Melt‐flow‐induced phase morphologies of a high‐density polyethylene/poly(ethylene‐co‐1‐octene) blend

A blend of high‐density polyethylene and an elastomeric poly(ethylene‐co‐1‐octene) resin, containing 25 mol % octene and long‐chain branching, was phase‐separated in the melt under quiescent conditions. After melt flow, the blend had fine globular or interconnected phase morphologies that were interpreted as originating from the various stages of coarsening after liquid–liquid phase separation through spinodal decomposition. It was inferred that the miscibility of the blend was enhanced under melt flow. After cessation of flow, concurrent liquid–liquid and solid–liquid phase separation took place, resulting in the formation of an interpenetrating morphology comprising amorphous polyethylene, copolymer, and crystalline polyethylene. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 380–389, 2001     

Polydispersity of ethylene sequence length in metallocene ethylene/α‐olefin copolymers. I. Characterized by thermal‐fractionation technique

In this article, the polydispersity of the ethylene sequence length (ESL) in ethylene/α‐olefin copolymers was studied by atomic force microscopy (AFM) and the thermal‐fractionation technique. The crystal morphology observation by AFM showed that morphology changed gradually with decreasing average ESL from complete lamellae over shorter and more curved lamellae to a granular‐like morphology, and the mixed morphology was observed after stepwise crystallization from phase‐separated melt. This result indicated that the ethylene sequence with different lengths crystallized into a crystalline phase with a different size and stability at the copolymer systems. The thermal‐fractionation technique was used to characterize the polydispersity of ESL. Three of the following statistical terms were introduced to describe the distribution of ESL and the lamellar thickness: the arithmetic mean L?_n, the weight mean L?_w, and the broadness index I = L?_w/L?_n. It was concluded that the polydispersity of ESL could be quantitatively characterized by the thermal‐fractionation technique. The effects of temperature range, temperature‐dependent specific heat capacity C_p of copolymer, and the molecular weight on the results of thermal fractionation were discussed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 813–821, 2002     

Effect of PBT molecular weight and reactive compatibilization on the dispersed‐phase coalescence of PBT/SAN blends

Poly(butylene terephthalate) (PBT)/styrene‐acrylonitrile copolymer (SAN) blends were investigated with respect to their phase morphology. The SAN component was kept as dispersed phase and PBT as matrix phase and the PBT/SAN viscosity ratio was changed by using different PBT molecular weights. PBT/SAN blends were also compatibilized by adding methyl methacrylate‐co‐glycidyl methacrylate‐co‐ethyl acrylate terpolymer, MGE, which is an in situ reactive compatibilizer for melt blending. In noncompatibilized blends, the dispersed phase particle size increased with SAN concentration due to coalescence effects. Static coalescence experiments showed evidence of greater coalescence in blends with higher viscosity ratios. For noncompatibilized PBT/SAN/MGE blends with high molecular weight PBT as matrix phase, the average particle size of SAN phase does not depend on the SAN concentration in the blends. However noncompatibilized blends with low molecular weight PBT showed a significant increase in SAN particle size with the SAN concentration. The effect of MGE epoxy content and MGE molecular weight on the morphology of the PBT/SAN blend was also investigated. As the MGE epoxy content increased, the average particle size of SAN initially decreased with both high and low molecular weight PBT phase, thereafter leveling off with a critical content of epoxy groups in the blend. This critical content was higher in the blends containing low molecular weight PBT than in those with high molecular weight PBT. At a fixed MGE epoxy content, a decrease in MGE molecular weight yielded PBT/SAN blends with dispersed nanoparticles with an average size of about 40 nm. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

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     

Synthesis of four‐armed poly(ε‐caprolactone)‐block‐poly(ethylene oxide) by diethylzinc catalyst

