Phase separation in semicrystalline blends of poly(phenylene sulfide) and poly(ethylene terephthalate). II. Effect of poly(phenylene sulfide) homopolymer solubilization of PPS‐graft‐PET copolymer on morphology and crystallization behavior

The morphology and crystallization behavior of poly(phenylene sulfide) (PPS) and poly(ethylene terephthalate) (PET) blends compatibilized with graft copolymers were investigated. PPS‐blend‐PET compositions were prepared in which the viscosity of the PPS phase was varied to assess the morphological implications. The dispersed‐phase particle size was influenced by the combined effects of the ratio of dispersed‐phase viscosity to continuous‐phase viscosity and reduced interfacial tension due to the addition of PPS‐graft‐PET copolymers to the blends. In the absence of graft copolymer, the finest dispersion of PET in a continuous phase of PPS was achieved when the viscosity ratio between blend components was nearly equal. As expected, PET particle sizes increased as the viscosity ratio diverged from unity. When graft copolymers were added to the blends, fine dispersions of PET were achieved despite large differences in the viscosities of PPS and PET homopolymers. The interfacial activity of the PPS‐graft‐PET copolymer appeared to be related to the molecular weight ratio of the PPS homopolymer to the PPS segment of the graft copolymer (M_H/M_A). With increasing solubilization of the PPS graft copolymer segment by the PPS homopolymer, the particle size of the PET dispersed phase decreased. In crystallization studies, the presence of the PPS phase increased the crystallization temperature of PET. The magnitude of the increase in the PET crystallization temperature coincided with the viscosity ratio and extent of the PPS homopolymer solubilization in the graft copolymer. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 599–610, 2000     

Block copolymers of telechelic poly(phenylene sulfide) and semiaromatic thermotropic liquid crystalline polyester segments

We report the synthesis and characterization of copolymers comprising poly(phenyl sulfide) (PPS) blocks and semiaromatic thermotropic liquid crystalline polymer (TLCP) blocks. The copolymers, synthesized by melt-transesterification of dicarboxy-terminated poly(phenylene sulfide) with poly(ethylene terephthalate-co-oxybenzoate) (PET/OB), were characterized using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and polarized light optical microscopy (PLOM). The crystallizability and liquid crystalline properties of the copolymers are greatly influenced by the extent of interchange reactions, the mole percent of oxybenzoate with respect to the PET, the PPS : PET/OB weight ratio, and the reaction time. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2707–2713, 1998     

Graft copolymerization kinetics of acrylic acid onto the poly(ethylene terephthalate) surface by atmospheric pressure plasma inducement

After one atmospheric pressure plasma treatment of poly(ethylene terephthalate) (PET) film, acrylic acid (AAc) in aqueous solution was successfully graft‐copolymerized onto PET films. The effects of reaction time, AAc monomer concentration and reaction temperature on grafting behavior of AAc were systematically studied. Possible reaction kinetics of plasma‐induced graft copolymerization, starting from initial hydroperoxide decomposition, were proposed. Through the Arrhenius analysis about graft copolymerization kinetics of AAc monomers on PET surface, it was revealed that the activation energies of decomposition, propagation and termination were 98.4, 63.5, and 17.5 kJ/mol, respectively. The temperature around 80 °C was favorable not only for the formation of oxide radicals through the thermal decomposition of hydroperoxide on PET surface but also for the extension of graft copolymer chain through direct polymer grafting. Poly(acrylic acid) (PAAc) grains grafted onto PET surfaces possessed relatively uniform size and both PAAc grain size and surface roughness increased with increasing the grafting degree of AAc. The increase of grain size with increasing grafting degree results from the possibility of forming long chain graft copolymers and their shielding of reactive sites. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1594–1601, 2008     

Investigation of transient species in pulse-irradiated poly(ethylene terephthalate) film

A pulse radiolysis study of poly(ethylene terephthalate), PET, film has been carried out with the main aims of investigating charge trapping. In PET, pulse radiolysis gives electron-positive hole pairs. Both charges can be stabilized by the reaction with polymeric matrix. In the first step, the PET radical anions and cations are formed (transient absorption maxima at ∼ 370 and 530 nm). During the second step, the electron is transferred from a PET radical anion to an ester group, followed by formation of an ester radical anion (transient absorption maximum at 430 nm). The recombination of these ionic species leads to an excited state formation observed during and after the 1-μs pulse. Spectral distribution of luminescence observed for pulse-irradiated PET (emission bands at ∼ 340, ∼ 370, and 400–410 nm) was similar to the one obtained for photoexcited PET. The detailed mechanism of ionic reactions in PET is proposed and discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2853–2862, 1999     

