequent crystallization. The lamellar rotation arises from a change in the orientation of the row nuclei that form after the melt is inflated and produces a consequent rotation of the preferred tear direction. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 97–106, 2005     

Libraries of methacrylic acid and oligo(ethylene glycol) methacrylate copolymers with LCST behavior

Homopolymers of methacrylic acid (MAA), monoethyleneglycol methyl ether methacrylate (MEOMA), diethyleneglycol methyl ether methacrylate (MEO₂MA), oligo(ethyleneglycol) methyl ether methacrylate (OEGMA₄₇₅ and OEGMA₁₁₀₀) and oligo(ethyleneglycol) ethyl ether methacrylate (OEGEMA₂₄₆) were synthesized with various chain lengths via reversible addition fragmentation chain transfer (RAFT) polymerization. The homopolymers of MAA, MEOMA and OEGMA₁₁₀₀ did not show any cloud point (CP) in the range of 0–100 °C, whereas at a pH value of 7, the CPs were found to be 20.6, 93.7, and 20.0 °C for p(MEO₂MA), p(OEGMA₄₇₅) and p(OEGEMA₂₄₆), respectively, with an initial monomer to initiator ratio of 50. Furthermore, statistical copolymer libraries of MAA with OEGMA₄₇₅ and OEGMA₁₁₀₀ were prepared. The cloud points of the random copolymers of MAA and OEGMA₄₇₅ were found to be in the range of 20–90 °C; surprisingly, even though the homopolymers of MAA and OEGMA₁₁₀₀ did not exhibit any LCST behavior, the copolymers of these monomers at certain molar ratios (up to 40% OEGMA₁₁₀₀) revealed a double responsive behavior for both temperature and pH. Finally, the cloud points were found to be in the range of 22–98 °C, measured at pH values of 2, 4, and 7, while no cloud point was detected at pH 10. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7138–7147, 2008     

Poly(ethylene terephthalate) copolymers containing 5‐nitroisophthalic units. II. Crystallization studies

The microstructure and crystallization behavior of a set of poly(ethylene terephthalate‐co‐5‐nitroisophthalate) copolymers (PETNI) containing 5‐nitroisophthalic units in the 10–50 mol % range were examined and compared to those of poly(ethylene terephthalate) (PET) and poly(ethylene terephthalate‐co‐isophthalate) (PETI) copolymers. A ¹³C NMR analysis of PETNI copolymers in a trifluoroacetic acid solution indicates that they are random copolymers with average sequence lengths in accordance with ideal polycondensation statistics. Differential scanning calorimetry (DSC) studies show that PETNI containing 5‐nitroisophthalic units up to 20 mol % are able to crystallize and that crystallization takes place in these copolymers at much slower rates than in PET. Wide‐angle X‐ray diffraction from powder and fibers reveals that crystallizable PETNI adopts the same triclinic crystal structure as PET, with the nitroisophthalate units being excluded from crystallites. Fourier transform infrared in combination with cross‐polarization/magic‐angle spinning ¹³C NMR spectroscopy demonstrates the occurrence of a gauche–trans conversion encompassing the crystallization process. A correlation between DSC and spectroscopic data leads us to conclude that the content of trans conformer in the noncrystallized phase of PETNI is higher than in both PET and PETI copolymers and suggests that secondary crystallization in the homopolymer must proceed by a mechanism different than that in copolymers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1553–1564, 2001     

Synthesis and characterization of functional gradient copolymers of allyl methacrylate and butyl acrylate

Functional spontaneous gradient copolymers of allyl methacrylate (A) and butyl acrylate (B) were synthesized via atom transfer radical polymerization. The copolymerization reactions were carried out in toluene solutions at 100 °C with methyl 2‐bromopropionate as the initiator and copper bromide with N,N,N′,N″,N″‐pentamethyldiethylenetriamine as the catalyst system. Different aspects of the statistical reaction copolymerizations, such as the kinetic behavior, crosslinking density, and gel fraction, were studied. The gel data were compared with Flory's gelation theory, and the sol fractions of the synthesized copolymers were characterized by size exclusion chromatography and nuclear magnetic resonance spectroscopy. The copolymer composition, demonstrating the gradient character of the copolymers, and the microstructure were analyzed. The experimental data agreed well with data calculated with the Mayo–Lewis terminal model and Bernoullian statistics, with monomer reactivity ratios of 2.58 ± 0.37 and 0.51 ± 0.05 for A and B, respectively, an isotacticity parameter for A of 0.24, and a coisotacticity parameter of 0.33. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5304–5315, 2006     