Biodegradable, amphiphilic, four‐armed poly(?‐caprolactone)‐block‐poly(ethylene oxide) (PCL‐b‐PEO) copolymers were synthesized by ring‐opening polymerization of ethylene oxide in the presence of four‐armed poly(?‐caprolactone) (PCL) with terminal OH groups with diethylzinc (ZnEt₂) as a catalyst. The chemical structure of PCL‐b‐PEO copolymer was confirmed by ¹H NMR and ¹³C NMR. The hydroxyl end groups of the four‐armed PCL were successfully substituted by PEO blocks in the copolymer. The monomodal profile of molecular weight distribution by gel permeation chromatography provided further evidence for the four‐armed architecture of the copolymer. Physicochemical properties of the four‐armed block copolymers differed from their starting four‐armed PCL precursor. The melting points were between those of PCL precursor and linear poly(ethylene glycol). The length of the outer PEO blocks exhibited an obvious effect on the crystallizability of the block copolymer. The degree of swelling of the four‐armed block copolymer increased with PEO length and PEO content. The micelle formation of the four‐armed block copolymer was examined by a fluorescent probe technique, and the existence of the critical micelle concentration (cmc) confirmed the amphiphilic nature of the resulting copolymer. The cmc value increased with increasing PEO length. The absolute cmc values were higher than those for linear amphiphilic block copolymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 950–959, 2004     

Stabilization of a cocontinuous phase morphology by a tapered diblock or triblock copolymer in polystyrene‐rich low‐density polyethylene/polystyrene blends

The stability against the thermal annealing of a cocontinuous two‐phase morphology developed in polystyrene (PS)/low‐density polyethylene (LDPE) blends containing 80 wt % PS was investigated. Blends containing 1, 5, and 10 wt % of a tapered diblock poly(styrene‐block‐hydrogenated butadiene) (P(S‐b‐hB)) or triblock poly(styrene‐block‐hydrogenated butadiene‐block‐styrene) (P(S‐hB‐S)) copolymer were melt‐blended with roll‐mill mixing equipment. The efficiency of each of the two copolymers in stabilizing against coalescence the cocontinuous morphology was examined. The tensile properties of the resulting blends, annealed and nonannealed, were also examined in relation to the morphology induced by thermal annealing. The phase morphology was studied by optical and scanning electron microscopy. With computer‐aided image analysis, it was possible to obtain a measurable characteristic parameter to quantify the cocontinuous phase morphology. When it was necessary, the extraction of one phase with a selective solvent was performed. Although the observed differences were subtle, the tapered diblock exhibited a more efficient compatibilizing activity than the triblock copolymer, particularly at a low concentration of about 2 wt %. The superiority of the tapered diblock over the triblock might be due to its ability to quantitatively locate at the LDPE/PS interface and consequently form a more efficient barrier against the subsequent breakup of the elongated structures of the cocontinuous phase morphology. The tensile properties of the triblock‐modified blends were more sensitive to thermal annealing than the tapered‐modified ones. This deficiency was ascribed to the phase morphology coarsening of the dispersed polyethylene phase. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 202–216, 2003     

Effect of chain blockiness on the phase behavior of ethylene‐octene copolymer blends

New challenges and opportunities for polyolefin blends arise from the recent introduction of olefin block copolymers (OBCs). In this study, the effect of chain blockiness on the miscibility and phase behavior of ethylene‐octene (EO) copolymer blends was studied. Binary blends of two statistical copolymers (EO/EO blends) that differed in comonomer content were compared with blends of an EO with a blocky EO copolymer (EO/OBC blends). The blends were rapidly quenched to retain the phase morphology in the melt and the phase volumes were obtained by atomic force microscopy (AFM). Two EOs of molecular weight about 100 kg/mol were miscible if the difference in octene content was less than about 10 mol % and immiscible if the octene content difference was greater than about 13 mol %. The blocky nature of the OBCs reduced the miscibility and broadened the partial miscibility window of the EO/OBC blends compared with the EO/EO blends. The EO/OBC blends were miscible if the octene content difference was less than 7 mol % and immiscible above 13 mol % octene content difference. It was also found that the phase behavior of EO/OBC blends strongly depended on blend composition even for constituent polymers of about the same molecular weight. Significantly more demixing was observed in an OBC‐rich blend (EO/OBC 30/70 v/v) than in an OBC‐poor blend (EO/OBC 70/30 v/v). An interpretation based on extractable fractions of the OBC described the major features of the EO/OBC (30/70 v/v) blends. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1554–1572, 2009     