Segmented block copolymers of poly(ethylene glycol) and poly(ethylene terephthalate)

A new series of segmented copolymers were synthesized from poly(ethylene terephthalate) (PET) oligomers and poly(ethylene glycol) (PEG) by a two‐step solution polymerization reaction. PET oligomers were obtained by glycolysis depolymerization. Structural features were defined by infrared and nuclear magnetic resonance (NMR) spectroscopy. The copolymer composition was calculated via ¹H NMR spectroscopy. The content of soft PEG segments was higher than that of hard PET segments. A single glass‐transition temperature was detected for all the synthesized segmented copolymers. This observation was found to be independent of the initial PET‐to‐PEG molar ratio. The molar masses of the copolymers were determined by gel permeation chromatography (GPC). © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4448–4457, 2004     

Essential role of chain ends in the nylon‐6/poly(ethylene terephthalate) exchange

A combination of NMR and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF) techniques were suitable tools for examining the exchange reactions that occur during the melt‐mixing of nylon‐6 and poly(ethylene terephthalate) (Ny6/PET) blends in the presence of p‐toluene sulfonic acid (TsOH) at 285 °C. Some researchers believe that TsOH is an efficient catalyst for the amide–ester exchange reactions in PET/Ny6 and PET/nylon‐66 blends in the molten state. Instead, we have found that TsOH is able to react in the molten state with PET, yielding PET oligomers terminated with carboxyl groups. Because the latter oligomers can quickly react with Ny6 producing a Ny6/PET copolymer, the role of TsOH in the melt‐mixing process is not that of a catalyst but of a reactant. Our study allowed the structural identification of the Ny6/PET copolyesteramide produced in the exchange as a function of melt‐mixing time. The results revealed the essential role of carboxyl end groups in the exchange reaction between Ny6 and PET and allowed a detailed mechanism for this reaction. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2778–2793, 2003     

Synthesis of double hydrophilic graft copolymer containing poly(ethylene glycol) and poly(methacrylic acid) side chains via successive ATRP

A well‐defined double hydrophilic graft copolymer, with polyacrylate as backbone, hydrophilic poly(ethylene glycol) and poly(methacrylic acid) as side chains, was synthesized via successive atom transfer radical polymerization followed by the selective hydrolysis of poly(methoxymethyl methacrylate) side chains. The grafting‐through strategy was first used to prepare poly[poly(ethylene glycol) methyl ether acrylate] comb copolymer. The obtained comb copolymer was transformed into macroinitiator by reacting with lithium diisopropylamine and 2‐bromopropionyl chloride. Afterwards, grafting‐from route was employed for the synthesis of poly[poly(ethylene glycol) methyl ether acrylate]‐g‐poly(methoxymethyl methacrylate) amphiphilic graft copolymer. The molecular weight distribution of this amphiphilic graft copolymer was narrow. Poly(methoxymethyl methacrylate) side chains were connected to polyacrylate backbone through stable C? C bonds instead of ester connections. The final product, poly[poly(ethylene glycol) methyl ether acrylate]‐g‐poly(methacrylate acid), was obtained by selective hydrolysis of poly(methoxymethyl methacrylate) side chains under mild conditions without affecting the polyacrylate backbone. This double hydrophilic graft copolymer was found be stimuli‐responsive to pH and ionic strength. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4056–4069, 2008     

Preparation of poly(ethylene terephthalate-co-isophthalate) by ester interchange reaction in the PET/PEI blend system

Optimum conditions for the synthesis of PEI of considerable molecular weight have been established. Poly(ethylene terephthalate-co-isophthalate) (PETI) has been prepared through the ester interchange reaction of a blend of poly(ethylene terephthalate) (PET) and poly(ethylene isophthalate) (PEI). NMR analysis has indicated that the PETI changes from a block-type copolymer to a random type copolymer as the ester interchange reaction proceeds. If the reaction is limited to 20 min, the resulting PETI is crystallizable. The effects of catalysts that have been used during the synthesis of PEI on the characteristics of PETI are also discussed. © 1997 John Wiley & Sons, Inc.     