All-dry synthesis and coating of methacrylic acid copolymers for controlled release

Initiated chemical vapor deposition (iCVD) is presented as an all-dry synthesis and coating method for applying methacrylic acid copolymers as pH-responsive controlled release layers. iCVD combines the strengths of liquid-phase chemical synthesis with a precision solvent-free chemical vapor deposition environment. Copolymers of methacrylic acid and ethyl acrylate were confirmed by a systematic shift in the carbonyl bond stretching mode with a shift in the comonomer ratio within the copolymer and by the ability to apply the Fineman-Ross copolymerization equation to describe copolymerization kinetics. Copolymers of methacrylic acid and ethylene dimethacrylate showed pH-dependent swelling behavior that was applied to the enteric release of fluorescein and ibuprofen.     

Synthesis and characterization of a fire-retardant polyester: Copolymers of ethylene terephthalate and 2-carboxyethyl(phenylphosphinic) acid

This article describes the synthesis and characterization of a polymer-bound nonhalogen fire retardant (NHFR). The reactive fire retardant used in this study is 2-carboxyethyl(phenylphosphinic) acid (CEPP); the polymer is poly(ethylene terephthalate) (PET). Fire-retardant and other modifiers of polymer properties must be bound to the polymer for use in fiber, medical, and food contact applications. Copolymers containing very high levels of CEPP have been prepared. Although fire retardancy in PET is achieved at relatively low levels of CEPP, our ability to produce copolymers with high levels of phosphorous makes them very attractive as polymeric nonfugitive fire retardants for other polymers, such as polycarbonate, nylon, acrylonitrile–butadiene–styrene (ABS), poly(butylene terephthalate) (PBT), and various polymer blends. This article also describes NHFR polyester compositions containing 4,4′-biphenyl dicarboxylic acid and CEPP. It is shown that an increase in aromaticity gained by incorporating the 4,4′-biphenyl dicarboxylic acid leads to higher limiting oxygen index values. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3119–3128, 1999     

Miniemulsion copolymerization of vinyl acetate and butyl acrylate. II. Mathematical model for the monomer transport

A mathematical model is presented to describe the monomer transport between monomer droplets, aqueous phase, and polymer particles during the course of an emulsion polymerization. The model was used to investigate the role of the cosurfactant (hexadecane) in the miniemulsion copolymerization of 50:50 molar ratio vinyl acetate-butyl acrylate monomer mixture, as well as the effect of the different components and process variables on the rate of copolymerization, monomer distribution between phases, and composition of the copolymer.     

Structure and properties of blends containing ethylene-methacrylate copolymers

The preparation, melting point, degree of crystallinity, mechanical properties, and morphology of a family of blends composed of a transition-metal-neutralized carboxylate semicrystalline ionomer (metal-neutralized ethylene-methacrylate copolymer) and an amorphous copolymer (styrene-4-vinyl pyridine copolymer) are described. These polymeric materials contain low levels (≤ 10.0 mol %) of interacting groups which are capable of forming interpolymeric complexes. These interactions are best described as transition metal-pyridine coordination complexes. A general characteristic of these blend systems is that the mechanical properties and morphology are directly influenced by the nature of the counterion and the specific composition ratio of amorphous to semicrystalline component. A nontransition metal counterion (sodium) is weakly interacting at best, while a transition metal counterion (zinc) is strongly interacting. Morphological studies (polarized-light microscopy and small-angle light-scattering measurements) confirm that the glassy component, if nonassociating, resides primarily in the interspherulite region, while the associating species will behave in a similar manner only after the stoichiometric ratio is reached. The morphology directly influences the stress-strain behavior of these blends. It is noteworthy that the spherulite size remains unchanged with nonassociating blends while a 50% reduction is noted in the associating blends. Thermal and wide-angle x-ray scattering measurements confirm the lamellar structure is unaffected by these associations. © 1992 John Wiley & Sons, Inc.