Synthesis of new 1‐decene‐based LLDPE resins and comparison with the corresponding 1‐octene‐ and 1‐hexene‐based LLDPE resins

This article extends the composition of linear low‐density polyethylene (LLDPE) resins to that containing 1‐decene comonomer units, and examines the effects of comonomer (type and concentration) to copolymerization and physical properties of LLDPE resins. CGC metallocene technology, under high temperature and high pressure (industrial reaction condition), was used to prepare three types of well‐defined LLDPE copolymers containing 1‐hexene, 1‐octene, and 1‐decene units. They show high molecular weight with narrow molecular weight and composition distributions, comparative catalyst activities, and similar comonomer effects. However, 1‐decene seems to exhibit significantly higher comonomer incorporation than 1‐hexene and 1‐octene, which may be associated with its high boiling point, maintaining liquid phase during the polymerization. The resulting LLDPE copolymers show a clear structure–property relationship. Melting temperature and crystallinity of the copolymer are governed by mole % of comonomer. The increase of branch density linearly decreases the LLDPE melting point and exponential reduction of its crystallinity. On the other hand, the density of the copolymer decreases with the increase of comonomer weight %, which shows a sharp linear relationship in the low comonomer content. The tensile properties of 1‐decene‐based LLDPE are very comparative with those of the commercial LLDPE resins with similar compositions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 639–649, 2007     

Crystallization and stereocomplexation behavior of poly(D‐ and L‐lactide)‐b‐poly(N,N‐dimethylamino‐2‐ethyl methacrylate) block copolymers

The thermal properties, crystallization, and morphology of amphiphilic poly(D ‐lactide)‐b‐poly(N,N‐dimethylamino‐2‐ethyl methacrylate) (PDLA‐b‐PDMAEMA) and poly (L ‐lactide)‐b‐poly(N,N‐dimethylamino‐2‐ethyl methacrylate) (PLLA‐b‐PDMAEMA) copolymers were studied and compared to those of the corresponding poly(lactide) homopolymers. Additionally, stereocomplexation of these copolymers was studied. The crystallization kinetics of the PLA blocks was retarded by the presence of the PDMAEMA block. The studied copolymers were found to be miscible in the melt and the glassy state. The Avrami theory was able to predict the entire crystallization range of the PLA isothermal overall crystallization. The melting points of PLDA/PLLA and PLA/PLA‐b‐PDMAEMA stereocomplexes were higher than those formed by copolymer mixtures. This indicates that the PDMAEMA block is influencing the stability of the stereocomplex structures. For the low molecular weight samples, the stereocomplexes particles exhibited a conventional disk‐shape structure and, for high molecular weight samples, the particles displayed unusual star‐like shape morphology. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1397–1409, 2011     

Polyolefin graft copolymers via living polymerization techniques: Preparation of poly(n‐butyl acrylate)‐graft‐polyethylene through the combination of Pd‐mediated living olefin polymerization and atom transfer radical polymerization

Poly(n‐butyl acrylate)‐graft‐branched polyethylene was successfully prepared by the combination of two living polymerization techniques. First, a branched polyethylene macromonomer with a methacrylate‐functionalized end group was prepared by Pd‐mediated living olefin polymerization. The macromonomer was then copolymerized with n‐butyl acrylate by atom transfer radical polymerization. Gel permeation chromatography traces of the graft copolymers showed narrow molecular weight distributions indicative of a controlled reaction. At low macromonomer concentrations corresponding to low viscosities, the reactivity ratios of the macromonomer to n‐butyl acrylate were similar to those for methyl methacrylate to n‐butyl acrylate. However, the increased viscosity of the reaction solution resulting from increased macromonomer concentrations caused a lowering of the apparent reactivity ratio of the macromonomer to n‐butyl acrylate, indicating an incompatibility between nonpolar polyethylene segments and a polar poly(n‐butyl acrylate) backbone. The incompatibility was more pronounced in the solid state, exhibiting cylindrical nanoscale morphology as a result of microphase separation, as observed by atomic force microscopy. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2736–2749, 2002     