End‐group modification of poly(2,6‐dimethyl‐1,4‐phenylene ether) and in situ synthesis of poly(2,6‐dimethyl‐1,4‐phenylene ether)‐b‐poly(ethylene terephthalate) block copolymer

The preparation of poly(2,6‐dimethyl‐1,4‐phenylene ether)‐b‐poly(ethylene terephthalate) block copolymer was performed by the reaction of the 2‐hydroxyethyl modified poly(2,6‐dimethyl‐1,4‐phenylene ether) (PPE‐EtOH) with poly(ethylene terephthalate) (PET) by an in situ process, during the synthesis of the polyester. The yield of the reaction of the 2‐hydroxyethyl functionalized PPE‐EtOH with PET was close to 100%. A significant proportion of the PET‐b‐PPE‐EtOH block copolymer was found to have short PET block. Nevertheless, the copolymer structured in the shape of micelles (20 nm diameter) and very small domains with 50–200 nm diameter, whereas unmodified PPE formed much larger domains (1.5 μm) containing copolymer. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3985–3991, 2008     

Bond interchange reactions in functionalized triglyceride oil/poly(ethylene terephthalate) compositions

Naturally functionalized triglyceride oils are renewable resources which contain reactive chemical groups, hydroxyl in the case of castor oil, and epoxide in the case of vernonia oil. In this article, the reaction of these groups, and the ester linkages between the glycerol and acid residue portions of the oil molecule with poly(ethylene terephthalate) (PET) is investigated through a variety of means. Multiple reactions are possible in the triglyceride–PET system, some of which form a copolymer that increases miscibility, and if allowed to continue, forms a completely random copolymer mixture. Among the numerous reactions possible, PET–ester exchange with the hydroxyl or epoxide functionality of the triglyceride oils is found to be the most significant, and the effects of these and other reactions are observed and structural implications discussed. © 1993 John Wiley & Sons, Inc.     

Strategies toward biocompatible artificial implants: Grafting of functionalized poly(ethylene glycol)s to poly(ethylene terephthalate) surfaces

Epoxide and aldehyde end‐functionalized poly(ethylene glycol)s (PEGs) (M_w = 400, 1000, 3400, 5000, and 20,000) were grafted to poly(ethylene terephthalate) (PET) film substrates that contained amine or alcohol groups. PET‐PAH and PET‐PEI were prepared by reacting poly(allylamine) (PAH) and polyethylenimine (PEI) with PET substrates, respectively; PET‐PVOH was prepared by the adsorption of poly(vinyl alcohol) (PVOH) to PET substrates. Grafting was characterized and quantified by the increase of the intensity of the PEG carbon peak in the X‐ray photoelectron spectra. Grafting yield was optimized by controlling reaction parameters and was found to be substrate‐independent in general. Graft density consistently decreased as PEG chain length was increased. This is likely due to the higher steric requirement of higher molecular weight PEG molecules. Water contact angles of surfaces containing long PEG chains (3400, 5000, and 20,000) are much lower than those containing shorter PEG chains (400 and 1000). This indicates that longer PEG chains are more effective in rendering surfaces hydrophilic. Protein adsorption experiments were carried out on PET‐ and PEG‐modified derivatives using collagen, lysozyme, and albumin. After PEG grafting, the amount of protein adsorbed was reduced in all cases. Trends in surface requirements for protein resistance are: surfaces with longer PEG chains and higher chain density, especially the former, are more protein resistant; PEG grafted to surfaces containing branched or network polymers is not effective at covering the underlying substrate, and thus does not protect the entire surface from protein adsorption; and substrates containing surface charge are less protein‐resistant. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5389–5400, 2004     

Compatibilizing effect of transesterification product between components in bisphenol-A polycarbonate/poly(ethylene terephthalate) blend

The compatibilizing effect of a random copolymer, which is the transesterification product, on its corresponding blend system of bisphenol-A polycarbonate/poly(ethylene terephthalate) (PC/PET) has been studied using a Differential Scanning Calorimeter and a Phase Contrast Microscope. It was found that after a long time of transesterification between PET and PC (50/50, wt %), the obtained product, that is, TCET random copolymer, is miscible with individual homopolymers of PC and PET. The addition of the TCET copolymer into the immiscible PC/PET blend can make the glass transitions of the PC-rich phase and PET-rich phase approach each other, and eventually merge into a single glass transition when the content of TCET in the ternary mixture reaches 60 wt %. Meanwhile, the phase structure images showed that with the increasing content of the TCET copolymer in the ternary blends, the size of the phase domains decreases and the phase domains further diminish at 60 wt % TCET. All these results proved the compatibilizing effect of TCET copolymer on the PC/PET blends in their ternary mixture. The mechanism of the compatibilizing effect is directly related to the reduction of the interfacial tension between PC-rich and PET-rich phase domains in the presence of increasing amounts of TCET copolymer in the ternary blends. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2960–2972, 1999     