Morphology engineering of a novel poly(L‐lactide)/poly(1,5‐dioxepan‐2‐one) microsphere system for controlled drug delivery

Morphology is presented as a powerful tool to control the in vitro degradation and drug release characteristics of novel drug delivery microspheres prepared from homopolymer blends of 1,5‐dioxepan‐2‐one, DXO, and L ‐lactide, L‐LA. Their performance in this respect was compared to analogous P(L‐LA‐co‐DXO) microspheres. Blends formed denser and less porous microspheres with a higher degree of matrix crystallinity than copolymers of corresponding L‐LA:DXO composition. The morphology differences of blends and copolymers, further adjustable by means of component ratio, are shown to have a vital impact on the in vitro performance. Sustained drug delivery was obtained from both copolymers and blends. Molecular weight loss was retarded and diffusion‐mediated release was inhibited in the latter case, further delaying the release process. The effects of storage on the physicochemical properties of these systems were evaluated under desiccated and moist conditions for 5 months. Storage‐induced physicochemical changes, such as matrix crystallization and molecular weight decrease, were accelerated at higher relative humidities. P(L‐LA‐co‐DXO) demonstrated higher moisture sensitivity than a PLLA‐PDXO blend of corresponding composition. The more crystalline and dense morphology of blend microspheres may thus be considered an improvement of the storage stability. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 786–796, 2000     

Melting behavior of polyethylene/α‐olefin copolymers: Narrow composition distribution copolymers and fractions from Ziegler–Natta and single‐site catalyst products

The melting temperature and heat of fusion were measured for an extensive series of compositionally uniform copolymers of ethylene with butene‐1, hexene‐1, and octene‐1. Fractions and whole polymers that exhibited minimal interchain compositional heterogeneity were from commercial copolymers made with either Ziegler–Natta (ZN) or single‐site metallocene catalysts. The present results do not support recent claims that ZN and corresponding metallocene catalyst copolymers melt at significantly different temperatures, nor the implication that comonomer incorporation is “blocky” in ZN copolymers. In five of the six comonomer/catalyst systems the dependencies of the melting temperature on comonomer type and amount were scarcely distinguishable. This common behavior is the same as that for a model random copolymer, so we conclude that most ethylene/α‐olefin copolymers have random distributions of ethylene sequences. The exception in the present study is a metallocene ethylene/butene‐1 copolymer that melts at lower temperatures and apparently has perceptibly alternating sequence distributions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3416–3427, 2004     

Effects of poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] on the charge distributions of low‐density polyethylene/polystyrene blends

The effect of the triblock copolymer poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] (SEBS) on the formation of the space charge of immiscible low‐density polyethylene (LDPE)/polystyrene (PS) blends was investigated. Blends of 70/30 (wt %) LDPE/PS were prepared through melt blending in an internal mixer at a blend temperature of 220 °C. The amount of charge that accumulated in the 70% LDPE/30% PS blends decreased when the SEBS content increased up to 10 wt %. For compatibilized and uncompatibilized blends, no significant change in the degree of crystallinity of LDPE in the blends was observed, and so the effect of crystallization on the space charge distribution could be excluded. Morphological observations showed that the addition of SEBS resulted in a domain size reduction of the dispersed PS phase and better interfacial adhesion between the LDPE and PS phases. The location of SEBS at a domain interface enabled charges to migrate from one phase to the other via the domain interface and, therefore, resulted in a significant decrease in the amount of space charge for the LDPE/PS blends with SEBS. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2813–2820, 2004     

Radical copolymerization of maleimide with ethyl α‐ethylacrylate and α‐ethylacrylic acid via RAFT

The copolymerization of maleimide (MI) with α‐ethylacrylic acid (EAA) and with ethyl α‐ethylacrylate (EEA) in the presence of 2‐phenylprop‐2‐yl dithiobenzoate (PPDB) was investigated. The copolymerization of MI and EAA was difficult to conduct with the reversible addition–fragmentation chain transfer (RAFT) mechanism because reinitiation of expelled radicals by fragmentation chain transfer was inhibited by the association of EAA in polar solvent and the strong interaction of the imino of MI with the carboxyl of EAA between the propagation chains. When the carboxylic group of EAA was esterified, then the copolymerization went well via RAFT, and alternating copolymers with controlled molecular weight were obtained. Combining by electron spin resonance showed a different result. It was found that before 30% of the comonomer conversion had occurred, the copolymer poly(EEA‐co‐MI) showed increasing molecular weight with the conversion and a rather narrow molecular weight distribution; then the molecular weight of the copolymer began to retard. This phenomenon of retardation was aggravated at high temperature. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3828–3835, 2004     

Stress–strain behavior of low‐density polyethylene/poly(methyl methacrylate) blends with modulated interfaces with a hydrogenated polybutadiene‐block‐poly(methyl methacrylate) diblock copolymer

The stress–strain diagrams and ultimate tensile properties of uncompatibilized and compatibilized hydrogenated polybutadiene‐block‐poly(methyl methacrylate) (HPB‐b‐PMMA) blends with 20 wt % poly(methyl methacrylate) (PMMA) droplets dispersed in a low‐density polyethylene (LDPE) matrix were studied. The HPB‐b‐PMMA pure diblock copolymer was prepared via controlled living anionic polymerization. Four copolymers, in terms of the molecular weights of the hydrogenated polybutadiene (HPB) and PMMA sequences (22,000–12,000, 63,300–31,700, 49,500–53,500, and 27,700–67,800), were used. We demonstrated with the stress–strain diagrams, in combination with scanning electron microscopy observations of deformed specimens, that the interfacial adhesion had a predominant role in determining the mechanism and extent of blend deformation. The debonding of PMMA particles from the LDPE matrix was clearly observed in the compatibilized blends in which the copolymer was not efficiently located at the interface. The best HPB‐b‐PMMA copolymer, resulting in the maximum improvement of the tensile properties of the compatibilized blend, had a PMMA sequence that was approximately half that of the HPB block. Because of the much higher interactions encountered in the PMMA phase in comparison with those in HPB (LDPE), a shorter sequence of PMMA (with respect to HPB but longer than the critical molecular weight for entanglement) was sufficient to favor a quantitative location of the copolymer at the LDPE/PMMA interface. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 22–34, 2005     

Preparation and characterization of biodegradable poly(trimethylenecarbonate‐ε‐caprolactone)‐block‐poly(p‐dioxanone) copolymers

A series of poly(trimethylenecarbonate‐ε‐caprolactone)‐block‐poly(p‐dioxanone) copolymers were prepared with varying feed rations by using two step polymerization reactions. Poly(trimethylenecarbonate)(ε‐caprolactone) random copolymer was synthesized with stannous‐2‐ethylhexanoate and followed by adding p‐dioxanone monomer as the other block. The ring opening polymerization was carried out at high temperature and long reaction time to get high molecular weight polymers. The monofilament fibers were obtained using conventional melting spun methods. The copolymers were identified by ¹H and ¹³C NMR spectroscopy and gel permeation chromatography (GPC). The physicochemical properties, such as viscosity, molecular weight, melting point, glass transition temperature, and crystallinity, were studied. The hydrolytic degradation of copolymers was studied in a phosphate buffer solution, pH = 7.2, 37 °C, and a biological absorbable test was performed in rats. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2790–2799, 2005     

Mutual influence of the morphology and capillary rheological properties in nylon/glass‐fiber/liquid‐crystalline‐polymer blends

Nylon‐6/glass‐fiber (GF)/liquid‐crystalline‐polymer (LCP) ternary blends with different viscosity ratios were prepared with three kinds of nylon‐6 with different viscosities as matrices. The rheological behaviors of these blends were characterized with capillary rheometry. The morphology was observed with scanning electron microscopy and polarizing optical microscopy. This study showed that although LCP did not fibrillate in binary nylon‐6/LCP blends, LCP fibrillated to a large aspect ratio in some ternary blends after GF was added. The addition of 5 wt % LCP significantly reduced the melt viscosity of nylon‐6/GF blends to such an extent that some nylon‐6/GF/LCP blends had quite low viscosities, not only lower than those of neat resins and nylon‐6/GF blends but also lower than those of corresponding nylon‐6/LCP blends. The mutual influence of the morphology and rheological properties was examined. The great reduction of the melt viscosity was considered the result of LCP fibrillation. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1619–1627, 2004     