Morphology evolution of nanocomposites based on poly(phenylene sulfide)/poly(butylene terephthalate) blend

Poly(phenylene sulfide) (PPS)/poly(butylene terephthalate) (PBT) (60/40 w/w) blend nanocomposites (PPS/PBTs) were prepared by direct melt compounding of PPS, PBT, and organoclay. The morphology and rheology of PPS/PBTs were investigated using scanning electron microscope and transmission electron microscope as well as parallel plate rheometer. The intercalated clay tactoids are selectively located in the continuous PBT phase due to their nice affinity. A novel morphology evolution of the immiscible blend matrices is observed with increase of clay loadings. Small addition of clay increases the discrete PPS spherulite domain size. With increasing loading levels, the PPS phase transform to the fibrous structure and finally, to the partial laminar structure at the high loading levels, in which shows a characteristic of large‐scaled phase separation. The presence of clay, however, does not impede the coalescence of the PPS phase because the phase size increases with increasing clay loadings. The elasticity and blend ratio of two matrices are proposed as the important roles on the morphological evolution. Moreover, the laminar structure of PPS phase is very sensitive to the steady shear flow and is easy to be broken down to spherulite droplet at the low shear rate. However, high shear level is likely to facilitate the coalescence of those PPS phase and finally to phase inversion, both contributing to increases of the dynamic modulus after steady shear flow. In conclusion, the morphology of the immiscible polymer blend nanocomposites depends strongly on both the clay loadings and shear history. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1265–1279, 2008     

Graft copolymerization induced by thermal reactions of the binary alkali salts of poly(carboxylic acid)–brominated carboxylic acid in bulk

Thermal reactions of the binary alkali salts of poly(carboxylic acid)–brominated carboxylic acid such as sodium or potassium poly(4-vinylbenzoate)-2-bromopropanoate [Na or K (PVBA-2-BPA)] in bulk were investigated. A methanol solution of binary acids was prepared by fixing the molar ratio of the repeating unit of polymeric acid to the fraction of brominated carboxylic acid. The binary salts were prepared by the neutralization of the binary acid solution. The product of the thermal reaction followed by esterification was identified as a graft copolymer containing PVBA in the main chain and polylactic acid in the side chain. The reaction of 1/15 K (PVBA-2-BPA) at 120 °C for 2 h yielded the highest percentage of grafting (300%). The grafting proceeded gradually for the initial 2 h and then somewhat. Reactivity of the K salt was higher than that of the corresponding Na salt. The thermal reaction of 1/10 K [polymethacrylate-2-BPA (PMA-2-BPA)] at 120 °C for 2 h also yielded a graft copolymer, and the percentage of grafting was 300%. However, reaction temperatures higher than 120 °C caused homopolycondensation of K 2-BPA prior to grafting, and homopolycondensation occurred prior to grafting in the reaction with Na (PMA-2-BPA). © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1877–1885, 2001     

Novel amphiphilic graft copolymers bearing hydrophilic poly(acrylic acid) backbones and hydrophobic poly(butyl methacrylate) side chains

A novel amphiphilic graft copolymer consisting of hydrophilic poly(acrylic acid) backbones and hydrophobic poly(butyl methacrylate) side chains was synthesized by successive atom transfer radical polymerization followed by hydrolysis of poly‐(methoxymethyl acrylate) backbone. A grafting‐from strategy was employed for the synthesis of graft copolymers with narrow molecular weight distributions (polydispersity index < 1.40). Hydrophobic side chains were connected to the backbone through stable C? C bonds instead of ester connections. Poly(methoxymethyl acrylate) backbone was easily hydrolyzed to poly(acrylic acid) backbone with HCl without affecting the hydrophobic side chains. The amphiphilic graft copolymer could form stable micelles in water. The critical micelle concentration in water was determined by a fluorescence probe technique. The morphology of the micelles was preliminarily explored with transmission electron microscopy and was found to be spheres. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6857–6868, 2006     

Chemical structure of poly(ethylene terephthalate)–styrene and nylon–styrene graft copolymers prepared by radiation techniques

The graft copolymerizations of styrene onto poly(ethylene terephthalate) (PET) and nylon fibers were carried out by the mutual irradiation and preirradiation methods. True graft copolymers were isolated from the products by extraction and characterized by hydrolysis and osmometry. Among the swelling agents employed, methanol was most effective for increasing the extent of grafting onto PET. In both methods of the grafting, the molecular weight of polystyrene formed in the substrate matrix was higher than one million if no chain-transfer agent was added to the monomer solution. Similar to the case of radiation grafting onto poly(vinyl alcohol) and cellulose, the isolated graft copolymer carried only one branch per copolymer molecule in both cases. Of great interest is the particularly low extent of grafting in the case of PET–styrene. This should be attributed to the low sensitivity of PET to radiation. The grafting site on the mother polymer molecule is discussed on the basis of the solution behavior of the branch polymers separated from the backbone.     

Surface‐initiated polymerization from poly(ethylene terephthalate)

The free‐radical polymerization of styrene initiated from a functionalized poly(ethylene terephthalate) (PET) surface yielded a tethered polymer layer. The anchoring of the initiator species on the PET surface was performed from surface‐reactive groups easily generated by an alkaline hydrolysis of PET. After each surface modification, PET films were characterized by X‐ray photoelectron spectroscopy, measurements of water contact angles, and time‐of‐flight secondary‐ion mass spectrometry. The influence of the polymerization duration, the grafted initiator density, and the grafting mode on the efficiency of the surface‐initiated polymerization of styrene was investigated. In some cases, the tethering of the polystyrene layer on PET could be a reversible process. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1347–1359, 2003     

Crystallization‐induced aging in poly(trimethylene terephthalate)/ poly(ethylene oxide terephthalate) segmented block copolymers

A new type poly(ether–ester) based on poly(trimethylene terephthalate) as rigid segments and poly(ethylene oxide terephthalate) as soft segments was synthesized and its aging behavior were investigated. Different from other polymer, the segmented block copolymers exhibited a unique aging mechanism. That is, the degradation of mechanical property within short term annealing was due to the overgrown crystals and dramatically increased crystallinity, which was proved by field emission scanning electron microscope (FE‐SEM) and differential scanning calorimetry (DSC), respectively. The deterioration in mechanical property after long term annealing was the results of both the increase in crystallinity and the decrease in molecular weight. Moreover, FE‐SEM showed many interesting flower‐like crystals presented on the surface of annealed sample. The flower‐like crystals consist of several radialized petal‐like arms and a more densely packed center, which has been seldom found in polymer bulk. Wide‐angle x‐ray diffraction results showed that the copolymer has the same crystal structure as PTT. Such poly(ether–ester) or its blends with other polymer could be suitable for rapid degradable products, such as package and vessel. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 411–416, 2010     

Synthesis,physical characterization,and acetone sorption kinetics in random copolymers of poly(ethylene terephthalate) and poly(ethylene 2,6-naphthalate)

Random copolymers of poly(ethylene terephthalate) (PET) and poly(ethylene 2,6-naphthalate) (PEN) were synthesized by melt condensation. In a series of thin, solvent cast films of varying PEN content, acetone diffusivity and solubility were determined at 35°C and an acetone pressure of 5.4 cm Hg. The kinetics of acetone sorption in the copolymer films are well described by a Fickian model. Both solubility and diffusivity decrease with increasing PEN content. The acetone diffusion coefficient decreases 93% from PET to PET/85PEN, a copolymer in which 85 weight percent of the dimethyl terephthalate in PET has been replace by dimethyl naphthalate 2,6-dicarboxylate. The acetone solubility coefficient in the amorphous regions of the polymer decreases by approximately a factor of two over the same composition range. The glass/rubber transition temperatures of these materials rise monotonically with increasing PEN content. Copolymers containing 20 to 80 wt % PEN are amorphous. Samples with <20% or >80% PEN contain measurable levels of crystallinity. Estimated fractional free volume in the amorphous regions of these samples is lower in the copolymers than in either of the homopolymers. Relative free volume as probed by positron annihilation lifetime spectroscopy (PALS) decreases systematically with increasing PEN content. Acetone diffusion coefficients correlate well with PALS results. Infrared spectroscopy suggests an increase in the fraction of ethylene glycol units in the trans conformation in the amorphous phase as the concentration of PEN in the copolymer increases. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2981–3000, 1998     

Synthesis of poly(p‐phenylene sulfide) from bis(4‐bromophenyl) disulfide

Improved reaction conditions for the preparation of poly(p‐phenylene sulfide) (PPS) directly from bis(4‐bromophenyl) disulfide (BBD) have been established. Heating BBD with magnesium metal afforded only a low molecular weight polymer. PPS with a melting temperature around 280 °C was obtained from BBD in the presence of sodium carbonate or zinc metal. The best results were obtained with the addition of a catalytic amount of KI to the zinc–BBD mixture. Polymers prepared by the above methods are semicrystalline and dissolve in 1‐chloronaphthalene and have properties comparable to commercial PPS. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 900–904, 2006