A study on melt grafting of maleic anhydride onto low‐density polyethylene and its blend with polyamide 6

Graft copolymerization of low‐density polyethylene (LDPE) with a maleic anhydride (MAH) was performed using intermeshing corotating twin‐screw extruder in the presence of benzoyl peroxide (BPO). The LDPE/polyamide 6 (PA6) and LDPE‐g‐MAH/PA6 blends were prepared in a corotating twin‐screw extruder. The melt viscosity of the grafted LDPE was measured by a capillary rheometer. The grafted copolymer was characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microcopy (SEM). The influence of the variation in temperature, BPO and MAH concentration, and temperature on the grafting degree and on the melt viscosity was studied. The grafting degree increased appreciably up to about 0.45 phr and then decreased continuously with an increasing BPO concentration. According to the FTIR analysis, it was found that the amount of grafted MAH on the LDPE chains was ～5.1%. Thermal analysis showed that melting temperature of the graft copolymers decreases with increasing grafting degree. In addition to this, loss modulus (E″) of the copolymers first increased little with increasing grafting and then obviously decreased with increasing grafting degree. Furthermore, the results revealed that the tensile strength of the blends increased linearly with increasing PA6 content. The results of SEM and mechanical test showed that the blends have good interfacial adhesion and good stability of the phase structure, which is reflected in the mechanical properties. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 267–275, 2010     

Synthesis of poly(ethylene‐co‐vinyl alcohol)‐g‐polystyrene graft copolymer and their applications for ordered porous film and compatibilizer

A series of new functional poly(ethylene‐co‐vinyl alcohol)‐g‐polystyrene graft copolymers (EVAL‐g‐PS) with controlled molecular weight (M_n = 38,000–94,000 g mol^?1) and molecular weight distribution (M_w/M_n = 2.31–3.49) were synthesized via a grafting from methodology. The molecular structure and component of EVAL‐g‐PS graft copolymers were confirmed by the analysis of their ¹H NMR spectra and GPC curves. The porous films of such copolymers were fabricated via a static breath‐figure (BF) process. The influencing factors on the morphology of such porous films, such as solvent, temperature, polymer concentration, and molecular weight of polymer were investigated. Ordered porous film and better regularity was fabricated through a static BF process using EVAL‐g‐PS solution in CHCl₃. Scanning electron microscopy observation reveals that the EVAL‐g‐PS graft copolymer is an efficient compatibilizer for the blend system of low‐density polyethylene/polystyrene. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 516–524     

A study of the blending of ethylene–styrene copolymers differing in the copolymer styrene content: Miscibility considerations

Blends of two or more ethylene–styrene (ES) copolymers that differed primarily in the comonomer composition of the copolymers were studied. Available thermodynamic models for copolymer–copolymer blends were utilized to determine the criteria for miscibility between two ES copolymers differing in styrene content and also between ES copolymers and the respective homopolymers, polystyrene and linear polyethylene. Model estimations were compared with experimental observations based primarily on melt‐blended ES/ES systems, particularly via the analysis of the glass‐transition (T_g ) behavior from differential scanning calorimetry (DSC) and solid‐state dynamic mechanical spectroscopy. The critical comonomer difference in the styrene content at which phase separation occurred was estimated to be about 10 wt % for ES copolymers with a molecular weight of about 10⁵ and was in general agreement with the experimental observations. The range of ES copolymers that could be produced by the variation of the comonomer content allowed the study of blends with amorphous and semicrystalline components. Crystallinity differences for the blends, as determined by DSC, appeared to be related to the overlapping of the T_g of the amorphous component with the melting range of the semicrystalline component and/or the reduction in the mobility of the amorphous phase due to the presence of the higher T_g of the amorphous blend component. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2976–2987, 2000